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1
Krivolutskaya, Nadezhda, Sheida Makvandi, Bronislav Gongalsky, Irina Kubrakova, and Natalia Svirskaya. "Chemical Characteristics of Ore-Bearing Intrusions and the Origin of PGE–Cu–Ni Mineralization in the Norilsk Area." Minerals 11, no. 8 (July 28, 2021): 819. http://dx.doi.org/10.3390/min11080819.
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The composition of the parental magmas of Cu–Ni deposits is crucial for the elucidation of their genesis. In order to estimate the role of magma in ore formation, it is necessary to compare the compositions of silicate rock intrusions with different mineralization patterns, as observed in the Norilsk region. The rock geochemistry of two massifs located in the same Devonian carbonate rocks—the Kharaelakh intrusion, with its world-class platinum-group element (PGE)–Cu–Ni deposit, and the Pyasinsky-Vologochansky intrusion, with its large deposit—was studied. Along with these massifs, the Norilsk 2 massif with noneconomic mineralization intruded in the Ivakinskaya-Nadezhdinskaya basalts was studied as well. Their settings allow the estimation of the parental magma composition, taking into account the possible assimilation of host rocks. Analyses of 39 elements in 97 samples demonstrated the similarity of the intrusions in terms of their major components. The Pyasinsky-Vologochansky intrusion contains the highest trace element contents compared with the Kharaelakh and Norilsk 2 massifs, evidencing its crystallization from evolved parental magma. No influence of host rocks on the silicate rock compositions was found, except for narrow (1–2 m) endo-contact zones. There is no correlation between the mineralization volume and the rock compositions of the studied intrusions. It is assumed that the intrusions were formed from one magma crustal source irregularly rich in sulfur (S). This source inhomogeneity in terms of the sulfur distribution resulted in deposits of varying sizes. The magmas served as a transporting agent for sulfides from deep zones to the surface.
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Makkonen, Hannu V., and Pekka Tuisku. "Geology and crystallization conditions of the Särkiniemiintrusion and related nickel-copper ore, central Finland – implications for depth of emplacement of 1.88 Ga nickel-bearing intrusions." Bulletin of the Geological Society of Finland 92, no. 2 (December 15, 2020): 111–30. http://dx.doi.org/10.17741/bgsf/92.2.003.
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Several Ni-Cu deposits occur within the Kotalahti area, central Finland, in proximity to an Archaean gneiss dome surrounded by a Palaeoproterozoic craton-margin supracrustal sequence comprising quartzites, limestones, calc-silicate rocks, black schists and banded diopside amphibolites. The geology of the area and age of the Ni-bearing intrusions (1.88 Ga) are similar to the Thompson Ni belt in the Canadian Trans-Hudson Orogen. The small mafic-ultramafic and Ni-Cu -bearing Särkiniemi intrusion, closely associated with the Archaean basement core of the Kotalahti Dome, is composed of a western peridotite and eastern gabbro body, both of which are mineralized. The eastern gabbro has a contact aureole several meters thick, consisting of orthopyroxene +/- cordierite bearing hornfels between the intrusion and the migmatites. Geochemically, the Särkiniemi intrusion shares many features in common with other Svecofennian mafic-ultramafic intrusions, including crustal contamination and nickel depletion. The related Ni-Cu deposit has a low Ni/Co value (15) and low nickel content in the sulphide fraction (2.8 wt.%), together with a low estimated magma/sulphide ratio of around 170. Svecofennian 1.88 Ga mafic-ultramafic intrusions occur in terrains of variable metamorphic grade (from low-amphibolite to granulite facies) and are likely to represent emplacement at different crustal depths. Multi-equilibrium thermobarometry indicates that the contact aureole at Särkiniemi reached equilibrium at pressures of 4.5–6 kbar (15–20 km depth) and temperatures of 600–670 °C. Combined with the results of earlier research on the Svecofennian intrusions, this study indicates that a depth of 15–20 km crustal level was favourable, along with other critical factors, for nickel sulfide deposition at 1.88 Ga.
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Malehmir, Alireza, Hans Thunehed, and Ari Tryggvason. "The Paleoproterozoic Kristineberg mining area, northern Sweden: Results from integrated 3D geophysical and geologic modeling, and implications for targeting ore deposits." GEOPHYSICS 74, no. 1 (January 2009): B9—B22. http://dx.doi.org/10.1190/1.3008053.
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The Kristineberg mining area in the western part of the Paleoproterozoic Skellefte Ore District, northern Sweden, is well known for its base-metal and recent gold discoveries. A pilot 3D geologic model has been constructed on a crustal scale, covering an area of [Formula: see text] to depths of [Formula: see text]. Constrained 3D inverse and forward gravity modeling have been performed to confirm and refine previous modeling along seismic profiles using mainly 2.5D techniques. The 3D inverse gravity modeling was geared to generating isodensity surfaces that enclose regions within the model of anomalous density contrast. The 3D forward gravity modeling was conducted to include faulting and folding systems that are difficult to include in the inversion. The 3D geologic model supports many previous interpretations but also reveals new features of the regional geology that are important for future targeting of base-metal and gold deposits. The margins of a thick granite in the south dip steeply inward, suggesting the possibility of room to accommodate another large base-metal deposit if the granitic rocks are juxtaposed with volcanic rocks at depth. Gravity modeling also suggests the observed Bouguer gravity high within the western metasediments can be explained by a large mafic intrusion that has dioritic to tonalitic composition and no significant magnetic signature. Because mafic-ultramafic intrusions within metasediments can indicate gold, this interpretation suggests the western metasediments have a high gold potential.
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Mathieu, Lucie. "Intrusion-Associated Gold Systems and Multistage Metallogenic Processes in the Neoarchean Abitibi Greenstone Belt." Minerals 11, no. 3 (March 3, 2021): 261. http://dx.doi.org/10.3390/min11030261.
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In gold-endowed greenstone belts, ore bodies generally correspond to orogenic gold systems (OGS) formed during the main deformation stage that led to craton stabilization (syntectonic period). Most OGS deposits postdate and locally overprint magmatic-hydrothermal systems, such as Au-Cu porphyry that mostly formed during the main magmatic stage (synvolcanic period) and polymetallic intrusion-related gold systems (IRGS) of the syntectonic period. Porphyries are associated with tonalite-dominated and sanukitoid plutons, whereas most IRGS are related to alkaline magmatism. As reviewed here, most intrusion-associated mineralization in the Abitibi greenstone belt is the result of complex and local multistage metallogenic processes. A new classification is proposed that includes (1) OGS and OGS-like deposits dominated by metamorphic and magmatic fluids, respectively; (2) porphyry and IRGS that may contain gold remobilized during subsequent deformation episodes; (3) porphyry and IRGS that are overprinted by OGS. Both OGS and OGS-like deposits are associated with crustal-scale faults and display similar gold-deposition mechanisms. The main difference is that magmatic fluid input may increase the oxidation state and CO2 content of the mineralizing fluid for OGS-like deposits, while OGS are characterized by the circulation of reduced metamorphic fluids. For porphyry and IRGS, mineralizing fluids and metals have a magmatic origin. Porphyries are defined as base metal and gold-bearing deposits associated with large-volume intrusions, while IRGS are gold deposits that may display a polymetallic signature and that can be associated with small-volume syntectonic intrusions. Some porphyry, such as the Côté Gold deposit, demonstrate that magmatic systems can generate economically significant gold mineralization. In addition, many deposits display evidence of multistage processes and correspond to gold-bearing or gold-barren magmatic-hydrothermal systems overprinted by OGS or by gold-barren metamorphic fluids. In most cases, the source of gold remains debated. Whether magmatic activity was essential or marginal for fertilizing the upper crust during the Neoarchean remains a major topic for future research, and petrogenetic investigations may be paramount for distinguishing gold-endowed from barren greenstone belts.
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Luzgin, B. N. "INTRUSIONS AND SKARNS OF THE INSKOY IRON-ORE DEPOSIT." International Geology Review 30, no. 4 (April 1988): 459–66. http://dx.doi.org/10.1080/00206818809466027.
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Xue, Song, Yaoling Niu, Yanhong Chen, Yining Shi, Boyang Xia, Peiyao Wang, Hongmei Gong, Xiaohong Wang, and Meng Duan. "Iron Isotope Fractionation during Skarn Cu-Fe Mineralization." Minerals 11, no. 5 (April 22, 2021): 444. http://dx.doi.org/10.3390/min11050444.
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Fe isotopes have been applied to the petrogenesis of ore deposits. However, the behavior of iron isotopes in the mineralization of porphyry-skarn deposits is still poorly understood. In this study, we report the Fe isotopes of ore mineral separations (magnetite, pyrite, chalcopyrite and pyrrhotite) from two different skarn deposits, i.e., the Tonglvshan Cu-Fe skarn deposit developed in an oxidized hydrothermal system and the Anqing Cu skarn deposit developed in a reduced hydrothermal system. In both deposits, the Fe isotopes of calculated equilibrium fluids are lighter than those of the intrusions responsible for the skarn and porphyry mineralization, corroborating the “light-Fe fluid” hypothesis. Interestingly, chalcopyrite in the oxidized-Tonglvshan skarn deposit has lighter Fe than chalcopyrite in the reduced-Anqing skarn deposit, which is best understood as the result of the prior precipitation of magnetite (heavy Fe) from the ore fluid in the oxidized-Tonglvshan systems and the prior precipitation of pyrrhotite (light Fe) from the ore fluid in the reduced-Anqing system. The δ56Fe for pyrite shows an inverse correlation with δ56Fe of magnetite in the Tonglvshan. In both deposits, the Fe isotope fractionation between chalcopyrite and pyrite is offset from the equilibrium line at 350 °C and lies between the FeS-chalcopyrite equilibrium line and pyrite-chalcopyrite equilibrium line at 350 °C. These observations are consistent with the FeS pathway towards pyrite formation. That is, Fe isotopes fractionation during pyrite formation depends on a path from the initial FeS-fluid equilibrium towards the pyrite-fluid equilibrium due to the increasing extent of Fe isotopic exchange with fluids. This finding, together with the data from other deposits, allows us to propose that the pathway effect of pyrite formation in the Porphyry-skarn deposit mineralization is the dominant mechanism that controls Fe isotope characteristics.
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Eshaghi, Esmaeil, Anya M. Reading, Michael Roach, Mark Duffett, Daniel Bombardieri, Matthew J. Cracknell, John L. Everard, Grace Cumming, and Stephen Kuhn. "Inverse modeling constrained by potential field data, petrophysics, and improved geologic mapping: A case study from prospective northwest Tasmania." GEOPHYSICS 85, no. 5 (July 28, 2020): K13—K26. http://dx.doi.org/10.1190/geo2019-0636.1.
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The Heazlewood-Luina-Waratah area is a prospective region for minerals in northwest Tasmania, Australia, associated with historically important ore deposits related to the emplacement of granite intrusions and/or ultramafic complexes. The geology of the area is poorly understood due to the difficult terrain and dense vegetation. We have constructed an initial high-resolution 3D geologic model of this area using constraints from geologic maps and geologic and geophysical cross sections. This initial model is improved upon by integrating results from 3D geometry and physical property inversion of potential field (gravity and magnetic) data, petrophysical measurements, and updated field mapping. Geometry inversion reveals that the Devonian granites in the south are thicker than previously thought, possibly connecting to deep sources of mineralization. In addition, we identified gravity anomalies to the northeast that could be caused by near-surface granite cupolas. A newly discovered ultramafic complex linking the Heazlewood and Mount Stewart Ultramafic Complexes in the southwest also has been modeled. This implies a greater volume of ultramafic material in the Cambrian successions and points to a larger obducted component than previously thought. The newly inferred granite cupolas and ultramafic complexes are targets for future mineral exploration. Petrophysical property inversion reveals a high degree of variation in these properties within the ultramafic complexes indicating a variable degree of serpentinization. Sensitivity tests suggest maximum depths of 2–3 km for the contact aureole that surrounds major granitic intrusions in the southeast, whereas the Heazlewood River complex is likely to have a deeper source up to 4 km. We have demonstrated the value of adding geologic and petrophysical constraints to 3D modeling for the purpose of guiding mineral exploration. This is particularly important for the refinement of geologic structures in tectonically complex areas that have lithology units with contrasting magnetic and density characteristics.
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Wang, Jian, Keiko Hattori, Yanchen Yang, and Haiqi Yuan. "Zircon Chemistry and Oxidation State of Magmas for the Duobaoshan-Tongshan Ore-Bearing Intrusions in the Northeastern Central Asian Orogenic Belt, NE China." Minerals 11, no. 5 (May 10, 2021): 503. http://dx.doi.org/10.3390/min11050503.
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The Duobaoshan (DBS)-Tongshan (TS) porphyry Cu–(Mo) deposit (4.4 Mt Cu, 0.15 Mt Mo) is located in the northeastern part of the central Asian orogenic belt (CAOB) in northeastern China. It is hosted by early Ordovician dioritic to granodioritic intrusions which are characterized by the subduction-related geochemical signatures including high concentrations of large ion lithophile elements (LILEs) and light rare earth elements (LREEs), and low concentrations of heavy REEs (HREEs) and high-field -strength elements (HFSEs), such as Nb, Ta, Zr and Ti in bulk rock compositions. Furthermore, they show adakitic geochemical signatures of high Sr/Y ratios (29~55) due to high Sr (290~750 ppm) and low Y (<18 ppm). Zircon trace element abundances and published Sr-Nd-Hf isotope data of these rocks suggest that the parental magmas for these ore-bearing intrusions were rich in H2O and formed by partial melting of a juvenile lower crust/lithospheric mantle or metasomatized mantle wedge during the northwestward subduction of the Paleo-Asian Ocean before the collision of the Songnen block with the Erguna-Xing’an amalgamated block in the early Carboniferous. Values of Ce4+/Ce3+ and Ce/Nd in zircons are 307~461 and 14.1~20.3 for mineralized granodiorites, and 231~350 and 12.4~18.2 for variably altered diorite and granodiorites in DBS, whereas those for DBS-TS microgabbros are 174~357 and 7.4~22, and 45.9~62.6 and 5.0~5.8 for the early Mosozoic Qz-monzonites, respectively. Zircon Eu/Eu* values are high and similar among mineralized granodiorites (~0.6), altered diorite and granodiorites (~0.6) and the Mesozoic Qz-monzonites (~0.8), whereas the values are low and variable for the DBS-TS microgabbros (0.3~0.6). The magma oxidation state calculated from zircon chemistry and whole rock compositions are FMQ +1.0 to +1.5 in mineralized samples, and FMQ +2.4 to +4.2 in altered samples. The values are comparable to those for the fertile intrusions hosting porphyry Cu-Mo-(Au) deposits in the central and western CAOB and elsewhere in the world. Elevated oxidation state is also observed in the TS microgabbros, FMQ +1.4 to +1.9, and the early Mesozoic Qz-monzonites, FMQ +2.4 to +2.5. Comparison of zircon geochemistry data from porphyry deposists elsewhere suggests that positive Ce anomalies are generally associated with fertile intrusions, but not all igneous rocks with high Ce anomalies are Cu fertile. The findings in this study are useful in exploration work and evaluating oxidation state of magmas for porphyry Cu-(Mo) deposits in the region and elsewhere.
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Lebedev, V. I., A. A. Borovikov, L. V. Gushchina, and I. S. Shabalin. "Physico-chemical modeling of hidrothermal mineralization processes at Ni-Co-As (± U-Ag), Co-S-As (± Au-W), Cu-Co-As (± Sb-Ag) deposits." Геология рудных месторождений 61, no. 3 (June 19, 2019): 31–63. http://dx.doi.org/10.31857/s0016-777061331-63.
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A generalization of the results of the study of the composition of metal-bearing fluids of cobalt deposits of hydrothermal Genesis, formed in different geodynamic settings in connection with the formation of alkaline and alkaline-basite intrusions and dikes. To determine the physical and chemical parameters of ore deposition from fluid inclusions in minerals, both traditional and new instrumental methods of thermobarogeochemistry were used: thermo-and cryometry, RAMAN spectroscopy, concentration of ore and petrogenic elements in individual fluid inclusions were evaluated by LA-ICP-MS. The obtained results served as the basis for the study, the main task of which was the thermodynamic modeling of the conditions of joint transport and deposition of Co, Ni, Cu, Fe, Mg, Ca, Ag, Au, Bi, U, Pt and Pd C calculation of a number of equilibrium States of the hydrothermal system, the composition close to the natural ore-forming fluids. Physical and chemical factors of native deposits-gold, silver, platinum and palladium in the ores of such deposits are revealed. The obtained data can serve as a basis for the development of correct genetic models of ore-forming systems of cobalt deposits and contribute to solving the problems of their search.
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Poitrenaud, Thomas, Éric Marcoux, Romain Augier, and Marc Poujol. "The perigranitic W-Au Salau deposit (Pyrenees, France): polyphase genesis of a late Variscan intrusion related deposit." BSGF - Earth Sciences Bulletin 192 (2021): 22. http://dx.doi.org/10.1051/bsgf/2020044.
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A field study combined with a laboratory study and 3D modeling have been performed in order to decipher the genesis of the Salau deposit W-Au mineralization (Pyrenees, France), one of the most important for tungsten in Europe. Results show the existence of two superimposed ore types, emplaced ca. 10 km depth and within decreasing temperature conditions: a calcic silicates skarn with rare scheelite and disseminated sulphides followed by a mineralized breccia with massive sulphides (pyrrhotite and chalcopyrite dominant), coarse-grained scheelite and gold, representing the main part of the ore mined in the past. This breccia is localized in ductile-brittle shear-zones which crosscut the granodiorite. U/Pb dating on zircon, apatite and scheelite, previously realized, confirmed this polyphase evolution. These two types of mineralization, linked to the emplacement of two successive intrusions as confirmed by sulphur isotopic analysis, granodioritic then leucogranitic, can be classified as belonging to the Intrusion-Related Gold Deposit type (IRGD). The emplacement of the high-grade gold and scheelite breccia was initiated by the progressive localization of the regional deformation in the Axial Zone of the Pyrenees during the Permian within E-W dextral-reverse faults.
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Kholodnov, V. V., E. S. Shagalov, G. A. Kallistov, G. Yu Shardakova, D. N. Salikhov, and E. V. Konovalova. "The Akhunovo–Petropavlovsk Granitoid Area as a Continental-Margin Center of the Long-Term Mantle–Crust Interaction: The Role of Subductional and Rift–Plume Sources." Russian Geology and Geophysics 62, no. 6 (June 1, 2021): 648–65. http://dx.doi.org/10.2113/rgg20194121.
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Abstract —The Akhunovo–Petropavlovsk area of the late Paleozoic granite magmatism is located in the northeast of the Magnitogorsk megazone (MMZ) in the South Urals. It is a series of successively intruded rocks (Petropavlovsk, Akhunovo, Karagai, and Uiskii Bor intrusions) differing not only in composition, the depth of formation, and ore content but also in the relationship with magmatic and fluid sources and in magma generation mechanisms. This area differs significantly in the number and composition of intrusive complexes from the igneous rocks and ore associations in the central and western parts of the MMZ. The granite magmatism pulses alternated with the collisional shearing/spreading and rifting stages. The Petropavlovsk mesoabyssal granite intrusion (347.0 ± 8.6 Ma) formed at the early stage of the area evolution. Its rocks are similar in composition to a suprasubductional series (melting products of a mantle source enriched not only in water fluid but also in Cl). Later (310–306 Ma), at the collision–compression stage, crustal intrusion of the Akhunovo–Karagai granodiorite–granite complex took place. The intruded rocks are similar to the Middle Urals continental-margin gabbro-tonalite–grano-diorite–granite plutons (320–290 Ma) bearing large gold–sulfide–quartz deposits (Berezovskoe etc.). At the final stage of the area evolution, during the transition from continental-margin regime to hard collision between the East European and Kazakhstan continents (late Carboniferous) and the intense shearing/spreading deformations, the Uiskii Bor granosyenite–granite intrusion (304.0 ± 4.8 Ma) rich in K and HFSE formed. Granite intrusions of this type have been revealed in the MMZ for the first time. Thus, the granitoid complexes of the Akhunovo–Petropavlovsk area formed under changes in geodynamic settings and are characterized by different compositions, depths of occurrence, and genesis. This permits us to consider the area a typical continental-margin center of the long-term mantle–crust interaction, where magma generation proceeded at different mantle and crust levels, with the participation of both suprasubductional and enriched plume-related rift sources.
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Sun, Xiang, Yongjun Lu, Qiang Li, and Ruyue Li. "A Downgoing Indian Lithosphere Control on Along-Strike Variability of Porphyry Mineralization in the Gangdese Belt of Southern Tibet." Economic Geology 116, no. 1 (November 23, 2020): 29–46. http://dx.doi.org/10.5382/econgeo.4768.
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Abstract The E-trending Gangdese porphyry copper belt in southern Tibet is a classic example of porphyry mineralization in a continental collision zone. New zircon U-Pb geochronological, zircon Hf-O, and bulk-rock Sr-Nd isotope data for the Miocene mineralizing intrusions from the Qulong, Zhunuo, Jiru, Chongjiang, and Lakange porphyry copper deposits and Eocene igneous rocks from the western Gangdese belt, together with literature data, show that both Paleocene-Eocene igneous rocks and Miocene granitoids exhibit coupled along-arc isotopic variations, characterized by bulk-rock ɛNd(t) and zircon ɛHf(t) values increasing from ~84° to ~92°E and then decreasing toward ~95°E. These are interpreted to reflect increasing contributions of subducted Indian continental materials from ~92° to ~84°E and from ~92° to ~95°E, respectively. The Miocene mineralizing intrusions were derived from subduction-modified Tibetan lower crust represented isotopically by the Paleocene-Eocene intrusions, with contributions from Indian plate-released fluids and mafic melts derived from mantle metasomatized by subducted Indian continental materials. Involvement of isotopically ancient Indian continental materials increased from east (Qulong) to west (Zhunuo), which is interpreted to reflect an increasingly shallower angle of the downgoing Indian slab from east to west, consistent with geophysical imaging. Exploration of Gangdese Miocene porphyry copper deposits should focus on the Paleocene-Eocene arc where the subarc mantle was mainly enriched by fluids from the subducted Neo-Tethyan oceanic slab. Neodymium-Hf isotope data for mineralizing igneous rocks from porphyry copper deposits globally show no obvious correlations with Cu endowment. Although Nd-Hf isotopes are useful for imaging lithospheric architecture through time, caution must be taken when using Nd-Hf isotopes to evaluate the potential endowment of porphyry copper deposits, because other factors such as tectonic setting, crustal thickening, magma differentiation, fluid exsolution, and ore-forming processes all play roles in determining Cu endowments and grades.
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Wang, Zepeng, Qinping Tan, Yong Xia, Jianzhong Liu, Chengfu Yang, Songtao Li, Junhai Li, et al. "Sm–Nd Isochron Age Constraints of Au and Sb Mineralization in Southwestern Guizhou Province, China." Minerals 11, no. 2 (January 21, 2021): 100. http://dx.doi.org/10.3390/min11020100.
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Southwestern Guizhou, China, is famous for hosting clusters of Carlin-type Au, Sb, and Hg-Tl deposits. These deposits are thought to be the products of a low-temperature hydrothermal metallogenic event. Calcite and fluorite are common and widespread gangue minerals in Au and Sb deposits, respectively. Ore-related calcite commonly coexists with stibnite, realgar, and orpiment at the periphery of high-grade orebodies in Au deposits, while ore-related fluorite is generally intergrown with stibnite in Sb deposits. In this study, ore-related calcite and fluorite samples from representative Au (Zimudang) and Sb (Dachang) deposits, respectively, were separated, and the rare earth element (REE) concentrations, Sm/Nd isotope ratios, and Sm–Nd isochron ages were analyzed. This study aims to determine the formation ages of the calcite and fluorite and to constrain the age of low-temperature metallogenic event in Southwestern Guizhou. The calcite and fluorite samples contain relatively high total concentrations of REEs (8.21–22.5 μg/g for calcite, 21.7–36.6 μg/g for fluorite), exhibit variable Sm/Nd ratios (0.51–1.01 for calcite, 0.35–0.49 for fluorite), and yield Sm–Nd isochron ages of 148.4 ± 4.8 and 141 ± 20 Ma, respectively. These ages are consistent with the age range constrained by the low-temperature thermochronology of zircon (132–160 Ma), crosscutting relationships of stratigraphy or intrusions (96–160 Ma), and previous dating results (135–150 Ma) in Southwestern Guizhou. Collectively, the ages obtained in this study add new evidence to previous geochronology studies, such that the low-temperature hydrothermal mineralization in Southwestern Guizhou can be constrained to 135–150 Ma, corresponding to the Yanshanian orogeny, which was associated with a weak extensional tectonic environment.
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Groves, David I., Liang Zhang, and M. Santosh. "Subduction, mantle metasomatism, and gold: A dynamic and genetic conjunction." GSA Bulletin 132, no. 7-8 (November 4, 2019): 1419–26. http://dx.doi.org/10.1130/b35379.1.
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Abstract Global gold deposit classes are enigmatic in relation to first-order tectonic scale, leading to controversial genetic models and exploration strategies. Traditionally, hydrothermal gold deposits that formed through transport and deposition from auriferous ore fluids are grouped into specific deposit types such as porphyry, skarn, high- and low-sulfidation–type epithermal, gold-rich volcanogenic massive sulfide (VMS), Carlin-type, orogenic, and iron-oxide copper-gold (IOCG), and intrusion-related gold deposits (IRGDs). District-scale mineral system approaches propose interrelated groups such as porphyry Cu-Au, skarn Cu-Au-Ag, and high-sulfidation Au-Ag. In this study, the temporal evolution of subduction-related processes in convergent margins was evaluated to propose a continuum of genetic models that unify the various types of gold deposits. At the tectonic scale of mineral systems, all hydrothermal gold deposits are interrelated in that they formed progressively during the evolution of direct or indirect subduction-related processes along convergent margins. Porphyry-related systems formed initially from magmatic-hydrothermal fluids related to melting of fertile mantle to initiate calc-alkaline to high-K felsic magmatism in volcanic arcs directly related to subduction. Formation of gold-rich VMS systems was related to hydrothermal circulation driven by magmatic activity during rifting of oceanic arcs. Orogenic gold deposits formed largely through fluids derived from devolatilization of the downgoing slab and overlying sediment wedge during late transpression in the orogenic cycle. Carlin-type deposits, IRGDs, and some continental-arc porphyry systems formed during the early stages of orogenic collapse via fluids directly or indirectly related to hybrid magmatism from melting of lithosphere that was metasomatized and gold-fertilized by earlier fluid release from subduction zones near margins of continental blocks. The IOCGs were formed during postorogenic asthenosphere upwelling beneath such subduction-related metasomatized and fertilized lithospheric blocks via fluid release and explosive emplacement of volatile-rich melts. Thus, importantly, subduction is clearly recognized as the key unifying dynamic factor in gold metallogenesis, with subduction-related fluids or melts providing the critical ore components for a wide variety of gold-rich deposit types.
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Barkov, A. Y., R. F. Martin, A. E. Izokh, A. A. Nikiforov, and V. N. Korolyuk. "Ultramagnesian Olivine in the Monchepluton (Fo96) and Pados-Tundra (Fo93) Layered Intrusions (Kola Peninsula)." Russian Geology and Geophysics 62, no. 03 (March 1, 2021): 324–38. http://dx.doi.org/10.2113/rgg20194091.
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Abstract —The paper focuses on compositional variations of olivine and chromian spinel in the Monchepluton and Pados-Tundra layered intrusions, which host significant chromitite mineralization. Ore-bearing dunite (with up to 25–30 vol.% Mcr) in the Sopcheozerskoe chromite deposit from the Monchepluton complex, Kola Peninsula, Russia, bears an assemblage of phases with exceptionally high magnesium contents: Fo96 + augite (Mg# = 94) + magnesiochromite, Mcr (Mg# ≈ 65); Mg# = 100·Mg/(Mg + Fe2+ + Mn). However, olivine in the host dunite has normal maximum values of Mg# comparable to those in cumulus olivine from layered intrusions worldwide (Fo≤91–92). The Fo96 phase in the Sopcheozerskoe deposit shows the most primitive composition ever reported from any layered intrusion. Magnesiochromite occurs as unzoned homogeneous euhedral crystals unaffected by subsolidus exchange or metasomatic effects. Olivine in ore-bearing dunite (20–25 vol.% magnesian chromite) from the Pados-Tundra complex attains Fo93, with the Mg# value notably higher than the range (Fo85.5–90.6) in olivine from orthopyroxenite, harzburgite, and dunite within the intrusion. Olivine and chromian spinel in the two complexes behave coherently, with covarying patterns of Mg# and Ni contents in olivine at R = 0.75 (n = 160) and positive correlation between Mg# in coexisting chromian spinel and olivine grains at R = 0.8 (n = 150). This behavior indicates that the two phases attained equilibrium during crystallization. It appears unlikely that the extremely high Mg enrichment in olivine (Fo96), as well as in all associated phases of the Monchepluton complex, would result from a subsolidus reaction between olivine and chromian spinel or low-temperature alteration of olivine. We suggest a more realistic explanation that the olivine (+ high-Mg augite)–chromian spinel assemblage crystallized from komatiitic magma under the conditions of progressively increasing oxygen fugacity (fO2). The high Mg# in the Mcr-chromite-enriched system, above the maximum values common in cumulus olivine from layered intrusions (up to Fo96 against Fo≤91–92), may be caused by shortage of ferrous iron.
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Gilmer, Amy, R. Sparks, Dan Barfod, Emily Brugge, and Ian Parkinson. "Duration of Hydrothermal Alteration and Mineralization of the Don Manuel Porphyry Copper System, Central Chile." Minerals 11, no. 2 (February 8, 2021): 174. http://dx.doi.org/10.3390/min11020174.
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The Don Manuel porphyry copper system, located in the Miocene–Pliocene metallogenic belt of central Chile, contains spatially zoned alteration styles common to other porphyry copper deposits including extensive potassic alteration, propylitic alteration, localized sericite-chlorite alteration and argillic alteration but lacks pervasive hydrolytic alteration typical of some deposits. It is one of the youngest porphyry copper deposits in the Andes. Timing of mineralization and the hydrothermal system at Don Manuel are consistent with emplacement of the associated intrusions (ca. 4 and 3.6 Ma). Two molybdenite samples yielded consistent ages of 3.412 ± 0.037 and 3.425 ± 0.037 Ma. 40Ar/39Ar ages on hydrothermal biotites (3.57 ± 0.02, 3.51 ± 0.02, 3.41 ± 0.01, and 3.37 ± 0.01 Ma) are associated with potassic alteration. These ages are younger than the youngest intrusion by ~300 k.y. recording the cooling of the system below 350 °C. Such a time gap can be explained by fluxing of hot magmatic fluids from deeper magmatic sources.
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Tomlinson, David H., Eric H. Christiansen, Jeffrey D. Keith, Michael J. Dorais, Rudy Ganske, Diego Fernandez, Nicholas Vetz, Mackenzie Sorensen, and Jens Gibbs. "Nature and Origin of Zoned Polymetallic (Pb-Zn-Cu-Ag-Au) Veins from the Bingham Canyon Porphyry Cu-Au-Mo Deposit, Utah." Economic Geology 116, no. 3 (May 1, 2021): 747–71. http://dx.doi.org/10.5382/econgeo.4798.
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Abstract Polymetallic veins (Pb-Zn-Cu-Ag-Au) at the world-class Bingham Canyon, Utah, porphyry Cu-Au-Mo deposit have long been recognized, but poorly understood. They are laterally zoned outward from the center of the porphyry deposit transitioning from Fe-Cu to Pb-Zn-Cu-Ag-Au mineralization. Physical and chemical characterization of these polymetallic veins provide insight into the origin, timing, and controls of ore deposition. These sheared, sulfide-rich, NE/SW- trending veins are dominated by pyrite and multiple generations of quartz, with lesser amounts of other sulfide and gangue minerals. Gold (0.27–4.61 ppm) provides the most value to the ore, though the veins contain substantial Cu and Ag as well. Host rocks include Eocene monzonite and Paleozoic limestone and quartzite—all of which can contain economic ore lodes. Associated alteration is predominantly sericitic and argillic, with mineralization in wall rocks restricted to 1.5 m from the vein margins. Mineral assemblages vary with distance from the center of the main porphyry Cu-Au-Mo deposit and the modal abundances are dependent on the host rock. The appearance of both galena and sphalerite (and tennantite to an extent) occur along a boundary that creates a halo around the center of the associated porphyry deposit. This is accompanied by a shift in metal ratios and an increased concentration of chalcophile trace elements in sulfides from the polymetallic veins as determined by electron microprobe analyses (EMPA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Significant hosts of Ag include galena and tennantite, and Cu is hosted primarily in chalcopyrite, tennantite, and sphalerite. The main host of Au could not be determined, but Au could be focused along fractures or hosted in inclusions found in pyrite. The δ34S values of vein pyrite have a narrow range (2.3–3.4‰) suggestive of a magmatic source, whereas δ18O of quartz is more variable (11.5–14.0‰). These values are similar to several other polymetallic vein deposits associated with porphyry Cu deposits. This can be explained by fractionation of magmatic fluids at lower temperatures (350°–250°C) and/or mixing with exchanged 18O-rich meteoric water. Ore grades (Cu, Ag, Au) improve with distance from the center of the porphyry deposit; however, this is accompanied by higher concentrations of deleterious elements (e.g., Pb, As, Bi) for downstream processing. These polymetallic veins were created sequentially throughout the formation of the deposit. Initial joints in the sedimentary rocks probably formed as a result of emplacement of a barren equigranular monzonite intrusion, with continued dilation and propagation in all host rocks with each subsequent intrusion. The northeast orientation of the joints was controlled by the regional stress field, which is more apparent distal to the center of the Bingham deposit. Vein mineralization appears to postdate all intrusions and the porphyry Cu-Au mineralization; however, it may be related to the late fluids responsible for Mo mineralization in the main porphyry orebody that followed intrusion of the quartz latite porphyry. Quartz-sericite-pyrite mineralization associated with the veins precedes galena-sphalerite-pyrite mineralization. This was followed by late precipitation of chalcopyrite and tennantite and late normal faulting.
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Štemprok, Miroslav, and Thomas Seifert. "An overview of the association between lamprophyric intrusions and rare-metal mineralization." Mineralogia 42, no. 2-3 (January 1, 2011): 121–62. http://dx.doi.org/10.2478/v10002-011-0011-x.
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An overview of the association between lamprophyric intrusions and rare-metal mineralizationGranite-related rare metal districts in orogenic settings are occasionally associated with lamprophyre dikes. We recorded 63 occurrences of lamprophyres in bimodal dike suites of about 200 granite bodies related to rare metal deposits. Most lamprophyres occur in Paleozoic and Mesozoic metallogenic provinces in the northern hemisphere. Lamprophyres which are associated with rare metal deposits are calc-alkaline (kersantites, minettes, spessartites) or more rarely alkaline lamprophyres (camptonites, monchiquites) which occur in the roof zone of complex granitic bodies as pre-granitic, intra-granitic, intra-ore or post-ore dikes. Most lamprophyres are spatially associated with dominant felsic dikes and/or with mafic dikes represented by diorites or diabases. Diorites and lamprophyres occasionally exhibit transitional compositions from one to another. Lamprophyres share common geochemical characteristics of highly evolved granitoids such as enrichment in K and F, increased abundances of Li, Rb, and Cs and enrichment in some HFSE (e.g. Zr, U, Th, Mo, Sn, W). Lamprophyres in rare metal districts testify to accessibility of the upper crust to mantle products at the time of rare metal mineralization and possible influence of mantle melts or mantle-derived fluids in the differentiation of granitic melts in the lower crust.
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Abidi, Riadh, Najet Slim-Shimi, Dominique Gasquet, Nouri Hatira, and Alireza Somarin. "Genesis of celestite – bearing cap rock formation from the Ain Allega ore deposit (northern Tunisia): contributions from microthermometric studies." Bulletin de la Société Géologique de France 182, no. 5 (September 1, 2011): 427–35. http://dx.doi.org/10.2113/gssgfbull.182.5.427.
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Abstract The Ain Allega ore deposit represents one of the most significant Pb-Zn Sr-Ba deposits of the flysch zone in northern Tunisia. The total quantity of sulphide produced is 22,700 metric tons, with 13,300 t of galena and 9,400 t of sphalerite. It is located on the eastern edge of the Triassic diapir of the Jebel Hamra. The main ore minerals include sphalerite, galena, pyrite and marcasite, and gangue minerals including dolomite, calcite, celestite, quartz and barite. The mineralization hosted by carbonate rocks, shows some evidence of dissolution and brecciation characteristic of cap-rock formation. The fluid inclusion study from the celestite suggests that the primary and secondary monophase liquid (L) inclusions are most abundant compared to the other types. The microthermometric analyses of two-phase primary inclusions display homogenization temperatures ranging from 136 to 208°C (average of 180°C) and salinities ranging from 11.34 to 24.38 equivalent weight % NaCl (average of 16.4). The calculated density, pressure and depth are 0.965 g/cm3, 18 bars and 80 m, respectively. The hydrothermal fluid resulted from mixing of basinal brines and magmatic-meteoric solutions. Geological, mineralogical and thermometric data indicate that the Ain Allega ore deposit results of a mixing of basinal fluids (Mississippi valley type deposit) and hydrothermal fluids related to a shallow intrusion.
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Su, Zhi-Kun, Xin-Fu Zhao, Xiao-Chun Li, Mei-Fu Zhou, Allen K. Kennedy, Jian-Wei Zi, Carl Spandler, and Yue-Heng Yang. "UNRAVELING MINERALIZATION AND MULTISTAGE HYDROTHERMAL OVERPRINTING HISTORIES BY INTEGRATED IN SITU U-Pb AND Sm-Nd ISOTOPES IN A PALEOPROTEROZOIC BRECCIA-HOSTED IOCG DEPOSIT, SW CHINA." Economic Geology 116, no. 7 (November 1, 2021): 1687–710. http://dx.doi.org/10.5382/econgeo.4840.
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Abstract Precambrian iron oxide copper-gold (IOCG) deposits are generally encountered with multistage hydrothermal overprints and hence have complex isotopic records. Precise dating of ore-forming and overprinting events and assessment of time-resolved metal sources are fundamental for understanding ore genesis. Here, we quantify the evolution history by integrating in situ U-Pb dating of texturally constrained allanite and Sm-Nd isotope data of ores and major rare earth element (REE) minerals in the breccia-hosted Lanniping Fe-Cu deposit in Kangdian region, southwestern China. The economically mineralized breccia in Lanniping Fe-Cu deposit is characterized by pervasive and texturally destructive replacement of polymictic clasts, including host metasedimentary packages, the intruded dolerite, and pre-ore halokinetic breccia. Ore minerals in cements are mainly composed of magnetite, chalcopyrite, bornite, and variable amounts of REE-rich minerals (e.g., apatite and allanite/epidote). Two types of allanite were identified in ores. Type I prismatic allanite texturally intergrown with magnetite has a SHRIMP U-Pb age of 1728 ± 20 Ma (1σ), which matches a zircon U-Pb age of 1713 ± 14 Ma (2σ) for the dolerite clasts and provides the direct age constraint on the Fe-Cu mineralization event. Type II anhedral allanite shows complex zoning and is spatially associated with, but texturally later than, magnetite, apatite, and chalcopyrite. This type of allanite yields significantly younger SHRIMP dates of 1015 ± 33 (1σ) and 800 ± 16 Ma (1σ) for cores and rims, respectively, which correspond to discrete regional magmatic events and hence record hydrothermal overprint/remobilization events of ore minerals in the deposit. Integrated Sm-Nd isotope compositions of type I allanite, apatite, and whole ores generally align along the reference Sm-Nd isochron of 1728 Ma, further confirming the primary ore formation at ~1.7 Ga. Corresponding εNd(1728 Ma) values ranging from –2.8 to 0.3 are significantly higher than those of the host metasedimentary rocks (–9.5 to –6.2) but comparable to those of contemporaneous igneous intrusions (–0.3 to 5.3) in the region, demonstrating that REE components of the primary ores were dominantly sourced from rocks of mantle-derived affinity. Both cores and rims of the younger type II allanite grains have Nd isotope compositions consistent with the unique time-evolved line of the ~1.7 Ga ores, implying that REEs incorporated into type II allanite were ultimately sourced from the primary ores in this deposit. The combined texture, chemical, U-Pb, and Sm-Nd isotope data thus demonstrate that REE remobilization was localized during post-ore hydrothermal overprint with negligible external inputs of REEs to the primary ores in the Lanniping deposit. In this contribution, we not only date primary ore formation but also recognize several younger allanite generations that record internal metal redistributions in response to post-ore tectonothermal events. Our study highlights the potential of ore-associated REE minerals such as allanite for resolving the age of multiple stages of hydrothermal events in complex ore deposits by ion probe, provided that careful examination of textural and paragenetic relationship of ores is conducted. Our finding of these younger allanite generations also exemplifies the significance of evaluation on time-resolved metal input for better characterizing the evolution history of the IOCG deposits.
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Sampson, Lee M., and Nicholas C. Williams. "The geophysical response of the Goldrush-Fourmile orebody and implications for camp-scale Carlin-type deposit exploration, Cortez District, Nevada." Leading Edge 40, no. 2 (February 2021): 122–28. http://dx.doi.org/10.1190/tle40020122.1.
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Since discovery of the Goldrush and Fourmile deposits, numerous geophysical surveys have been acquired over the footprint of mineralization and surrounding areas to focus exploration. The Goldrush-Fourmile system extends more than 7 km in strike length and averages approximately 300 m wide. Most of the orebody lies more than 300 m below ground surface and continues to depths of more than 900 m. Direct detection of the ore system using geophysical tools is impeded by several factors. The system is relatively flat lying and sits in the hinge of a doubly plunging anticline. This gives the shallowest zones a very small lateral footprint. The ore consists of thin strata-bound zones of silica-sulfide mineralization with a tight alteration selvage. Structural controls along faults are limited, with only small displacements. Strong petrophysical contrasts exist between unaltered rock units. Finally, the terrain is rugged. Resistivity inversions of airborne electromagnetic data show that mineralization sits within a complex zone of resistivity responses. Close to intrusions, the host stratigraphy is resistive. Away from intrusions, the same stratigraphic units show highly variable but commonly very low resistivities. This suggests the possibility of redistribution of carbon around intrusions during premineralization metasomatism. Within the orebody, sulfide content increases conductivity within individual formations related to the distribution of fine-grained sooty pyrite. The geometry of the Red Hill Anticline is imaged as a positive density contrast in the observed gravity and geologically constrained gravity inversions. The positive density contrast represents the gross geophysical signature of denser carbonates within the Paleozoic stratigraphy. Magnetic surveys are crucial for mapping the distribution of igneous rocks and potentially hornfelsed sedimentary rocks. The challenges associated with exploring for deeply buried Carlin mineralization notwithstanding, the application of innovative geophysical tools tuned to assess specific geologic questions, combined with best-practice geologic and geochemical modeling, is helping drive exploration for additional Carlin-type mineralization across the Cortez District.
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Stepanov, Sergey Y., Roman S. Palamarchuk, Dmitry A. Varlamov, Darya V. Kiseleva, Ludmila N. Sharpyonok, Radek Škoda, and Anatoly V. Kasatkin. "The Features of Native Gold in Ore-Bearing Breccias with Realgar-Orpiment Cement of the Vorontsovskoe Deposit (Northern Urals, Russia)." Minerals 11, no. 5 (May 19, 2021): 541. http://dx.doi.org/10.3390/min11050541.
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This paper describes native gold in ore-bearing breccias with realgar-orpiment cement from the Vorontsovskoe gold deposit (Northern Urals, Russia). Particular attention is paid to the morphological features of native gold and its relation to other minerals. The latter include both common (orpiment, barite, pyrite, prehnite, realgar) and rare species (Tl and Hg sulfosalts, such as boscardinite, dalnegroite, écrinsite, gillulyite, parapierrotite, routhierite, sicherite, vrbaite, etc.). The general geological and geochemical patterns of the Turyinsk-Auerbakh metallogenic province, including the presence of small non-economic copper porphyry deposits and general trend in change of the composition of native gold (an increase in the fineness of gold from high-temperature skarns to low-temperature realgar-orpiment breccias) confirm that the Vorontsovskoe deposit is an integral part of a large ore-magmatic system genetically associated with the formation of the Auerbakh intrusion.
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Jackisch, Madriz, Zimmermann, Pirttijärvi, Saartenoja, Heincke, Salmirinne, Kujasalo, Andreani, and Gloaguen. "DroneBorne Hyperspectral and Magnetic Data Integration: Otanmäki FeTiV Deposit in Finland." Remote Sensing 11, no. 18 (September 5, 2019): 2084. http://dx.doi.org/10.3390/rs11182084.
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The technical evolution of unmanned aerial systems (UAS) for mineral exploration advances rapidly. Recent sensor developments and improved UAS performance open new fields for research and applications in geological and geophysical exploration among others. In this study, we introduce an integrated acquisition and processing strategy for droneborne multisensor surveys combining optical remote sensing and magnetic data. We deploy both fixedwing and multicopter UAS to characterize an outcrop of the Otanmäki FeTiV deposit in central Finland. The lithology consists mainly of gabbro intrusions hosting ore bodies of magnetiteilmenite. Large areas of the outcrop are covered by lichen and low vegetation. We use two droneborne multi and hyperspectral cameras operating in the visible to nearinfrared parts of the electromagnetic spectrum to identify dominant geological features and the extents of ore bodies via ironindicating proxy minerals. We apply band ratios and unsupervised and supervised image classifications on the spectral data, from which we can map surficial ironbearing zones. We use two setups with threeaxis fluxgate magnetometers deployed both by a fixedwing and a multicopter UAS to measure the magnetic field at various flight altitudes (15 m, 40 m, 65 m). The total magnetic intensity (TMI) computed from the individual components is used for further interpretation of ore distribution. We compare to traditional magnetic groundbased survey data to evaluate the UASbased results. The measured anomalies and spectral data are validated and assigned to the outcropping geology and ore mineralization by performing surface spectroscopy, portable Xray fluorescence (pXRF), magnetic susceptibility, and traditional geologic mapping. Locations of mineral zones and magnetic anomalies correlate with the established geologic map. The integrated survey strategy allowed a straightforward mapping of ore occurrences. We highlight the efficiency, spatial resolution, and reliability of UAS surveys. Acquisition time of magnetic UAS surveying surpassed ground surveying by a factor of 20 with a comparable resolution. The proposed workflow possibly facilitates surveying, particularly in areas with complicated terrain and of limited accessibility, but highlights the remaining challenges in UAS mapping.
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Keays, Reid R., and Peter C. Lightfoot. "Mafic intrusions in the footwall of the Sudbury Igneous Complex: Origin of the Sudbury impact melt sheet and its associated ore deposits." Ore Geology Reviews 120 (May 2020): 103435. http://dx.doi.org/10.1016/j.oregeorev.2020.103435.
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Rundkvist, Tatiana, and Pavel Pripachkin. "Accessory Cr-Spinels in the Section of the Nude-Poaz Massif in the Monchegorsk (2.5 Ga) Mafic-Ultramafic Layered Complex (Kola Peninsula, Russia): Comparison with Ore-Forming Chromites." Minerals 11, no. 6 (June 3, 2021): 602. http://dx.doi.org/10.3390/min11060602.
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The paper studies accessory Cr-spinels from deep drill holes crossing the Nude-Poaz massif, which is a part of the Monchegorsk mafic-ultramafic layered complex (2.5 Ga, Kola Peninsula, Russia). Cr-spinels occur as two morphological types that differ in their chemical composition, i.e., Cr-spinels of the first type are more aluminous, while Cr-spinels of the second type are more ferruginous and titaniferous. Cr-spinels of the Nude-Poaz massif are characterized by a Fe-Ti trend known for layered intrusions in the world. Cr-spinels of the Nude-Poaz massif quite clearly differ in composition from chromites of the Sopcheozero deposit: they are more ferruginous and less chromous. The specific composition of Cr-spinels in rocks of the Nude-Poaz massif can be correlated with the sequence of the magmatic phases intrusion.
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Ouyang, Hegen, Jingwen Mao, Ruizhong Hu, John Caulfield, and Zhenhua Zhou. "CONTROLS ON THE METAL ENDOWMENT OF PORPHYRY Mo DEPOSITS: INSIGHTS FROM THE LUMING PORPHYRY Mo DEPOSIT, NORTHEASTERN CHINA." Economic Geology 116, no. 7 (November 1, 2021): 1711–35. http://dx.doi.org/10.5382/econgeo.4850.
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Abstract Processes controlling the metal endowment of arc-related porphyry Mo deposits are not well understood. Located in northeastern China, the arc-related Luming porphyry Mo deposit has a proven reserve of 0.75 Mt Mo at an average grade of 0.092 wt % and is characterized by multiple pulses of alteration and mineralization. These features make this deposit an ideal location to investigate the role of multiple pulses of magmatism and fluid release in the evolution and formation of an arc-related porphyry Mo deposit. Molybdenum mineralization at Luming is typically observed as a series of molybdenite-bearing veins hosted within a composite intrusive complex, referred to as the Luming Intrusive Suite. Crosscutting relationships between intrusive units and offset veins indicate that the Luming Intrusive Suite is composed of five major, successive granitic intrusions: the premineralization plutonic biotite monzogranite and monzogranite units, and the synmineralization stock- and dike-like porphyritic monzogranite, granite porphyry, and syenogranite units. Each synmineralization unit is associated with similar vein sequences that comply with the general form of early EB-type biotite veins, through A-type quartz ± biotite and B-type quartz-molybdenite veins, to late D-type quartz-molybdenite ± pyrite ± chalcopyrite, molybdenite, quartz-pyrite ± calcite, and calcite ± clays veins. The intensity and volume of alteration and mineralization within a given synmineralization unit decrease from early- through inter- to late-mineralization units. Although minor Mo mineralization is associated with potassic alteration along B-type veins, the majority of the ore is associated with D-type quartz-molybdenite-pyrite and molybdenite veins rimmed by sericite-chlorite-pyrite alteration, which are primarily hosted in the two premineralization units. A combination of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) zircon U-Pb and hydrothermal biotite 40Ar/39Ar studies, together with available isotope dilution-inductively coupled plasma-mass spectrometry (ID-ICP-MS) molybdenite Re-Os data, has resulted in a substantial reappraisal of the timing of magmatism and its association with molybdenite mineralization at Luming. The volumetrically dominant premineralization intrusive units have indistinguishable zircon U-Pb weighted mean 206Pb/238U ages ranging from 187.5 ± 2.8 to 186.5 ± 3.6 Ma (2σ), whereas the synmineralization units yield weighted mean 206Pb/238U ages from 178.6 ± 2.2 to 175.6 ± 3.0 Ma (2σ). The zircon U-Pb weighted mean 206Pb/238U ages of the synmineralization units are indistinguishable from the mean molybdenite Re-Os model (178.1 ± 2.7; 2σ) and hydrothermal biotite 40Ar/39Ar plateau (174.7 ± 1.1 Ma; 2σ) ages within uncertainty, confirming a genetic link with mineralization. Melt inclusion data show that the synmineralization intrusions were Mo poor, with Mo concentrations <4 ppm. The data presented here suggest that molybdenite mineralization at Luming was most likely accomplished through three discrete magmatic-hydrothermal events during assembly of the Mo-poor synmineralization intrusive complex. The giant Luming deposit appears to be related to multiple pulses of magmatic-hydrothermal activities, resulting in the superposition of temporally distinct mineralization events. Our results suggest that pulsed release of ore-forming magmas and fluids, which are channeled along focusing structures like small porphyry fingers within a focused area, from a large magma chamber at depth may play a major role in the formation of large to giant porphyry Mo deposits of both the arc-related and Climax types. This conclusion is in line with field observations of a number of large to giant porphyry Mo deposits, which commonly show reversals in magmatic-hydrothermal evolutionary trend and are associated with multiple pulses of small stocks and dikes that are separate in time and space.
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Müller, Stefan G., Bryan Krape, Mark E. Barley, and Ian R. Fletcher. "Giant iron-ore deposits of the Hamersley province related to the breakup of Paleoproterozoic Australia: New insights from in situ SHRIMP dating of baddeleyite from mafic intrusions." Geology 33, no. 7 (2005): 577. http://dx.doi.org/10.1130/g21482.1.
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Hu, Hao, Jian-Wei Li, Daniel E. Harlov, David R. Lentz, Christopher R. M. McFarlane, and Yue-Heng Yang. "A genetic link between iron oxide-apatite and iron skarn mineralization in the Jinniu volcanic basin, Daye district, eastern China: Evidence from magnetite geochemistry and multi-mineral U-Pb geochronology." GSA Bulletin 132, no. 5-6 (August 30, 2019): 899–917. http://dx.doi.org/10.1130/b35180.1.
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Abstract Various styles of ore deposits may form from a single magmatic-hydrothermal system. Identification of a possible genetic link between different ore types in a region is not only of critical importance for a better understanding of the magmatic-hydrothermal processes, but can also help in successful mineral exploration. Both iron oxide-apatite (IOA) and iron skarn deposits are closely associated with intrusive rocks of intermediate to felsic in composition, but whether these two ore types can form from the same magmatic intrusion remains poorly understood. In this study, we present a comparative study between a newly identified subsurface IOA ore body located at the apex of a diorite porphyry and the iron skarn ore bodies located immediately above it in the Jinniu volcanic basin of the Daye district, Middle-Lower Yangtze River metallogenetic belt (MLYRMB), eastern China in order to highlight a genetic link between these two styles of mineralization. The IOA ores are dominated by Ti-rich magnetite with variable amounts of fluorapatite, diopside, and actinolite. This mineralogical assemblage is distinctly different from the iron skarn ores, which consist mainly of Ti-depleted magnetite and subordinate pre-ore garnet and diopside, and post-ore quartz, chlorite, calcite, and pyrite. In addition, magnetite from the IOA ores is characterized by well-developed ilmenite lamellae and has high concentrations of Ni, V, Co, and Ga, consistent with high temperature crystallization, whereas magnetite grains from the iron skarn ores usually exhibit oscillatory growth zones and contain much lower Ni, V, Co, and Ga, indicating their formation under relatively low temperatures. Titanite and fluorapatite from the IOA ores have U-Pb ages of 132.5 ± 2.4 Ma to 128.4 ± 3.0 Ma, which match a titanite U-Pb age for the associated iron skarn ores (132.3 ± 2.0 Ma), and are consistent with zircon U-Pb ages for the ore-hosting diorite porphyry (130.4 ± 0.7 Ma to 130.3 ± 0.5 Ma). This age consistency supports a possible genetic link among the diorite porphyry, IOA ores, and iron skarn ores. We propose that the IOA and skarn ores are the products of two consecutive mineralization stages of the same magmatic-hydrothermal system, involving a high-temperature, hypersaline fluid coexisting with the diorite porphyry magma during emplacement and a subsequent low temperature, diluted hydrothermal fluid. Other IOA and iron skarn deposits of similar ages (130 Ma) are found in a series of volcanic basins in the MLYRMB, which forms one of the world’s largest IOA metallogenic belts. The close association of the two ore styles identified at Daye provides a useful exploration guide for IOA and iron skarn deposits both on a local and regional scale.
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Corral, Isaac. "Comment to "Porphyry-related high-sulfidation mineralization early in Central American Arc Development: Cerro Quema deposit, Azuero Peninsula, Panama" by Perelló et al., (2020)." Boletín de la Sociedad Geológica Mexicana 73, no. 1 (April 1, 2021): A121220. http://dx.doi.org/10.18268/bsgm2021v73n1a121220.
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The Cerro Quema Au-Cu deposit is hosted by a dacite dome complex of the Río Quema Formation, a Late Campanian-Maastrichtian volcano-sedimentary sequence of the Panamanian magmatic arc. Its formational age is constrained at ~49 Ma by field evidences, crosscutting relationships and 40Ar/39Ar geochronology (Corral et al., 2016, Corral, 2021). The recent molybdenite Re-Os dates by Perelló et al. (2020) claim that ore is spatially and temporally related to the host volcanic domes at ~71 Ma. After a thorough review of the geologic, geochemical and geochronological data from the Cerro Quema area, it is concluded that the Re-Os dates of Perelló et al. (2020) are not representative of the Cerro Quema formational age. Their proposed formational age at ~71 Ma is significantly older than the age of the host rock (~67 Ma). Furthermore, they invoke a previously unrecognized regional-scale magmatic event solely based on their molybdenite Re-Os dates. Instead, the Cerro Quema genetic model discussed here, in which magmatic-hydrothermal fluids derived from porphyry copper-like intrusions associated with the Valle Rico batholith produced the Au-Cu mineralization at ~49 Ma, is consistent with the geology, geochemistry and geochronology of the Azuero Peninsula.
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Idrus, Arifudin, Aji Syailendra Ubaidillah, I. Wayan Warmada, and Syafruddin Maula. "Geology, Rock Geochemistry and Ore Fluid Characteristics of the Brambang Copper-Gold Porphyry Prospect, Lombok Island, Indonesia." Journal of Geoscience, Engineering, Environment, and Technology 6, no. 1 (March 29, 2021): 67–73. http://dx.doi.org/10.25299/jgeet.2021.6.1.6145.
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Brambang is one of the porphyry copper-gold prospects/deposits situated along eastern Sunda arc. This study is aimed to understand geological framework, alteration geochemistry and ore fluid characteristics of the prospect. Fieldworks and various laboratory analyses were performed including petrography, ore microscopy, rock geochemistry, chlorite chemistry and fluid inclusion microthermometry. The prospect is composed of andesitic tuff and diorite which are intruded by tonalite porphyries. Tonalite porphyries are interpreted as ore mineralisation-bearing intrusion. Various hydrothermal alterations are identified including potassic, phyllic, propylitic, advanced argillic and argillic types. Ore mineralisation is characterized by magnetite and copper sulfides such as bornite and chalcopyrite. Potassic alteration is typified by secondary biotite, and associated with ore mineralisation. Mass balance calculation indicates SiO2, Fe2O3, K2O, Cu and Au are added during potassic alteration process. Ore forming fluid is dominated by magmatic fluid at high temperature (450-600ºC) and high salinity (60-70 wt. % NaCl eq.). Hydrothermal fluid was diluted by meteoric water incursion at low-moderate temperature of 150-400ºC and salinity of 0.5-7 wt. % NaCl eq.
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Mitchell, A. H. G., and J. C. Carlile. "Mineralization, antiforms and crustal extension in andesitic arcs." Geological Magazine 131, no. 2 (March 1994): 231–42. http://dx.doi.org/10.1017/s001675680001075x.
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AbstractThe distribution and stratigraphic position of porphyry copper and epithermal gold deposits in andesitic arcs of the western Pacific and eastern Europe suggest that porphyry copper and epithermal vein deposits of adularia–sericite type develop successively under different stress regimes in an evolving arc, rather than being genetically related as commonly supposed. Absence of coeval high-level stocks in the root zones of many adularia-sericite deposits suggests that circulation of the dominantly meteoric hydrothermal fluids is not driven by shallow intrusions. The location of several world-class deposits on basement geanticlines, and on more localized antiforms of which at least one has been interpreted as a metamorphic core complex, implies that elevation of the arc, emplacement of magmatic sills at depth and adularia–sericite type gold mineralization are genetically related to subduction-induced crustal extension. Ascent of deep hydrothermal fluids, predominantly meteoric but with a metamorphic or magmatic component, may be controlled by regional low-angle structures at depth, analogous to those inferred for some mesothermal gold deposits. Mineralization at shallow (epithermal) depths in high-angle structures largely reflects the high geothermal gradient and mixing of deep fluid with cool meteoric water in or at the base of the permeable volcanic cover. Andesitic magmatism may resume following porphyry copper mineralization, adularia–sericite epithermal gold mineralization, or continued extension to form a ‘back arc’ spreading system, depending on the relative plate motion.
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Zhao, Chuntao, Jinggui Sun, Yang Liu, Xiaolei Chu, Zhikai Xu, Jilong Han, Wenqing Li, Liang Ren, and Chenglin Bai. "Constraints of magmatism on the Ergu Fe–Zn polymetallic metallogenic system in the central Lesser Xing’an Range, NE China: evidence from geochronology, geochemistry and Sr–Nd–Pb–Hf isotopes." Geological Magazine 158, no. 10 (July 23, 2021): 1862–90. http://dx.doi.org/10.1017/s0016756821000479.
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AbstractThe medium-sized Ergu Fe–Zn polymetallic skarn deposit is located in the central Lesser Xing’an Range, NE China. The ore bodies are mainly hosted in the contact zone between granodiorite intrusions and lower Cambrian dolomitic crystalline limestones or skarns. To reveal the magmatic influence on the mineralization, resource potential and metallogenic geodynamic process of this deposit, a systematic study of the geology, petrology, zircon U–Pb dating, element geochemistry, amphibole geochemistry and Sr–Nd–Pb–Hf isotopes of the Ergu deposit intrusives was conducted. The results show the following: (1) The major rock types in the mine area are medium-grained granodiorite and porphyritic granite, and the rock related to mineralization is medium-grained granodiorite. Zircon U–Pb dating suggests that the granodiorite and porphyritic granite formed at 181.9–183.8 Ma and 182.7 Ma, respectively. Thus, an Early Jurassic magmatic event led to the formation of the Ergu deposit. (2) The granodiorite and porphyritic granite are high-K calc-alkaline I-type granites that formed by comagmatic evolution with varying degrees of fractional crystallization and were likely derived from partial melting of the lower crust. The Ergu deposit occurred in an active continental-margin tectonic setting. (3) The high water content (5.69 wt % H2O), high oxygen fugacity (ΔFMQ = +1.75 to +1.82) and intermediate-plutonic emplacement (3.13 km) of the granodioritic magma are key factors in the formation of the Ergu deposit. The porphyry granite is characterized by high water content (>4 wt % H2O), reduced oxygen fugacity (ΔFMQ = −0.47) and shallow emplacement (<3 km).
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Stephens, Julian R., John L. Mair, Nicholas H. S. Oliver, Craig J. R. Hart, and Timothy Baker. "Structural and mechanical controls on intrusion-related deposits of the Tombstone Gold Belt, Yukon, Canada, with comparisons to other vein-hosted ore-deposit types." Journal of Structural Geology 26, no. 6-7 (June 2004): 1025–41. http://dx.doi.org/10.1016/j.jsg.2003.11.008.
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Andrews, A. J., L. Owsiacki, R. Kerrich, and D. F. Strong. "The silver deposits at Cobalt and Gowganda, Ontario. I: Geology, petrography, and whole-rock geochemistry." Canadian Journal of Earth Sciences 23, no. 10 (October 1, 1986): 1480–506. http://dx.doi.org/10.1139/e86-143.
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The Ag–sulpharsenide vein deposits of northeastern Ontario occur along the north and northeastern margins of the Cobalt Embayment, a large irregular domain of Huronian-age clastic sediments intruded by Nipissing diabase sills and crosscut by regional-scale fault systems. The vein systems are mostly fault controlled, with mineralization always occurring adjacent to or within the diabase sills. Many of the mineralized structures crosscut the sills. All the economically productive deposits occur in close proximity to the Huronian–Archean unconformity where diabase sills and steeply dipping Archean volcanic sequences coincide.The vein systems show remarkable consistencies in their mineralogy, textures, and paragenesis. Their formation involved the precipitation of silicates (mainly quartz, chlorite, actinolite ± K-feldspar) during initial, limited dilation; this was followed by the introduction of significant quantities of carbonate (mainly calcite ± dolomite) during subsequent dilatant episodes. Most of the ore was precipitated during the silicate to carbonate transition. Wall-rock alteration haloes exhibit a silicate to carbonate paragenesis similar to that evident in the veins. Feldspathization is an important consequence of the alteration process, manifesting in the ubiquitous occurrence of albite in Nipissing diabase wall rocks and sporadic occurrences of K-feldspar in Archean basalt wall rocks.The mineralogy and chemistry of the veins and altered wall rocks indicate that CO2, Ca, Na, K, Ag, As, Co, Pb, rare earth elements, and in some cases Hg and Au were among the components introduced with the hydrothermal fluids. This was accompanied by significant net loss of Si, Fe, Mg, Zn, B, Li, and Sc from the wall rocks. The nature of the wall-rock alteration suggests that the mineralizing fluids were of high alkalinity and relatively low [Formula: see text]. They were not derived through lateral secretion but were introduced from a source remote from the immediate environment of ore deposition.Wall-rock alteration postdates the establishment of a low-temperature, regional alteration of the diabases and a chlorite spotting alteration in the Huronian sediments; the latter is a contact metamorphic effect accompanying diabase intrusion. These data indicate that Ag–sulpharsenide vein formation postdated intrusion of the diabases and much (possibly all) of their cooling histories.Collectively, our data discourage the theory that the Nipissing diabase sills acted purely as a heat and (or) fluid source in vein formation. A structural model is proposed in which the diabase sills acted as mechanically favourable sites for fracture generation during regional fault activity. This factor, together with the advent of boiling and (or) degassing of the mineralizing fluids at these specific sites are viewed as possible critical parameters mediating the localization and deposition of Ag–sulpharsenide ore. This model provides a reasonable explanation for the local and regional distribution of the deposits and appears to best satisfy all the geological, petrographic, and geochemical criteria.
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Blevin, Phillip L., Bruce W. Chappell, and Charlotte M. Allen. "Intrusive metallogenic provinces in eastern Australia based on granite source and composition." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 87, no. 1-2 (1996): 281–90. http://dx.doi.org/10.1017/s0263593300006684.
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ABSTRACT:Ore element ratios in intrusion-related mineralisation are in part a function of the relative oxidation state and degree of fractionation of the associated granite suite. A continuum from Cu-Au through W to Mo dominated mineralisation related to progressively more fractionated, oxidised I-type magmas can be traced within single suites and supersuites. Such systematic relationships provide strong evidence for the magmatic source of ore elements in granite-related mineral deposits and for the production of the observed ore element ratios dominantly through magmatic processes. The distribution of mineralised intrusive suites can be used to define a series of igneous metallogenic provinces in eastern Australia. In general, there is a correlated evolution in the observed metallogeny (as modelled based on the compatibility of ore elements during fractionation) with increasing degree of chemical evolution of the associated magmatic suite. This is from Cu-Au associated with chemically relatively unevolved magmas, through to Sn and Mo-rich mineralisation associated with highly evolved magmas that had undergone fractional crystallisation. Provinces recognised in that way do not necessarily correlate with the tectonostratigraphic boundaries defined by the near-surface geology, indicating that the areal distribution of some granite source regions in the deep crust is unrelated to upper crustal geology.
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Oo, Toe, Agung Harijoko, and Lucas Setijadji. "Origin of the Kyaukmyet Low-Sulfidation Epithermal Gold Prospect, Monywa District, Central Myanmar." Iraqi Geological Journal 54, no. 1E (May 31, 2021): 1–18. http://dx.doi.org/10.46717/igj.54.1e.1ms-2021-05-22.
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The Kyaukmyet prospect is one of the principal epithermal gold prospects in the Monywa District, Central Myanmar; its gold- and base metal-bearing quartz veins contain around 3 g/t gold. Ore minerals are mainly hosted by volcanic and volcaniclastic rocks of the Late Oligocene to Middle Miocene Magyigon Formation. The distribution of magmatic intrusions in the area is controlled by ENE-WSW trending faults; these faults are likely related to ore mineralization. Common ore minerals at the Kyaukmyet prospect include pyrite, sphalerite, galena, chalcopyrite, and electrum. They occur in mineralized crustiform-textured brecciated quartz veins and banded (colloform) and massive quartz veins. Mineralized rock is accompanied by silicification and propylitic and argillic alterations. The alteration mineral assemblages include quartz, adularia, calcite, chlorite, illite/smectite, sericite, and illite. Fluid inclusions in the quartz veins have homogenization temperatures ranging from 148 °C to 304 °C and salinities from 0.35 wt % to 2.75 wt % NaCl equiv. The quartz in the mineralized quartz veins was most likely precipitated at a depth ranges165-256 m below the paleosurface. The precipitation of gold at the Kyaukmyet prospect may have been formed by mixing large amounts of meteoric fluid with small amounts of magmatic fluid. The coexistence of liquid-rich and vapor-rich inclusions and presence of adularia and bladed calcite indicate that fluid boiling is caused the main mechanism of ore formation. The vein textures, ore mineral assemblages, alteration minerals and fluid inclusion data suggest that the Kyaukmyet prospect is a polymetallic low-sulfidation epithermal gold deposit.
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Martin, D. McB. "Giant iron-ore deposits of the Hamersley province related to the breakup of Paleoproterozoic Australia: New insights from in situ SHRIMP dating of baddeleyite from mafic intrusions: Comment and reply: COMMENT." Geology 34, no. 1 (January 1, 2006): e96-e96. http://dx.doi.org/10.1130/g22464.1.
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Muller, S. G., B. Krapeandzcaron, M. E. Barley, and I. R. Fletcher. "Giant iron-ore deposits of the Hamersley province related to the breakup of Paleoproterozoic Australia: New insights from in situ SHRIMP dating of baddeleyite from mafic intrusions: Comment and reply: REPLY." Geology 34, no. 1 (January 1, 2006): e97-e97. http://dx.doi.org/10.1130/g22654.1.
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Kononets, S. N., M. G. Valitov, and T. A. Kharchenko. "Magmatic control of gold mineralization in Western Primorye (by geophisical data)." Геология рудных месторождений 61, no. 4 (August 13, 2019): 44–60. http://dx.doi.org/10.31857/s0016-777061444-60.
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An analysis of the regional gravitational field of the north-east of China, Korea and Western Primorye was carried out. The distribution of gold deposits was compared with the development of Mesozoic magmatism and negative anomalies of the gravitational field. Based on the analysis of geological, mineragenic, petrophysical and geophysical materials, geological and geophysical zoning of the western part of the Khanka massif was performed, and a scheme for interpreting geological and geophysical data with elements of minerageny was drawn up. A connection was established between the anomalies of the magnetic and gravitational fields and the position of the supposed gold-bearing ore regions and nodes located in the zone of joints of the North China Triassic-Jurassic volcanic-plutonic belt with the Proterozoic substrates of the Khanka massif. According to geophysical data, Early Jurassic intrusions were identified as, controlling the location of the gold nodes. It was concluded that the gold mineralization is related to the Jurassic magmatism, which increases the prospects for the discovery of gold mineralization in the Khanka district of the Western Primorye.
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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 (November 11, 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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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 (January 19, 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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Yan, Shuang, Renjie Zhou, He-Cai Niu, Yue-xing Feng, Ai Duc Nguyen, Zhen-hua Zhao, Wu-Bin Yang, Qian Dong, and Jian-xin Zhao. "LA-MC-ICP-MS U-Pb dating of low-U garnets reveals multiple episodes of skarn formation in the volcanic-hosted iron mineralization system, Awulale belt, Central Asia." GSA Bulletin 132, no. 5-6 (October 14, 2019): 1031–45. http://dx.doi.org/10.1130/b35214.1.
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Abstract Volcanic-hosted iron deposits of the eastern Awulale metallogenetic belt in Central Asia possess a reserve of over 1.2 billion tons of iron ores and constitute one of the most important basements for high-grade iron resources in China. Skarns are widespread in these deposits and closely associated with iron mineralization. The ages of these skarns are unclear, and their genesis remains debated, preventing further investigation into their metallogenic processes. We focused on garnets in nine ore-bearing skarns from three large-scale iron deposits (Chagangnuoer, Dunde, and Beizhan) in the eastern Awulale belt. U-Pb dating was conducted on these garnets using our in-house reference material, the Taochong garnet (TC-13, Pb-Pb isochron age: 126.2 ± 2.3 Ma, initial 207Pb/206Pb ratio: 0.845 ± 0.022). Laser-ablation–multicollector–inductively coupled plasma–mass spectrometry (LA-MC-ICP-MS) was employed in the garnet U-Pb dating, and high-precision U-Pb ages (0.3%–1.6%) were obtained, highlighting the advantages of LA-MC-ICP-MS in dating low-U minerals. The garnet U-Pb ages of the nine skarn samples fall into three groups, i.e., 329.0 ± 5.1–326 ± 3.3 Ma (two samples), 316.3 ± 2.9–311.2 ± 2.4 Ma (six samples), and 295.6 ± 1.0 Ma (one sample), implying three episodes of skarn alteration in the volcanic-hosted iron mineralization system. The first and second episodes of skarns formed as a result of contact metasomatism between coeval volcanic rocks and limestone, and they have economically important iron mineralization. The third was likely caused by a local postcollision granitic intrusion, but its metallogenic potential deserves further assessment.
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Novikov, D. A., A. I. Gordeeva, A. V. Chernykh, F. F. Dultsev, and L. M. Zhitova. "The Influence of Trap Magmatism on the Geochemical Composition of Brines of Petroliferous Deposits in the Western Areas of the Kureika Syneclise (Siberian Platform)." Russian Geology and Geophysics 62, no. 6 (June 1, 2021): 701–19. http://dx.doi.org/10.2113/rgg20194079.
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Abstract —We present the results of study of the influence of trap magmatism on the geochemical composition of brines and on the geothermal regime of the Earth’s interior in the western areas of the Kureika syneclise. The Siberian trap province, which unites all cutting and layered tholeiite–basic magmatic intrusions and erupted basaltic lava, is the world’s largest Phanerozoic continental basalt province. Brines, hydrocarbon deposits, and organic matter of the sedimentary cover were subjected to a significant thermal impact as a result of the Permo-Triassic trap magmatism. During the trap intrusion, the maximum paleotemperatures in major Silurian (D’yavolskii), Ordovician (Baikit), and Cambrian (Deltula–Tanachi, Abakun, and Moktakon) productive horizons reached 650 °C. The Paleozoic and Proterozoic deposits of the study area contain brines with TDS = 50–470 g/dm3. By chemical composition, they are of Na, Na–Ca, Ca–Na, Ca–Mg, and Ca chloride types (according to the classification by S.A. Shchukarev), with mixed Ca–Na and Na–Ca chloride brines dominating. The studied brines can be divided into three groups according to the degree of metamorphism: low (S1), medium (S2), and high (S3). The first group includes mainly sodium chloride brines with TDS = 50–370 g/dm3 (rNa/rCl = 0.60–0.95; S ≤ 100). The second (dominating) group comprises Na–Ca, Ca–Na, Ca, and Ca–Mg chloride brines with TDS = 150–470 g/dm3 (rNa/rCl = 0.10–0.87; 100 ≤ S ≤ 300). The third group is Ca–Na and Ca chloride brines with TDS = 223–381 g/dm3 (rNa/rCl = 0.12–0.45; S ≥ 300). We have first established changes in the hydrogeochemical field (major- and trace-component and gas compositions) with distance from the contacts of intruded dolerite sills and dikes. Hydrocarbons (CH4, C2H6, C3H8, i-C4H10, n-C4H10, i-C5H12, n-C5H12, and C6H14) and water-soluble components I, B, and NH4 were most actively subjected to destruction. For example, at a distance of 100 m from the intrusion zone, the water-dissolved gases are dominated by CO2 (>90 vol.%), and CH4 amounts to 5 vol.%, whereas at a distance of 250 m, the concentration of CO2 decreases to 30 vol.%, and that of CH4 increases to 60–70 vol.%. In addition to the negative effect on the hydrocarbon preservation in the contact zone (≤400 m), the intrusive trap magmatism favored the formation of hydrocarbons in remote horizons. The reaction of intruding traps with brines of the sedimentary cover led to the saturation of the latter with iron, aluminum, and silica, which suggests extraction of metals in the form of salts from magmatic melts into an ore-bearing fluid.
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Harlaux, Matthieu, Christian Marignac, Julien Mercadier, Marc Poujol, Marie-Christine Boiron, Kalin Kouzmanov, Alfredo Camacho, et al. "Multistage development of a hydrothermal W deposit during the Variscan late-orogenic evolution: the Puy-les-Vignes breccia pipe (Massif Central, France)." BSGF - Earth Sciences Bulletin 192 (2021): 33. http://dx.doi.org/10.1051/bsgf/2021023.
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The Puy-les-Vignes W deposit, located in the northwestern French Massif Central (FMC), is a rare occurrence of a wolframite-mineralized hydrothermal breccia pipe hosted in high-grade metamorphic gneisses. We present an integrated study of this deposit aiming to characterize the ore-forming hydrothermal system in link with the Variscan late-orogenic evolution of the FMC. Based on a set of representative samples from the host rocks and mineralization, we describe a detailed paragenetic sequence and we provide the major and trace element geochemistry of the granitic rocks and W–Nb–Ta–Sn–Ti oxide minerals, in situ U/Pb and 40Ar/39Ar geochronology, and a fluid inclusion study of quartz and wolframite. We demonstrate that the formation of this W-mineralized breccia pipe results from a multistage development related to four major episodes during the late Carboniferous. The first episode corresponds to the emplacement of an unexposed peraluminous granite at ca. 324 Ma, which generated microgranite dykes exposed at the present-day surface. The second episode is the formation of the quartz-supported breccia pipe and wolframite mineralization at ca. 318 Ma at a paleodepth of 7 km. The mineralizing fluids have a H2O–NaCl–CO2–CH4–N2 composition, a moderate-salinity (< 9 wt.% NaCl eq) and were trapped at high-temperatures (> 400 °C) during lithostatic to hydrostatic pressure variations caused by hydrofracturing of the host rocks. Wolframite deposition is interpreted to result from a W-rich intermediate-density magmatic fluid that exsolved from an evolved leucogranite and interacted with volatile-rich metasedimentary country rocks and/or possibly mixed with low-salinity metamorphic fluids of deep origin. The third episode corresponds to magmatic-hydrothermal Nb–Ta mineralization overprinting the W-mineralized system interpreted to be related to the intrusion at ca. 311 Ma of a rare-metal granite, which is part of a regional peraluminous rare-metal magmatism during the 315–310 Ma period. Finally, the last episode corresponds to disseminated Bi ± Au–Ag mineralization emplaced at ca. 300 Ma, which shares similar mineralogical features with late Carboniferous orogenic gold deposits in the FMC. The Puy-les-Vignes W deposit records, therefore, a multistage and long-lived development that extends over a timespan of 25 million years in a regional setting dominated by protracted peraluminous magmatism and high-temperature and low-pressure metamorphism. Although the local environment of ore deposition is atypical, our results show that the mineral assemblages, alteration styles, and fluid characteristics of the Puy-les-Vignes breccia pipe are similar to those of other peri-granitic W deposits in the FMC.
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Grinenko, L. N. "HYDROGEN SULFIDE-CONTAINING GAS DEPOSITS AS A SOURCE OF SULFUR FOR SULFURIZATION OF MAGMA IN ORE-BEARING INTRUSIVES OF THE NORIL'SK AREA." International Geology Review 27, no. 3 (March 1985): 290–92. http://dx.doi.org/10.1080/00206818509466416.
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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 (June 1, 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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Maxeiner, Ralf O., and Nicole M. Rayner. "Geology, U–Pb zircon geochronology, and geochemistry of PGE-bearing Neoarchean and Paleoproterozoic gabbroic rocks of the Peter Lake domain, southern Hearne craton, Canada." Canadian Journal of Earth Sciences 54, no. 6 (June 2017): 587–608. http://dx.doi.org/10.1139/cjes-2016-0104.
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The Peter Lake domain, a component of the Hearne craton in Saskatchewan, includes several intrusive complexes ranging in age from 2.70 to 1.83 Ga. Two gabbroic complexes (Swan River and Porter Bay) together represent one of the largest accumulations of Precambrian mafic intrusion, both metamorphosed at amphibolite facies. Sulfide-poor PGE occurrences are found in both complexes and share many textural and lithological characteristics with magmatic contact-type PGE–(Ni–Cu) deposits such as the chaotic Lac des Iles pluton and with layered stratiform deposits of large layered intrusions such as Bushveld or Stillwater. Lithologically, both complexes are dominated by leucocratic gabbronorite and gabbro, locally characterized by cumulate layering, cross-bedding, brecciated, and pegmatitic textures. U–Pb zircon crystallization ages between 2562 and 2560 Ma were obtained for the Swan River complex. sulfide formation is interpreted to be of magmatic origin rather than remobilized, as had been speculated by exploration geologists, and is therefore of the same age as the host gabbro. Geochemical data support the interpretation of a mantle plume origin in a subduction environment for the Swan River complex. The Porter Bay complex is much more restricted in areal extent and a leucocratic gabbronorite yielded a U–Pb zircon age of 1913 ± 1 Ma, which is interpreted as the crystallization age and the time of sulfide formation. Major and trace element geochemical data of Porter Bay complex rocks show a considerably more evolved character than the Swan River complex, and is interpreted as indicating emplacement in a continental arc environment.
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Zhu, Ligang, Jiajun Liu, Leon Bagas, Emmanuel John M. Carranza, Degao Zhai, Guangzhi Meng, Jianping Wang, Yinhong Wang, Fangfang Zhang, and Zhenjiang Liu. "The Yinachang Fe-Cu-Au-U-REE deposit and its relationship with intermediate to mafic intrusions, SW China: Implications for ore genesis and geodynamic setting." Ore Geology Reviews 104 (January 2019): 190–207. http://dx.doi.org/10.1016/j.oregeorev.2018.11.005.
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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 (April 26, 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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Gray, Tim, Judith Kinnaird, Justin Laberge, and Alejandro Caballero. "Uraniferous Leucogranites in the Rössing Area, Namibia: New Insights from Geologic Mapping and Airborne Hyperspectral Imagery." Economic Geology 116, no. 6 (September 1, 2021): 1409–34. http://dx.doi.org/10.5382/econgeo.4828.
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Abstract This study combines historical exploration data with new mapping, underpinned by airborne hyperspectral imagery, to provide a detailed camp-scale geologic view of the Rössing uranium mine area in the Damara orogen, Namibia. The Neoproterozoic Damaran metasedimentary host rocks to uranium deposits of the Rössing area structurally overlie Paleoproterozoic basement rock. Both units were subjected to polyphase deformation and upper amphibolite to lower granulite facies metamorphism during Pan-African orogenesis. The sequence was voluminously intruded by leucogranites, where younger phases may contain ore-grade uranium as magmatic uraninite and traces of betafite, together with secondary uranium minerals. Early, postdepositional modifications to the Damaran sequence included partial dolomitization of marble units and development of evaporite dissolution and diapiric breccias. Major pre-D3 extensional structures developed in conjunction with recumbent, isoclinal folding and acted to focus the intrusion of early, mostly barren leucogranites generated primarily through anatexis of Damaran metasediments. Syn-D4 leucogranites overprint complex interference fold geometries that resulted from D3 deformation. D4 leucogranites were emplaced under predominantly ductile, transtensional conditions, into NNE-trending zones oriented highly oblique to all preexisting structures. These steeply dipping zones provided the prerequisite conditions for partial melt material to be derived from uraniferous basement lithologies. The concentration of magmatic uranium was promoted where leucogranite melt material interacted with carbonates and sulfide-bearing Damaran metasedimentary units. In the Rössing area these horizons occur at the Khan-Rössing Formation contact zone for the SJ, SK, SH, Z20, and Husab deposits and within and above the Arandis Formation for the Z19 deposit leucogranites.