Academic literature on the topic 'Ore deposits - Pacific Rim'

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.

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.

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.

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.

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.

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.

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).

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.

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.