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The Xianghualing large tin-polymetallic skarn deposit is located in the Nanling W-Sn metallogenic belt, South China, showing distinct spatial zoning of mineralization. From the contact between granite and carbonate rocks, the mineralization transitions from proximal skarn Sn ore to cassiterite-sulfide ore and more distal Pb–Zn-sulfide ore. This study reveals the fluid evolution and genetic links among these different ore types. The physical and chemical characteristics of fluid inclusions from each ore types indicate that the skarn Sn ore, cassiterite-sulfide ore, and Pb–Zn-sulfide ore all originated from the identical magmatic fluid exsolved from the Laiziling granite. Their formation, however, is controlled by diverse fluid evolutionary processes and host rock characteristics. The Sn–Pb-Zn-rich fluids were primarily derived from cooled and diluted magmatic brine, which is generated by boiling of initial single phase magmatic fluid. Mixing of magmatic brine with meteoric water is crucial to form skarn Sn ore. Redox reactions of aqueous Sn (II) complexes with As (III) species and/or minor CO2 during short cooling period of ore-forming fluid is likely an effective mechanism to form high-grade cassiterite-sulfide ores, accompanied by favorable pH conditions maintained through interaction with carbonate host rocks. The later stage addition of meteoric water prompts the formation of Pb–Zn-sulfide ore. Comparing these findings with the characteristics of initial or pre-ore magmatic fluids in both mineralized and barren granitic systems indicates that high Sn content in the pre-ore fluids and the suitable fractional crystallization degree of the parent magma may determine high Sn mineralization potential in granitic magmatic-hydrothermal systems.

The Baotan tin deposit (23 Mt @ 0.43% Sn) is located in the Jiuwandashan–Yuanbaoshan area, South China. It is hosted in Neoproterozoic mafic/metasedimentary rocks and apical portions of the Pinying granite pluton. Six alteration and mineralization stages have been identified: pre-ore alteration, cassiterite greisen, cassiterite–tourmaline–quartz vein, cassiterite–quartz vein, cassiterite–sulfide vein, and post-ore quartz/calcite–quartz vein stages. Tin mineralization is mainly in the cassiterite greisen, cassiterite–tourmaline–quartz, and cassiterite–quartz vein stages. The deposit is characterized by widespread tourmalinization. Both pre-ore and ore-stage tourmaline is schorl. Tourmaline from pre-ore tourmaline–quartz nodules has elevated Al2O3 and F contents and Fe/(Fe + Mg) and Na/(Na + Ca) ratios, which are probably controlled by the initial magmatic fluid. Ore-stage tourmaline shows low Al2O3 and F contents and Fe/(Fe + Mg) and Na/(Na + Ca) ratios, which are likely influenced by the surrounding mafic rocks. LA–ICP–MS U–Pb dating on two cassiterite samples from disseminated cassiterite–tourmaline–quartz ore and cassiterite–quartz vein yields 206Pb/238U weighted mean ages of 832 ± 5 Ma and 834 ± 4 Ma (2 σ), respectively. These two dates are consistent with the previously reported zircon U–Pb ages of 834–835 Ma for the Pingying granite, which indicates that tin mineralization is related to the granite. The granite has low magnetic susceptibility and zircon Ce4+/Ce3+ ratios, which are similar to those of Sn-bearing ilmenite-series granites. Our study confirms the Neoproterozoic tin mineralization event in South China and indicates that the Neoproterozoic highly fractionated S-type granites in the southeastern margin of Yangtze Block have a great potential for tin mineralization.

The Ayawilca deposit in Pasco, Peru, represents the most significant recent base-metal discovery in the central Andes and one of the largest undeveloped In resources globally. As of 2018, it hosts an 11.7 Mt indicated resource grading 6.9% Zn, 0.16% Pb, 15 g/t Ag, and 84 g/t In, an additional 45.0 Mt inferred resource grading 5.6% Zn, 0.23% Pb, 17 g/t Ag, and 67 g/t In, and a separate Sn-Cu-Ag inferred resource of 14.5 Mt grading 0.63% Sn, 0.21% Cu, and 18 g/t Ag. Newly obtained U–Pb dates for cassiterite by LA-ICP-MS (22.77 ± 0.41 and 23.05 ± 2.06 Ma) assign the Ayawilca deposit to the Miocene polymetallic belt of central Peru. The polymetallic mineralization occurs as up to 70-m-thick mantos hosted by carbonate rocks of the Late Triassic to Early Jurassic Pucará Group, and subordinately, as steeply dipping veins hosted by rocks of the Pucará Group and overlying Cretaceous sandstones-siltstones of the Goyllarisquizga Group. Relicts of a distal retrograde magnesian skarn and cassiterite (stage pre-A) were identified in the deepest mantos. The volumetrically most important mineralization at Ayawilca comprises a low-sulfidation assemblage (stage A) with quartz, pyrrhotite, arsenopyrite, chalcopyrite, Fe-rich sphalerite, and traces of stannite and herzenbergite. Stage A sphalerite records progressive Fe depletion, from 33 to 10 mol% FeS, which is compatible with the observed transition from low- to a subsequent intermediate-sulfidation stage (B) marked by the crystallization of abundant pyrite and marcasite. Finally, during a later intermediate-sulfidation stage (C) sphalerite (up to 11 mol% FeS), galena, native bismuth, Cu-Pb-Ag sulfosalts, siderite, Mn-Fe carbonates, kaolinite, dickite, and sericite were deposited. This paragenetic evolution shows striking similarities with that at the Cerro de Pasco Cordilleran-type polymetallic deposit, even if at Ayawilca stage C did not reach high-sulfidation conditions. The occurrence of an early retrograde skarn assemblage suggests that the manto bodies at Ayawilca formed at the transition between distal skarn and skarn-free (Cordilleran-type) carbonate-replacement mineralization. Mineral assemblages define a T-fS2 evolutionary path close to the pyrrhotite-pyrite boundary. Buffering of hydrothermal fluids by underlying Devonian carbonaceous phyllites of the Excelsior Group imposed highly reduced conditions during stage A mineralization (logfO2 <  − 30 atm). The low fO2 favored efficient Sn mobility during stages pre-A and A, in contrast to other known ore deposits in the polymetallic belt of central Peru, in which the occurrence of Sn minerals is minor. Subsequent cooling, progressive sealing of vein walls, and decreasing buffering potential of the host rocks promoted the shift from low- (stage A) to intermediate-sulfidation (stages B and C) states. LA-ICP-MS analyses reveal significant In contents in Fe-rich sphalerite (up to 1.7 wt%), stannite (up to 1908 ppm), and chalcopyrite (up to 1185 ppm). The highest In content was found in stage A sphalerite that precipitated along with chalcopyrite and stannite, thus pointing to the early, low-sulfidation assemblage as prospective for this high-tech metal in similar mineral systems. Indium was likely incorporated into the sphalerite crystal lattice via Cu+  + In3+  ↔ 2 Zn2+ and (Sn, Ge)4+  + (Ga, In)3+  + (Cu + Ag)+  ↔ 4 Zn2+ coupled substitutions. Indium incorporation mechanisms into the stannite and chalcopyrite crystal lattices remain unclear.

The Yinyan porphyry tin deposit in western Guangdong is spatially associated with quartz porphyry and granite porphyry. LA–ICP–MS zircon U–Pb dating defined an emplacement age of 78.5 ± 0.4 Ma for the quartz porphyry and 79.2 ± 0.9 Ma for the granite porphyry. LA–ICP–MS cassiterite U–Pb dating yielded Tera–Wasserburg lower intercept ages of 78.5 ± 0.6, 78.6 ± 1.2, and 78.2 ± 0.7 Ma, for cassiterite from a cassiterite–sulfide vein, cassiterite–sulfide ore, and a cassiterite–topaz–quartz stringer, respectively. Re–Os dating of molybdenite from seven different veins yielded an isochron age of 77.0 ± 0.5 Ma. All these new age data are indistinguishable within analytical uncertainty and, therefore, indicate a genetic relationship between the Sn mineralization and the porphyry magmatism in the Yinyan deposit. The REE tetrad effect and very low Nb/Ta and Zr/Hf ratios indicate that the quartz porphyry and the granite porphyry are highly evolved. The U–Pb dated cassiterite is enriched in Fe, W, and U and in high field strength elements (HFSEs) such as Zr, Hf, Nb, and Ta. The high Fe, Nb, and Ta contents may be responsible for the dark luminescence of cassiterite in CL images. The Zr/Hf ratio of cassiterite may potentially be used to distinguish the mineralization type. Cassiterite from pegmatites has lower Zr/Hf ratios (~ 5–6) in comparison with granite/greisen-related (~ 9–30) cassiterite. Cassiterite from the early hydrothermal stage typically contains higher amounts of Ti, Nb, Ta, Zr, and Hf than that from the late hydrothermal stage. In combination with published geochronological data of other Sn–W deposits in the western Guangdong Province, two Sn–W metallogenic events at ca. 85 and 77–80 Ma have been identified. These two metallogenic events are part of a larger-scale 75–100 Ma Sn–W mineralization event in South China, which we suggest was probably related to the subduction of the Neo-Tethyan oceanic plate.

Economic interest in indium (In) and other critical metals has accelerated efforts to understand how such elements occur in nature and the controls on their mineralogy. In this contribution, the distribution of In and other trace elements in the Dulong Zn–Sn–In deposit, China, is described, using a holistic approach which targets not only sulfides but also the potential for In and Sn within co-existing oxides and skarn silicates. Sphalerite is the most significant In carrier. Four distinct types of sphalerite are identified, which differ with respect to ore texture and the concentration of In (0.74–4572 ppm). Subordinate amounts of In also occur within chalcopyrite and within andradite garnet, an abundant mineral in the skarn at Dulong and possibly accounting for a significant proportion of total In. Tin is not especially concentrated in either sphalerite or chalcopyrite, occurring instead as cassiterite but with measurable concentrations also in magnetite and skarn silicates. The study confirms that the dominant substitution for In in sphalerite is 2Zn2+ ↔ Cu+ + In3+ but that Ag and Sn may also play a subordinate role in some sphalerite sub-types via the substitution: 3Zn2+ ↔ Ag+ + Sn2+ + In3+. The study highlights that concentrations of In in sphalerite are likely to be heterogeneous at scales from single mineral grains to that of the deposit. The observed partitioning of both In and Sn into skarn silicates, and to a lesser extent, oxides, is a critical factor that may significantly compromise estimations of by-product elements that would be economically recoverable during exploitation of sulfide ores.

Many medicinal plants found in Africa, such as Dovyallis caffra, have been reported to contain various bioactive compounds, which have been found to reduce metal salts into their corresponding metal-based nanoparticles. In this paper, the evaluation of synthesis, characterization, and biological properties of Dovyallis caffra-mediated cassiterite (SnO2) nanoparticles was carried out. The physicochemical properties of the synthesized material were investigated using X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The characterization studies revealed that the material possessed a single tetragonal cassiterite SnO2 phase, having a cluster-like foam appearance and an irregular spherical morphology with diameters ranging from 6.57 to 34.03 nm. The biological screening revealed that the prepared cassiterite (SnO2) nanoparticles exhibited cytotoxicity against the MCF-7 breast cancer cells, with an IC50 value of 62.33 µg mL−1, better than the standard drug 5-fluorouracil, with an IC50 value of 71.21 µg mL−1. The radical scavenging potential of the nanoparticles, using the DPPH assay, showed that it possessed a slightly better activity than ascorbic acid, a common antioxidant. These results suggest that the Dovyallis caffra-mediated cassiterite (SnO2) nanoparticles possess the potential to simultaneously generate and scavenge excess ROS, which in turn results in the exhibition of good cytotoxicity and antioxidant properties.

Rare Earth Element (REE) are a commodity that continues in increase due to technological advancements. Rare earth metals are not widely know for their resources. The scarcity of rare earth metals identifies the need to search for their geological existence by characterizing the megascopic and microscopic characteristics of rocks. The research was conducted in the Parmonangan subdistrict, North Sumatera. Sampling was carried out in the outcrop area. The rock samples were prepared by making slabs 2-3 cm thick, then cutting them into chips to fit the slides for a polarizing microscope, and subsequently characterized megascopically dan microscopically. Megascropical petrology results show that the rock type is plutonic with reddish brown and yellowish brown, with a massive structure with granite, tonalite, syienite and biotite granite. The results of the microscopic characteristics obtained a rock texture with phaneritic and porphyritic granularity with fine-medium crystal sizes (<1-5 mm). The average primary mineral composition is 20-50% quartz, 20-40 % feldspar, 12-20% biotite, and 5-10% secondary minerals cassiterite, 5-10% monazite and 3-10% zircon.

The large-scale Maoping W–Sn deposit in the Gannan metallogenic belt of the eastern Nanling Range, South China, spatially associated with the Maoping granite pluton, hosts total ore reserves of 103,000 t WO3 and 50,000 t Sn. Two different types of mineralization developed in this deposit: Upper quartz vein-type mineralization, mostly within the Cambrian metamorphosed sandstone and slate, and underneath greisen-type mineralization within the Maoping granite. Cassiterites from both types of mineralization coexist with wolframite. Here we report for the first time in situ U–Pb data on cassiterite and zircon of the Maoping deposit obtained by LA-ICP-MS. Cassiterite from quartz vein and greisen yielded weighted average 206Pb/238U ages of 156.8 ± 1.5 Ma and 156.9 ± 1.4 Ma, respectively, which indicates that the two types of mineralization formed roughly at the same time. In addition, the two mineralization ages are consistent with the emplacement age of the Maoping granite (159.0 ± 1.5 Ma) within error, suggesting a close temporal and genetic link between W–Sn mineralization and granitic magmatism. The two types of mineralization formed at the same magmatic-hydrothermal event. Cassiterite from both types of mineralization shows high Fe, Ta, and Zr contents with a low Zr/Hf ratio, suggesting that the ore-forming fluid should be derived from the highly differentiated Maoping granite pluton. Cassiterite in greisen has higher contents of Nb and Ta but a lower concentration of Ti compared with that in quartz vein, indicating that the formation temperature of greisen-type mineralization is little higher than that of quartz-vein-type mineralization.

This paper evaluates controls on cassiterite crystallization under hydrothermal conditions based on the textural setting and geochemistry of cassiterite from six different mineralization environments from the world-class Gejiu tin district, southwest China. The cassiterite samples feature diverse internal textures, as revealed by cathodoluminescence (CL) imaging, and contain a range of trivalent (Ga, Sc, Fe, Sb), quadrivalent (W, U, Ti, Zr, Hf), and pentavalent (Nb, Ta, V) trace elements, with Fe, Ti, and W being the most abundant trace elements. Cassiterite Ti/Zr ratios tend to decrease with distance away from the causative granite intrusion, and so has potential to be used as a broad tool for vectoring toward a mineralized intrusive system. Elemental mapping of cassiterite grains reveals that trace-element concentration variations correspond closely to CL zoning patterns. The exceptions are distinct irregular domains that sharply cut across the primary oscillatory zoning, as defined by the concentrations of W, U, Sb, and Fe. These zones are interpreted to have formed after primary cassiterite growth via fluid-driven dissolution-reprecipitation processes. Zones with low W and U (and Sb) and high Fe are interpreted to have formed during interaction with relatively oxidized fluids in which W and U are stripped from cassiterite due to cation exchange with Fe3+. Systematics of W, U, Sb, and Fe partitioning into cassiterite can, therefore, be used as a monitor of the relative oxidation state of the hydrothermal fluid from which cassiterite precipitates. Cassiterite U-Pb geochronology results obtained by LA-ICP-MS return ages between 77 and 83 Ma, which is consistent with previous geochronology from the region. Ages determined on zones of dissolution-reprecipitation are similar to ages for primary cassiterite growth, indicating a short (<3 m.y.) timespan of hydrothermal activity. These results confirm the potential of U-Pb dating of cassiterite for directly constraining the timing of Sn deposition.

Huangshaping is a world-class skarn deposit hosting abundant W–Sn polymetallic mineralization in the Nanling Range, South China. Although the geochemistry of skarn-hosted mineral deposits has been extensively studied, the role of the prograde-to-retrograde stage transition in the enrichment and precipitation of metallic elements in high-temperature systems has received little study to date. Here, we analyzed garnet, scheelite, and cassiterite in high-temperature granite porphyry-related W–Sn polymetallic system of the Huangshaping deposit to investigate these processes. Three generations of garnet (Grt I, Grt II, and Grt III), two generations of scheelite (Sch I and Sch II), and two types of cassiterite (Cst I and Cst II) were distinguished with regard to their mineral associations, microscopic characteristics, and geochemical features. The results show that grossular–andradite garnet formed from Al-rich andradite (Grt I, Al2O3: 8.18 wt%) in the early prograde stage and pure Fe-andradite (Grt III, Al2O3: 0.15 wt%) in the late prograde stage. Mo-rich scheelite (Sch Ia, MoO3: 19.41 wt%) formed in the prograde stage and coexisted with Grt III, sharing the same REE patterns. A shift from HREE enrichment in Grt I to HREE depletion in Grt III reflects progressive uptake of REEs by secondary mineral phases. Grt III has the highest average contents of W (905 ppm), Mo (19 ppm), and Sn (5610 ppm), suggesting an enrichment of metallic elements at the end of the prograde stage. In contrast, Mo-poor scheelite (Sch II, MoO3: 0.63 wt%) co-crystallized with molybdenite and fluorite in the retrograde stage and shares similar REE patterns with the granite porphyry. Skarn mineralization at Huangshaping was a two-step process controlled by metamorphic stage. The prograde stage was characterized by high temperatures and fO2 and a Cl-rich fluid, and it resulted in enrichment of ore-forming elements with minor scheelite precipitation. The retrograde stage was characterized by lower temperatures and fO2 and a F-rich fluid, and it resulted in major precipitation of ore minerals (scheelite, molybdenite, and cassiterite). Dissolution–reprecipitation reactions played an important role in extraction of metallic elements from decomposing anhydrous skarn minerals and formation of ore minerals. A decrease in the high-field-strength element (HFSE) content of cassiterite from proximal skarn (Cst I) to distal skarn (Cst II) indicates declining temperature accompanied by precipitation of fluorite. This study examines the transition from the prograde stage to the retrograde stage in the Huangshaping deposit, and it provides insights into the genesis of other skarn W–Sn polymetallic deposits in the Nanling magmatic–tectonic–metallogenic belt.