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1
Sidorov, А. А., A. V. Volkov, and А. L. Galyamov. "About metallogeny of the pacific volcanic belts." Вулканология и сейсмология, no. 6 (November 12, 2019): 23–35. http://dx.doi.org/10.31857/s0203-03062019623-35.
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The article discusses the actual aspects of the metallogeny of the Pacific volcanic belts (PVB), which are a complexes of volcanogenic-plutogenic formations associated with the development of the marginal lithosphere and has an expressive specificity of ore formation. It is shown that over time the notions of metallogenic homogeneity of PVB have received a new justification from the position of global plate tectonics. Metallogenic significance of Ag/Au relationships in ore deposits of the PVB is shown. The correlation between porphyry-epithermal and the VMS ore-forming systems, regenerated and rejuvenated epithermal deposits is discussed. Global metallogenic homogeneity of the Pacific ore belt suggests a wide development of analogues of American volcanogenic deposits in its Asian half, including in the North-East of Russia. The main part of the internal zone of the Okhotsko-Chukchi marginal volcanic belt the Udo-Murgal island-arc belt, as well as the Uyandino-Yasachensky and Oloysky volcanic belts, are similar in geological structure not only to the Japanese green tuffs province, but also to other Pacific volcanic zones of the island-arc type and, therefore, within their limits, there is a high probability of revealing the entire variety of deposits of the VMS ore-formation series.
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Goldfarb, R. J., G. N. Phillips, and W. J. Nokleberg. "Tectonic setting of synorogenic gold deposits of the Pacific Rim." Ore Geology Reviews 13, no. 1-5 (1998): 185–218. http://dx.doi.org/10.1016/s0169-1368(97)00018-8.
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Volkov, A. V., and A. A. Sidorov. "The mineral wealth of the Pacific Ore Belt." Вестник Российской академии наук 89, no. 2 (2019): 157–65. http://dx.doi.org/10.31857/s0869-5873892157-165.
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Positive dynamics of world prices and the revival of exploration financing promote continued large investments in the construction of new mines to increase the production of minerals in the Pacific Ore Belt (POB). Several large deposits have been discovered, explored, and prepared for development in the countries of this region, thus attracting increased attention from mining companies. The total potential of mineral extraction in the POB, including in the East of Russia, could increase by 1.5–2 times over the coming years.
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Ernowo, Ernowo, and Penny Oktaviani. "REVIEW OFCHROMITE DEPOSITS OF INDONESIA." Buletin Sumber Daya Geologi 5, no. 1 (2010): 1–10. http://dx.doi.org/10.47599/bsdg.v5i1.250.
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Chromites (Fe,Mg)Cr O is an oxide mineral in spinel group. It is one of metallic mineral which classified in to alloy and ferro alloy metallic mineral group along with iron, nickel, titanium, manganese, cobalt, and bauxite. Chromites is the only ore mineral of metallic chromium and chromium compounds and chemicals. Because of this fact, chromites and chrome ore are used synonymously in trade literature. It is used for refractory material, because it has high heat stability. In Indonesia, chromites deposits are widely distributed in the eastern part of Indonesia, which rich in metal bearing ultramafic to mafic intrusive especially in South Kalimantan, Sulawesi, Maluku, Halmahera, Gebe, Gag, Waigeo, and Papua. These deposits are resulted from weathering of ophiolite rocks as part of the Pacific plate.
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Safina, Nataliya P., Irina Yu Melekestseva, Nuriya R. Ayupova, et al. "Authigenesis at the Urals Massive Sulfide Deposits: Insight from Pyrite Nodules Hosted in Ore Diagenites." Minerals 10, no. 2 (2020): 193. http://dx.doi.org/10.3390/min10020193.
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The pyrite nodules from ore diagenites of the Urals massive sulfide deposits associated with various background sedimentary rocks are studied using optical and electron microscopy and LA-ICP-MS analysis. The nodules are found in sulfide–black shale, sulfide–carbonate–hyaloclastite, and sulfide–serpentinite diagenites of the Saf’yanovskoe, Talgan, and Dergamysh deposits, respectively. The nodules consist of the core made up of early diagenetic fine-crystalline (grained) pyrite and the rim (±intermediate zone) composed of late diagenetic coarse-crystalline pyrite. The nodules are replaced by authigenic sphalerite, chalcopyrite, galena, and fahlores (Saf’yanovskoe), sphalerite, chalcopyrite and galena (Talgan), and pyrrhotite and chalcopyrite (Dergamysh). They exhibit specific accessory mineral assemblages with dominant galena and fahlores, various tellurides and Co–Ni sulfoarsenides in sulfide-black shale, sulfide–hyaloclastite–carbonate, and sulfide-serpentinite diagenites, respectively. The core of nodules is enriched in trace elements in contrast to the rim. The nodules from sulfide–black shale diagenites are enriched in most trace elements due to their effective sorption by associated organic-rich sediments. The nodules from sulfide–carbonate–hyaloclastite diagenites are rich in elements sourced from seawater, hyaloclastites and copper–zinc ore clasts. The nodules from sulfide–serpentinite diagenites are rich in Co and Ni, which are typical trace elements of ultramafic rocks and primary ores from the deposit.
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Ju, Nan, Sen Zhang, Lin-Lin Kou, et al. "Source and Tectonic Setting of Porphyry Mo Deposits in Shulan, Jilin Province, China." Minerals 9, no. 11 (2019): 657. http://dx.doi.org/10.3390/min9110657.
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The Shulan area in Jilin Province is a part of the Lesser Xing’an–Zhangguangcai Range polymetallic ore belt, which is an important Cu–Mo ore region of northeast China. The discovery of three large Mo ore deposits (Fu’anbu, Chang’anbu, and Jidetun) highlights its potential for porphyry Mo ore deposits. Here we investigated the tectonic setting and mineralization of Mo ore deposits in the Shulan area, based on comparative study of the Fu’anbu, Chang’anbu, and Jidetun deposits. The ore-controlling structures are NE–SW- and NW–SE-trending faults. The main ore mineral in all three deposits is molybdenite. The ore bodies are all hosted in granites, have a stratiform or lenticular shape, and have strongly altered wall rocks. These observations indicate the Mo deposits in the Shulan area are typical porphyry Mo deposits. All were formed during the early Yanshanian (199.6–133.9 Ma). Biotite adamellites from the Chang’anbu deposit yield a U–Pb age of 182.10 ± 1.20 Ma. Molybdenites from the Fu’anbu and Jidetun deposits have Re–Os isochron ages of 166.9 ± 6.7 and 169.1 ± 1.8 Ma, respectively. Quartz and ore minerals were analysed for H–O and S–Pb isotopes, respectively. The results suggest the ore-forming materials were predominantly of upper-mantle origin, with secondary contributions from the lower crust. The ore-hosting granites have high concentrations of SiO2 (66.67–75.43 wt.%) and Al2O3 (12.91–16.44 wt.%), low concentrations of MgO (0.09–1.54 wt.%), and Ritman index (σ = K2O + Na2O)2/(SiO2 − 43)) ratios of 2.09–2.57. The granites are enriched in large-ion lithophile elements and depleted in high-field-strength elements, and have negative Eu anomalies. The ore-hosting rocks are geochemically similar to granites in northeastern China that were generated in a collisional orogeny. We conclude that early Yanshanian (199.6–133.9 Ma) mantle–crust-derived magmatism caused by the subduction of the Palaeo-Pacific Plate was the main source of Mo deposits in the Shulan area.
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Wei, Chen, Lin Ye, Zhilong Huang, Yusi Hu, and Haoyu Wang. "In situ trace elements and S isotope systematics for growth zoning in sphalerite from MVT deposits: A case study of Nayongzhi, South China." Mineralogical Magazine 85, no. 3 (2021): 364–78. http://dx.doi.org/10.1180/mgm.2021.29.
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AbstractZoning texture in sphalerite has been described in many studies, although its genesis and ore formation process are poorly constrained. In this investigation, we compare the in situ trace element and isotopic composition of colour-zoned sphalerites from Nayongzhi, South China, to explain the zoning growth process. Petrographic observations identified two broad types of zoned sphalerite, core–rim (CR) and core–mantle–rim (CMR) textures. Each zoned sphalerite displays two or three colour zones, including brown core, light colour bands and/or pale-yellow zones. In situ laser ablation inductively coupled plasma mass spectrometry trace-element analyses show that the three colour zones display variable trace-element compositions. Brown cores exhibit distinctly high Mn, Fe, Co, Ge, Tl and Pb concentrations, whereas pale-yellow and light colour zones have elevated Ga, Cd, Sn, In and Sb concentrations. Copper, Sb, In and Sn show slight variations between pale-yellow and light zones, the latter having higher In and Sn, but lower Cu and Sb abundances. Given the low concentration range of Pb, Ge, Tl, Mn Sb, Cd, etc., the colour of sphalerite is attributed mainly to Fe compositional variation. The δ34S values of sphalerite from Nayongzhi range from +22.3 to +27.9‰, suggesting reduced sulfur was generated by thermochemical sulfate reduction of marine sulfate in ore-hosted strata. Single-crystal colour-zoned sphalerite exhibits intracrystalline δ34S variation (up to 4.3‰), which is attributed to the δ34S composition of H2S in the original fluid. The lack of correlation between trace elements and δ34S values indicates episodic ore solution influxes and mixes with the reduced sulfur-rich fluid derived from the aquifers of the ore-hosted strata, which play a key role in the formation of the zoned Nayongzhi sphalerite. In conclusion, in situ trace element and S isotope studies of zoned sphalerite crystals might provide insight into the ore-forming process of MVT deposits.
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Moritz, Robert, and Timothy Baker. "Metallogeny of the Tethyan Orogenic Belt: From Mesozoic Magmatic Arcs to Cenozoic Back-Arc and Postcollisional Settings in Southeast Europe, Anatolia, and the Lesser Caucasus: An Introduction." Economic Geology 114, no. 7 (2019): 1227–35. http://dx.doi.org/10.5382/econgeo.4683.
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Introduction The Tethyan mountain ranges stretch from northwestern Africa and western Europe to the southwest Pacific Ocean and constitute the longest continuous orogenic belt on Earth. It is an extremely fertile metallogenic belt, which includes a wide diversity of ore deposit types formed in very different geodynamic settings, which are the source of a wide range of commodities mined for the benefit of society (Janković, 1977, 1997; Richards, 2015, 2016). There are other ore deposit types in this segment of the Tethyan metallogenic belt that are not covered in this special issue, such as bauxite and Ni laterite deposits (Herrington et al., 2016), ophiolite-related chromite deposits (Çiftçi et al., 2019), sedimentary exhalative and Mississippi Valley-type deposits (Palinkaš et al., 2008; Hanilçi et al., 2019), or deposits related to surficial brine processes (Helvacı, 2019).
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Gopon, Phillip, James O. Douglas, Maria A. Auger, et al. "A Nanoscale Investigation of Carlin-Type Gold Deposits: An Atom-Scale Elemental and Isotopic Perspective." Economic Geology 114, no. 6 (2019): 1123–33. http://dx.doi.org/10.5382/econgeo.4676.
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Abstract Carlin-type gold deposits are one of the most important gold mineralization styles in the world. Despite their economic importance and the large volume of work that has been published, there remain crucial questions regarding their metallogenesis. Much of this uncertainty is due to the cryptic nature of the gold occurrence, with gold occurring as dispersed nanoscale inclusions within host pyrite rims that formed on earlier formed barren pyrite cores. The small size of the gold inclusions has made determining their nature within the host sulfides and the mechanisms by which they precipitated from the ore fluids particularly problematic. This study combines high-resolution electron probe microanalysis (EPMA) with atom probe tomography (APT) to constrain whether the gold occurs as nanospheres or is dispersed within the Carlin pyrites. APT offers the unique capability of obtaining major, minor, trace, and isotopic chemical information at near-atomic spatial resolution. We use this capability to investigate the atomic-scale distribution of trace elements within Carlin-type pyrite rims, as well as the relative differences of sulfur isotopes within the rim and core of gold-hosting pyrite. We show that gold within a sample from the Turquoise Ridge deposit (Nevada) occurs within arsenian pyrite overgrowth (rims) that formed on a pyrite core. Furthermore, this As-rich rim does not contain nanonuggets of gold and instead contains dispersed lattice-bound Au within the pyrite crystal structure. The spatial correlation of gold and arsenic within our samples is consistent with increased local arsenic concentrations that enhanced the ability of arsenian pyrite to host dispersed gold (Kusebauch et al., 2019). We hypothesize that point defects in the lattice induced by the addition of arsenic to the pyrite structure facilitate the dissemination of gold. The lack of gold nanospheres in our study is consistent with previous work showing that dispersed gold in arsenian pyrite can occur in concentrations up to ~1:200 (gold/arsenic). We also report a method for determining the sulfur isotope ratios from atom probe data sets of pyrite (±As) that illustrates a relative change between the pyrite core and its Au and arsenian pyrite rim. This spatial variation confirms that the observed pyrite core-rim structure is due to two-stage growth involving a sedimentary or magmatic-hydrothermal core and hydrothermal rim, as opposed to precipitation from an evolving hydrothermal fluid.
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BINGEN, BERNARD, FERNANDO CORFU, HOLLY J. STEIN, and MARTIN J. WHITEHOUSE. "U–Pb geochronology of the syn-orogenic Knaben molybdenum deposits, Sveconorwegian Orogen, Norway." Geological Magazine 152, no. 3 (2014): 537–56. http://dx.doi.org/10.1017/s001675681400048x.
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AbstractPaired isotope dilution – thermal ionization mass spectrometry (ID-TIMS) and secondary ion mass spectrometry (SIMS) zircon U–Pb data elucidate geochronological relations in the historically important Knaben molybdenum mining district, Sveconorwegian Orogen, south Norway. This polyphase district providedc. 8.5 Mt of ore with a grade of 0.2%. It consists of mineralized quartz veins, silica-rich gneiss, pegmatites and aplites associated with a heterogeneous, locally sulphide-bearing, amphibolites facies gneiss called Knaben Gneiss, and hosted in a regional-scale monotonous, commonly weakly foliated, granitic gneiss. An augen gneiss at the Knaben I deposit yields a 1257±6 Ma magmatic zircon age, dating the pre-Sveconorwegian protolith of the Knaben Gneiss. Mineralized and non-mineralized granitic gneiss samples at the Knaben II and Kvina deposits contain some 1488–1164 Ma inherited zircon and yield consistent intrusion ages of 1032±4, 1034±6 and 1036±6 Ma. This age links magmatism in the district to the regional 1050–1020 Ma Sirdal I-type granite suite, corresponding to voluminous crustal melting during the Sveconorwegian orogeny. A high-U, low-Th/U zircon rim is present in all samples. It defines several age clusters between 1039±6 and 1009±7 Ma, peaking atc. 1016 Ma and overlapping with a monazite age of 1013±5 Ma. The rim records protracted hydrothermal activity, which started during the main magmatic event and outlasted it. This process was coeval with regional high-grade Sveconorwegian metamorphism. Molybdenum deposition probably started during this event when silica-rich mineralizing fluids or hydrous magmas were released from granite magma batches. An analogy between the Knaben district and shallow, short-lived porphyry Mo deposits is inappropriate.
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Nevstruyev, Viktor, and Olga Kozlova. "Geodynamic and structural factors of porphyritic objects localization in Sikhote-Alin." E3S Web of Conferences 56 (2018): 04020. http://dx.doi.org/10.1051/e3sconf/20185604020.
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Ore bearing porphyritic systems of Sikhote-Alin form linear zones in Cretaceous volcanic belt. They are limited to zones of tectonic disturbances at Moho depths of 19-25 mi (30-40 km). Pacific slab lies at around 340 miles (548 km) below the volcanic belt, which matches the slab depth of porphyritic deposits formation belts in the Andes and Indonesia-Tonga region. Formation of porphyry copper systems is linked to the processes of metalliferous fluids intrusion at slab destruction areas near asthenosphere.
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Dill, H. G. "A comparative study of APS minerals of the Pacific Rim fold belts with special reference to south American argillaceous deposits." Journal of South American Earth Sciences 16, no. 5 (2003): 301–20. http://dx.doi.org/10.1016/s0895-9811(03)00099-3.
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Eliopoulos, D. G., and M. Economou-Eliopoulos. "Palladium and platinum in hydrothermal systems: The case of porphyry-Cu systems and sulfides associated with ophiolite complexes." Bulletin of the Geological Society of Greece 47, no. 4 (2016): 1618. http://dx.doi.org/10.12681/bgsg.11002.
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Data on the Pt and Pd contents in sea-floor massive sulfides related to ophiolite complexes indicated elevated Pt contents, up to 1 wt % Pt in sulfides from East Pacific Rise, up to 1000 ppb Pd or Pt in sulfides from mid-Atlantic Ridge and the Pindos ophiolite complex (Greece). Recently, elevated levels of Pd and Pt, have been reported from mineralization associated with alkaline porphyry deposits, such as the Skouries porphyry deposit (Greece), Cordillera of British Columbia, Elatsite (Bulgaria), Santo Tomas II in the Philippines and elsewhere. Current state of knowledge on the solubility of platinum-group elements was applied on hydrothermal systems related to the mineralization in ophiolite complexes and porphyry Cu-Mo-Au±Pd±Pt deposits toward a better understanding of the PGE mineralization in hydrothermal systems and the unknown Pd and Pt potential in porphyry-Cu systems. Ore reserves, mineralogical and geochemical ore data for porphyry-Cu systems are considered to be an encouraging factor for the presence of precious metals. In particular, the occurrence of merenskyite (palladium telluride) associated with chalcopyrite, coupled with the experimental data indicate that porphyry systems are capable to transport significant amounts of Pd and Pt.
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Zhao, He-Dong, Kui-Dong Zhao, Martin R. Palmer, Shao-Yong Jiang, and Wei Chen. "Magmatic-Hydrothermal Mineralization Processes at the Yidong Tin Deposit, South China: Insights from In Situ Chemical and Boron Isotope Changes of Tourmaline." Economic Geology 116, no. 7 (2021): 1625–47. http://dx.doi.org/10.5382/econgeo.4868.
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Abstract Owing to the superimposition of water-rock interaction and external fluids, magmatic source signatures of ore-forming fluids for vein-type tin deposits are commonly overprinted. Hence, there is uncertainty regarding the involvement of magmatic fluids in mineralization processes within these deposits. Tourmaline is a common gangue mineral in Sn deposits and can crystallize from both the magmas and the hydrothermal fluids. We have therefore undertaken an in situ major, trace element, and B isotope study of tourmaline from the Yidong Sn deposit in South China to study the transition from late magmatic to hydrothermal mineralization. Six tourmaline types were identified: (1) early tourmaline (Tur-OE) and (2) late tourmaline (Tur-OL) in tourmaline-quartz orbicules from the Pingying granite, (3) early tourmaline (Tur-DE) and (4) late tourmaline (Tur-DL) in tourmaline-quartz dikelets in the granite, and (5 and 6) core (Tur-OC) and rim (Tur-OR), respectively of hydrothermal tourmaline from the Sn ores. Most of the tourmaline types belong to the alkali group and the schorl-dravite solid-solution series, but the different generations of magmatic and hydrothermal tourmaline are geochemically distinct. Key differences include the hundredfold enrichment of Sn in hydrothermal tourmaline compared to magmatic tourmaline, which indicates that hydrothermal fluids exsolving from the magma were highly enriched in Sn. Tourmaline from the Sn ores is enriched in Fe3+ compared to the hydrothermal tourmaline from the granite and displays trends of decreasing Al and increasing Fe content from core to rim, relating to the exchange vector Fe3+Al–1. This reflects oxidation of fluids during the interaction between hydrothermal fluids and the mafic-ultramafic wall rocks, which led to precipitation of cassiterite. The hydrothermal tourmaline has slightly higher δ11B values than the magmatic tourmaline (which reflects the metasedimentary source for the granite), but overall, the tourmaline from the ores has δ11B values similar to those from the granite, implying a magmatic origin for the ore-forming fluids. We identify five stages in the magmatic-hydrothermal evolution of the system that led to formation of the Sn ores in the Yidong deposit based on chemical and boron isotope changes of tourmaline: (1) emplacement of a B-rich, S-type granitic magma, (2) separation of an immiscible B-rich melt, (3) exsolution of an Sn-rich, reduced hydrothermal fluid, (4) migration of fluid into the country rocks, and (5) acid-consuming reactions with the surrounding mafic-ultramafic rocks and oxidation of the fluid, leading to cassiterite precipitation.
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Miller, William. "Examples of Mesozoic and Cenozoic Bathysiphon (Foraminiferida) from the Pacific Rim and the taxonomic status of Terebellina Ulrich, 1904." Journal of Paleontology 69, no. 4 (1995): 624–34. http://dx.doi.org/10.1017/s0022336000035162.
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The generic name Terebellina was proposed by E. O. Ulrich for large (> 100 mm long, several millimeters wide), siliceous, tubular fossils from Cretaceous rocks of southern Alaska. Originally interpreted as annelid tubes, these unusual agglutinated fossils are locally abundant in Triassic to Neogene flysch and other basinal deposits of the Pacific borderlands. Other generic names employed for the same fossils include Torlessia (used in New Zealand) and Yokoia (in Japan). Although most authors have regarded the tubes as body fossils of worms, some workers have speculated recently that Pacific Terebellina are really large bathysiphonid foraminiferids. At the same time, the name has been co-opted by trace fossil workers for thick-walled, grain-lined burrows usually occurring in outer-shelf to slope facies.Based on comparisons with modern and fossil bathysiphonids, including a new species (Bathysiphon harperi) from the Cretaceous of southwestern Oregon, the body fossils called Terebellina are here reinterpreted as large species of Bathysiphon, and the name Terebellina is therefore a junior synonym of this foraminiferid genus. Except for the compression and recrystallization of tubes, Pacific Terebellina resemble very closely the tests of larger species of modern Bathysiphon. Terebellina should not be salvaged for use as an ichnogenus. Most of the trace fossils identified with this name in the recent literature could be accommodated in other established ichnogenera, primarily Palaeophycus (where grain-lined burrows occur individually and are dominantly horizontal) and Schaubcylindrichnus (where they occur in curved bundles).
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Wang, Yan, Zhongwei Wu, Xiaoming Sun, et al. "He–Ar–S Isotopic Compositions of Polymetallic Sulphides from Hydrothermal Vent Fields along the Ultraslow-Spreading Southwest Indian Ridge and Their Geological Implications." Minerals 8, no. 11 (2018): 512. http://dx.doi.org/10.3390/min8110512.
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Noble gases have become a powerful tool to constrain the origin and evolution of ore-forming fluids in seafloor hydrothermal systems. The aim of this study was to apply these tracers to understand the genesis of newly discovered polymetallic sulphide deposits along the ultraslow-spreading Southwest Indian Ridge (SWIR). The helium, argon, and sulphur isotope compositions of metal sulphide minerals were measured for a number of active/inactive vent fields in the Indian Ocean. The helium concentrations and isotopic ratios in these ore samples are variable (4He: 0.09–2.42 × 10−8 cm3STP∙g−1; 3He: 0.06–3.28 × 10−13 cm3STP∙g−1; 3He/4He: 1.12–9.67 Ra) and generally greater than the modern atmosphere, but significantly lower than those in massive sulphides from the fast-spreading East Pacific Rise (EPR), especially for three Cu–Fe-rich samples from the ultramafic-hosted Tianzuo and Kairei vent fields. On the contrary, most of the SWIR sulphide deposits have somewhat higher 40Ar/36Ar ratios of trapped fluids (ranging from 290.6 to 303.4) when compared to the EPR ore samples. Moreover, the majority of sulphide minerals from the Indian Ocean have much higher δ34S values (3.0‰–9.8‰, ~5.9 on average, n = 49) than other basaltic-hosted active hydrothermal systems on the EPR. Overall, these He–Ar–S results are well within the range of seafloor massive sulphide deposits at global sediment-starved mid-ocean ridges (MORs), lying between those of air-saturated water (ASW) and mid-ocean ridge basalt (MORB) end members. Therefore, our study suggests that the helium was derived mainly from the MORB mantle by degassing during the high-temperature stage of hydrothermal activity, as well as from a mixture of vent fluids with variable amounts of ambient seawater during either earlier or late-stage low-temperature hydrothermal episodes, whereas the argon in ore-forming fluids trapped within sulphide minerals was predominantly derived from deep-sea water. Additionally, relatively high δ34S values exhibit a great estimated proportion (up to nearly 40%) of seawater-derived components. In summary, sub-seafloor extensive fluid circulation, pervasive low-temperature alteration, shallow seawater entrainment, and mixing processes, may make a larger contribution to the SWIR hydrothermal ore-forming systems, compared to fast-spreading centres.
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Huang, Xiao-Wen, and Georges Beaudoin. "Textures and Chemical Compositions of Magnetite from Iron Oxide Copper-Gold (IOCG) and Kiruna-Type Iron Oxide-Apatite (IOA) Deposits and Their Implications for Ore Genesis and Magnetite Classification Schemes." Economic Geology 114, no. 5 (2019): 953–79. http://dx.doi.org/10.5382/econgeo.4651.
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Abstract Textural and compositional data of magnetite from Igarapé Bahia, Alemao, Sossego, Salobo, and Candelaria iron oxide copper-gold (IOCG) and El Romeral Kiruna-type iron oxide-apatite (IOA) deposits show that some magnetite grains display oscillatory zoning or have been reequilibrated by oxy-exsolution, coupled dissolution and reprecipitation (CDR) reactions, and/or recrystallization. Textures formed via CDR are most widespread in the studied samples. The original oscillatory zoning was likely derived from the crystal growth during fluctuating fluid compositions rather than from variation in temperature and oxygen fugacity. The oxy-exsolution of ilmenite in magnetite is attributed to increasing oxygen fugacity and decreasing temperature with alteration and mineralization, resulting in product magnetite with lower Ti and higher V contents. Recrystallization of some magnetite grains is commonly due to high-temperature annealing that retained primary compositions. Two different types of CDR processes are defined according to textures and chemical compositions of different generations of magnetite. The first generation of magnetite (Mag-1) is an inclusion-rich and trace element-rich core, which was replaced by an inclusion-poor and trace element-poor rim (Mag-2). The third generation of magnetite (Mag-3), inclusion poor but trace element rich, occurs as veins replacing Mag-2 along fractures or grain margins. Type 1 CDR process transforming Mag-1 to Mag-2 is more extensive and is similar to processes reported in skarn deposits, whereas type 2 CDR process is local, transforming Mag-2 to Mag-3. During type 1 CDR process, minor and trace elements Si, K, Ca, Mg, Al, and Mn in magnetite are excluded, and Fe contents increase to various extents, in contrast to type 2 CDR process, which is characterized by increased contents of Si, K, Ca, Mg, Al, and Mn. Type 1 CDR process is possibly induced by the changing fluid composition and/or decreasing temperature during progressive alteration and ore formation, whereas type 2 CDR process can be interpreted as post-ore replacement due to a new pulse of magmatic-hydrothermal fluids. The identification of magnetite core (Mag-1) with igneous origin and rim (Mag-2) with magmatic-hydrothermal origin in the Sossego IOCG and El Romeral IOA deposits supports a fluid changing from magmatic to magmatic-hydrothermal during IOCG and IOA formation and indicates a genetic link between these two deposit types. The large data set here further demonstrates that magnetite is susceptible to textural and compositional reequilibration during high-temperature magmatic and magmatic-hydrothermal processes. Reequilibrated magnetite, particularly that formed by CDR processes, has a chemical composition that can be different from that of primary magnetite. Modified magnetite, therefore, cannot be used to discriminate its primary origin or to interpret its provenance in overburden sediments. Therefore, in situ chemical analysis of magnetite combined with textural characterization is necessary to understand the origin of magnetite in IOCG and IOA deposits.
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Kempe, U., and J. Götze. "Cathodoluminescence (CL) behaviour and crystal chemistry of apatite from rare-metal deposits." Mineralogical Magazine 66, no. 1 (2002): 151–72. http://dx.doi.org/10.1180/0026461026610019.
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AbstractApatite samples from rare-metal mineralization were investigated by a combination of cathodoluminescence (CL) microscopy and spectroscopy, microchemical analysis and trace element analysis. Internal structures revealed by CL can be related to variations in the crystal chemistry and may sometimes reflect changes in the composition of the mineralizing fluids.Apatite from mineralization related to alkaline rocks and carbonatites (Type 1) typically exhibits relatively homogeneous blue and lilac/violet CL colours due to activation by trace quantities of rare earth element ions (Ce3+, Eu2+, Sm3+, Dy3+ and Nd3+). These results correlate with determined trace element abundances, which show strong light rare earth element (LREE) enrichment for this type of apatite. However, a simple quantitative correlation between emission intensities of REE3+/2+ and analysed element concentrations was not found.Apatite from P-rich altered granites, greisens, pegmatites and veins from Sn-W deposits (Type 2) shows strong Mn2+-activated yellow-greenish CL, partially with distinct oscillatory zoning. Variations in the intensity of the Mn2+-activated CL emission can be related either to varying Mn/Fe ratios (quenching of Mn activated CL by Fe) or to self-quenching effects in zones with high Mn contents (>2.0 wt.%). The REE distribution patterns of apatite reflect the specific geological position of each sample and may serve as a “tracer” for the REE behaviour within the ore system. Although the REE contents are sometimes as high as several hundred parts per million, the spectral CL measurements do not exhibit typical REE emission lines because of dominance of the Mn emission. In these samples, REE-activated luminescence is only detectable by time-resolved laser-induced luminescence spectroscopy.Both types of apatite (Type 1 in the core and Type 2 in the rim) were found in single crystals from the Be deposit Ermakovka (Transbaikalia). This finding proves the existence of two stages of mineralization within this deposit.
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Rodriguez-Mustafa, Maria A., Adam C. Simon, Irene del Real, et al. "A Continuum from Iron Oxide Copper-Gold to Iron Oxide-Apatite Deposits: Evidence from Fe and O Stable Isotopes and Trace Element Chemistry of Magnetite." Economic Geology 115, no. 7 (2020): 1443–59. http://dx.doi.org/10.5382/econgeo.4752.
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Abstract Iron oxide copper-gold (IOCG) and iron oxide-apatite (IOA) deposits are major sources of Fe, Cu, and Au. Magnetite is the modally dominant and commodity mineral in IOA deposits, whereas magnetite and hematite are predominant in IOCG deposits, with copper sulfides being the primary commodity minerals. It is generally accepted that IOCG deposits formed by hydrothermal processes, but there is a lack of consensus for the source of the ore fluid(s). There are multiple competing hypotheses for the formation of IOA deposits, with models that range from purely magmatic to purely hydrothermal. In the Chilean iron belt, the spatial and temporal association of IOCG and IOA deposits has led to the hypothesis that IOA and IOCG deposits are genetically connected, where S-Cu-Au–poor magnetite-dominated IOA deposits represent the stratigraphically deeper levels of S-Cu-Au–rich magnetite- and hematite-dominated IOCG deposits. Here we report minor element and Fe and O stable isotope abundances for magnetite and H stable isotope abundances for actinolite from the Candelaria IOCG deposit and Quince IOA prospect in the Chilean iron belt. Backscattered electron imaging reveals textures of igneous and magmatic-hydrothermal affinities and the exsolution of Mn-rich ilmenite from magnetite in Quince and deep levels of Candelaria (>500 m below the bottom of the open pit). Trace element concentrations in magnetite systematically increase with depth in both deposits and decrease from core to rim within magnetite grains in shallow samples from Candelaria. These results are consistent with a cooling trend for magnetite growth from deep to shallow levels in both systems. Iron isotope compositions of magnetite range from δ56Fe values of 0.11 ± 0.07 to 0.16 ± 0.05‰ for Quince and between 0.16 ± 0.03 and 0.42 ± 0.04‰ for Candelaria. Oxygen isotope compositions of magnetite range from δ18O values of 2.65 ± 0.07 to 3.33 ± 0.07‰ for Quince and between 1.16 ± 0.07 and 7.80 ± 0.07‰ for Candelaria. For cogenetic actinolite, δD values range from –41.7 ± 2.10 to –39.0 ± 2.10‰ for Quince and from –93.9 ± 2.10 to –54.0 ± 2.10‰ for Candelaria, and δ18O values range between 5.89 ± 0.23 and 6.02 ± 0.23‰ for Quince and between 7.50 ± 0.23 and 7.69 ± 0.23‰ for Candelaria. The paired Fe and O isotope compositions of magnetite and the H isotope signature of actinolite fingerprint a magmatic source reservoir for ore fluids at Candelaria and Quince. Temperature estimates from O isotope thermometry and Fe# of actinolite (Fe# = [molar Fe]/([molar Fe] + [molar Mg])) are consistent with high-temperature mineralization (600°–860°C). The reintegrated composition of primary Ti-rich magnetite is consistent with igneous magnetite and supports magmatic conditions for the formation of magnetite in the Quince prospect and the deep portion of the Candelaria deposit. The trace element variations and zonation in magnetite from shallower levels of Candelaria are consistent with magnetite growth from a cooling magmatic-hydrothermal fluid. The combined chemical and textural data are consistent with a combined igneous and magmatic-hydrothermal origin for Quince and Candelaria, where the deeper portion of Candelaria corresponds to a transitional phase between the shallower IOCG deposit and a deeper IOA system analogous to the Quince IOA prospect, providing evidence for a continuum between both deposit types.
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Zachariáš, J., J. Frýda, B. Paterová, and M. Mihaljevič. "Arsenopyrite and As-bearing pyrite from the Roudný deposit, Bohemian Massif." Mineralogical Magazine 68, no. 1 (2004): 31–46. http://dx.doi.org/10.1180/0026461046810169.
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AbstractThe major- and trace-element chemistry of pyrite and arsenopyrite from the mesothermal Roudný gold deposits was studied by electron microprobe and laser ablation ICP-MS techniques. In total, four generations of pyrite and two of arsenopyrite were distinguished. The pyrite is enriched in As through an Fe (AsxS1–x)2 substitution mechanism. The As-rich zones of pyrite-2 (up to 4.5 wt.% As) are also enriched in gold (up to 20 ppm), lead (commonly up to 220 ppm, exceptionally up to 1500 ppm) and antimony (commonly <600 ppm, rarely up to 1350 ppm). Positive correlation of As and Au in the studied pyrites is not coupled with an Fe deficiency, in contrast to Au-rich As-bearing pyrites in Carlintype gold deposits. The As-rich pyrite-2 coprecipitated with the Sb-rich (1 –4.2 wt.%) and Au-rich (40 –150 ppm) arsenopyrite-1. The younger arsenopyrite-2 is significantly less enriched in these elements (0 –70 ppm of Au).The chemical zonality of pyrites in the Roudný gold deposits reflects the chemical evolution of orebearing fluids that are not observed in any other mineral phases. The data available suggest relatively high activity of sulphur and low activities of arsenic and gold during crystallization of the older pyrite generation (pyrite-1). Later, after particular dissolution of pyrite-1, Au-rich As-bearing pyrite-2 and arsenopyrite precipitated. These facts suggest a marked increase in the arsenic and gold activities in ore-bearing fluids. The As-content of pyrite-2 decreases in an oscillatory manner from the core to the rim, reflecting changes in the As activity or/and in the P-T conditions. The As-bearing pyrites were formed at temperatures of at least 320–330°C, based on arsenopyrite thermometers and fluid inclusion data.
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PLETNEV, S. P., and T. E. SEDYSHEVA. "The early stages of ferromanganese ore genesis on the guyots of the Magellan Seamounts (The Pacific Ocean)." Geology and Mineral Resources of World Ocean 16, no. 3 (2020): 3–12. http://dx.doi.org/10.15407/gpimo2020.03.003.
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Fe-Mn crusts play an important role in marine mineral deposit research because of their widespread occurrence and high concentrations of valuable and rare metals. Most Fe-Mn crust deposits occur on the tens of thousands of seamounts found in the ocean. Data on the structure, texture, composition, age, and deposit characteristics will help define which factors are key for the creation of mineral accumulation and which combination of factors leads to the formation of potentially economic concentrations of metals. In this paper, we address the structure and characteristics of the oldest Fe-Mn crust stratigraphic sections (Late Cretaceous and Paleocene) collected from the Magellan seamounts. A complete section of the crusts on the Magellan Seamounts includes four layers, each 2—4 cm thickness: the Late Paleocene (?) Early Eocene layer I 1, the Mid Late Eocene layer I—2, the Miocene layer II and the Quaternary layer III. In some cases, the main CMC section is underlain by relict layers. The chemical and mineral composition of the layers was determined both by X-ray diffraction and precision methods; concentrations of the main ore components and phosphorus were determined by the methods of classical chemistry. The age of 12 samples was determined, the mineral composition of four, the chemical composition of 22 samples. The results of the relict layers analysis allow to distinguish two groups of samples among them. Among the relict layers, two age ranges are established — the second half of Late Cretaceous (R1) and the first half of Paleocene (R2). High concentrations of barium, lithium, gallium, and zinc suggest that hydrothermal sources could be the source of the material. But not through direct delivery, but via the phase of transfer of sea bottom water. Thus, the analysis of lithological and geochemical parameters and fossil fauna of foraminifera in the relict layers of the Magellan Seamounts ore section indicates two stages of their formation: Late Campan Maastricht and Early Middle Paleocene. The discreteness of the formation of relict layers in time once again proves that the sharply changing environmental conditions controlled the growth of the CMC ore section.
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Zhang, Yu, Pete Hollings, Yongjun Shao, Dengfeng Li, Huayong Chen, and Hongbin Li. "Magnetite texture and trace-element geochemistry fingerprint of pulsed mineralization in the Xinqiao Cu-Fe-Au deposit, Eastern China." American Mineralogist 105, no. 11 (2020): 1712–23. http://dx.doi.org/10.2138/am-2020-7414.
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Abstract The origin of stratabound deposits in the Middle-Lower Yangtze River Valley Metallogenic Belt (MLYRB), Eastern China, is the subject of considerable debate. The Xinqiao Cu-Fe-Au deposit in the Tongling ore district is a typical stratabound ore body characterized by multi-stage magnetite. A total of six generations of magnetite have been identified. Mt1 is commonly replaced by porous Mt2, and both are commonly trapped in the core of Mt3, which is characterized by both core-rim textures and oscillatory zoning. Porous Mt4 commonly truncates the oscillatory zoning of Mt3, and Mt5 is characterized by 120° triple junction texture. Mt1 to Mt5 are commonly replaced by pyrite that coexists with quartz, whereas Mt6, with a fine-grained foliated and needle-like texture, commonly cuts the early pyrite as veins and is replaced by pyrite that coexists with calcite. The geochemistry of the magnetite suggests that they are hydrothermal in origin. The microporosity of Mt2 and Mt4 magnetite, their sharp contacts with Mt1 and Mt3, and lower trace-element contents (e.g., Si, Ca, Mg, and Ti) than Mt1 and Mt3 suggest that they formed via coupled dissolution and reprecipitation of the precursor Mt1 and Mt3 magnetite, respectively. This was likely caused by high-salinity fluids derived from intensive water-rock interaction between the magmatic-hydrothermal fluids associated with the Jitou stock and Late Permian metalliferous black shales. The 120° triple junction texture of Mt5 suggests it is the result of fluid-assisted recrystallization, whereas Mt6 formed by replacement of hematite as a result of fracturing. The geochemistry of the magnetite suggests that the temperature increased from Mt2 to Mt3 and implies that there were multiple pulses of fluids from a magmatic-hydrothermal system. Therefore, we propose that the Xinqiao stratiform mineralization was genetically associated with multiple influxes of magmatic hydrothermal fluids derived from the Early Cretaceous Jitou stock. This study demonstrates that detailed texture examination and in situ trace-elements analysis under robust geological and petrographic frameworks can effectively constrain the mineralization processes and ore genesis.
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Griscom, D. L. "In plain sight: the Chesapeake Bay crater ejecta blanket." Solid Earth Discussions 4, no. 1 (2012): 363–428. http://dx.doi.org/10.5194/sed-4-363-2012.
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Abstract. The discovery nearly two decades ago of a 90 km-diameter impact crater below the lower Chesapeake Bay has gone unnoted by the general public because to date all published literature on the subject has described it as "buried". To the contrary, evidence is presented here that the so-called "upland deposits" that blanket ∼5000 km2 of the U.S. Middle-Atlantic Coastal Plain (M-ACP) display morphologic, lithologic, and stratigraphic features consistent with their being ejecta from the 35.4 Ma Chesapeake Bay Impact Structure (CBIS) and absolutely inconsistent with the prevailing belief that they are of fluvial origin. Specifically supporting impact origin are the facts that (i) a 95 %-pure iron ore endemic to the upland deposits of southern Maryland, eastern Virginia, and the District of Columbia has previously been proven to be impactoclastic in origin, (ii) this iron ore welds together a small percentage of well-rounded quartzite pebbles and cobbles of the upland deposits into brittle sheets interpretable as "spall plates" created in the interference-zone of the CBIS impact, (iii) the predominantly non-welded upland gravels have long ago been shown to be size sorted with an extreme crater-centric gradient far too large to have been the work of rivers, but well explained as atmospheric size-sorted interference-zone ejecta, (iv) new evidence is provided here that ~60 % of the non-welded quartzite pebbles and cobbles of the (lower lying) gravel member of the upland deposits display planar fractures attributable to interference-zone tensile waves, (v) the (overlying) loam member of the upland deposits is attributable to base-surge-type deposition, (vi) several exotic clasts found in a debris flow topographically below the upland deposits can only be explained as jetting-phase crater ejecta, and (vii) an allogenic granite boulder found among the upland deposits is deduced to have been launched into space and sculpted by hypervelocity air friction during reentry. An idealized calculation of the CBIS ejecta-blanket elevation profile minutes after the impact was carried out founded on well established rules for explosion and impact-generated craters. This profile is shown here to match the volume of the upland deposits ≥170 km from the crater center. Closer to the crater, much of the "postdicted" ejecta blanket has clearly been removed by erosion. Nevertheless the Shirley and fossil-free Bacons Castle Formations, located between the upland deposits and the CBIS interior and veneering the present day surface with units ∼10–20 m deep, are respectively identified as curtain- and excavation-phase ejecta. The neritic-fossil-bearing Calvert Formation external to the crater is deduced to be of Eocene age (as opposed to early Miocene as currently believed), preserved by the armoring effects of the overlying CBIS ejecta composed of the (distal) upland deposits and the (proximal) Bacons Castle Formation. The lithofacies of the in-crater Calvert Formation can only have resulted from inward mass wasting of the postdicted ejecta blanket, vestiges of which (i.e. the Bacons Castle and Shirley Formations) still overlap the crater rim and sag into its interior, consistent with this expectation. Because there appear to be a total of ∼10 000 km2 of CBIS ejecta lying on the present-day surface, future research should center the stratigraphic, lithologic, and petrologic properties of these ejecta versus both radial distance from the crater center (to identify ejecta from different ejection stages) and circumferentially at fixed radial distances (to detect possible anisotropies relating the impact angle and direction of approach of the impactor). The geological units described here may comprise the best preserved, and certainly the most accessible, ejecta blanket of a major crater on the Earth's surface and therefore promise to be a boon to the field of impact geology. As a corollary, a major revision of the current stratigraphic column of the M-ACP will be necessary.
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Hu, Liang, Zheng, Zhou, Yang, and Zhu. "Tectonic Transformation and Metallogenesis of the Yanshan Movement during the Late Jurassic Period: Evidence from Geochemistry and Zircon U-Pb Geochronology of the Adamellites in Xingcheng, Western Liaoning, China." Minerals 9, no. 9 (2019): 518. http://dx.doi.org/10.3390/min9090518.
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The Yanshan Movement occurred mainly during the Middle-Late Jurassic, and gave rise to NE trending structures, magmatic events, volcanism and mineral resources. The transformation and evolution of the movement during the Middle-Late Jurassic were investigated from the rock assemblage, geochemistry, and chronology in adamellites which were exposed in the Xingcheng area, western Liaoning. Two types of adamellites were recognized—biotite adamellites with the formation age of 172–168 Ma and garnet-bearing adamellites of 158–152 Ma. All the samples of the two types of adamellites displayed enriched characteristics with high content of SiO2 (66.86–75.55 wt.%) and total alkali (Na2O + K2O = 7.56–8.71 wt.%), high large ion lithophile element (LILE: K, Rb, Sr), and low high field strength element (HFSE: Ce, Ta, P, Ti). The biotite adamellites belong to metaluminous-peraluminous I-type granites, and show volcanic arc granite characteristics, and were formed by partial melting of the ancient crust in the compressional setting that resulting from the subduction of the Paleo-Pacific plate beneath the north margin of the North China Craton (NCC). The garnet-bearing adamellites are also metaluminous-peraluminous I-type granites, with characteristics of both the compressional and extensional regimes, which were formed at the middle-late stages of the continuing subduction of the Paleo-Pacific plate, while simultaneously, the frontal side of the subduction slab began to roll back, leading to an extensional environment. Combining with regional geophysical studies and our petrological and geochemical studies, we propose that the eastern segment of the northern margin of NCC may have been controlled by the Paleo-Pacific tectonic domain at the latest in the Middle Jurassic, while the initiation of the tectonic regime from a compressional to an extensional environment was during the Late Jurassic (158–152 Ma) as a response of the Yanshan Movement. Simultaneously, geochronological statistics of the ore deposits in western Liaoning show that the Mesozoic endogenetic metalliferous deposits formed in a compressive environment influenced by the subduction of the Paleo-Pacific plate, similar to the magma events in ages, and the magmatism provided the thermodynamic condition and the source of metallogenic hydrothermal fluid for mineralization.
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Slack, John F., Leonid A. Neymark, Richard J. Moscati, et al. "Origin of Tin Mineralization in the Sullivan Pb-Zn-Ag Deposit, British Columbia: Constraints from Textures, Geochemistry, and LA-ICP-MS U-Pb Geochronology of Cassiterite." Economic Geology 115, no. 8 (2020): 1699–724. http://dx.doi.org/10.5382/econgeo.4761.
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Abstract Textural, geochronological, and geochemical data are presented here for cassiterite from the giant (149.7 million tonnes [Mt]) Mesoproterozoic Sullivan Pb-Zn-Ag deposit, which has been subjected to several tectonothermal events. These data provide constraints on the age and origin of the tin concentrations and new insights into related base metal mineralization. Sullivan is rare among sediment-hosted, stratiform Pb-Zn-Ag deposits in having high tin contents in ore (up to 2.5 wt %; avg 310 ppm Sn). Cassiterite occurs in all facies of this deformed and metamorphosed deposit, including (1) high-grade veins with arsenopyrite and pyrrhotite, (2) bedded Pb-Zn-Ag ores, (3) massive pyrrhotite, (4) footwall and hanging-wall tourmalinites, and (5) other altered wall rocks. New in situ U-Pb dates for Sullivan cassiterite obtained by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) are modeled by a multicomponent-based algorithm that yields three age peaks: 1475 ± 4 Ma (51% of the data), 1366 ± 10 Ma (25%), and 1074 ± 7 Ma (24%). These dates are attributed, respectively, to primary tin mineralization at ca. 1475 Ma, the East Kootenay orogeny at ca. 1370 to 1300 Ma, and the Grenvillian orogeny at ca. 1100 to 980 Ma. Based on the presence and local abundance of cassiterite in all ore and ore-related rocks at Sullivan, the U-Pb date of 1475 ± 4 Ma reported here represents the first direct age for ore mineralization in the deposit. Occurrence of texturally discordant rims on Sullivan cassiterite grains having U-Pb dates coeval with the East Kootenay and Grenvillian orogenies suggests that these young dates reflect dissolution-reprecipitation processes associated with channelized metamorphic fluid flow. LA-ICP-MS U-Pb dates obtained on low-U (&lt;10 ppm) cassiterite also indicate that U-Pb dates for cassiterite from other metamorphosed deposits should be viewed with caution and not assumed to record an age of primary tin mineralization. Aqueous transport conditions for tin are evaluated to gain insights into the cassiterite mineralization at Sullivan. Based on fO2-pH topology of aqueous tin species at 250°C, tin transport was dominated by an SnCl3− complex at fO2 of about –40 and pH of &lt;4.0, conditions that were constrained, respectively, by widespread occurrence of pyrrhotite in deep footwall siliciclastic metasedimentary rocks of the host Aldridge Formation and by release of CO2 from shallow mafic sills and resulting formation of carbonic acid in condensed brine. The low fO2 value also reflects inferred production of CH4 from heating of organic matter in the sediments during emplacement of these sills. Based on a fluid pH restriction of &lt;4.0 and a requirement for sparse or no K-feldspar in the source, the tin likely derives from previously altered Lower Aldridge strata. This model relies on the early diagenetic dissolution of K-feldspar from these sediments by basinal brines, followed by interaction with a later, more acidic hydrothermal fluid generated during the emplacement of large mafic sills in the shallow subsurface that leached tin from accessory minerals such as titanite in siliciclastic sediments of the Lower Aldridge Formation. Mass balance calculations suggest that derivation of the tin from this sedimentary source (avg 2.0 ppm Sn) required ~40 km3 and a cylinder diameter of 3.2 km (height 5.0 km) in order to supply the 0.1 Mt of tin contained in the deposit. The presence of mafic sills in the footwall of several other tin-bearing, sediment-hosted, stratiform Pb-Zn-Ag deposits and in modern, tin-rich, sediment-hosted sulfide deposits in the northeast Pacific Ocean suggests that siliciclastic marine basins that contain mafic sills—with or without stratiform sulfide deposits—should be evaluated for possible tin mineralization.
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Jin, Xiao-Ye, Jian-Xin Zhao, Yue-Xing Feng, et al. "CALCITE U-Pb DATING UNRAVELS THE AGE AND HYDROTHERMAL HISTORY OF THE GIANT SHUIYINDONG CARLIN-TYPE GOLD DEPOSIT IN THE GOLDEN TRIANGLE, SOUTH CHINA." Economic Geology 116, no. 6 (2021): 1253–65. http://dx.doi.org/10.5382/econgeo.4870.
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Abstract The ages of Carlin-type gold deposits in the Golden Triangle of South China have long been questioned due to the general lack of minerals unequivocally linked to gold deposition that can be precisely dated using conventional radiogenic isotope techniques. Recent advances in U-Pb methods show that calcite can be used to constrain the ages of hydrothermal processes, but few studies have been applied to ore deposits. Herein, we show that this approach can be used to constrain the timing of hydrothermal activity that generated and overprinted the giant Shuiyindong Carlin-type gold deposit in the Golden Triangle. Three stages of calcite (Cal-1, Cal-2, and Cal-3) have been recognized in this deposit based on crosscutting relationships, cathodoluminescence colors, and chemical (U, Pb, and rare earth element [REE]) and isotope (C, O, Sr) compositions. Cal-1 is texturally associated with ore-stage jasperoid and disseminated Au-bearing arsenian pyrite in hydrothermally altered carbonate rocks, which suggests it is synmineralization. Cal-2 fills open spaces and has a distinct orange cathodoluminescence, suggesting that it precipitated during a second fluid pulse. Cal-1 and Cal-2 have similar carbonate rock-buffered chemical and isotopic compositions. Cal-3 occurs in veins that often contain realgar and/or orpiment and are chemically (low U, Pb, and REE) and isotopically (higher δ13C, lower δ18O and Sri values) distinct from Cal-1 and Cal-2, suggesting that it formed from a third fluid. U-Pb isotope analyses, by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) for U-rich Cal-1 and Cal-2 and by LA-multicollector (MC)-ICP-MS for U-poor Cal-3, yield well-defined age constraints of 204.3 to 202.6, 191.9, and 139.3 to 137.1 Ma for Cal-1, Cal-2, and Cal-3, respectively. These new ages suggest that the Shuiyindong gold deposit formed in the late Triassic and was overprinted by hydrothermal events in the early Jurassic and early Cretaceous. Given the association of Cal-3 with orpiment and realgar, and previous geochronologic studies of several other major gold deposits in the Golden Triangle, we infer that the latest stage of calcite may be associated with an early Cretaceous regional gold metallogenic event. Combined with existing isotopic ages in the region, these new ages lead us to propose that Carlin-type gold deposits in the Golden Triangle formed during two metallogenic episodes in extensional settings, associated with the late Triassic Indochina orogeny and early Cretaceous paleo-Pacific plate subduction. This study shows that the calcite U-Pb method can be used to constrain the timing of Carlin-type gold deposits and successive hydrothermal events.
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Mouat, Jeremy. "Creating a New Staple: Capital, Technology, and Monopoly in British Columbia’s Resource Sector, 1901-1925." Victoria 1990 1, no. 1 (2006): 215–37. http://dx.doi.org/10.7202/031017ar.
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Abstract This paper examines the mining industry of British Columbia, the province's leading staple during the period when the region was brought within the network of world trade. Specifically, it describes the emergence of zinc production as the most profitable sector of the industry, from the early 1900s through to the mid-1920s. A good deal of importance was attached to discovering some means of treating zinc ore in the early 1900s. Increasing amounts of zinc were being found in the silver-lead ore of eastern British Columbia. Zinc was seen as a contaminant, and smelters penalised mine-owners who shipped ore that was over 10 per cent zinc. The presence of zinc rendered relatively valuable ore (in terms of its silver and lead content) uneconomical. Concern over “the zinc problem” was such that, by 1905, the federal government, responding to the lobbying efforts of mine-owners, appointed a commission “to Investigate the Zinc Resources of British Columbia and the Conditions Affecting Their Exploitation”. During the next twenty years, mining companies in the Kootenays explored a number of different ways to overcome zinc's unfortunate impact upon the mining industry. These efforts to discover an adequate means to treat zinc ore illustrate the way in which technology and capital became the key ingredients of a distinctively new mining industry. The paper argues that the emergence of zinc mining reflected a fundamental restructuring of the industry, as the focus shifted from the discovery and exploitation of bonanza deposits of gold and silver to the less spectacular production of copper, lead, and zinc. Technology, economies of scale, and substantial capital investment were the hallmarks of the new industry. Not only was the industry profoundly altered — experiencing what other scholars have described as the second industrial revolution — but new vertically integrated companies displaced the traditional mining company. The paper describes the clearest example of this trend, outlining the early career of the Consolidated Mining and Smelting Company of Canada [Cominco], a subsidiary of the Canadian Pacific Railway. Cominco was able to put in place the necessary technology to tap its enormous lead-zinc deposit at Kimberley, and successfully treat zinc at its Trail refinery. Within two decades, and largely as a result of its ability to treat zinc, Cominco became the most profitable mining company ever to operate in British Columbia. The conclusion suggests some consequences of Cominco's ascendancy.
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Khomich, V. G., and N. G. Boriskina. "ORE, OIL-AND-GAS REGIONS OF THE SOUTH OKHOTSK SEA PROVINCE AND DEEP GEODYNAMICS." Tikhookeanskaya Geologiya 39, no. 6 (2020): 3–24. http://dx.doi.org/10.30911/0207-4028-2020-39-6-3-24.
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In the South Okhotsk Sea province – on the islands of Sakhalin, Kunashir, Iturup, Urup and surrounding sea areas – many occurrences of rare, noble metal and other mineralizations as well as of oil-and-gas fields, gas hydrate accumulations, and isolated areas of active emission of water-hydrocarbon gases are known. Occurrences and deposits of solid, liquid and gaseous mineral resources are controlled by hidden deep fault transform zones: Nosappu (Tuscarora), Iturup, and Urup. These long-lived extended (more than 1000 km) zones are distinguished at the N-W Pacific megaplate margin near the S-E flank of the Kuril-Kamchatka trogue. Using the seismotomographic methods we have established their extension to the west from the seismic focal zone in the oceanic slab that subducted into the transition zone of the mantle. In the areas of strike-slip extension the faults accounted for the active formation of the drainage channels for the penetration of the sea water in the lithosphere with the following serpentinization of its ultramafites, and for decompressional generation of ascending mantle-derived abiogenic fluid flows. The latter penetrated from the underslab asthenosphere in the oversubduction mantle wedge and beneath the lithospheric mantle, where they accounted for the development of the processes of metasomatism. The subsequent migration of flows initiated the creation of primary magma reservoirs in the lower parts of the continental lithosphere, and intermediate and peripheral chambers in the Earth’s crust. The injection of melts from the chambers in the consolidated Earth's crust led to the formation of abyssal, hypabyssal intrusive massifs, arch-dome uplifts and magmatogenic-ore (ore-magmatic) systems predominantly among the rocks of the pre-Pliocene basement. The concentration of oil and gas accumulations mainly from the mantle-derived abiogenic hydrocarbons containing mercury, gold, rhenium, and PGE in the Cenozoic sedimentary basins amidst the reservoirs under the impermeable beds also resulted from deep under- and overslab fluid flows.
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Van Dover, Cindy Lee. "Mining seafloor massive sulphides and biodiversity: what is at risk?" ICES Journal of Marine Science 68, no. 2 (2010): 341–48. http://dx.doi.org/10.1093/icesjms/fsq086.
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Abstract Van Dover, C. L. 2011. Mining seafloor massive sulphides and biodiversity: what is at risk? – ICES Journal of Marine Science, 68: 341–348. Scientific exploration of the deep sea in the late 1970s led to the discovery of seafloor massive sulphides at hydrothermal vents. More recently, sulphide deposits containing high grades of ore have been discovered in the southwest Pacific. In addition to metal-rich ores, hydrothermal vents host ecosystems based on microbial chemoautotrophic primary production, with endemic invertebrate species adapted in special ways to the vent environment. Although there has been considerable effort to study the biology and ecology of vent systems in the decades since these systems were first discovered, there has been limited attention paid to conservation issues. Three priority recommendations for conservation science at hydrothermal vent settings are identified here: (i) determine the natural conservation units for key species with differing life histories; (ii) identify a set of first principles for the design of preservation reference areas and conservation areas; (iii) develop and test methods for effective mitigation and restoration to enhance the recovery of biodiversity in sulphide systems that may be subject to open-cut mining.
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Fan, Gao-Hua, Jian-Wei Li, Xiao-Dong Deng, Wen-Sheng Gao, and Si-Yuan Li. "Age and Origin of the Dongping Au-Te Deposit in the North China Craton Revisited: Evidence from Paragenesis, Geochemistry, and In Situ U-Pb Geochronology of Garnet." Economic Geology 116, no. 4 (2021): 963–85. http://dx.doi.org/10.5382/econgeo.4810.
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Abstract Dongping is the largest Au-Te vein deposit (~120 t Au) in the North China craton, but its age, origin, and setting remain unsolved. Here, we integrate paragenesis, geochemistry, and in situ U-Pb geochronology of garnet to constrain the timing and possible origin of the Dongping Au-Te deposit. Gold mineralization at Dongping is hosted in the Shuiquangou alkaline complex (ca. 401–390 Ma) and dominated by quartz-sulfide veins with minor ores in adjacent alteration envelopes. Andradite to grossular garnets are recognized in pre-, syn-, and post-ore quartz veins as well as mineralized alteration envelopes and are closely associated with a variety of ore and gangue minerals, mainly including K-feldspar, quartz, specularite, magnetite, pyrite, tellurides, epidote, and calcite. The paragenetic, textural, fluid inclusion, and compositional data suggest that garnets precipitated directly from a low-salinity fluid at 302° to 383°C and 90 to 330 bar. Garnets from various veins and alteration envelopes have similar U contents ranging from 0.80 to 13.89 mg/kg and yield reproducible U-Pb dates of 142 ± 5 to 139 ± 6 Ma (1σ) by laser ablation-inductively coupled plasmamass spectrometry. The dating results suggest that gold mineralization at Dongping occurred in the Early Cretaceous and thus preclude a genetic link between Au-Te mineralization and the ore-hosting alkaline intrusion as commonly suggested. When combined with independent geologic, geochemical, and geochronological studies, the new garnet U-Pb dates allow us to classify the Dongping Au-Te deposit as an oxidized intrusion-related gold deposit, with the causative magma likely derived from melting of an ancient enriched lithospheric mantle source due to destruction of the subcontinental lithospheric keel beneath the North China craton—a catastrophic event induced by the westward subduction of the Paleo-Pacific plate. This study highlights garnet U-Pb dating as a potential robust geochronometer for gold vein deposits elsewhere.
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Zhai, Degao, Anthony E. Williams-Jones, Jiajun Liu, et al. "The Genesis of the Giant Shuangjianzishan Epithermal Ag-Pb-Zn Deposit, Inner Mongolia, Northeastern China." Economic Geology 115, no. 1 (2020): 101–28. http://dx.doi.org/10.5382/econgeo.4695.
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Abstract The newly discovered Shuangjianzishan Ag-Pb-Zn deposit, with 145 Mt of ore grading 128.5 g/t Ag (locally up to 32,000 g/t) and 2.2 wt % Pb + Zn, is located in the Great Hinggan Range metallogenic belt, northeastern China, and is currently the largest Ag deposit in Asia. The Ag-Pb-Zn orebodies occur as veins and are hosted primarily by a Permian slate. Recent drilling and core logging have identified a partially Mo mineralized granite porphyry intrusion adjacent to the Ag-Pb-Zn mineralized veins. This well-preserved magmatic-hydrothermal system therefore offers an excellent opportunity to evaluate the possible temporal and genetic relationship between Mo-mineralized porphyry intrusions and Ag-Pb-Zn veins. Three primary paragenetic stages of veining have been recognized: (I) early pyrite + quartz ± K-feldspar, (II) main ore sulfide + sulfosalt + quartz + calcite + sericite + chlorite ± epidote, and (III) post-ore quartz. The silver mineralization occurs mainly in the late paragenetic part of Stage II, in which canfieldite (Ag8SnS6), argentite (Ag2S) and freibergite [(Ag, Cu)12Sb4S13] are the dominant Ag-bearing ore minerals. A combination of ore mineral chemical and sulfur isotope geothermometers and physicochemical calculations suggest that the Ag-Pb-Zn mineralization took place at a temperature of 250° to 200°C, a pH of 6.7 to 5.6, and a Δlogfo2 (HM) of –2.4 to –8.7. A conspicuous enrichment of Sn and Se in the ore, which is represented by minerals containing the metal suite Ag-Pb-Zn-(Cu-Sn-Se-Sb), likely reflects a close genetic association between the base metal mineralization and a magma. In situ analyses show that the δ34S values of the sulfides and Ag-bearing sulfosalts from the Ag-Pb-Zn mineralized veins vary from –4.67 to +2.44‰; the mean value is –2.11 ± 1.49‰ (n = 77). The calculated mean δ34SH2S value of the ore-forming fluid is –1.65 ± 0.83‰, which is indicative of a magmatic sulfur source. In situ Pb isotope analyses of the ore minerals yielded a narrow range of values (206Pb/204Pb of 18.243–18.310, 207Pb/204Pb of 15.503–15.563 and 208Pb/204Pb of 38.053–38.203, n = 59). Comparisons to corresponding isotopic data for the various rock units in the area and sulfides from nearby ore deposits indicate that there were substantial contributions of Pb and other metals (e.g., Ag and Zn) to the Shuangjianzishan deposit from a Mesozoic granitic source. Diorite-granodiorite dikes and dacite are crosscut by the Ag-Pb-Zn veins, and therefore, predate ore formation. These rock units have zircon U-Pb ages of 250.2 ± 2.0 and 133.9 ± 1.4 Ma, respectively. A concealed, weakly Mo mineralized granite porphyry intrusion proximal to the Ag-Pb-Zn mineralized vein system yielded zircon U-Pb ages of 134.4 ± 1.0 (MSWD = 0.1) and 134.4 ± 1.0 Ma (MSWD = 0.2), for coarse- and fine-grained facies, respectively. These ages are indistinguishable within the uncertainty from the zircon ages for the dacite and a granite intrusion ~2 km north of the mineralized veins, which has a weighted mean zircon U-Pb age of 135.2 ± 1.4 Ma (MSWD = 0.78). Molybdenite from three quartz vein/veinlet samples hosted by slate immediately above the porphyry intrusion yielded Re-Os model ages from 136.3 ± 0.9 to 133.7 ± 1.2 Ma and a weighted mean Re-Os age of 134.9 ± 3.4 Ma. Finally, three pyrite samples separated from the Ag-Pb-Zn mineralized veins have a weighted mean Re-Os model age of 135.0 ± 0.6 Ma. The very similar zircon U-Pb ages for the Mo-mineralized granite porphyry and dacite, and Re-Os ages for molybdenite and pyrite in the Shuangjianzishan ore district indicate that the Mesozoic magmatic-hydrothermal activity was restricted to a relatively short time interval (~136–133 Ma). They also suggest that the weakly Mo mineralized granite porphyry was likely the source of the fluids and metals that produced the Ag-Pb-Zn mineralization. Based on our geological observations and an extensive analytical database, a model is proposed for the genesis of the giant Shuangjianzishan Ag-Pb-Zn deposit in which the ore-forming fluid and its metals (i.e., Ag, Pb, and Zn) were exsolved during crystallization of the final phase of a composite granite porphyry intrusion. This fluid transported metals to the distal parts of the system, where they were deposited in preexisting faults or fractures created by the withdrawal of magma during the waning stages of the magmatic-hydrothermal event. The present study of the Shuangjianzishan Ag-Pb-Zn deposit and those of other magmatic-hydrothermal ore deposits in the region provide compelling evidence that the widespread Mesozoic felsic magmatism and Ag-Pb-Zn mineralization in the southern Great Hinggan Range took place in an intracontinental extensional tectonic setting, which was synchronous with, and spatially associated to, Paleo-Pacific slab rollback and lithospheric delamination and thinning.
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Zhu, Lü-Yun, Shao-Yong Jiang, Run-Sheng Chen, and Ying Ma. "Origin of the Shangfang Tungsten Deposit in the Fujian Province of Southeast China: Evidence from Scheelite Sm–Nd Geochronology, H–O Isotopes and Fluid Inclusions Studies." Minerals 9, no. 11 (2019): 713. http://dx.doi.org/10.3390/min9110713.
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The Shangfang deposit is a recently discovered large-scale tungsten deposit (66,500 t at 0.23% WO3), which is located near the western boundary of the Southeastern Coastal Metallogenic Belt (i.e., Zhenghe–Dafu fault), and adjacent to the northeast of the Nanling Range Metallogenic Belt. Unlike many other W–Sn deposits in this region that occur within or near the granites, the orebodies in the Sangfang deposit all occur within the amphibolite of Palaeoproterozoic Dajinshan Formation and have no direct contact to the granite. In this study, we carry out a thermal ionization mass spectrometer (TIMS) Sm-Nd isotope analysis for the scheelites from the orebody, which yields a Sm–Nd isochron age of 157.9 ± 6.7 Ma (MSWD = 0.96). This age is in good agreement with the previously published zircon U–Pb age (158.8 ± 1.6 Ma) for the granite and the molybdenite Re–Os age (158.1 ± 5.4 Ma) in the deposit. Previous studies demonstrated that the W–Sn deposits occurring between Southeastern Nanling Range and Coastal Metallogenic Belt mainly formed in the two periods of 160–150 Ma and 140–135 Ma, respectively. The microthermometry results of fluid inclusions in scheelite and quartz are suggestive of a near-isothermal (possibly poly-baric) mixing between two fluids of differing salinities. The H–O isotope results illustrate that the ore-forming fluids are derived from magma and might be equilibrated with metamorphic rocks at high temperature. The Jurassic granite pluton should play a critical role for the large hydrothermal system producing the Shangfang W deposit. Furthermore, the negative εNd(t) of −14.6 obtained in the Shanfang scheelite suggests for the involvement of the deep crustal materials. In general, subduction of the paleo-Pacific plate caused an extensional tectonic setting with formation of the Shangfang granites and related W mineralization, the geological background of which is similar to other W deposits in the Nanling Range Metallogenic Belt.
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Zhang, Xiao-Tian, Jing-Gui Sun, Zheng-Tao Yu, and Quan-Heng Song. "LA-ICP-MS zircon U–Pb and sericite 40Ar/39Ar ages of the Songjianghe gold deposit in southeastern Jilin Province, Northeast China, and their geological significance." Canadian Journal of Earth Sciences 56, no. 6 (2019): 607–28. http://dx.doi.org/10.1139/cjes-2018-0254.
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The Songjianghe deposit is a newly discovered altered gold deposit in the southeastern Jiapigou-Haigou Gold Metallogenic Belt (JHGMB) in southeastern Jilin Province of NE China. The host rocks were considered to be the Mesoproterozoic Seluohe Group, and the metallogenic epoch lacked accurate isotopic constraints. To determine the age and metallogenic setting of the deposit, we describe the geologic characteristics of the deposit and present the results of petrographic and geochronologic analyses of the host rocks and ores. The ore bodies are hosted within a suite of amphibolite facies metamorphic rocks superimposed by greenschist facies indicative of retrograde metamorphism. Zircon U–Pb dating results indicate that the host rocks belong to the Jiapigou Group that formed at the end of the Neoarchean (2543–2527 Ma). Subsequently, the rocks successively underwent metamorphism during the late Neoarchean (2521–2506 Ma), retrograde metamorphism caused by the closure of the Paleo-Asian Ocean during the late Permian to Early Triassic (262–250 Ma), and extension after the closure of the Paleo-Asian Ocean during the Late Triassic (231–210 Ma). Sericite 40Ar/39Ar dating results suggest that the Songjianghe deposit formed during the Late Jurassic between 157 Ma and 156 Ma. By combining these new insights with those of previous studies, we propose that the Songjianghe deposit is a mesothermal gold deposit and that mineralization occurred during the extensional period in the intermittent stage that followed the first subduction of the Paleo-Pacific Plate. All the gold deposits in the JHGMB formed from the late Permian to Early Cretaceous by multi-stage mineralization events that corresponded temporally with the tectonic evolution of the Paleo-Asian Ocean and the episodic subduction of the Paleo-Pacific Plate.
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Fei, Xianghui, Zhaochong Zhang, Zhiguo Cheng, and M. Santosh. "Factors controlling the crystal morphology and chemistry of garnet in skarn deposits: A case study from the Cuihongshan polymetallic deposit, Lesser Xing'an Range, NE China." American Mineralogist 104, no. 10 (2019): 1455–68. http://dx.doi.org/10.2138/am-2019-6968.
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Abstract The grossular-andradite solid solutions in garnet from skarn deposits in relation to hydrothermal processes and physicochemical conditions of ore formation remain controversial. Here we investigate garnet occurring in association with calcic and magnesian skarn rocks in the Cuihongshan polymetallic skarn deposit of NE China. The calcic skarn rocks contain three types of garnets. (1) Prograde type I Al-rich anisotropic garnets display polysynthetic twinning and a compositional range of Grs18–80Adr10–75. This type of garnet shows markedly low rare earth element (REE) contents (3.27–78.26 ppm) and is strongly depleted in light rare earth elements (LREE, 0.57–44.65 ppm) relative to heavy rare earth elements (HREE, 2.31–59.19 ppm). They also display a significantly negative Eu anomaly (Eu/Eu* of 0.03–0.90). (2) Fe-rich retrograde type II garnets are anisotropic with oscillatory zoning and own wide compositional variations (Grs1–47Adr30–95) with flat REE (13.73–377.08 ppm) patterns. (3) Fe-rich retrograde type III isotropic garnets display oscillatory zoning and morphological transition from planar dodecahedral {110} crystal faces to {211} crystal faces in the margin. Types III garnets exhibit relatively narrow compositional variations of Grs0.1–12Adr85–97 with LREE-enrichment (0.80–51.87 ppm), flat HREE patterns (0.15–2.46 ppm) and strong positive Eu anomalies (Eu/Eu* of 0.93–27.07 with almost all >1). The magnesian skarn rocks contain euhedral isotropic type IV Mn-rich garnet veins with a composition of Grs10–23Sps48–62Alm14–29. All calcic garnets contain considerable Sn and W contents. Type II garnet containing intermediate compositions of andradite and grossular shows the highest Sn contents (64.36–2778.92 ppm), albeit the lowest W range (1.11–468.44 ppm). Birefringence of garnet is probably caused by strain from lattice mismatch at a twinning boundary or ion substitution near intermediate compositions of grossular-andradite. The fine-scale, sharp, and straight garnet zones are probably caused by self-organization, but the compositional variations of zones from core to rim are probably caused by external factors. The zoning is likely driven by external factors such as composition of the hydrothermal fluid. REE concentrations are probably influenced by the relative proportion and temperature of the system. Moreover, the LREE-HREE fractionation of garnet can be attributed to relative compositions of grossular-andradite system. The W and Sn concentrations in garnet can be used as indicators for the exploration of W-Sn skarn deposits.
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Wang, Li, Liu, Jiang, and Chen. "Geochronology of Magmatism and Mineralization in the Dongbulage Mo-Polymetallic Deposit, Northeast China: Implications for the Timing of Mineralization and Ore Genesis." Minerals 9, no. 5 (2019): 255. http://dx.doi.org/10.3390/min9050255.
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The recently discovered Dongbulage Mo-polymetallic deposit is located in the southern part of the Great Xing’an Range, northeast China. Mineralization is closely related to the emplacement of Middle–Late Jurassic granitoids. In order to understand the petrogenetic link between mineralization and host granitoids, this study presents new zircon U–Pb ages, bulk-rock geochemistry, and molybdenite Re–Os ages for the Dongbulage deposits. LA-ICP-MS zircon U–Pb dating of the monzogranite and syenogranite intrusions yielded two weighted mean 206Pb/238U ages: of 164 ± 2 Ma and 165 ± 3 Ma, respectively. The subvolcanic rocks (red porphyritic granite and rhyolite) yielded a time interval between 161 ± 2 and 162 ± 3 Ma. In addition, molybdenite from the Dongbulage deposit gave a Re–Os isochron age of 162.6 ± 1.5 Ma, which was interpreted as the age of the mineralization. The new geochronology has established the close temporal and genetic relationships between the mineralization event and the emplacement of the Middle–Late Jurassic granitoids. Bulk-rock geochemistry shows that the Dongbulage granitoids are characterized by high SiO2, K2O, and A/CNK [Al2O3/(CaO + Na2O + K2O)(molar ratio)] values, and low TiO2, CaO, and MgO values, indicating a metaluminous to peraluminous, high-K calc-alkaline affinity. The granitoids also featured enrichments of large ion lithophile elements and light rare earth elements (LREE), and a relative depletion of high field strength elements (HFSE), along with an increasing negative δEu anomaly. The high differentiation index (DI), ranging from 81.75 to 94.76, and obvious fractionation between LREE and HREE, indicate that the Dongbulage granitoids are highly fractionated, metaluminous–peraluminous, and high-K calc-alkaline I-type granites. Combined with the regional geology, the Dongbulage granitoids may have formed during post-orogenic extension that followed the Mongol–Okhotsk Ocean closure coeval with subduction of the paleo-Pacific plate.
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VOZNYAK, D. K., E. V. ., LEVASHOVA, S. G. SKUBLOV, et al. "Formation Mechanism of the Velyka Vyska Syenite Massif (Korsun-Novomyrhorod Pluton, Ukrainian Shield) Derived from Melt Inclusions in Zircon." Mineralogical Journal 43, no. 1 (2021): 3–15. http://dx.doi.org/10.15407/mineraljournal.43.01.003.
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The formation of leucosyenites in the Velyka Vyska syenite massif was provoked by the liquation layering of magmatic melt. This assumption is based on the presence of two primary melt inclusions of different chemical composition in zircon crystals from Velyka Vyska leucosyenites. They correspond to two types of silicate melts. Type I is a leucosyenite type that contains high SiO2 concentrations (these inclusions dominate quantitatively); type II is a melanosyenite type that contains elevated Fe and smaller SiO2 concentrations. The liquation layering of magmatic melt was slow because the liquates are similar in density; leucosyenite melt, which is more abundant than melt of melanosyenite composition, displays greater dynamic viscosity; the initial sizes of embryos of melanosyenite composition are microscopic. Sulphide melt, similar in composition to pyrrhotite, was also involved in the formation of the massif. Zircon was crystallized at temperatures over 1300°С, as indicated by the homogenization temperatures of primary melt inclusions. The REE distribution spectra of the main parts (or zones,) of zircon crystals from the Velyka Vyska massif are identical to those of zircon from the Azov and Yastrubets syenite massifs with which high-grade Zr and REE (Azov and Yastrubets) ore deposits are associated. They are characteristic of magmatically generated zircon. Some of the grains analyzed contain rims that are contrasting against the matrix of a crystal, look dark-grey in the BSE image and display flattened REE distribution spectra. Such spectra are also typical of baddeleyite, which formed by the partial replacement of zircon crystals. The formation of a dark-grey rim in zircon and baddeleyite is attributed to the strong effect of high-pressure СО2-fluid on the rock. The formation patterns of the Velyka Vyska and Azov massifs exhibit some common features: (а) silicate melt liquation; (b) high ZrO2 concentrations in glasses from hardened primary melt inclusions; (c) the supply of high-pressure СО2-fluid flows into Velyka Vyska and Azov hard rocks. Similar conditions of formation suggest the occurrence of high-grade Zr and REE ores in the Velyka Vyska syenite massif.
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Yang, Dong-Guang, Jian-Hua Wu, Feng-Jun Nie, et al. "Petrogenetic Constraints of Early Cenozoic Mafic Rocks in the Southwest Songliao Basin, NE China: Implications for the Genesis of Sandstone-Hosted Qianjiadian Uranium Deposits." Minerals 10, no. 11 (2020): 1014. http://dx.doi.org/10.3390/min10111014.
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The tectonic inversion of the Songliao Basin during the Cenozoic may have played an important role in controlling the development of sandstone-type uranium deposits. The widely distributed mafic intrusions in the host sandstones of the Qianjiadian U ore deposits provided new insights to constrain the regional tectonic evolution and the genesis of the U mineralization. In this study, zircon U-Pb dating, whole-rock geochemistry, Sr-Nd-Pb isotope analysis, and mineral chemical compositions were presented for the mafic rocks from the Qianjiadian area. The mafic rocks display low SiO2 (44.91–52.05 wt.%), high TFe2O3 contents (9.97–16.46 wt.%), variable MgO (4.59–15.87 wt.%), and moderate K2O + Na2O (3.19–6.52 wt.%), and can be subdivided into AB group (including basanites and alkali olivine basaltic rocks) and TB group (mainly tholeiitic basaltic rocks). They are characterized by homogenous isotopic compositions (εNd (t) = 3.47–5.89 and 87Sr/86Sr = 0.7032–0.7042) and relatively high radiogenic 206Pb/204Pb (18.13–18.34) and Nb/U ratios (23.0–45.6), similar to the nearby Shuangliao basalts, suggesting a common asthenospheric origin enriched with slab-derived components prior to melting. Zircon U-Pb and previous Ar-Ar dating show that the AB group formed earlier (51–47 Ma) than the TB group (42–40 Ma). Compared to the TB group, the AB group has higher TiO2, Na2O, K2O, P2O5, Ce, and HREE contents and Ta/Yb and Sr/Yb ratios, which may have resulted from variable depth of partial melting in association with lithospheric thinning. Combined with previous research, the Songliao Basin experienced: (1) Eocene (~50–40 Ma) lithospheric thinning and crustal extension during which mafic rocks intruded into the host sandstones of the Qianjiadian deposit, (2) a tectonic inversion from extension to tectonic uplift attributed to the subduction of the Pacific Plate occurring at ~40 Ma, and (3) Oligo–Miocene (~40–10 Ma) tectonic uplift, which is temporally associated with U mineralization. Finally, the close spatial relation between mafic intrusions and the U mineralization, dike-related secondary reduction, and secondary oxidation of the mafic rocks in the Qianjiadian area suggest that Eocene mafic rocks and their alteration halo in the Songliao Basin may have played a role as a reducing barrier for the U mineralization.
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Xu, Zhitao, Jinggui Sun, Xiaolong Liang, Zhikai Xu, and Xiaolei Chu. "Geochronology, Geochemistry, and Pb–Hf Isotopic Composition of Mineralization-Related Magmatic Rocks in the Erdaohezi Pb–Zn Polymetallic Deposit, Great Xing’an Range, Northeast China." Minerals 10, no. 3 (2020): 274. http://dx.doi.org/10.3390/min10030274.
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Late Mesozoic intermediate–felsic volcanics and hypabyssal intrusions are common across the western slope of the Great Xing’an Range (GXAR). Spatiotemporally, these hypabyssal intrusions are closely associated with epithermal Pb–Zn polymetallic deposits. However, few studies have investigated the petrogenesis, contributions and constraints of these Pb–Zn polymetallic mineralization-related intrusions. Therefore, we examine the representative Erdaohezi deposit and show that these mineralization-related hypabyssal intrusions are composed of quartz porphyry and andesite porphyry with concordant zircon U–Pb ages of 160.3 ± 1.4 Ma and 133.9 ± 0.9 Ma, respectively. These intrusions are peraluminous and high-K calc-alkaline or shoshonitic with high Na2O + K2O contents, enrichment in large ion lithophile elements (LILEs; e.g., Rb, Th, and U), and depletion in high field strength elements (HFSEs; e.g., Nb, Ta, Zr, and Hf), similar to continental arc intrusions. The zircon εHf(t) values range from 3.1 to 8.0, and the 176Hf/177Hf values range from 0.282780 to 0.282886, with Hf-based Mesoproterozoic TDM2 ages. No differences exist in the Pb isotope ratios among the quartz porphyry, andesite porphyry and ore body sulfide minerals. Detailed elemental and isotopic data imply that the quartz porphyry originated from a mixture of lower crust and newly underplated basaltic crust, while the andesite porphyry formed from the partial melting of Mesoproterozoic lower crust with the minor input of mantle materials. Furthermore, a magmatic–hydrothermal origin is favored for the Pb–Zn polymetallic mineralization in the Erdaohezi deposit. Integrating new and published tectonic evolution data, we suggest that the polymetallic mineralization-related magmatism in the Erdaohezi deposit occurred in a back-arc extensional environment at ~133 Ma in response to the rollback of the Paleo-Pacific Plate.
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Graham, G. "Ores and Orogenesis: Circum-Pacific Tectonics, Geologic Evolution, and Ore Deposits.: JON E. SPENCER and SPENCER R. TITLEY, Editors. Pp. 618. 2008. Arizona Geological Society, Digest 22. ISBN-10: 978-1-891924-10-1. Price US$75.00." Economic Geology 104, no. 5 (2009): 760–61. http://dx.doi.org/10.2113/gsecongeo.104.5.760.
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Yin, Rong, Li Han, Xiao-Long Huang, Jie Li, Wu-Xian Li, and Lin-Li Chen. "Textural and chemical variations of micas as indicators for tungsten mineralization: Evidence from highly evolved granites in the Dahutang tungsten deposit, South China." American Mineralogist 104, no. 7 (2019): 949–65. http://dx.doi.org/10.2138/am-2019-6796.
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Abstract The Dahutang tungsten deposit, located in the Yangtze Block, South China, is one of the largest tungsten deposits in the world. Tungsten mineralization is closely related to Mesozoic granitic plutons. A drill core through a pluton in the Dalingshang ore block in the Central segment of the Dahutang tungsten deposit shows that the pluton is characterized by multi-stage intrusive phases including biotite granite, muscovite granite, and Li-mica granite. The granites are strongly peraluminous and rich in P and F. Decreasing bulk-rock (La/Yb)N ratios and total rare earth element (ΣREE) concentrations from the biotite granite to muscovite granite and Li-mica granite suggest an evolution involving the fractional crystallization of plagioclase. Bulk-rock Li, Rb, Cs, P, Sn, Nb, and Ta contents increase with decreasing Zr/Hf and Nb/Ta ratios, denoting that the muscovite granite and Li-mica granite have experienced a higher degree of magmatic fractionation than the biotite granite. In addition, the muscovite and Li-mica granites show M-type lanthanide tetrad effect, which indicates hydrothermal alteration during the post-magmatic stage. The micas are classified as lithian biotite and muscovite in the biotite granite, muscovite in the muscovite granite, and Li-muscovite and lepidolite in the Li-mica granite. The Li, F, Rb, and Cs contents of micas increase, while FeOT, MgO, and TiO2 contents decrease with increasing degree of magmatic fractionation. Micas in the muscovite granite and Li-mica granite exhibit compositional zonation in which Si, Rb, F, Fe, and Li increase, and Al decreases gradually from core to mantle, consistent with magmatic differentiation. However, the outermost rim contains much lower contents of Si, Rb, F, Fe, and Li, and higher Al than the mantle domains due to metasomatism in the presence of fluids. The variability in W contents of the micas matches the variability in Li, F, Rb, and Cs contents, indicating that both the magmatic and hydrothermal evolutions were closely associated with W mineralization in the Dahutang deposit. The chemical zoning of muscovite and Li-micas not only traces the processes of W enrichment by magmatic differentiation and volatiles but also traces the leaching of W by the fluids. Therefore, micas are indicators not only for the magmatic–hydrothermal evolution of granite, but also for tungsten mineralization.
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Sato, K., S. V. Kovalenko, N. P. Romanovsky, M. Nedachi, N. V. Berdnikov, and T. Ishihara. "Crustal control on the redox state of granitoid magmas: tectonic implications from the granitoid and metallogenic provinces in the circum-Japan Sea Region." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 95, no. 1-2 (2004): 319–37. http://dx.doi.org/10.1017/s0263593300001103.
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ABSTRACTFelsic magmatism has occurred over a large region of East Asia since Jurassic times and has provided important mineral resources such as tin, tungsten, base metals and gold. The circum-Japan Sea region preserves various geological records of active continental margins, including Jurassic to Early Tertiary magmatic arcs and subduction zones and pre-Jurassic continental basements, which were separated by the opening of the Japan Sea during the Miocene. The felsic magmatism in this region shows a wide variation in terms of redox state and related mineralisation, encompassing east–west contrasts around the Pacific Ocean. A review of granitoids and associated ore deposits in this region indicates that the character of the crust, sedimentary versus igneous, is an essential factor to control the redox state, and a tectonic setting may be an additional factor in some cases.The reduced-type granitoids, characterised by tin mineralisation, were generated in carbonbearing sedimentary crust which was composed mainly of accretionary complex material and not influenced by previous magmatism. Involvement of sedimentary materials is corroborated by oxygen, sulphur and strontium isotope data. The oxidised-type granitoids, characterised by gold or molybdenum mineralisation, were generated in igneous crust which was depleted in reducing agents as a result of previous magmatism. Granitoid magmatism in a given area tends to become more oxidised with time.Jurassic accretionary complexes in East Asia are thought to have been largely displaced from the original place of accretion and stacked up against the northeastern margin in the Khingan and Sikhote–Alin Mountains. This region, dominated by sedimentary crust, was subsequently subjected to Cretaceous felsic magmatism and converted to a large province of reduced-type granitoids and tin–tungsten mineralisation. Diverse geodynamic processes, including the change of the arc-trench system, the creation and collapse of the back-arc basin and the collision of continents, may have prepared many favourable sites for the generation of reduced-type granitoids in northeast Asia. These processes may have resulted in a remarkable contrast with the Pacific margin of North America, where repeated arc magmatism during the Mesozoic formed granitoid batholiths of the oxidised-type.The granitoid types may also be controlled by the tectonic setting and mode of magma emplacement. In the northern Kitakami area of Northeast Japan, Early Cretaceous episodic magmatism occurred in a Jurassic accretionary complex, and formed the oxidised-type granitoids accompanied by submarine bimodal volcanism associated with kuroko mineralisation. Granitoids of fissure-filling type emplaced under extensional environments may be oxidised, irrespective of basement geology, because of insignificant crustal input.
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Pho, Nguyen Van, Pham Tich Xuan, and Pham Thanh Dang. "Occurrence of supergene nickel ores in the Ha Tri Massive, Hoa An District, Cao Bang Province." VIETNAM JOURNAL OF EARTH SCIENCES 40, no. 2 (2018): 154–65. http://dx.doi.org/10.15625/0866-7187/40/2/11676.
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Nickel (Ni) laterites are regolith materials derived from ultramafic rocks and play an important role in the world's Ni production. Ni-laterite deposits are the supergene enrichment of Ni formed from the intense chemical and mechanical weathering of ultramafic parental rocks. In Vietnam, the weathering profile containing Ni laterite was first discovered in the Ha Tri massive (Cao Bang). This profile develops on the Ha Tri serpentinized peridotite rocks classified to the Cao Bang mafic-ultramafic complex (North Vietnam) and exhibits thick weathered zone (10 - 15m). This work carried out a detailed study of the weathering profile at the center of Ha Tri massive. Samples from different horizons of the profile were collected and analyzed in detail by XRF, XRD and SEM-EDX methods to establish the relationship between the Ni-rich supergene products and the parental peridotites (lherzolite) rocks in Ha Tri massive. The results show that the saprolite horizon is most Ni-rich in the weathering profile in Ha Tri. In this horizon, Ni-silicate minerals of garnierite group such as pimelite, nepouite and other Mg-Ni silicates have been found. The appearance of minerals of garnierite group is due to the exchange of Mg by Ni during weathering of peridotite minerals, especially olivine, which leads to the enrichment of the supergene Ni. The occurrence of Ni silicates suggests the existence of the supergene Ni ore in the weathering profile of the Ha Tri massive.References Bosio N.J., Hurst J.V., Smith R.L., 1975. Nickelliferousnontronite, a 15 Å garnierite, at Niquelandia, Goias Brazil. Clays Clay Miner., 23, 400-403. Brand N.W., Butt C.R.M., Elias M., 1998. Nickel Laterites: Classification and features. AGSO Journal of Australian Geology & Geophysics, 17(4), 81-88. Bricker O.P., Nesbitt H.W. and Gunter W.D., 1973. The stability of talc. American Mineralogist, 58, 64-72. Brindley G.W. and Hang P.T., 1973. The nature of garnierites. Structures, chemical composition and color characteristics. Clay and Clay Minerals, 21, 27-40. Brindley G.W. and Maksimovic Z., 1974. The nature and nomenclature of hydrous nickel-containing silicates. Clay Minerals, 10, 271-277. Brindley G.W. and Wan H.M., 1975. Composition structures and thermal behavior of nickel containing minerals in thelizardite-ne´pouite series. American Mineralogist, 60, 863-871. Brindley G.W., Bish D.L. and Wan H.M., 1979. Compositions, structures and properties of nickel containing minerals in the kerolite-pimelite series. American Mineralogist, 64, 615-625. Cluzel D. and Vigier B., 2008. Syntectonic mobility of supergene nickel ores from New Caledonia (Southwest Pacific). Evidence from faulted regolith and garnierite veins. Resource Geology, 58, 161-170. Colin F., Nahon D., Trescases J.J., Melfi A.J., 1990. Lateritic weathering of pyroxenites at Niquelandia, Goais, Brazil: The supergene behavior ofnickel: Economic Geology, 85, 1010-1023. Das S.K., Sahoo R.K., Muralidhar J., Nayak B.K., 1999. Mineralogy and geochemistry of profilesthrough lateritic nickel deposits at Kansa,Sukinda, Orissa. Joural of Geoogical. SocietyIndia, 53, 649-668. Decarreau A., Colin F., Herbillon A., Manceau A., Nahon D., Paquet H., Trauth-Badaud D.,Trescases J.J., 1987. Domain segregation in NiFe-Mg-Smectites. Clay Minerals, 35, 1-10. Freyssinet P., Butt C.R.M. and Morris R.C., 2005. Oreforming processes related to lateritic weathering. Economic Geology, 100th aniversary volume, 681-722.Garnier J., Quantin C., Martins E.S., Becquer T., 2006. Solid speciation and availability of chromium in ultramafic soils from Niquelandia, Brazil. Journal of Geochemical Exploration, 88, 206-209. Garnier J., Quantin C., Guimarães E., Becquer T., 2008. Can chromite weathering be a source of Cr in soils? Mineralogy Magazine, 72, 49-53. Gleeson S.A., Butt C.R. and Elias M., 2003. Nickel laterites: A review. SEG Newsletter, 54, 11-18. Gleeson S.A., Butt C.R., Wlias M., 2003. Nickellaterites: a review. SEG Newsletter, Society of Economic Geology, 54. Available from www.segweb.org. Golightly J.P., 1981. Nickeliferous laterite deposits. Economic Geology, 75th Anniversary volume, 710-735. Golightly J.P., 2010. Progress in understanding the evolution of nickel laterite. Society of Economic Geology, In Special Publication, 15, 451-485. Manceau A. and Calas G., 1985. Heterogeneous distribution of nickel in hydrous silicates from New Caledonia ore deposits. American Mineralogist, 70, 549-558. Nguyen Van Pho, 2013. Tropic weathering in Vietnam (in Vietnamese). Pubisher Science and Technology, 365p.Ngo Xuan Thanh, Tran Thanh Hai, Nguyen Hoang, Vu Quang Lan, S. Kwon, Tetsumaru Itaya, M. Santosh, 2014. Backarc mafic-ultramafic magmatism in Northeastern Vietnam and its regional tectonic significance. Journal of Asian Earth Sciences, 90, 45-60.Pelletier B., 1983. Localisation du nickel dans les minerais ‘‘garnieritiques’’ de Nouvelle-Caledonie. Sciences Ge´ologique: Me´moires, 73, 173-183.Pelletier B., 1996. Serpentines in nickel silicate ores from New Caledonia. In Grimsey E.J., and Neuss I. (eds): Nickel ’96, Australasian Institute of Miningand Metallurgy, Melbourne, Publication Series 6(9), 197-205. Proenza J.A., Lewis J.F., Galı´ S., Tauler E., Labrador M., Melgarejo J.C., Longo F. and Bloise G., 2008. Garnierite mineralization from Falcondo Ni-laterite deposit (Dominican Republic). Macla, 9, 197-198. Soler J.M., Cama J., Galı´ S., Mele´ndez W., Ramı´rez, A., andEstanga, J., 2008. Composition and dissolution kinetics ofgarnierite from the Loma de Hierro Ni-laterite deposit,Venezuela. Chemical Geology, 249, 191-202. Springer G., 1974. Compositional and structural variations ingarnierites. The Canadian Mineralogist, 12, 381-388. Springer G., 1976. Falcondoite, nickel analogue of sepiolite. The Canadian Mineralogist, 14, 407-409.Svetlitskaya T.V., Tolstykh N.D., Izokh A.E., Phuong Ngo Thi, 2015. PGE geochemical constraints on the origin of the Ni-Cu-PGE sulfide mineralization in the Suoi Cun intrusion, Cao Bang province, Northeastern Vietnam. Miner Petrol, 109, 161-180.Tran Trong Hoa, Izokh A.E., Polyakov G.V., Borisenko A.S., Tran Tuan Anh, Balykin P.A., Ngo Thi Phuong, Rudnev S.N., Vu Van Van, Bui An Nien, 2008. Permo-Triassic magmatism and metallogeny of Northern Vietnam in relation to the Emeishan plume. Russ. Geol. Geophys., 49, 480-491.Trescases J.J., 1975. L'évolution supergene des roches ultrabasiques en zone tropicale: Formation de gisements nikelifères de Nouvelle Caledonie. Editions ORSTOM, Paris, 259p.Tri T.V., Khuc V. (eds), 2011. Geology and Earth Resources of Vietnam. Publishing House for Science and Technology, 645p (in English). Villanova-de-Benavent C., Proenza J.A., GalíS., Tauler E., Lewis J.F. and Longo F., 2011. Talc- and serpentine-like ‘‘garnierites’’ in the Falcondo Ni-laterite deposit, Dominican Republic. ‘Let’s talk ore deposits’, 11th Biennial Meeting SGA 2011, Antofagasta, Chile, 3p.Wells M.A., 2003. Goronickel laterite deposit. New Caledonia. CRC LEME, p.3.
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Deng, Changzhou, Guangyi Sun, Yimeng Rong, et al. "Recycling of mercury from the atmosphere-ocean system into volcanic-arc–associated epithermal gold systems." Geology, November 4, 2020. http://dx.doi.org/10.1130/g48132.1.
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Photochemical processes generate mass-independent fractionation (MIF) of mercury (Hg) isotopes in the atmosphere-ocean system, and the subduction of marine sediments or hydrated oceanic crust may recycle the resultant Hg isotope signature into the volcanic-arc environment. This environment typically hosts epithermal gold deposits, which are characterized by a specific Hg-Sb-As metal association. We investigated the Hg isotopic composition of seven volcanic-arc–related epithermal gold deposits in northeast China and revisited the isotopic composition of Hg in hydrothermal ore deposits in circum-Pacific and Mediterranean volcanic arcs. The gold ore samples in northeast China mostly display positive Δ199Hg values (0.11‰ ± 0.07‰, 1σ, n = 48) similar to those observed in the Pacific Rim (0.07‰ ± 0.09‰, 1σ, n = 182) and the Mediterranean Cenozoic volcanic belt (0.09‰ ± 0.08‰, 1σ, n = 9). Because Hg in marine sediments and seawater has positive Δ199Hg, we infer that Hg-bearing epithermal deposits in active continental margin settings receive most Hg from recycled seawater in marine sediments, through the release of Hg by dehydration from the subducting oceanic slab. However, negative to near-zero Δ199Hg values were observed in Hg-bearing deposits in the South China craton (–0.09‰ ± 0.05‰, 1σ, n = 105) and in the intraplate magmatic-hydrothermal Almadén Hg deposit in Spain (–0.02‰ ± 0.06‰, 1σ, n = 26), which are considered to relate to basement and mantle sources, respectively. Hg isotopes have the potential to trace lithospheric Hg cycling.
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Ivan Y. Nekrasov. "Mineralogical and Genetic Features of Volcanic Gold-Silver Deposits of the Pacific Ore Belt: ABSTRACT." AAPG Bulletin 74 (1990). http://dx.doi.org/10.1306/20b2234b-170d-11d7-8645000102c1865d.
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Pletnev, S. P. "MAIN TYPES OF PALEOGENE SEDIMENTARY ROCKS AND CONDITION OF THEIR FORMATION ON THE GUYOTS OF THE MAGELLAN SEAMOUNTS (PACIFIC OCEAN)." Tikhookeanskaya Geologiya, 2021, 99–111. http://dx.doi.org/10.30911/0207-4028-2021-40-1-99-111.
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The Paleocene-Eocene sedimentary complex is most widely developed among the sedimentary cover sediments of the Magellan Seamounts. It is made up of pelagic (nanoforaminiferal) and reef limestones, edaphogenic breccias and volcanoclastic rocks. The most widespread pelagic limestones form narrow (0.5–1.5 km) and extensive (up to 20 km) ribbon-like bodies which cover the upper parts of the slopes and the rim of the summit plateau. The maximum area of their development is marked on Fyodorov Guyot – 315 km2. Pelagic limestones and edaphogenic breccias are exposed over large areas and have mutual facies transitions. The Oligocene hiatus in sedimentation was established in the sections of the Cenozoic sedimentary cover deposits of the studied guyots.
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Laurence P. James. "Problems in Exploration and Genesis of Young (0.5-3 MA) Hydrothermal Gold-Silver Deposits in the Asian Pacific Rim Region: ABSTRACT." AAPG Bulletin 74 (1990). http://dx.doi.org/10.1306/20b220ad-170d-11d7-8645000102c1865d.
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Kolomoets, A. V., A. V. Snachev, and M. A. Rassomakhin. "Gold-tourmaline mineralization in carbonaceous shales of the Kumak deposit (South Ural)." Gornyi Zhurnal, December 22, 2020, 11–15. http://dx.doi.org/10.17580/gzh.2020.12.02.
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The article discusses the geological structure of the Kumak gold ore deposit, confined to the Early Carboniferous Anikhov graben of the East Ural uplift. It is composed of sericite-quartz-carbon and quartz-carbon-tourmaline schists of the Bredy Formation (C1bd). Black shale deposits are carbonaceous type and belong to terrigenous-carbonaceous and silicon-carbonaceous formations. Among the main minerals in shales are noted: quartz, sericite, carbonates, sulfides, tourmaline and carbonaceous matter. The field is characterized by a wide variety of gold ore mineralization. Rich ore zones are noted at the intersection of the East Anikhov faults oriented in the north–south direction and the branching tensile fractures in the north-north-east and north-west directions. In the ore mineral association prevailing here, finely dispersed gold is associated with small crystals of pyrite, arsenopyrite and concentrates nearby abundant tourmaline areas. The fine intergrowth of tourmaline and gold indicates the synchronism of their formation and allows us to distinguish a quartz-tourmaline gold ore formation within the Kumak deposit, comparable with a number of objects in East Transbaikal and Tuva. The most probable source of tourmaline mineralization in sericite-quartz-carbon schists could be metamorphically transformed boron-containing marine sediments saturated with clay particles and Corg. The microprobe study of gold grains taken from carbonaceous shales and weathering crusts made it possible to attribute them to the high-grade (919–1000) type, which is the leading one in the gold ore mineralization of the considered deposit. It is established that in the zone of hypergenesis, gold grains are not homogeneous. Here, secondary redeposition of gold takes place in the form of small spongy high-grade aggregates, as well as the formation of a rim on some grains with clear signs of refinement and purification from impurity elements. The geological works were carried out under State Contract No. 0246-2019-0078. The analyses were supported by the regional Grant for Science and R&D, Agreement No. 23 dated August 18, 2019. The studies into gold composition were executed in the framework of state-financed scientific topic No. AAAA-A19-119072390050-9. The authors express thanks to S. A. Yagudin for the analysis implementation and to E. O. Kalistratov for the help in description of polished sections. Further thanks are extended to R. S. Kisil and V. S. Panteleev for the help in the field works.
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Ratkin, V. V., L. F. Simanenko, V. A. Pakhomova, and O. A. Eliseeva. "TAEZHNY EPITHERMAL DEPOSIT OF SILVER ORE (SIKHOTE-ALIN): REGIONAL POSITION, FORMATION CONDITIONS, GEOCHEMISTRY AND MINERAL COMPOSITION." Tikhookeanskaya Geologiya, 2021, 21–38. http://dx.doi.org/10.30911/0207-4028-2021-40-2-21-38.
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The Taezhny is a silver with gold (Au:Ag = 1:100) vein deposit with a pronounced mineralogical and geochemical selenium specializationof ores. The deposit is located in the eastern part of the Sikhote-Alin orogenic belt, 700 km north of Vladivostok. The regional position of the describable ore-bearing area, similar to the Mexican deposits of the Guanajuato area typical of the Pacific region, is determined by its relationto the Early Cretaceous island-arc terrane with a distinct geochemical enrichment in silver of its folded rock complex. Quartz vein bodies are located in submeridional fracturesfeathering NE-trending sinistral strike slip faults.The near-ore alteration is dominated bysericitization and silicification of host sandstones. The main silver minerals are freibergite, acanthite, and Se-containing pyrargyrite, polybasite, stephanite. Kustelite, electrum, aguilarite, allargentum, and discrasite are much less abundant. The mineralogical and geochemical zoning of ore bodies emphasized by a highly productive Ag-sulfosalt assemblage enriched in Sein the upper part of veins and the poor ores with predominant acanthite at depth is revealed.The veins were formed with the participation of sodium chloride solutions saturated with CO2 and CH4, at the temperature range from 400 to 150° C. The deposition of productive sulfosalt-bearingassemblages occurred with a suddendecrease in pressure under conditions of discharge of magmatic-meteoric fluids in circulation zones in the sandstones under the screen of volcanic rocks overlying the Kema terrane.
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Xing, Kai, Qihai Shu, and David R. Lentz. "Constraints on the Formation of the Giant Daheishan Porphyry Mo Deposit (NE China) from Whole-Rock and Accessory Mineral Geochemistry." Journal of Petrology 62, no. 4 (2021). http://dx.doi.org/10.1093/petrology/egab018.
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Abstract There are more than 80 porphyry (or skarn) Mo deposits in northeastern China with Jurassic or Cretaceous ages. These are thought to have formed mainly in a continental arc setting related to the subduction of the Paleo-Pacific oceanic plate in the Jurassic and subsequent slab rollback in the early Cretaceous. The Jurassic Daheishan porphyry Mo deposit is one of the largest Mo deposits in NE China, which contains 1·09 Mt Mo with an average Mo grade of 0·07 %. To better understand the factors that could have controlled Mo mineralization at Daheishan, and potentially in other similar porphyry Mo deposits in NE China, the geochemical and isotopic compositions of the ore-related granite porphyry and biotite granodiorite, and the magmatic accessory minerals apatite, titanite and zircon from the Daheishan intrusions, were investigated so as to evaluate the potential roles that magma oxidation states, water contents, sulfur and metal concentrations could have played in the formation of the deposit. Magmatic apatite and titanite from the causative intrusions show similar εNd(t) values from –1·1 to 1·4, corresponding to TDM2 ages ranging from 1040 to 840 Ma, which could be accounted for by a mixing model through the interaction of mantle-derived basaltic melts with the Precambrian lower crust. The Ce and Eu anomalies of the magmatic accessory minerals have been used as proxies for magma redox state, and the results suggest that the ore-forming magmas are highly oxidized, with an estimated ΔFMQ range of +1·8 to +4·1 (+2·7 on average). This is also consistent with the high whole-rock Fe2O3/FeO ratios (1·3–26·4). The Daheishan intrusions display negligible Eu anomalies (Eu/Eu* = 0·7–1·1) and have relatively high Sr/Y ratios (40–94) with adakitic signatures; they also have relatively high Sr/Y ratios in apatite and titanite. These suggest that the fractionation of amphibole rather than plagioclase is dominant during the crystallization of the ore-related magmas, which further indicates a high magmatic water content (e.g. &gt;5 wt%). The magmatic sulfur concentrations were calculated using available partitioning models for apatite from granitoids, and the results (9–125 ppm) are indistinguishable from those for other mineralized, subeconomic and barren intrusions. Furthermore, Monte Carlo modelling has been conducted to simulate the magmatic processes associated with the formation of the Daheishan Mo deposit, and the result reveals that a magma volume of ∼280 km3 with ∼10 ppm Mo was required to form the Mo ores containing 1·09 Mt Mo in Daheishan. The present study suggests that a relatively large volume of parental magmas with high oxygen fugacities and high water contents is essential for the generation of a giant porphyry Mo deposit such as Daheishan, whereas a specific magma composition (e.g. with unusually high Mo and/or S concentrations) might be less critical.
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Wang, Qiang, Yu-Long Yang, Yao Tang, Wen-Qi Guo, and Tian-Xin Xiao. "Textural and geochemical characteristics of garnet from the Luoyang Fe skarn deposit, eastern China: implications for ore-forming fluid evolution and mineralization conditions." Geological Magazine, July 12, 2021, 1–14. http://dx.doi.org/10.1017/s0016756821000431.
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Abstract The late Palaeozoic Yong’an–Meizhou depression belt is an important iron (Fe) and polymetallic metallogenic belt in southern China. It has undergone a transformation from Tethys to the circum-Pacific tectonic domain. The Luoyang deposit is one of the typical Fe skarn deposits in the Yong’an–Meizhou depression belt of eastern China. Garnet is a characteristic mineral in the deposit. Two generations of garnets are detected in the deposit based on their textural characteristics and trace-element contents, and are represented by Fe-enriched andradite. The first generation of garnets (Grt1) have two types of garnets (Grt1-A and Grt1-B). Type A garnets of the first generation (Grt1-A) (Adr80-88) replaced by massive diopside-magnetite assemblage exhibit distinct oscillatory zonings and display patterns of enriched light rare earth elements (LREE) to weak heavy rare earth elements (HREE), with weak negative to positive Eu anomalies, and highest U, ΣREE and Sn contents. Type B garnets of the first generation (Grt1-B) are irregular zones (Adr94-96) coexisting with magnetite, in which Grt1-A is generally dissolved, and have obviously LREE-enriched and HREE-depleted patterns, with weak negative to positive Eu anomalies, and moderate U, ΣREE and Zn contents. Garnets of the second generation (Grt2) (Adr96-99) that replaced massive magnetite together with sphalerite show unzoned patterns, with a flat REE pattern and pronounced negative Eu anomalies as well as contents of lowest U and ΣREE, and highest W. The substitution of REEs in garnets occurs as [X2+]VIII –1[REE3+]VIII +1[Si4+]IV –1[Z3+]IV +1in an Al-enriched environment. Luoyang hydrothermal fluids shifted from reducing conditions with relatively high-U and -ΣREE characteristics to oxidizing conditions with relatively low-U and -ΣREE characteristics. The reduced siderophile elements and increased fO2 in fluid during Grt1-B formation caused magnetite mineralization and reduced Zn contents during Grt2 formation, causing the deposition of sphalerite. All garnets formed from magmatic fluid and were controlled by infiltrative metasomatism in an opened system.