The paper discusses aspects of metallogenic classification of W, Sn, and Mo deposits and considers their affinities corresponding to different geodynamic settings. Most large W deposits correspond to the tungsten-polymetallic and tungsten-molybdenum metallogenic types and were formed in post-subduction (post-collisional and transform margin) settings. Tin-polymetallic deposits could be formed in post-subduction (post-collisional) and within-plate settings as well as in subduction settings, the latter, however, associated with steep-dipping subduction and asthenosphere mantle upwelling yet at the subduction stage. Consistently, this made the geodynamic regime similar to that in post-subduction (post-collisional) setting. Large W–Sn deposits more distinctly formed in post-subduction (post-collisional) settings. Rare metal-tin-tungsten, Sn-polymetallic, and W-Mo deposits formed also in the transitional (to within-plate) post-collisional and actual within-plate settings. Molybdenum deposits formed in subduction (Cu–Mo–Au deposits), post-collisional (Mo–W deposits), transitional, and within-plate (Mo, Mo–Au, and Mo–U deposits) settings. In the areas of polycyclic tectonic development, which included within-plate regime, polychronous W, Sn, and Mo deposits could be formed. Two evolutionary trends (“series”) of metallogenically-related W, Sn, and Mo deposits can be distinguished: (1) a “series” of molybdenum-free deposits (W-polymetallic, W–Sn, Sn-polymetallic and rare metal–Sn–W deposits), and (2) a “series” of deposits with significant Mo mineralization (Cu–Mo–Au, W–Mo–Cu–Au, Mo–W, Mo, and Mo–U deposits), with the respective differences of magmatic sources of productive intrusions. These evolutional trends of deposits are spatially separated in different metallogenic belts and segments, which correspond to belts/segments of ilmenite- and magnetite-series granitoids, respectively. In this regard, molybdenum-free deposits formed mostly in turbidite terranes of the accretion prism, whereas deposits with significant Mo mineralization formed in cratonic terranes with thick continental (cratonic granitic-gneissic) crust. W, Sn and Mo deposits are associated dominantly with magmatic complexes of mixed mantle-crust affinity including “hybrid” granitoid complexes, monzonitoid complexes of shoshonitic series, and anorogenic (A-type) granitic complexes. Melting of the Earth’s crust with various thickness and compositions could have been induced by deep-seated sources both in the oxidized metasomatized lithospheric mantle and in the reduced asthenospheric mantle, with their respective redox differences affecting the redox-potential of the final hybrid magmas.
The Xiangyangshan Pb-Zn deposit, situated in the eastern Xicheng ore field of the West Qinling region, extends the Changba-Lijiagou Pb–Zn mineralization. This deposit lies within a major Chinese polymetallic belt rich in Pb, Zn, and other metals. To clarify its poorly understood genesis, we conducted geological surveys, LA-ICP-MS trace element analysis, and sulfur isotope studies on sphalerite from different mineralization stages. Results show that later-generation sphalerite (Sp2) is enriched in Mn, Fe, Cu, Co, and In, while earlier Sp1 is richer in Cd and Ag. Geochemical indicators, including Zn/Cd and Zn/Fe ratios coupled with principal component analysis, suggest a moderate-temperature ore-forming environment, with Sp2 forming at higher temperatures (299–304°C) than Sp1 (254–263°C). Trace elements like Fe, Cd, and Ag enter the sphalerite lattice mainly via isomorphism. Sulfur isotopes indicate that sulfur originated from seawater sulfate or reduced sulfur in strata, with thermochemical sulphate reduction (TSR) as the primary reduction mechanism. The geological features of the Xiangyangshan deposit and the trace element distributions in sphalerite are consistent with characteristics of sedimentary exhalative (SEDEX) deposits. However, the ore bodies exhibit significant post-mineralization tectonic and metamorphic deformation. Taken together, the deposit is interpreted as a hydrothermal exhalative sedimentary-hydrothermal superimposed transformation deposit.
The distribution of platinum-group elements (PGE) in a newly identified type of high-Rh ores from the three Norilsk deposits (Norilsk 1, Norilsk 2 and Talnakh) have been investigated using inductively coupled plasma mass spectrometry with laser ablation (LA-ICP-MS) and scanning electron microscopy. The high-Rh pyrrhotite ores are distinguished by the elevated contents of Rh, Ir, Os, Ru (Rh + IPGE) > 2 g/t, low Pd/Rh < 10 and Cu/Ni < 2 ratios, compared to other types of the Norilsk ores, and form the spatially distinct parts within the orebodies. More than 80–90
The territory of Southeastern Eurasia includes areas of Russian Transbaikalia, Mongolia and China, where hydrothermal and infiltration uranium deposits are widespread, formed in the Mesozoic–Cenozoic period in the area of postplatform tectonic-magmatic activation or, in terms of plate tectonics, in an “extensive rift system.” It is shown that the accumulation of ore-bearing volcanogenic-sedimentary strata and uranium mineralization of different genesis is synchronized in time with the processes of rifting and magmatism, which in turn are a consequence of the interaction of the Eurasian, Indian, and Pacific plates. The stretching conditions ensured the emergence of depressions in which sedimentary basins and volcano-tectonic structures were formed. The successive alternation of orogenic uplifts and riftlike depressions in the Mesozoic–Cenozoic period created favorable hydrodynamic conditions for the emergence of uranium mineral systems in this area, from Late Jurassic to Early Cretaceous hydrothermal to late Cenozoic infiltration systems. Hydrothermal and infiltration uranium systems of Southeastern Eurasia are characterized by multifluidity associated with a variety of processes of formation of solutions circulating in the depths of the territories of development of tectonic-magmatic activation. In these systems, due to the emergence of hydraulic gradients as a result of relief differentiation, cold meteoric waters capable for carrying uranium entered from the surface. Thermal fluids formed above magmatic chambers and thermal brines formed in deep horizons of sedimentary basins came from the basement or depths of the basins to the same systems. The potential of uranium volcanogenic ore genesis is associated with the development of thermoconvective circulation of uranium-transporting fluids whereas the potential for infiltration formation of exogenous mineralization was most fully realized in the arid climate zone. High-grade uranium mineralization was formed in areas where solutions of different genesis were mixed, which indicates such an important characteristic of mineral systems as multifluidity.
The chemical composition, zonation, and crystallization sequence of minerals of the columbite and wodginite groups in quartz-albite-potassium feldspar-muscovite pegmatites, albitites, quartz-muscovite rocks and muscovite-lepidolite glimmerites of the Vishnyakovskoye rare metal pegmatite deposit were studied. The Ta/(Ta + Nb) (Ta*) = 0.39‒0.50 and Mn/(Mn + Fe) (Mn*) >0.80 ratios in the first crystallized columbite-(Mn) show that the pegmatite melt underwent deep differentiation before its emplacement and was enriched in fluorine. The evolution of the composition of columbite-group minerals is reflected in the increase of Ta* values from 0.80 to 0.91 with an increase in Mn* to 1.00. Wodginite is represented by a Sn- and Mn-rich variety with Sn/ΣB = 0.59‒0.82, Ti/ΣB < 0.20, and Mn/ΣA = 0.88‒1.00. The shape of the grains, their zonation, and the evolution of the chemical composition indicate a predominantly magmatic genesis of the columbite-group minerals and wodginite in quartz-albite-potassium feldspar-muscovite pegmatites. In the albitization and greisenization zones, the columbite-group minerals (CGM) are largely inherited from the pegmatites; in the quartz-muscovite zone, partial dissolution of tantalite-(Mn) and removal of Ta and Nb occur, and in the muscovite-lepidolite glimmerites, tantalite-(Mn) and wodginite are again formed. Wodginite-group minerals (WGM) from different zones of pegmatite veins have highly variable compositions, indicating an important role of post-magmatic processes in their genesis. In muscovite-lepidolite glimmerites, Ta- and Mn-rich wodginite with Ta/ΣB = 0.50‒0.70 and Mn/ΣA = 0.90‒1.00 (tantalowodginite) is formed, after which wodginite itself with Sn/ΣB = 0.50‒0.82 crystallizes. In albitites, wodginite is replaced by Ti- and Fe-rich wodginite and ferrotitanowodginite with Ti/ΣB = 0.52‒0.76 and Mn/ΣA = 0.29‒0.49. The albitization and acid leaching processes manifested in pegmatites do not significantly affect the distribution of ore components, but anomalous accumulation of Ta, Sn, and Nb is noted in locally developed muscovite-lepidolite glimmerites.
