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The Lanuoma and Cuona sediment-hosted Pb-Zn deposits hosted by Upper Triassic limestone and sandstone, respectively, are located in the Changdu area, SW China. Mercury concentrations and Hg isotopic compositions from sulfide minerals and potential source rocks (e.g., the host sedimentary rocks and the metamorphic basement) were investigated to constrain metal sources and mineralization processes. In both deposits, sulfide minerals have higher mercury (Hg) concentrations (0.35 to 1185 ppm) than the metamorphic basement rocks (0.05 to 0.15 ppm) and sedimentary rocks (0.02 to 0.08 ppm). Large variations of mass-dependent fractionation (3.3‰ in δ202Hg) and mass-independent fractionation (0.3‰ in Δ199Hg) of Hg isotopes were observed. Sulfide minerals have Hg isotope signatures that are similar to the hydrothermal altered rocks around the deposit, and similar to the metamorphic basement, but different from barren sedimentary rocks. The variation of ∆199Hg suggests that Hg in sulfides was mainly derived from the underlying metamorphic basement. Mercury isotopes could be a geochemical tracer in understanding metal sources in hydrothermal ore deposits.

The Xihuashan tungsten deposit, hosted in the late Jurassic granitic pluton in the Nanling Range of South China, has a total resource of about 81,300 tonnes of WO3 with an average ore grade of 1.08% WO3. Wolframite is the dominant ore mineral and intergrown with quartz in the main mineralization stage. Ore-forming fluids trapped in wolframite have δD and δ18O values from −82‰ to −64‰ and 7.4‰ to 8.8‰, respectively. Those in quartz have similar δD (−72‰ to −58‰) and δ18O (6.8‰ to 8.0‰) values, indicative of a magmatic fluids simultaneously trapped by quartz and wolframite. LA-ICP-MS analyses for individual fluid inclusion show that this mineralizing fluid contains measurable Li, Rb, Cs, K, Na, Ti, Cu, Zn, As and W (1–125 ppm with average of 19 ppm) while depleted in Fe and Mn. The wolframite from the Xihuashan tungsten deposit contains high FeO (10.9–17.7 wt%) and MnO (5.9–12.7 wt%) contents with Fe/(Fe + Mn) atomic ratio of 0.46 to 0.75, thus requires the availability of external Fe and Mn. We detect that the Fe and Mn contents in mica from the greisen are remarkably lower than primary mica from granite. Some magmatic micas were observed in greisen and were subjected to hydrothermal alteration. Compared to the core, the rim of these micas depleted in Fe, Mn, F, and Na. The siderite and pyrophanite are formed along cleavage planes of altered magmatic mica that are evidence to be due to Fe and Mn release during granite alteration. Thus, we demonstrate quantitatively that magmatic fluids at Xihuashan provide W in solution, whereas the hosted granite alteration contributes Fe and Mn to precipitate wolframite. It is also supported by wolframites have trace and rare earth elements characteristics similar to those of granite and some characteristics similar to the greisen. Therefore, the ore-forming fluids has components derived from the last highly evolved residual granitic melt and components acquired by releasing through the hosted granite alteration. Fluid-rock interaction exert a principle control on wolframite precipitation. Based on mineralogy, fluid inclusion and stable isotope, we proposed three-stage process to illustrate the genetic link between tungsten mineralization and granite.

The Lanuoma deposit, located in the Sanjiang Tethyan metallogenic domain, shows a characteristic assemblage of Pb-Zn-Sb mineralization, distinguished from those in other sediment-hosted base metal deposits of this region. The ore textures reveal two mineralization stages: the early stage is characterized by Zn mineralization with occurrences of porous pyrite (Py2) and yellowish-brown sphalerites (Sp1), and the late stage is characterized by Sb-Pb mineralization with occurrences of subhedral-euhedral pyrite (Py3), yellowish-white sphalerites (Sp2), sulfosalts consisting of boulangerite, zinkenite, sorbyite and plagionite and calcite veins. The framboidal pyrites (Py1) predate Pb-Zn-Sb mineralization. Py2 has higher Zn contents (16.97–621.67 ppm, mean: 181.17 ppm) than Py3 (Zn: 0.76–323.44 ppm, mean: 29.58 ppm) by up to one order of magnitude. The Se contents of Py2 (Se: 5.46–87.82 ppm, mean: 50.96 ppm) are also one order of magnitude higher than those of Py3 (Se: 1.64–10.99 ppm, mean: 4.35 ppm). Sp1 is characterized by one order of magnitude higher contents of Fe (381.99–9046.64, mean: 4875.50 ppm) and Se (4.02–72.51 ppm, mean: 34.70 ppm) than Sp2 (Fe: 287.53–584.02 ppm, mean: 416.75 ppm; Se: 2.89–10.80 ppm, mean: 6.20 ppm). However, the average content of Cd (4256.38 ppm) in Sp2 is almost twice that in Sp1 (2635.74 ppm). The higher Se contents in Py2 coupled with higher Se and Fe contents in Sp1 indicate that Py2 and Sp1 had higher precipitation temperatures than Py3 and Sp2. Sulfur isotope compositions of pyrites and sphalerites acquired by NANO-SIMS and LA-MC-ICP-MS suggest two origins: the sulfur of Py2 (δ34S: −3.0 to 2.3‰), Sp1 (δ34S: 0.2–0.9‰) and Sp2 (δ34S: 0.7–2.5‰) was mainly of magmatic source, and sulfur reduced via thermochemical sulfate reduction participated in the formation of Py3 (δ34S: 0.2–6.0‰) and S-Sb-Pb minerals intergrown with Py3. The sulfur isotope compositions of Py1 (δ34S: −31.8 to −19.4‰) indicate a biogenic origin associated with bacterial sulfate reduction. A fluid mixing model is suggested to interpret the genesis of the Lanuoma Pb-Zn-Sb deposit: mixing of a reduced S-bearing fluid with a metalliferous basinal brine resulted in the precipitation of sulfides. Temperature was the most important factor controlling metal precipitation in the Lanuoma deposit.

More than 90% of the tungsten resources of China are in the Nanling region of South China, and the Yaogangxian vein deposit is the largest tungsten deposit in this region. The tungsten deposits have ages of 150–160 Ma, and are spatially, temporally and genetically related to granites which were previously believed to be produced by crustal anatexis. This paper provides He and Ar isotope data of fluid inclusions in pyrite and arsenopyrite from the Yaogangxian W veins. 3He/4He ratios range from 0.41 to 3.03 Ra (where Ra is the 3He/4He ratio of air = 1.39 × 10−6), and 40Ar/36Ar ratios from 328 to 1,191. Moreover, there are excellent correlations between He and Ar isotopic compositions. The results suggest that the ore-forming fluids are a mixture between a crustal fluid containing atmospheric Ar and crustal 4He and a fluid containing mantle components. It is likely that the former is a low temperature meteoric fluid, and the later is a fluid exsolved from the W-associated granitic magma, which formed by crustal melting induced by intrusion of a mantle-derived magma.

The Xihuashan tungsten deposit, Jiangxi province, China, is a world-class vein-type ore deposit hosted in Cambrian strata and Mesozoic granitic intrusions. There are two major sets of subparallel ore-bearing quartz veins. The ore mineral assemblage includes wolframite and molybdenite, with minor amounts of arsenopyrite, chalcopyrite, and pyrite. There are only two-phase aqueous-rich inclusions in wolframite but at least three major types of inclusions in quartz: two- or three-phase CO2-rich inclusions, two-phase pure CO2 inclusions and two-phase aqueous inclusions, indicating boiling. Fluid inclusions in wolframite have relatively higher homogenization temperatures and salinities (239–380°C, 3.8–13.7 wt.% NaCl equiv) compared with those in quartz (177–329°C, 0.9–8.1 wt.% NaCl equiv). These distinct differences suggest that those conventional microthermometric data from quartz are not adequate to explain the ore formation process. Enthalpy–salinity plot shows a linear relationship, implying mixing of different sources of fluids. Although boiling occurred during vein-type mineralization, it seems negligible for wolframite deposition. Mixing is the dominant mechanism of wolframite precipitation in Xihuashan. δ34S values of the sulfides range from −1.6 to +0.1‰, indicative of a magmatic source of sulfur. δ18O values of wolframite are relatively homogeneous, ranging from +4.8‰ to +6.3‰. Oxygen isotope modeling of boiling and mixing processes also indicates that mixing of two different fluids was an important mechanism in the precipitation of wolframite.

The Xujiashan antimony deposit is hosted by marine carbonates of the Upper Sinian Doushantuo and Dengying Formations in Hubei Province, South China. Our Sr isotopic data from pre- and syn-mineralization calcites that host the mineralization show that the pre-mineralization calcite displays a narrow range of 87 Sr/ 86 Sr ratios (0.7096 to 0.7097), similar to the ratios of the Sinian seawater, and high Sr concentrations (2645 to 8174 ppm). In contrast, the syn-mineralization calcite exhibits low Sr concentrations (785 to 2563 ppm) and high 87 Sr/ 86 Sr ratios (0.7109 to 0.7154), which is interpreted as the result of addition of radiogenic strontium during the antimony mineralization. The study of Sr isotopes suggests that their Sr component to the pre-mineralization calcite derived directly from the host rocks (i.e. the Sinian marine carbonates), while radiogenic 87 Sr for the syn-mineralization calcite derived from the underlying Mesoproterozoic Lengjiaxi Group basement through hydrothermal fluid circulation along the major fault that hosts the mineralization. The Pb isotopic ratios of stibnite are subdivided into two groups (Group A and Group B), Group A is characterized by higher radiogenic lead, with 206 204 Pb/

In this paper the authors present the REE concentrations and Sr and Nd isotopic compositions of fluorites from the Bailashui tin deposit of the Furong ore field, southern Hunan Province. The results showed that the total amount of REE in fluorites is usually low, ranging from 0.705 to 8.785 μg/g with the chondrite-normalized REE distribution patterns similar to those of the Qitianling granites in the study area, characterized by LREE-enrichment patterns with pronounced negative Eu anomalies. The fluorites vary in Sr isotopic composition within the range of 0.7083–0.7091, the values are lower than those of the granites and higher than those of the host carbonate rocks in this area. The ɛNd(t) values of fluorites vary between −9.4 and +10.3, revealing that both the crust-and mantle-source materials were involved in the ore-forming hydrothermal fluids. Combined with previous studies on this ore deposit, the Bailashui tin deposit is temporally and spatially closely related with granitic magmatism in this area. The hydrothermal fluorites are the product of fluid/rock interactions between granitic magmatic hydrothermal fluid and marine carbonate rocks. The REE and F in the ore-forming fluid were derived from the granites, whereas Sr in the ore-forming fluid came mainly from the granitic magmatic hydrothermal fluid and marine carbonate rocks, although variations in Sr isotopic composition cannot be explained by a simple mixture of these two end-members. Evidence demonstrated that the ore-forming fluids are of crustal-mantle mixing origin, but that the fluids were probably incompletely homogenized and this may be caused by inhomogeneous mixing of the fluids of different sources.

South China is rich in vein-type hydrothermal uranium deposits hosted in granitic, volcanic, and carbonaceous and siliceous pelitic sedimentary rocks. The uranium deposits are spatially associated with extensional structures and/or mantle-derived mafic dikes. Both the uranium deposits and mafic dikes are Cretaceous to Tertiary in age, temporally coincident with the crustal extension. Carbon isotope analyses of calcite deposited in the main-stage mineralization in the veins from 12 representative uranium deposits yield δ13C values of ore-forming fluids mainly from −4 to −8 per mil, which are permissive of a mantle origin for the CO2 in the ore-forming fluids. A mantle origin is consistent with the association of the deposits with mafic dikes and the 3He/4He ratios of ore-forming fluids (e.g., 0.10–2.02 Ra for the volcanic-hosted Xiangshan uranium deposit). Isotopic compositions of H and O demonstrate that water in the ore-forming fluids is predominantly meteoric in origin. Ore-forming temperatures ranged approximately from 150° to 250°C. Uranium-rich crustal rocks in South China may have been the sources for the uranium. Crustal extension and associated mafic magmatism are considered to have heated the rocks and allowed CO2 (possibly from mantle sources) to migrate upward and to mix with CO2-poor meteoric water. The CO2-rich hydrothermal fluids mobilized uranium from the source rocks and then the uranium was deposited in various host rocks to form the uranium deposits.

The Furong tin deposit, located in southern Hunan Province, China, is a large, newly discovered deposit with an estimated Sn reserve of about 700,000 tons. The deposit is spatially and temporally associated with the A-type Qitianling granite. The 3He/4He ratios of fluid inclusions trapped in sulfides from the deposit range from 0.13 to 2.95 Ra, indicating a mixed crust-mantle source, similar to that of the Qitianling granite complex. Lead isotopes in feldspars of the granite (mostly in the range of 206Pb/204Pb = 18.547–19.180, 207Pb/204Pb = 15.598–15.825, 208Pb/204Pb = 37.912–39.068) and in sulfide minerals (206Pb/204Pb = 18.467–18.836, 207Pb/204Pb = 15.503–15.772, 208Pb/204Pb = 38.607–39.099) are essentially the same, indicating that the lead in both was derived mainly from the upper crust, with a small mantle component. The sulfur isotopic values of the ore minerals vary widely, ranging from − 26.1‰ to + 10.4‰, but are mainly within the range of + 0.2‰ to + 10.4‰, implying that the S in the hydrothermal fluids was derived mainly from magmatic fluids, with minor contributions from the mantle, sedimentary rocks and biogenic material. The He, Pb and S isotopes all confirm that the ore-forming fluids of the Furong deposit were magmatic in origin, derived from the melts that produced the Qitianling A-type granite. The tin mineralization occurs within, or along the margins of, the Qitianling granite complex, and the timing of the mineralization coincides with the intrusive age of the granite. The available data suggest that the emplacement of the granites and the mineralization was related to mantle upwelling and extension of the lithosphere in South China during the Mesozoic.

The Furong tin orefield, located in southern Hunan, China, is a newly-discovered super-large tin orefield. In contrast to most other tin deposits associated with S-type granites, the Furong tin deposit is closely associated with the Qitianling A-type granite. The 3He/4He ratios of fluid inclusions in pyrite and arsenopyrite from this orefield range from 0.13 to 2.95 Ra. The influence of various post-mineralization processes on the helium isotopic composition of ore-forming fluid inclusions are estimated negligible. Thus, the analytical values of helium isotopic composition basically represent the original values of ore-forming fluids at the time they were trapped. The 3He/4He ratios of ore-forming fluids from the Furong orefield indicate the existence of mantle-source components. It supports the idea that both the Furong tin orefield and Qitianling granite formed under the geodynamic background of mantle upwelling and crustal extension.

187Os/188Os ratios in all sub-layers of the Co-rich ferromanganese crust MP5D17 from Line Seamount in Central Pacific have been systematically determined. The 187Os/188Os values in this crust are highly variable, ranging from 0.4262 to 1.0155. From the bottom to the top, the osmium isotopic ratios of the crust display a regular variation trend, which correlates well with its changes in structure and texture in the vertical profile. In comparison with the evolution curve of Os isotopic composition in seawater over the past 80 Ma, a similar evolution tendency can be found with respect to the Os isotopic composition of the crust in this study. It is preliminarily concluded that the crust MP5D17 began to grow at about 72 Ma, and underwent three growth hiatuses, corresponding to the geological ages of 64, 53 and 37 Ma, respectively.

The Xikuangshan antimony mine located at Central Hunan, China, is the largest antimony deposit in the world. Hydrothermal calcites from the Xikuangshan Mine display relatively large variations in REE abundance and Sm/Nd ratios and are characterized by MREE- and HREE-enriched and LREE-depleted patterns. Sm–Nd isotopic compositions of syn-sulfide calcites fall on well-defined lines in the isochron plot. Calcites from early- and late-stage mineralization form two distinct isochrons corresponding to 155.5±1.1 and 124.1±3.7 Ma, respectively. The isochron ages suggest that Sb mineralization took place during the Late Jurassic–Early Cretaceous Period in the Xikuangshan district, consistent with previous geological observations and with independent isotope data. Samarium–neodymium dating of calcites shows potential for determining ages of hydrothermal mineralization.

The research on Samarium-Neodymium isotope systematics of hydrothermal calcites from the Xikuangshan antimony deposit, Central Hunan, places precise timing constraints on the Sb mineralization in this area. It is revealed that the Xikuangshan deposit formed during the late Jurassic-early Cretaceous Period, the early- and latestage mineralization took place at (155.5± 1.1) Ma and (124.1±3.7) Ma, respectively. The accurate age determination of mineralization is very crucial for revealing the super-enrichment mechanism of the element Sb at the Xikuangshan mine, and lays some foundations for the further understandings of its ore genesis and mineralization mechanism.