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The Tongcun deposit is a medium-sized porphyry Mo deposit in the eastern section of the Qin-Hang metallogenic belt, South China. Fluid inclusions and scanning electron microscope -cathodoluminescence (SEM-CL) of different generations of quartz from multi-stage veins were studied to reconstruct the evolution of the porphyry hydrothermal system at the Tongcun Mo deposit. Four stages of hydrothermal veins were recognized at Tongcun, including the early barren quartz vein, the main ore-stage quartz-molybdenite vein and quartz-polymetallic vein, and the late quartz-calcite (± pyrite) vein. SEM-CL imaging revealed that these veins were composed of at least four successive quartz generations (A, B, C and D) in which only the quartz B and C are in close association with Mo mineralization. Fluid inclusions from the Tongcun deposit can be classified into four types, namely three- or four-phase CO 2 -rich (C), two-phase vapor-rich (V), two-phase liquid-rich (L) and three-phase liquid-rich solid-bearing (S) type. The C type fluid inclusions were further divided into C1 subtype with higher carbonic proportion (50–70% vol%), C2 subtype with lower carbonic proportion (25–40% vol%) and molybdenite daughter mineral, and C3 subtype with lower carbonic proportion (25–40% vol%) but no daughter mineral. The V type fluid inclusions were further divided into V1 subtype with higher filling degree (0.2 to 0.3) and V2 subtype with lower filling degree (< 0.1). The C1 and V1 subtypes were secondary inclusions in quartz phenocrysts (P) and primary inclusions in quartz A, and show homogenization temperatures (Th) of 257–378 °C, with salinities of 0.6–9.6 wt% NaCl equivalent. The immiscibility assemblage of coexisting C2 and V2 subtype inclusions in quartz B exhibit a Th of 237–285 °C and salinities of 1.2–4.4 wt% NaCl equivalent. C3 subtype inclusions in quartz C display Th of 191–267 °C and salinities of 0.2–4.6 wt% NaCl equivalent. Finally, the L and S type inclusions in quartz D display Th of 133–245 °C and salinities of 0.4–7.0 wt% NaCl equivalent. The fluid immiscibility is restricted in quartz B and only generated low salinity end member inclusions, similar to the immiscible behavior commonly observed in orogenic gold deposits. The likely molybdenite daughter minerals were only observed in C2 subtype inclusions in quartz B, indicating enrichment of Mo had occurred during fluid immiscibility. Combined with SEM-CL texture and Raman analysis, we proposed that a rapid Mo precipitation occurred in the narrow interval during or immediately after fluid immiscibility and thus formed the Tongcun Mo deposit. The CO 2 -rich ore-forming fluid and continental arc setting of the Tongcun deposit provide a special case of CO 2 -rich porphyry Mo system in non-collision settings. [ABSTRACT FROM AUTHOR]

• Types and temporal-spatial distribution of W and Sn mineralization in South China are summarized based on over 130 major deposits. • Metallogenic models illustrating the combination of diverse mineralization styles or metal assemblages are proposed for W-Sn deposits in South China. • Fluid and melt inclusion compositions are tested as new index to evaluate W and Sn mineralization potential in granitic system. South China is one of the most important tungsten-tin metallogenic areas in the world. Based on the up-to-date geological and chronological data of more than 130 deposits of economic significance, this paper preliminarily summarized the main types and temporal-spatial distribution characteristics of the large-scale tungsten and tin mineralization related to granite in South China. The statistical results show that skarn and quartz-vein types are the most important tungsten metallogenic styles, while skarn and cassiterite-sulfide types are the most important tin metallogenic styles in South China. Tungsten and tin mineralization related to granite in South China are multi-aged, but the largest scale of mineralization is developed within the Yanshanian period. Tungsten mineralization, the majority of which represented by the Nanling and Ganbei metallogenic belts, mainly formed from the Late Jurassic to Early Cretaceous (160 ∼ 120 Ma), while the most important tin mineralization formed in the Late Cretaceous (110 ∼ 80 Ma, peaking at 90 ∼ 80 Ma) and Late Jurassic (160 ∼ 150 Ma) as represented by the Youjiang Basin and Nanling metallogenic belt, respectively. The combined occurrence of different mineralization styles or metal assemblages in individual deposit and sometimes within the same orefield is the most striking feature of granite-related tungsten-tin deposits in South China, and a comprehensive understanding of their patterns are of great significance to guide ore prospecting. To address this issue, this paper proposed several combined metallogenic models and prospecting directions for tungsten-tin mineralization in South China based on recent researches and exploration progresses from typical examples including the Yaogangxian, Chuankou, Maoping, Shizhuyuan, Dachang and Gejiu deposits or orefields. In addition, conventional petrological and mineralogical characteristics that differentiates tungsten and tin granites are summarized, and on this basis the chemical composition of both melt inclusion and early stage fluid inclusion from granitic magmatic-hydrothermal systems were tested as new index to evaluate the tungsten and tin mineralization potential of granitic system. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

[Display omitted] • The hydrothermal process is divided into four stages from early to late, and two stages of Sn mineralization are identified. • Fluid mixing may be the predominant mechanism for the minor Sn mineralization occurred in stage II. • Fluid cooling may be the predominant mechanism for the abundant cassiterite precipitation in stage III. • The ore-forming fluid mainly derived from highly evolved granitic magma, and the genesis of cassiterite is consistent with typical skarn-type Sn deposits. The Xianghualing Sn-polymetallic deposit is a large skarn-type Sn deposit located in the Nanling polymetallic metallogenic belt, South China. The ore bodies are controlled by NE-trending faults and mainly hosted in the contact of Middle Devonian carbonate rock and granite. The Xianghualing deposit is divided into four mineralization stages, and two stages of Sn mineralization are identified. The mineralization stages from early to late include stage I (prograde stage), stage II (retrograde stage), stage III (cassiterite-magnetite-arsenopyrite-topaz-quartz stage), stage IV (sphalerite-galena-pyrite-chalcopyrite-quartz-calcite stage). Stage II is the initial stage of Sn mineralization where only minor cassiterite precipitates, and stage III is the main Sn mineralization stage where abundant cassiterite precipitates. On this basis, fluid inclusion microthermometry and Raman spectroscopy analyses were carried out for ore and/or gangue minerals at different stages. In addition, trace element composition analysis was also conducted on cassiterite. These data can contribute to reveal the fluid properties, evolution and formation mechanism of Xianghualing deposit. Three types of fluid inclusions were identified in different mineralization stages, including halite-bearing multi-phase inclusions (Type B), liquid-rich two-phase inclusions (Type L) and vapor-rich two-phase inclusions (Type V). Garnet (stage I) contains Type B inclusions and Type V inclusions, with homogenization temperatures and salinities of 511–549 °C, 37.6–48.9 wt% NaCl equiv. and 551–559 °C, 4.0–5.1 wt% NaCl equiv., respectively. Topaz (stage II) contains Type L inclusions with homogenization temperatures of 408–445 °C and salinities of 9.5–12.4 wt% NaCl equiv. Cassiterite (stage III) contains Type L inclusions with homogenization temperatures of 368–417 °C and salinities of 8.7–11.5 wt% NaCl equiv. Quartz (stage IV) contains Type L inclusions with homogenization temperatures of 162–227 °C and salinities of 2.6–5.0 wt% NaCl equiv. The temperature and salinity of the fluid from stage I to stage II decreased significantly, recording intense meteoric water mixing. The temperature of the fluid decreased from stage II to stage III, while the salinity changed little, indicating that, except for minor meteoric water mixing, cooling of fluid is predominant. The temperature and salinity of the fluid from stage III to stage IV continued to decrease, recording the further mixing of meteoric water. From stage II to stage III, the evolution temperature of the fluid is basically consistent with the temperature indicated by trace elements (Nb, Ta, Ti) of cassiterite in the two stages. Fluid mixing may be the predominant mechanism for the minor Sn mineralization occurred in stage II. Fluid cooling may be the predominant mechanism for the abundant cassiterite precipitation in stage III, which is accompanied by redox reactions of Sn (II)-Cl complexes with As (III) and/or CO 2 as potential oxidants, and acid neutralization of carbonate rocks. Combined with the cassiterite composition, it is indicated that the ore forming fluid of the Xianghualing deposit mainly derived from the highly evolved granitic magma in the region, and the genesis of cassiterite is consistent with that of typical skarn-type Sn deposits. [ABSTRACT FROM AUTHOR]

The Maoping tungsten deposit is a wolframite–quartz vein type deposit located in southern Jiangxi province, China. Both steeply and gently dipping veins are developed and are characteristics of vertical zonation that can be divided into five zones depending on the thickness of the veins from the top to the bottom: (I) thread zone, (II) veinlet zone, (III) moderate vein zone, (IV) thick vein zone, and (V) thin out zone. Quartz from zones III–V contains two–phase aqueous inclusions (type Iq) and two– or three–phase CO 2 –bearing inclusions (type IIq). However, quartz from zone I contains only type Iq inclusions. Wolframite from zones III–V contains ubiquitous two–phase aqueous inclusions (type Iw), with rare CO 2 –bearing inclusions (type IIw) occurring in wolframite from zone IV. In quartz from zones III–V, coexisting type Iq and type IIq inclusions as well as their microthermometric behaviors suggest that fluid immiscibility had occurred during quartz deposition. Fluid inclusion data obtained from zone I show a trend of temperature decrease along with decreasing salinity, indicating that fluid mixing took place. In contrast, type Iw inclusions in wolframite from zones III–V record a distribution pattern of large homogenization temperature range but relatively constant salinity. We therefore propose that wolframite precipitation was predominantly triggered by simple cooling rather than immiscibility or fluid mixing which has been recorded by fluid inclusions in coexisting quartz. Spatially, the widespread type Iq inclusions in quartz from zone V up to zone I exhibit an overall slight and continuous decrease of homogenization temperature and salinity, whereas type Iw inclusions in wolframite from these zones are identical regardless of the depth. This may imply that wolframite was precipitated from an early, hot and short–lived fluid pulse that flushed out of the magma into hydrothermal system via fractures and nucleated wolframite crystals along the vein edges by simple cooling. The vein quartz however, was formed by subsequent fluid pulses which may reside for a longer time until the depletion of the heat source. Hydrogen and oxygen isotope data of quartz (δ 18 O fluid = 2.4‰ to 7.1‰ V–SMOW and δD = − 43‰ to − 83‰ V–SMOW) and wolframite (δ 18 O fluid = 6.1‰ to 8‰ V–SMOW and δD = − 45‰ to − 64‰ V–SMOW) indicate ore–forming fluids had a magmatic source, with limited input of meteoric water occurring only in zone Ι. By integrating the deposit geology, mineral assemblages, fluid inclusion and H–O isotopes, we propose that the gently dipping veins in the Maoping tungsten deposit are consistent with the “five floor” model that may have broader applications to exploration of wolframite–quartz vein type deposits. [ABSTRACT FROM AUTHOR]

The Fujiawu Cu–Mo deposit is located in the southeastern part of South China. Mineralization and alteration at Fujiawu include stage 1 barren quartz-K-feldspar ± biotite veins and stage 2 quartz-molybdenite veins with potassic alteration, stage 3 quartz-pyrite-chalcopyrite veins with phyllic alteration, and stage 4 barren quartz-pyrite-calcite-chlorite ± epidote veins with propylitization. Two-phase liquid-rich (type I), two-phase gas-rich (type II) and halite-bearing (type III) aqueous inclusions were identified at Fujiawu. The last two types of fluid inclusions are absent in stages 1 and 4. Type I inclusions in stage 1 veins demonstrate homogenization temperatures (Th) of 409 to 556 °C, with salinities of 7.8–14.4 wt.% NaCl equivalent. Type III inclusions that homogenize by vapor bubble disappearance (type III a) and coexisting type II inclusions in stage 2 veins have Th of 370–460 °C and 374–505 °C, with salinities of 37.9–52.7 and 3.1–8.2 wt.% NaCl equivalent, respectively. Type IIIa inclusions that homogenize by vapor bubble disappearance and coexisting type II inclusions in stage 3 veins yield Th 277–454 °C and 323–450 °C, with salinities of 33.5–49.8 and 1.5–7.9 wt.% NaCl equivalent, respectively. Type I inclusions in stage 4 have Th of 146 to 279 °C, with salinities lower than 4.9 wt.% NaCl equivalent. Type III inclusions that homogenize by halite disappearance (type III b) in stages 2 and 3 of veins were not formed during fluid boiling processes and could yield extremely high trapping pressures. The abundant presence of boiling fluid inclusion assemblages at Fujiawu suggests that extensive multi-stage boiling events promoted the large scale Cu–Mo mineralization. Type IIIb inclusions cannot be regard as the end member of boiling inclusion assemblages and cannot be used to calculate trapping conditions. The estimated trapping pressures estimated by type IIIa inclusions are 132 to 284 bars and 44 to 264 bars in stages 2 and 3, respectively. Re–Os dating of molybdenite gives a weighted average 187 Re/ 187 Os model age of 172 ± 1 Ma, in response to a localized extensional environment due to a far-field stress at the South China plate margin resulting from the initial paleo-Pacific plate northwestward subduction. The high Re contents in molybdenite, in combination of previously reported high MgO contents of ore-related porphyries and regional history, indicate that ancient subduction-modified lithospheric mantle was crucial for the Fujiawu Cu–Mo deposit. [ABSTRACT FROM AUTHOR]

The Huangshan gold deposit is hosted in the ductile shear zone of the metamorphosed Precambrian Chencai Group in the Jiangshan-Shaoxing fault zone between the Yangtze and the Cathaysia blocks. The mineralization can be divided into three stages: pre-ore stage barren quartz-sericite veins, ore stage quartz-pyrite veins, and post-ore stage calcite-quartz veins. A combination of fluid inclusion microthermometry and Raman spectroscopy analysis reveals three types of fluid inclusions: H 2 O-CO 2 -NaCl (type I), CO 2 -rich aqueous (type II), and aqueous fluid inclusions (type III). Primary fluid inclusions in the pre-ore stage quartz veins are mainly type I with low salinities (≤ 6 wt.% NaCl equivalents) that homogenized to liquid at moderate temperatures (298 to 371 °C). Primary fluid inclusions in the ore stage quartz veins contain the following: type I fluid inclusions with variable CO 2 volumetric ratios, which homogenized to liquid at moderate temperatures (287 to 376 °C) and with moderate salinity (2.0 to 7.7 wt.% NaCl equivalents), type II (CO 2 rich) inclusions of low salinity (1.6 to 4.8 wt.% NaCl equivalents), and type III fluid inclusions of low-moderate salinity (4.7 to 9.5 wt.% NaCl equivalents). In particular, some type II and III inclusions occur in the same isolated cluster or fracture, where type II inclusions homogenized into the CO 2 phase (263 to 304 °C) and type III inclusions into the aqueous phase (226 to 305 °C) at almost the same temperature. This occurrence indicates that fluid immiscibility took place during ore-forming processes. Aqueous secondary fluid inclusions in the trans-granular fracture of quartz grains and primary inclusions in the post-ore stage calcite display low homogenization temperature (135 to 227 °C and low to moderate salinity (0.2 to 5.5 wt.% NaCl equivalents). Trapping pressures of the immiscible fluid inclusion assemblages from ore stage veins are between 87 and 162 MPa, indicating the gold-bearing quartz veins were precipitated deeper than 3.2 km. These pressures are too high and exclude the previously proposed epithermal model for this deposit. Raman spectroscopy shows that volatile compositions in the CO 2 -bearing inclusions are primarily CO 2 with minor N 2 . The oxygen and hydrogen isotope compositions (δD = − 56‰ to − 67‰; δ 18 O = 3.3‰ to 4.4‰) imply a likely metamorphic origin of the ore stage fluids. Sulfur (+ 4.1‰ to + 5.4‰) and lead ( 206 Pb/ 204 Pb: 17.606 to 17.704; 207 Pb/ 204 Pb: 15.490 to 15.536; 208 Pb/ 204 Pb: 37.701 to 38.083) isotopes of the ore minerals show similar signatures to the host rocks of the Chencai Group. These data strongly indicate that the Huangshan gold deposit is an orogenic-type deposit. Combined with previously published geochronology data and the geological setting, we stress the existence of a Caledonian orogenic gold belt along the Jiangshan-Shaoxing fault zone and thus suggest an extensive target area for further gold exploration along the Jiangshan-Shaoxing fault zone. [ABSTRACT FROM AUTHOR]

The Dongxiang copper deposit is located in northeastern Jiangxi Province, South China. Ore bodies in the Zishan Formation of this province are primarily stratoid and lentiform and show a close spatial association with Jurassic intrusive rocks. The current debates generally concentrate on whether the Dongxiang copper deposit is a Carboniferous sedimentary deposit or, alternatively, a Jurassic porphyry–skarn deposit. Three stages of mineralization can be observed in this deposit: the pre-ore, main ore, and post-ore stages. The massive sulfide ore bodies are identified as the main ore stage, whereas the pyrite-quartz veins and barren quartz veins are identified as pre-ore and post-ore stages, respectively. Three fluid inclusion types were recognized: two-phase vapor-rich fluid inclusions (type 1), two-phase liquid-rich fluid inclusions (type 2), and halite-bearing fluid inclusions (type 3). All three of these types of inclusions are present in the main copper mineralization stage, but only type 2 inclusions occur in both the pre-ore and post-ore stages. Type 2 inclusions in the pre-ore stage display homogenization temperatures (Th) of 349–392 °C, with salinities of 1.4–8.1 wt.% NaCl equivalent. In the main ore stage, types 1 and 3 inclusions show similar Th at 289–346 °C and 273–348 °C but contrasting salinities of 0.4–4.5 and 29.4–41.9 wt.% NaCl equivalent, respectively. In the post-ore stage, type 2 inclusions have Th of 144–228 °C and salinities of 0.4–6.0 wt.% NaCl equivalent. The coexisting types 1 and 3 inclusions in the main ore stage have similar Th ranges but contrasting salinities, which indicates that fluid boiling occurred. The determined hydrogen and oxygen isotopic values for these fluids (δD from − 42‰ to − 69‰; δ 18 O H2O 5.04‰ to 9.01‰), based on analysis of fluid inclusions and host quartz, imply that the inferred ore fluids were principally derived from magmatic water. The lead isotopic compositions of sulfides from the ores and plagioclases from the adjacent porphyry indicate that they share a common origin. The sulfides from the ores show δ 34 S values of 0.3–3.2‰, also suggests a magmatic source. As the fluid inclusions and isotopic compositions strongly suggest a magmatic origin, this argues against a SEDEX origin for this deposit. In addition, the presence of stratoid and lentiform ore bodies and the absence of skarn alteration minerals suggest that the Dongxiang copper deposit is best described as a Manto-type rather than a porphyry–skarn deposit. [ABSTRACT FROM AUTHOR]

The Yongping copper deposit is located in the Gandongbei metallogenic belt, South China. Stratiform-like copper ore bodies are hosted in limestones of the Upper Carboniferous Outangdi Formation. These ore bodies were previously believed to be products of the Carboniferous sedimentary exhalative (Sedex) mineralization, but they also appear to be related to the Late Mesozoic intermediate-acidic stocks at Yongping. The ore minerals are pyrite, chalcopyrite, with minor magnetite, sphalerite and galena. The gangue minerals are quartz, sericite, garnet, diopside, scapolite, wollastonite, tremolite, epidote, calcite and chlorite. Four stages of alteration and mineralization can be observed. Garnet, diopside and scapolite were formed in the earliest prograde skarn stage. The pre-ore barren quartz–pyrite veins that accompany tremolite, epidote, magnetite and chlorite, were subsequently formed due to the destruction of the earlier skarn. The stratiform-like copper ore bodies, with minor quartz–polymetallic veins, were formed in the main mineralization stage. The post-ore stage is characterized by late quartz–calcite ± pyrite veins. Fluid inclusions in quartz from the pre-ore barren quartz–pyrite veins, stratiform-like copper ore bodies, and post-ore quartz–calcite ± pyrite veins were studied. Fluid inclusion petrography shows that two-phase liquid-rich (type I), two-phase vapor-rich (type II), and halite-bearing (type III) fluid inclusions are present in these three generations of hydrothermal quartz. Type II and type III inclusions occur only in quartz from the stratiform-like copper ore bodies, whereas type I inclusions occur in all stages of hydrothermal quartz. Type I inclusions in pre-ore quartz–pyrite veins have homogenization temperatures of 300–398 °C and salinities of 3.6–8.1 wt.% NaCl equivalent. Type II and coexisting type III inclusions in the stratiform-like copper ore bodies share similar homogenization temperatures of 233–324 °C and two contrasting salinity groupings of 0.4–3.2 wt.% and 28.2–39.0 wt.% NaCl equivalent, respectively. The coexistence of type II and type III inclusions and their similar homogenization temperatures but contrasting salinities suggest that fluid boiling processes occurred. Type I inclusions in the post-ore quartz–calcite veins have homogenization temperatures of 122–250 °C and salinities of 0.2–6.8 wt.% NaCl equivalent. The hydrogen and oxygen isotopic compositions of hydrothermal quartz indicate that the mineralizing fluids gradually evolved from a magmatic to meteoric source. The Pb–Pb dating of pyrite from stratiform-like copper ore bodies suggests that mineralization took place in the Jurassic. The skarn alteration, inferred boiling fluid inclusion assemblages, stable isotopic features of magmatic fluids, and Jurassic ages imply that the Yongping copper deposit is a Jurassic skarn copper deposit rather than a Carboniferous Sedex deposit. [ABSTRACT FROM AUTHOR]

The giant Dexing porphyry copper deposit is one of the largest porphyry copper deposits in South China. This paper presents new LA-ICP-MS zircon U–Pb dating, element and Sr–Nd–Hf isotopic data for the ore-related porphyries in the Dexing porphyry deposit. The Dexing ore-related porphyries were emplaced during the Middle Jurassic (ca. 170 Ma), and were characterized by high-Mg adakitic geochemical features, including high MgO and Sr contents and high Mg#, Sr/Y and La N /Yb N ratios, low Y and Yb contents, and lacking a negative Eu anomaly, which suggest that they were probably derived from the delaminated thickened lithosphere. A non-arc setting in the Middle Jurassic is indicated by the absence of arc rocks and the presence of rifting-related igneous rock associations in the interior of South China. The non-arc setting suggests that the copper-rich lithosphere in the Dexing area was enriched by an ancient subduction event prior to the Late Mesozoic. The regional geological history and the Neoproterozoic two-stage Nd–Hf isotope model ages imply that the ancient subduction event occurred in the Neoproterozoic in response to the Jiangnan Orogen between the Yangtze and Cathaysia blocks. Thus, we infer that the giant Dexing porphyry copper deposit was formed in the Middle Jurassic by remelting of the copper-rich Neoproterozoic subduction-modified lithosphere. Previous studies of the low-Mg ore-related porphyries in the adjacent Yinshan copper polymetallic deposit proposed a copper-rich juvenile crust as their magma source. In this study, the high Mg contents of the Dexing ore-related porphyries stress the significant contribution of the subduction-modified lithospheric mantle or a higher melting temperature. [ABSTRACT FROM AUTHOR]

There are several gold deposits in the eastern section of the regional Jiang−Shao Fault between the Yangtze and Cathaysia Blocks in South China. Auriferous quartz veins in these deposits are strictly hosted in second-order NE-trending ductile shear zones. The ores generally contain low amounts of sulfide minerals (<5%), with pyrite as the most common sulfide mineral hosting native gold. Detailed fluid inclusion work and Rb–Sr dating were conducted on the auriferous quartz veins from the Pingshui and Huangshan deposits. H 2 O–CO 2 inclusions (type I) and aqueous inclusions (type II) ubiquitously coexist in the main mineralization stage veins in the Huangshan and Pingshui deposits. Type I and II inclusions in the Huangshan deposit have similar homogenization temperatures at 214–282 °C, but different salinities with 1.2–6.0 and 2.7–8.7 wt.% NaCl equivalent, respectively. In the gold orebodies from the Pingshui deposit, type I and II inclusions also have similar homogenization temperatures ranging from 236 to 304 °C, but different salinities ranging from 1.2 to 6.4 and from 3.2 to 9.8 wt.% NaCl equivalent, respectively. Fluid inclusion observations and microthermometric results show that the ore fluids are low salinity and CO 2 -rich. Petrography and microthermometric results of fluid inclusions suggest that extensive fluid immiscibility occurred during the gold mineralization stage. Rb–Sr dating of quartz-hosted fluid inclusions (ca. 450 Ma) for the gold mineralization at Pingshui, combined with previous radiometric age data (ca. 397 Ma) of gold mineralization at Huangshan, suggest that the regional gold mineralization was formed in the Early Paleozoic. This study suggests that there is an Early Paleozoic orogenic gold belt in the eastern section of the Jiang−Shao Fault, formed in response to the coeval northward underthrusting of the Cathaysia Block beneath the Yangtze Block during the Caledonian Orogeny in South China. [ABSTRACT FROM AUTHOR]

Numerous wolframite–quartz vein type tungsten deposits are present in the Gannan metallogenic belt, South China, including the Piaotang and Dangping deposits in the Chong-You-Yu ore cluster, the Dajishan deposit in the Jiulianshan ore cluster, and the Pangushan deposit in the Yushan ore cluster. The ores generally consist of quartz and wolframite, with variable amounts of base metal sulfides. Wolframite and quartz are intergrown, but the genetic relationships between them are still ambiguous. Quartz contains two-phase aqueous inclusions (type I) and two- or three-phase CO 2 -bearing inclusions (type II), but wolframite only contains two-phase aqueous inclusions (type Iw). The homogenization temperatures for primary inclusions in wolframite are generally 40 to 100 °C higher than those in quartz in a single deposit. Moreover, there are variable amounts of CO 2 in inclusions in quartz, but no CO 2 -rich inclusions are identified in coexisting wolframite. Type I fluid inclusions in quartz from the Piaotang deposit show that fluid mixing is predominant in the formation of quartz veins, whereas fluid inclusions from the Dangping deposit suggest that simple cooling is the primary factor. Quartz from the Dajishan and Pangushan deposits contains both type I and coexisting type II inclusions, indicating a process of fluid immiscibility. The homogenization temperatures of two-phase aqueous inclusions (type Iw) in wolframite from all of these deposits show a clearly decreasing trend with constant salinities, implying a simple cooling process. Hence, simple cooling, fluid mixing, and fluid immiscibility take place in quartz but only simple cooling happens in wolframite. Our results show that the gangue and ore minerals from the Late Mesozoic tungsten deposits in the Gannan metallogenic belt have different homogenization temperatures, volatile compositions, and fluid processes. The gangue minerals do not provide reasonable estimates of the depositional conditions of the ore minerals even though they are intimately intergrown. [ABSTRACT FROM AUTHOR]

• The Yaogangxian granitic intrusion is a composite complex formed with ages of 161 ± 3 and 157 ± 2 Ma. • Granites in the intrusion belong highly fractionated S-type variety. • Melt-fluid interaction and Proterozoic W-rich wall-rocks control W mineralization. • Granites and W deposits in Nanling were related to the Jurassic lithospheric extension. The Yaogangxian (YGX) W deposit in the central Nanling W province, South China, is one of the largest W deposits worldwide. Both vein-type wolframite and skarn-type scheelite orebodies were exposed in YGX. These scheelite and wolframite mineralization are spatially associated with the YGX granitic intrusion. The exposed intrusion contains two main intrusive phases: lower zone, coarse-grained two-mica granite and upper zone, fine-grained muscovite granite. An integrated study of whole-rock geochemistry, LA ICP-MS zircon U–Pb geochronology, and zircon Hf isotopic geochemistry of the YGX granitic intrusion was undertaken to constrain its magmatic source and petrogenesis. Cassiterite LA ICP-MS U–Pb dating was also undertaken to constrain the connection between the intrusion and hydrothermal W mineralization. Zircon U–Pb dating yielded weighted-mean ages of 161 ± 3 and 157 ± 2 Ma for the two-mica and muscovite granites, respectively. Cassiterite crystals from wolframite–quartz veins display growth zonation under cathodoluminescence, and have a weighted-mean zircon U–Pb age of 158 ± 2 Ma. The formation of the muscovite granite and related W mineralization in the YGX deposit was thus initiated during the early Yanshanian. The YGX granites display typical metaluminous to strongly peraluminous characteristics with high SiO 2 (73.5–79.1 wt%) and K 2 O (3.0–5.0 wt%) contents. They are enriched in heavy rare earth elements (REEs) comparative to light REEs. Notably, they exhibited strong negative Eu anomalies, and are depleted in Sr, Ba, P, and Ti. In addition, muscovite granites in YGX are more significantly enriched in heavy REEs relative to light REEs than two-mica granites, indicating that the former experienced higher degree fractionation than the latter. Zircon grains of the YGX granitoids have strongly negative ε Hf (t) (–15 to –10.3), with two-stage Hf model ages of 2.15–1.86 Ga, indicating a magma source of reworked ancient crustal material without obvious involvement of juvenile materials. The results of petrology and geochemistry indicate that the YGX granitic intrusion is a highly fractionated S-type granite emplaced during widespread 160–150 Ma granitic magmatism in the Nanling region. Further evolution to late stage for multiphase YGX granitic intrusion is needed to enrich ore-forming elements after magmatic emplacement. It is suggested that the extensional environment of continental lithosphere caused by the northwest subduction of the paleo-Pacific plate may play an key role in the genesis of YGX S-type granite. W-rich Proterozoic basement rocks and fractional crystallization may provide material for the formation of the granite-related tungsten mineralization. [ABSTRACT FROM AUTHOR]