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Recently, the mineral potential of the area surrounding the granitic batholiths in the Nanling Range was highlighted by the discovery of a series of tungsten and tin deposits or occurrences hosted in or near the Penggongmiao and Guidong batholiths in southern Hunan Province, South China. However, the lack of high-precision geochronological data from these deposits has hampered the understanding of their ore genesis and further W-Sn exploration progress. Based on detailed geological investigations, we obtained precise Secondary Ion Mass Spectroscopy (SIMS) zircon U-Pb and muscovite Ar-Ar ages from the greisen-dominated Liuyuan tin deposit and Zhuyuanli tungsten deposit, which are located on the western margin of the Guidong batholith. The results show that the 40Ar/39Ar plateau age of muscovite (153.10 ± 0.96 Ma) from the Liuyuan tin deposit is consistent with the 40Ar/39Ar plateau age of muscovite (151.64 ± 0.96 Ma) from the Zhuyuanli tungsten deposit within analytical error. These data indicate that the W-Sn mineralization in the region occurred during the Late Jurassic, which is significantly later than the emplacement of the Caledonian (Early Paleozoic) ore-hosting Guidong granite batholith, as evidenced by the SIMS zircon U-Pb age data from the Liuyuan greisen (438.1 ± 2.6 Ma) and the Zhuyuanli greisenized granite (433.8 ± 3.1 Ma). The remarkable differences in age between the Guidong batholith emplacement and formation of these two W-Sn ore deposits indicate that the regional tungsten and tin mineralization is temporally and genetically associated with possibly concealed Late Jurassic granite at depth rather than with the surrounding Caledonian granite batholith. The uniform W-Sn mineralization age (153–151 Ma) of the Liuyuan and Zhuyuanli deposits suggests that significant Late Jurassic W-Sn ore-forming potential exists along the western margin of the Guidong batholith.

The Nanling Range, South China, was world-famous for hosting abundant granitoid-related copper-lead-zinc (Cu-Pb-Zn) polymetallic ore deposits and quartz vein-type wolframite (W) ore deposits, both of which have roughly similar formation ages predominately between 150 and 160 Ma with a peak of ca. 156 Ma. In this study, accessory minerals from typical Cu-Pb-Zn-bearing and W-bearing granitic rocks are compared in terms of elemental and isotopic compositions. Apatite from W-bearing granites in the Xihuashan pluton has lower eNd(t) value (−11.9 to −8.6) than that from Cu-Pb-Zn-bearing granitic rocks in Shuikoushan with eNd(t) value of −8.7 to −4.2 and initial 87Sr/86Sr ratio of 0.7097–0.7109. Zircon grains in Xihuashan, yielded eHf(t) value from −14.9 to −11.4, δ18O value from 8.6‰ to 10.4‰, and highly variable and negative δ7Li value (−45.8‰ to −3.8‰), whereas those in Shuikoushan have relatively higher eHf(t) value (−10.6 to −8.1), lower δ18O value (8.4‰–9.7‰), and highly variable δ7Li values from −12.7‰ to +17.6‰. In situ Hf-O-Li isotopic compositions of zircon and Sr-Nd isotopes of apatite, suggesting that the Shuikoushan granitic pluton was likely generated from dehydration melting of amphibolite from a metal-fertile mafic source in the middle-to-lower crust, whereas the Xihuashan granitic pluton could be derived from partial melting of metapelite with minor amphibolite in the middle to upper crust. The geochemical records in accessory minerals fingerprint that the Shuikoushan granitic magma was characterized by high Cl content (0.11–1.44 wt%) and logfo2 value (>ΔFMQ+1), whereas the Xihuashan granitic magma have elevated F (3.51–4.80 wt%) and Li (3.49–42.4 ppm) contents with low logfo2 value (

The Mesozoic Shuikoushan granitoid intrusion in the Jiangnan orogen between the Yangtze and the Cathaysia blocks in southern Hunan Province, South China, provides an opportunity to probe deep-crustal composition and structure, and to investigate the geodynamic evolution of South China. The intrusion is composed of granodiorite with I-type geochemical affinities and contains zircon with an U–Pb concordant age of 158.3 ± 1.2 Ma. Rocks from the intrusion have variable SiO2 from 58.4 wt.% to 65.2 wt.%, Al2O3 from 15.0 wt.% to 17.2 wt.%, TiO2 from 0.57 wt.% to 0.76 wt.%, and P2O5 from 0.27 wt.% to 0.52 wt.%. They have A/CNK from 0.97 to 1.23 (1.04 on average) and are dominantly peraluminous. They are characterized by enrichment in LREE ([La/Sm]N = 3.47–5.19) and LIL (e.g., K, Rb) and depletion in HFSE (e.g., U, Th) in primitive mantle normalized trace element diagrams. These geochemical features indicate that the rocks are I-type granodiorites and have undergone extensive fractional crystallization of hornblende, biotite, titanite, and apatite. All samples show negative eHf(t) (−10.6 to −8.1) and eNd(t) (−5.92 to −6.13) values, with relatively high initial 87Sr/86Sr (ISr) (0.7101–0.7102) and δ18O ratios (8.4–9.7‰). These values significantly differ from mantle values, suggesting that they are generated by the amphibole-dehydration melting of a mafic source in the middle-to-lower crust beneath the Jiangnan orogen. The emplacement of the Shuikoushan granitoid intrusion is contemporaneous with the late Jurassic to early Cretaceous extension within the Shi-Hang rift zone, indicating that it may have been formed under an extensional regime in response to both the Pacific superplume activity and westward subduction of the Pacific Plate. The extensional processes along with asthenosphere upwelling and basaltic underplating may have triggered the widespread late Jurassic granitoid intrusion in southern Hunan Province and possibly in South China.

The Shuikoushan ore district, located in southern Hunan Province, South China, contains Pb–Zn–Au mineralization hosted in the Devonian to Triassic strata and Mesozoic granodiorite intrusions. Ore minerals are mainly pyrite, sphalerite, galena and minor molybdenite. Molybdenite, usually intergrown with pyrite, formed during Pb–Zn hydrothermal mineralization. In order to determine the precise age of Pb–Zn mineralization and further understand the relationship between magma emplacement and hydrothermal mineralization in the ore district, molybdenite Re–Os dating and zircon SIMS U–Pb dating were undertaken. The zircon U–Pb dating reveals that the granodiorite intrusion was emplaced at 158.8 ± 1.8 Ma (MSWD = 0.40). Re–Os isotopic age of seven molybdenite samples yields model ages ranging from 157.5 ± 2.5 Ma to 161.0 ± 2.4 Ma, and gives a well-defined 187Re–187Os isochron age of 157.8 ± 1.4 Ma (2σ, MSWD = 1.3), indicating the timing of Pb–Zn mineralization in the Shuikoushan ore district at about 158 Ma. This date coincides well with the zircon SIMS U–Pb age of the granodiorite, revealing a genetic association between the Pb–Zn mineralization and the granitic magmatism. Combined with geochronological data published for other Pb–Zn–(Cu) deposits in southern Hunan, it can be concluded that the granodiorite-related Pb–Zn mineralization throughout southern Hunan mainly occurred at 160–156 Ma, rather than 180–170 Ma or 170–160 Ma as considered previously. The Pb–Zn mineralization and major W–Sn mineralization in southern Hunan are coeval and may be related to the same geological event.

Lead–zinc–copper (Pb–Zn–Cu) deposits in the western Kunlun Orogen of China are mostly distributed along the Keziletao–Kusilafu fault zones in the Palaeozoic clastic–carbonate rocks, which formed in a late Palaeozoic subsidence belt at the south-west margin of the Tarim platform. Geological and geochemical studies were conducted on these deposits including detailed field observation, petrographic study, and geochemical and isotopic analyses of sulfur, lead, strontium, rhenium–osmium, and argon isotopes, as well as fluid inclusion geochemistry. The characteristics of the deposits include: (1) Except for the Tiekelike Pb–Cu deposit associated with mid-Devonian rocks, all of the other deposits were developed in the lower layers of the early Carboniferous strata. These strata mostly comprise sedimentary dolomitic limestone, sandy limestone, black limestone, and calcareous shale. (2) The ore bodies are stratiform and host veins. The stratiform ores are coeval with host rocks (yielding ore-forming ages of 331–337 Ma), while the vein ore bodies are mostly massive deposits formed at 206–235 Ma. The isotopic compositions of the sulfur and lead reveal that the ore-forming elements originated from various sources. (3) The mineralization in cements of brecciated ore is a veinlet type, while in the breccias it is a disseminated type. The stratoid, disseminated, and framboidal structures of the ore reveal the synsedimentary ore-formation. However, the veins, mesh-veins, and massive structures indicate late stage hydrothermal mineralization. (4) The principal metallic minerals include sphalerite, galena, and pyrite, while the secondary oxide minerals include variable distributions of cerussite, anglesite and limonite. The gangue minerals include dolomite, calcite, quartz, sericite, and gypsum, with minor chert and barite. (5) The original host rocks likely experienced dolomitization, calcitization, and minor silicification. The ore deposits underwent hydrothermal alterations, sub-greenschist facies metamorphism, and brecciation. The ore deposits may have initially formed via syndeposition in a subsidence belt along the southwest margin of the late Paleozoic Tarim platform; these deposits were further modified during later hydrothermal alteration and orogenesis during the Triassic period.

The Xuebaoding deposit in the Songpan–Garze orogenic belt, western China, spatially associated with the Xuebaoding granitic complex, is a unique pegmatite-type Sn–W–Be deposit within the giant Songpan–Garze polymetallic belt. A lack of precise geochronological constraints on the timing of mineralization for this deposit has precluded definitive statements relating to a genetic link between ore formation and granitoid intrusion, up to now. To address the temporal relationship between the emplacement of granite and the spatially associated Sn–W–Be polymetallic mineralization in the Xuebaoding deposit, systematic cassiterite U–Pb and muscovite Ar–Ar dating were undertaken. U–Pb data of cassiterite analyzed by In-situ LA-MC-ICP-MS provided an isochron age of 193.6 ± 6 Ma (at 95% confidence level, MSWD = 4). The 40 Ar/ 39 Ar dating on the muscovite intergrown with the cassiterite sample yielded a plateau age of 194.50 ± 1.02 Ma (MSWD = 1.26), and an inverse isochron age of 194.53 ± 1.05 Ma (MSWD = 1.34). Both the Ar–Ar dates overlap the U–Pb date within uncertainties, placing the timing of tin mineralization at ~ 193–194 Ma. This is consistent with field geological relationships that show veins cutting marble and granite, and with previous Sm–Nd dating, within experimental error, for scheelite and indicates that Sn–W polymetallic mineralization at the Xuebaoding deposit occurred during the Early Jurassic. Combined with previous published trace element and REE data from the Xuebaoding granites and other ore minerals, as well as the timing of granite emplacement, the temporal and genetic associations between granite intrusion events and Sn–W mineralization of this deposit have been discussed in this paper. The results suggest that the Pankou granite is genetically related to the polymetallic mineralization in Xuebaoding Sn–W–Be deposit, and further demonstrate that the latest-phase of granitic intrusion is commonly favorable for Sn and/or W mineralization. Although the Pukou granite also exhibits close relationships with the ore formation in its spatial distribution and element characteristics, the possibility as a parent for this deposit is excluded duo to the time span from its emplacement to mineralization event that exceed the estimated life of modern geothermal systems (

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.

The Xihuashan complex intrusion in South China, which is emplaced at ca. 154 Ma, mainly comprises medium-grained porphyritic biotite granite, medium-grained biotite granite, and fine-grained two-mica granite. Medium-grained biotite and fine-grained two-mica granites are important tungsten-bearing granites and contain an unusual amount of garnet. Garnets from this intrusion are dominated by almandine and spessartine, which constitute 94% to 99% of the total molecular composition of the garnet. These garnets display unusual compositional zoning. The cores of these garnets are rich in heavy rare earth element (HREE), Y, Ca, and contain abundant HREE- and Y-rich mineral inclusions. Their rims are free of mineral inclusions and have low of these elements. Two types of fluorite inclusions exist in garnet: Y fluorite and Y-poor fluorite. Garnet exhibits specific Mn zoning with a relatively Mn-poor core but a relatively Mn-rich rim, thus constituting a specific “spessartine inverse bell-shaped profile” that belongs to typical magmatic garnets. All analyzed garnets have high REE content and exhibit HREE-enriched and LREE-depleted patterns with strong negative Eu anomalies. The incorporation of REE into garnet is in part controlled by its crystal chemistry, with REE3 + following a coupled substitution of the type [Fe2 +,Mn2 +]− 1VIII[REE3 +]+ 1VIII[Si4 +]− 1IV[Z3 +]+ 1IV. The texture and compositional zoning of garnet suggest that garnet growth is largely controlled by the pressure–temperature–composition condition of magmatic evolution, internal crystal-chemical parameters, and kinetics during mineral growth. The garnet core grows in near equilibrium with magmatic melt under a relatively high pressure–temperature (P–T) condition. By contrast, the garnet rim grows rapidly by the coexisting melt-fluid phase and CO2-rich volatile environment under a relatively low P–T condition, which is virtually unfavorable for the incorporation of REE into the magmatic garnet structure. Garnet fingerprints the magmatic-hydrothermal transition during crystallization of these granites.

The Xihuashan tungsten deposit in the central Nanling region, South China, is an important vein-type ore deposit hosted in Cambrian strata and Mesozoic granitic intrusions. Wolframite and molybdenite are the principal ore minerals. The gangue minerals are mainly quartz and muscovite. Wolframite and molybdenite are products of the first stage hydrothermal activity, whereas muscovite formed dominantly at the second stage. Molybdenite Re–Os and muscovite 40Ar/39Ar dating have been carried out to investigate the age of mineralization. Re–Os isotopic dating for molybdenite associated with wolframite yield a precise, well-constrained isochron age of 157.8 ± 0.9 Ma (MSWD = 1.5). Ar–Ar isotopic analyses of muscovite yield a plateau age of 152.8 ± 1.6 Ma, in agreement with an inverse isochron age of 152.8 ± 1.6 Ma, which is ~ 5 mys younger than the Re–Os age. The molybdenite Re–Os age is interpreted as the age of tungsten mineralization. This age coincides well with the zircon U–Pb age of the host granitic intrusion reported previously. The ~ 5 mys difference between molybdenite Re–Os and muscovite 40Ar/39Ar ages probably represents the duration of hydrothermal activity. The results show that the Xihuashan tungsten deposit is one of many important tungsten–tin deposits formed during 150 to 160 Ma associated with large-scale lithospheric extension in South China.

Northern Guangdong is an important part of Nanling tungsten–tin metallogenic belt, South China. The tungsten mineralization in this area consists of mainly quartz–wolframite vein-type mineralization, with W–Sn polymetallic deposits mostly distributed at the outer contact zone between concealed Late Jurassic granitic stocks and Cambrian–Ordovician low-metamorphosed sandstones and shales. Molybdenite Re–Os and muscovite 40Ar/39Ar isotopic dating of three typical tungsten vein-type deposits (Yaoling, Meiziwo, and Jubankeng) in northern Guangdong, show that two episodes of Late Jurassic W–Sn polymetallic mineralization occurred in this area: an early episode during the Late Jurassic (158–159 Ma) represented by the Yaoling, Hongling, and Meiziwo tungsten deposits, and a younger event during the Early Cretaceous (138 Ma) represented by the Jubankeng deposit. Analysis of available radiometric ages of several W–Sn deposits in the Nanling region indicate that these deposits formed at several intervals during the Mesozoic at 90–100, 134–140, 144–162, and 210–235 Ma, and that large-scale W–Sn mineralization in this region occurred mainly between 150 and 160 Ma.

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 Shizhuyuan ore deposit in southern Hunan Province is a world-class W–Sn–Bi–Mo occurrence hosted by Devonian limestone in the thermal aureole of the Qianlishan granite. Mineralization coincided with intrusion of the granite pluton during Mesozoic crustal extension in South China. We present new He and Ar isotope data for volatiles released from pyrite in the Shizhuyuan deposit. Concentrations of 40Ar range from 0.21 to 2.38 × 10−6 cm3 STP 40Ar/g, and 4He concentrations range from 0.8 to 65.1 × 10−6 cm3 STP 4He/g. 3He/4He ratios vary from 0.06 to 1.66 Ra (where Ra is the 3He/4He ratio of air = 1.39 × 10−6) and 40Ar/36Ar ratios range from 293 to 1072. The isotopic compositions of He and Ar indicate that the ore-forming fluids were mantle-derived, modified by air-saturated crustal fluids. Shallow-level boiling increased 3He concentrations, whereas crustal contamination decreased 3He/4He ratios in the magmatic fluids. The occurrence of mantle-derived components in the magmatic fluid indicates that the asso...

We report the first precise U–Pb isotope data on cassiterite from the large Xianghualing tin-polymetallic deposit in the central Nanling district, South China. The results show that four separates from sample XF-51 have a relatively narrow range of 206Pb/238U apparent ages, varying from 152 to 157 Ma, and the three 206Pb/238U apparent ages yield a weighted average value of 156 ± 4 Ma (MSWD = 0.32). Separates from two other cassiterite samples do not have sufficient radiogenic Pb to generate a reliable 206Pb/238U age. Seven separates from the above three cassiterite samples define a well-constrained 238U–206Pb isochron corresponding to an age of 157 ± 6 Ma (MSWD = 34). A comparison of the U–Pb cassiterite ages with published Ar–Ar dates on muscovite from this deposit and K–Ar age data on biotite from the pluton genetically related to the tin mineralization in this area demonstrates that the U–Pb isotope system of cassiterite is a potential geochronometer. Combined with the Ar–Ar dates of muscovite from this deposit, we can constrain the absolute age of tin-polymetallic mineralization in Xianghualing at 154–157 Ma. The dates obtained in this study, consistent with the published geochronological results from other important deposits in this region, reveal that the large-scale tungsten–tin mineralization in the central Nanling region was predominantly emplaced during 150–161 Ma.

The Yaogangxian deposit in the central Nanling region, South China consists of vein-type ore bodies hosted in Cambrian to Jurassic strata and Mesozoic granitic intrusions. Wolframite and molybdenite are the dominant ore minerals intergrown with gangue minerals of quartz, feldspar, phlogopite, and muscovite. We have carried out molybdenite Re–Os and phlogopite and muscovite 40Ar/39Ar dating to better understand the timing and genesis of mineralization. Re–Os dating of eight molybdenite samples yielded model ages ranging from 152.0±3.5 to 161.1±4.5 Ma, with an average of 156.0 Ma. The Re–Os analyses give a well-defined 187Re/187Os isochron with an age of 154.9±2.6 Ma (MSWD=2.4). Hydrothermal phlogopite and muscovite display extremely flat 40Ar/39Ar age spectra. Phlogopite yields a 40Ar/39Ar plateau age of 153.0±1.1 Ma, whereas muscovite yields a plateau age of 155.1±1.1 Ma. Both 40Ar/39Ar ages are in good agreement with the Re–Os ages, placing the timing of tungsten mineralization at about 154 Ma. This age is consistent with the field relationships. Our new data, when combined with published geochronological results from other major deposits in this region, suggest that large scale W–Sn mineralization occurred throughout the central Nanling region in the Late Jurassic.

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.