Huangshaping Deposit Research Articles

Pyrite geochemical fingerprinting on skarn ore-forming processes: A case study from the Huangshaping W–Sn–Cu–Pb–Zn deposit in the Nanling Range, South China

Pyrite geochemistry has been extensively used to reveal ore-forming processes in diverse ore deposits, but its application in skarn systems is not well understood. The Huangshaping deposit in the Nanling Range (South China) uniquely develops W–Sn–Pb–Zn and Cu–Pb–Zn skarn mineralization systems, and both two systems have formed multi-types of pyrite, which provides a good window to reveal the mineralization histories of different skarn systems using pyrite trace element geochemistry. In the Cu–Pb–Zn system, texturally homogeneous Py1 mainly occurs in calcite veins within the host rock, whereas texturally homogeneous Py2 in the calcite-sulfide stage mainly occurs in skarn orebodies. Py3 in the siderite-sulfide stage replaces Py2 and commonly develops abundant pores or fractures, resembling the “bird's eye” texture. In the W–Sn–Pb–Zn system, Py4 in calcite veins can be divided into the oscillatory-zoned Py4a and irregular Py4b under BSE, and Py4b commonly replaces Py4a as veins or overgrowth. Texturally homogeneous Py5 in the calcite-sulfide stage occurs in skarn orebodies and is replaced by Py6 with a “bird's eye” texture in the siderite-sulfide stage.In the Cu–Pb–Zn system, Py1 may have formed by fluid cooling during its ascent along the hydraulic fractures indicated by its enrichment of Co, Ni, As, Sb, and Tl, whereas Py2 is likely formed under higher temperature and pH conditions caused by intense fluid-rock interactions evidenced by its depletion of Co, Ni, As, Sb, and Tl as well as its enrichment of Zn and Ag. In the W–Sn–Pb–Zn system, Py4b has higher contents of Co, Ni, As, Sb, and Tl than Py4a and similar contents of Ag, Zn, and Mo with Py4a, suggesting that decreasing temperature may have controlled the formation of Py4b. Py5 is featured by the depletion of As, Sb, Tl, and Mo as well as the enrichment of Zn and Ag, indicating that Py5 is likely formed under higher temperature and pH conditions resulting from the intense fluid-rock interactions. Marcasite replaces pyrrhotite and then is replaced by pyrite may be an important precipitation mechanism for pyrite with a “bird's eye” texture (Py3 and Py6) in both two skarn systems at Huangshaping. This study demonstrates that fluid-rock interaction is an important mechanism for sulfide precipitation at Huangshaping, which shows that pyrite geochemistry has good potential to reveal mineralization histories in skarn systems.

Ore-forming process of the W–Sn and Cu skarn mineralization in the Huangshaping deposit (Nanling Range): Constraints from scheelite geochemistry and cassiterite U–Pb geochronology

The Nanling Range in South China is endowed with abundant Jurassic W–Sn and Cu skarn deposits; however, the ore-forming age and process of these deposits lack adequate comparative studies. The Huangshaping deposit in the Nanling Range coincidently develops both W–Sn and Cu skarn mineralization systems, providing a good window to address these issues. Multiple generations of hydrothermal scheelite were identified at Huangshaping, including SchA-1, SchA-2, and SchA-3 in the W–Sn system, and SchB-1, SchB-2, and SchB-3 in the Cu system. Scheelite in the two systems has similar textural evolution, presenting as regular oscillatory zoning (SchA-1, SchB-1), chaotic oscillatory zoning (SchA-2, SchB-2) truncating the regular oscillatory zoning of SchA-1 and SchB-1, respectively, and homogeneous texture (SchA-3, SchB-3) replacing the early scheelite in the respective system. Rare earth elements (REEs) substitute into SchA-1 and SchB-1 mainly via mechanism of 3Ca2+ = 2(REEs, Y)3+ + □Ca, whereas those incorporate into SchA-2, SchA-3, SchB-2, and SchB-3 via mechanisms of Ca2+ + W6+ = (REEs, Y)3+ + Nb5+ and 3Ca2+ = 2(REEs, Y)3+ + □Ca. Continuously decreasing Mo concentrations and increasing Eu anomalies from SchA-1 to SchA-3 and from SchB-1 to SchB-3 reflect progressively decreasing oxygen fugacity (fO2) of hydrothermal fluids in the two systems. The higher Sr concentrations in scheelite from the W–Sn system than that from the Cu system indicate stronger fluid-rock interaction in the W–Sn system, consistent with its more development of skarn. Cassiterite U–Pb geochronology from the W–Sn and Cu systems at Huangshaping yielded lower intercept ages of 159.1 ± 0.6 Ma (MSWD = 1.8, N = 38) and 161.5 ± 0.8 Ma (MSWD = 1.6, N = 25), respectively. Combined with previously published age data from the regional W–Sn and Cu skarn deposits in the Nanling Range, it is inferred that Cu skarn mineralization may have formed earlier than W–Sn with age boundary of ∼ 159 Ma. And the age of ∼ 159 Ma might represent an important shifting time for the Cu mineralization to W–Sn mineralization in the Nanling Range. This study highlights that the textural and geochemical evolution of scheelite can provide important constraints on the ore-forming process in different skarn mineralization systems.

Ore-forming environment of Pb−Zn mineralization related to granite porphyry at Huangshaping skarn deposit, Nanling Range, South China

Multiple metallogenic types (skarn-type and vein-type) related to hypabyssal granites are found at the Huangshaping polymetallic deposit in the Nanling Range, South China. To constrain the crystallization and mineralization processes of skarn formation, three generations of magnetite and pyrrhotite from the hydrous silicate stage, oxide stage, early quartz–sulfide stage, and late quartz–sulfide stage were distinguished. The geochemical compositions of magnetite and pyrrhotite were obtained by electron probe microanalyzer (EPMA) and in-situ ablation−inductively coupled plasma−mass spectrometry (LA-ICP-MS). The results show that there may be silicate inclusions in magnetite and interaction of wall rock occurred in the mineralization process. The geochemical trends recorded in pyrrhotite show the influence of limestone during the crystallization of pyrrhotite. The re-equilibration temperatures of Po I, Po II, and Po III are 420.46, 380.45, and 341.81 °C, respectively, which suggests a continuous evolution following the high-temperature W–Sn mineralized system. The content change of Ni and V reflects a gradual decrease of oxygen fugacity from Mag I to Mag III, while the sulfur fugacity calculated from pyrrhotite gradually decreases. This continuous skarn mineralization evolution process helps us to better understand the change of metallogenic environment in the retrograde stage of the Huangshaping deposit.

Differentiated enrichment of magnetite in the Jurassic W–Sn and Cu skarn deposits in the Nanling Range (South China) and their ore-forming processes: An example from the Huangshaping deposit

Abundant Jurassic magnetite-rich W–Sn and magnetite-poor Cu skarn deposits were discovered in the Nanling Range of South China. However, their ore-forming processes and the mechanism of differentiated magnetite enrichment are still poorly constrained. The Huangshaping represents a typical skarn deposit in the Nanling Range, which developed both W–Mo–Sn and Cu mineralization systems, providing a good window to address this issue. In the Huangshaping W–Mo–Sn system, abundant magnetite was formed in three generations (Mag-1, Mag-2, and Mag-3). Mag-1 shows core (Mag-1c)-mantle (Mag-1 m)-rim (Mag-1r) texture, with abundant nano-inclusions trapped in the oscillatory-zoned Mag-1 m. Porous Mag-2 replaced Mag-1 along sharp and irregular boundaries, and both Mag-1 and Mag-2 were replaced by cassiterite. Mag-3 occurred along with quartz-bismuthinite veins and also replaced Mag-1. Magnetite-4 (Mag-4) has a homogeneous texture and occurs locally in the Huangshaping Cu system. The mineral assemblage, texture, and geochemistry suggest a hydrothermal origin for all these magnetite types and possible magmatic-hydrothermal pulses in the W-Mo-Sn system. The first magmatic-hydrothermal pulse was likely associated with granite porphyry and formed Mag-1 in a closed system with increasing oxygen fugacity (fO2) and decreasing concentrations of trace elements. The abundant nano-inclusions in Mag-1 m suggest probable local supersaturation of trace elements in the magnetite-fluid interface. The irregular contact, porosities, and lower trace element concentrations (e.g., Mg, Al, Si, Ca, and Mn) of Mag-2 reveal that it may have formed via the dissolution and reprecipitation process (DRP) of Mag-1. This process was possibly controlled by decreasing fO2. The second magmatic-hydrothermal pulse derived from the granite porphyry may have formed Mag-3, evidenced by the increasing temperature, decreasing fO2, and high trace element concentrations (e.g., Mg, Al, Si, Ca, and Mn). In the Cu system, the quartz porphyry-derived ore fluid may have formed Mag-4 under lower temperature and fO2 than in the W–Mo–Sn system. Besides, we suggested that the paucity of magnetite in these Jurassic Cu skarn deposits of the Nanling Range was likely caused by the low Fe concentration in the ore-related magma, genetically associated with the amphibole fractionation during the magma formation. This may respond to the extensional formation environment of Jurassic Cu and W–Sn skarn deposits in the Nanling Range, caused by the asthenosphere upwelling linked to the Paleo-Pacific subduction.

Constructing the deep-spreading pattern of tectono-geochemical anomalies and its implications on the Huangshaping W–Sn–Pb–Zn polymetallic deposit in southern Hunan, China

Huangshaping large W–Mo–Pb–Zn polymetallic deposit is a typical representative of the Cu–Sn metallogenic system in Nanling Range, South China. This deposit located in the superimposed tectonic setting of the Qinzhou–Hangzhou and Nanling metallogenic belts. Skarn-type W–Sn orebodies and hydrothermal vein-type Pb–Zn–Cu orebodies located in the faults and contact zone between late Jurassic porphyry and late Paleozoic limestone. Many studies have been conducted on the geological and geochemical characteristics of the deposit, but the comprehensive understanding of the deep-spreading pattern of the tectono-geochemical anomalies remains unclear. The geochemical data of tectonites in deep level adits (−136 m, −176 m, −256 m and −296 m) were studied the distribution characteristics of ore-forming trace elements and the depth index of tectonic geochemical anomalies. Finally, four element combination anomalies were extrated from the cluster analysis and factor analysis. They are generally consistent with the known Cu–Pb–Zn and W–Sn–Mo–Bi metallogenic systems. In addition, from altered porphyry to limestone of the Shidengzi Formation, the plane and profile anomaly contour maps delineated by different factors have regular variation characteristics. High anomalous values usually occur in the part where ore-forming porphyry changes from convex to concave. Comprehensive study trace element combination anomalies shows that the connection line of high value anomalous zones corresponds to the swelling and shrinking characteristics of porphyry, showing periodic wave-like changes. Thus, the deep index and deep-spreading pattern of ore-controlling structure were constructed. The length, width and height of the deep-seated orebodies indicated by the main anomalies are evaluated. The anomalous vertical variation indicates the migration of ore-forming fluid from SE to NW to the shallow. The strike of orebodiesy are consistent with the ore-controlling faults and dip to SE. Overall, the tectonic geochemical anomalies are consistent with the locations where the orebodies were identified, indicating that the method is feasible and effective. This study has an important significance for the layout of deep-prospecting and exploration projects in the Huangshaping deposit and even in southern Hunan.

Ore genesis of the Huangshaping skarn W–Mo–Pb–Zn deposit, southern Hunan Province, China: insights from in situ LA-MC-ICP-MS sulphur isotopic compositions

AbstractThe Huangshaping deposit is unique in southern Hunan Province, China, as it hosts economic reserves of both W–Mo and Pb–Zn mineralization, which are usually associated with granite and granodiorite porphyry in this area, respectively. This study reports results of in situ LA-MC-ICP-MS sulphur isotopic composition analyses conducted on sulphides from both W–Mo and Pb–Zn mineralization from the Huangshaping deposit with the aim of constraining ore genesis for this deposit. All samples from the proximal W–Mo mineralization have relatively uniform and high δ34S values (8.7 ‰ to 16.0 ‰), close to the range for carbonate sediments in this deposit (13.8 ‰ to 18.1 ‰). These patterns suggest that the granite porphyry in this deposit was the sulphur source for W–Mo mineralization, and that the assimilation of evaporite from the carbonate sediments led to the high δ34S values of the granite porphyry. Sulphides from the Pb–Zn mineralization have δ34S values (2.2 ‰ to 10.3 ‰) lower than those of the W–Mo mineralization, and generally increase in this paragenetic order, with the lowest δ34S values being similar to those of the basement (3.8 ‰ to 7.7 ‰). These patterns indicate that the original sulphur for the Pb–Zn mineralization was most likely derived from the basement, with input of sulphur from the carbonate sediments increasing during the evolution of ore-forming fluids. On the basis of the measured sulphur isotopic compositions, it is suggested that the ore-forming materials for the W–Mo mineralization were derived from the granite porphyry, whereas ore-forming materials extracted from the basement dominated the Pb–Zn mineralization.

Trace elements in sulfide minerals from the Huangshaping copper-polymetallic deposit, Hunan, China: Ore genesis and element occurrence

The Huangshaping copper-polymetallic deposit, which is located in southern Hunan Province, China, is an important resource base for Pb–Zn minerals. This study used the major sulfides (sphalerite, pyrite, pyrrhotite), which formed during the Pb–Zn mineralization stage of the Huangshaping deposit, to determine the genesis of the Pb–Zn ore minerals and element occurrence. In-situ LA-ICP-MS analysis of minerals was conducted to determine their trace element concentrations and reveal the distribution and occurrence of trace elements in different sulfides. The formation temperature and genesis of the Pb–Zn ore minerals were also constrained based on the deposit geology and trace element data. Trace elements were significantly different among different sulfides in the Pb–Zn mineralization stage of the deposit. Sphalerite primarily enriches Mn, Cu, Ag, Sn, and Pb and is the main carrier mineral of Ga, In, and Cd. Pyrite relatively enriches Tl, Sb, W, and Se, and pyrrhotite primarily enriches Ge. In sphalerite, Fe, Mn, Cd, Ga, In, Cu, Sn, Ag, and Ge exist by substituting for other elements (such as Zn). The replacement method of Ge is Ge4++2Cu+↔3Zn2+, whereas that of In (Ga) is In3+(Ga3+) + Cu+↔2Zn2+. In pyrrhotite, Ge is incorporated through coupling substitution, and the abnormal concentrations of Pb, Ag, and Se are caused by galena that has replaced pyrrhotite. In pyrite, W occurs as a solid solution. When galena replaces pyrite, it causes abnormal concentrations of Pb, Tl, Sb, and Ag. The sphalerite is characterized by high concentrations of high-temperature ore-forming elements (e.g., Fe, Mn, In, and Sn) and relatively low concentrations of Cd, Ge, Ga, and other elements. Thus, the sphalerite was formed at a medium–high temperature (288–341 °C). The trace element characteristics of sphalerite are consistent with those of high-temperature hydrothermal deposits. The deposit geology, pyrite Co/Ni ratio (averaging 0.13, n = 29), S/Se ratio (averaging 173,905, n = 19), pyrrhotite Co/Ni ratio (averaging 0.10, n = 26), and binary diagram of trace elements in sphalerite indicate that Pb–Zn mineralization is related to the late-stage hydrothermal activity of skarn mineralization. The Pb–Zn mineralization and W–Mo(Fe) mineralization together constitute a skarn-type mineralization system.

Using garnet geochemistry discriminating different skarn mineralization systems: Perspective from Huangshaping W-Mo-Sn-Cu polymetallic deposit, South China

Important Mid-Late Jurassic W-Mo-Sn and Cu polymetallic skarn deposits are widely distributed in South China, yet differences in ore-forming processes and physiochemical conditions between these two skarn deposit types are poorly constrained. The large Huangshaping deposit in South China developed both W-Mo-Sn skarn (named 301 system) and Cu skarn (named 304 system) mineralization systems, which are genetically linked to granite porphyry and quartz porphyry, respectively. Both skarn systems are characterized by abundant garnet. Three types of garnet were distinguished in the 301 system, i.e., the texturally homogeneous Grt301a and veined Grt301b from deep-level (−176 m), and oscillatory-zoned Grt301c from shallow-level (−96 m). Moreover, Grt301a is commonly cut by Grt301b vein. Meanwhile, two types of garnet were identified in the 304 system, i.e., the texturally anisotropic Grt304a and oscillatory zoned Grt304b, with the former being commonly replaced by the latter.Trace element geochemistry shows that REE3+ entered garnet mainly by YAG-type substitution ([Ca2+]VIII −1[REE3+]VIII + 1[Si4+]IV −1[Z3+]IV + 1) in the 301 system and menzerite substitution ([Ca2+]VIII −1[REE3+]VIII + 1[Al3+]VI −1[Y2+]VI + 1) in the 304 system. Grt301a, Grt301b and Grt304a are HREE-enriched, suggesting that they were formed under nearly-neutral pH and low water/rock (W/R) ratios in closed and stable systems via diffusive metasomatism. Meanwhile, Grt301c and Grt304b are LREE-enriched, suggesting that they were formed under mildly-acidic pH and high W/R ratios in open and fluctuating systems via infiltration metasomatism. The elevated Sn content in Grt301c (median 5039 ppm) indicates its higher oxygen fugacity (fO2) than Grt301a (median 1861 ppm) and Grt301b (median 1776 ppm). Similarly, the high Sn content in Grt304b (median 1444 ppm) also suggests higher fO2 than that of Grt304a (median 338 ppm). The different formation conditions between deep-level garnet (Grt301a and Grt301b) and shallow-level garnet (Grt301c) in the 301 system are not consistent with garnet in the 304 system that shows similar texture, trace element geochemistry and formation conditions at different depths. This reveals differences of formation environments between two skarn systems at Huangshaping. Partial least squares-discriminant analysis (PLS-DA) suggests that W in garnet can discriminate the 301 and 304 skarn systems, which may be related to the lower fO2 and higher fractionation of the ore-causative granite porphyry in the former, which favors W enrichment in corresponding magmatic-hydrothermal fluids in 301 system. Moreover, Mo can discriminate garnet from the deep- and shallow-levels of the 301 system, which may be related to the higher fO2 in the latter. We highlight the importance of garnet trace element geochemistry on tracing hydrothermal fluid evolution and discriminating between different skarn systems.

The prograde-to-retrograde evolution of the Huangshaping skarn deposit (Nanling Range, South China)

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.

Accumulation of sulfides in the basement of southern Hunan Province, China: Implications for Pb–Zn mineralization related to reduced granitoids

Southern Hunan Province lies at the intersection of the Shi–Hang zone and Nanling belt, and is characterized by extensive Mesozoic igneous rocks and coeval polymetallic deposits, including early granodiorite porphyry-related Cu–Pb–Zn polymetallic mineralization (ca. 160 Ma) and late granite-related W–Sn polymetallic mineralization (ca. 155 Ma). Amongst these deposits, the Huangshaping deposit is unique for the coexistence of economic W–Mo and Pb–Zn mineralization, which is associated with reduced granitoids, including quartz porphyry, felsite, and granite porphyry. Unlike the W–Mo mineralization, which has a close temporal–spatial relationship with granite porphyry, the sources of Pb–Zn mineralization have not yet been clarified, mainly because of its distal orebodies of unknown age. Abundant granodioritic enclaves have recently been found in quartz porphyry of the Huangshaping deposit, with zircon U–Pb ages consistent with the quartz porphyry and containing abundant sulfides including chalcopyrite, sphalerite, and pyrrhotite. This study involved in situ LA–ICP–MS determinations of trace element compositions of these sulfides, for comparison with those of sulfides in distal ores and carbonate strata to elucidate the sources of Pb–Zn mineralization in this deposit. Sulfides from granodioritic enclaves have higher Co/Ni ratios, but similar Zn/Cd, Cu/In, and Pb/Sb ratios, compared with those of distal Pb–Zn ores, indicating that sulfides in both enclaves and ores were precipitated from hydrothermal fluids derived from the same single source, although with higher precipitation temperatures for the former. As sulfides in the ores have Pb isotopic compositions distinct from those of other granitoids, we suggest that intrusion of the granodiorites (~5 Myrs before the granitoids) resulted in the accumulation of ore-forming metals in the metamorphic or crystalline basement. These metals were then scavenged by hydrothermal circulation triggered by later intrusions of felsite and granite porphyry, especially fluorine-rich granite porphyry, forming the distal Pb–Zn mineralization near the surface of the deposit. The accumulation of sulfides triggered by earlier granodioritic activity was likely crucial for the formation of distal sulfide mineralization, and perhaps also for that in other W–Mo deposits related to reduced granites in southern Hunan Province.

Timing and origin of multi-stage magmatism and related W–Mo–Pb–Zn–Fe–Cu mineralization in the Huangshaping deposit, South China: An integrated zircon study

The Huangshaping deposit (South China) is closely related to hypabyssal granites (e.g., quartz porphyry, granophyre, and granite porphyry), developing massive skarn-type W–Mo–Fe polymetallic mineralization, skarn-type Pb–Zn–Cu mineralization, and vein-type PbZn (Cu) mineralization. To better constrain the geochronology, fluid composition, magma source, metallogenic affinity, and source of ore-forming materials in the Huangshaping deposit, morphological, textural, in situ geochronological, compositional, and LuHf isotopic studies on zircons hosted in granitoids, skarns (ores), and wall rocks have been carried out. Overall, five types of zircons are identified: low-U magmatic (abbreviated as LUMZ), high-U magmatic (HUMZ), hydrothermally-altered metamict (HAZ), inherited, and detrital types. Round-shaped inherited and detrital zircons with low trace element compositions are rarely captured in the granite porphyry and largely hosted in sulfide skarn ores and wall rocks. The HUMZ are mainly observed in the granophyre and are easily distinguished from LUMZ by their much higher U, Th, and Y contents, black CL images, and stronger Eu anomalies. In addition, the crystallization time of HUMZ was later than that of LUMZ. The HAZ uniquely exists in granite porphyry and genetic-related skarns with cracked and porous textures and strong enrichment of many trace elements. These zircons were originally HUMZ that have undergone rapid partial metamictization and subsequent fluid-zircon interaction. This study demonstrates that the granophyre is a two-stage intrusion with ages of 179 ± 0.3 Ma and 163 ± 0.7 Ma, whereas the granite porphyry yields younger ages of 157 ± 0.5 Ma. The discovery of Triassic inherited zircons in the latter leads us to propose the presence of a concealed Triassic pluton (~220 Ma). The zircon populations of W−Mo−Fe mineralized garnet skarns are mainly composed of ~160 and 180 Ma magmatic zircons, whereas magnetite skarn ores contain both magmatic zircons (~50%) and inherited zircons (~50%). In contrast, inherited zircons are the dominant zircon population of the skarn Pb−Zn ores. This may indicate that the granite porphyry (the foremost one) and granophyre mostly contributed to the skarn-type W−Mo−Fe mineralization, whereas the Carboniferous and Devonian carbonate strata significantly contributed to the skarn-type Pb−Zn (Cu) mineralization. Fluids separated from the granite porphyry that modified the zircons are likely the principal ore-forming fluids, which are enriched in F, U, Th, Y, REE, Nb, Ta, Hf, Ca, P, Ti, Pb W, Mo, and Fe. Zircon Hf isotopes suggest that these magmas, at least the granophyre and granite porphyry, were generated by reworking of Mesoproterozoic crustal rocks without significant input of mantle materials. This study highlights the use of different types and generations of zircons from variable rock types to reveal fluid compositions and mineralization potentials in complex metallogenic systems.

A newly Found Biotite Syenogranite in the Huangshaping Polymetallic Deposit, South China: Insights into Cu Mineralization

The W-Sn-Mo-Cu-Pb-Zn polymetallic mineralization in the Huangshaping Deposit is associated with different types of Jurassic granitic intrusions such as quartz porphyry, granophyre and granite porphyry. In this study, we carried out detailed mineralogical, petrological, geochemical, zircon U-Pb geochronological and Hf isotopic studies on a newly found, Cu-mineralization-related fine-grained biotite syenogranite at Huangshaping. This syenogranite is mainly composed of quartz (40%), K-feldspar (30%), plagioclase (15%) and biotite (5%), enriching in SiO2 (75.58 wt.%–76.02 wt.%), K2O (5.24 wt.%–5.78 wt.%), Al2O3 (12.23 wt.%–12.46 wt.%), Rb (405 ppm–504 ppm), U (18.5 ppm–40.7 ppm), Th (47 ppm–52.3 ppm), Nb (49.6 ppm–57.5 ppm), and Cu (54 ppm–288 ppm) whereas depleting in P2O5 (0.01 wt.%), TiO2 (0.05 wt.%–0.06 wt.%), Ba (5 ppm–13.1 ppm), Sr (6.8 ppm–23.9 ppm) and Eu (0.04 ppm–0.05 ppm), with A1-type alkaline granite characteristics. Magmatic and hydrothermal zircons were separated from a Cu-mineralized syenogranite sample and yielded the 206Pb/238U concordant ages of 156.5±1.8 and 154.4±2.9 Ma, representing the intrusive age of the pluton and probable Cu-mineralization time at the Huangshaping Deposit, respectively. Zircon Hf isotopes suggest a crust-derived (partial melting of Paleoproterozoic basement) magma for the syenogranite, with some degree of crust-mantle interaction. We infer that the syenogranite is a transitional phase between the granophyre and the granite porphyry, not only contributed greatly to the Cu mineralization but also provided W-Sn polymetallic ore-forming metals for the Huangshaping Deposit.

Magnetite as an indicator of mixed sources for W–Mo–Pb–Zn mineralization in the Huangshaping polymetallic deposit, southern Hunan Province, China

The Huangshaping polymetallic deposit, located in southern Hunan Province in China, hosts abundant W–Mo–Pb–Zn mineralization that is associated with a large-scale skarn system at the contact zone between late Mesozoic granitoids and Carboniferous carbonates. To better understand the processes of polymetallic mineralization in the Huangshaping deposit, trace element concentrations of magnetites from different skarn stages were obtained by in situ laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS). The results show that two groups of magnetites were distinguished based on their trace element signatures. Group-1 magnetites, found in medium-grained garnet and calcite, have relatively low concentrations of Na, K, Ca, Si, Ge, Sn, and W, and relatively high concentrations of Mg, Al, Ti, V, Zn, Ni, and Co. The opposite is true for the Group-2 magnetites, which occur in coarse-grained garnet, tremolite, and bulk iron ore. These findings suggest that two compositional endmembers of hydrothermal fluids may be responsible for mineralization in the Huangshaping deposit. Group-2 magnetites likely precipitated from evolved magmatic hydrothermal fluids from which other minerals, such as garnet and tremolite, precipitated during the early skarn stages. The high Na, K, Ca, and Si contents of these hydrothermal fluids can be attributed to dissolution of the host rocks, which include limestone, sandstone, and evaporite horizons. On the other hand, the Group-1 magnetites precipitated from hydrothermal fluids with low Na, K, Ca, and Si contents. These low-salinity fluids may have been subjected to large-scale circulation, extracting Mg, Al, and Zn from the underlying Zn-rich metamorphic basement and the Mg- and Al-rich strata in this region. The high Ti, V, Ni, and Zn concentrations of Group-1 magnetites also suggest that these hydrothermal fluids had lower oxygen fugacity than the fluids from which the Group-2 magnetites precipitated. The results of this study demonstrate that the trace element concentrations of magnetites can be used to infer the composition and physicochemical conditions of the hydrothermal fluids from which they precipitated. In the case of the Huangshaping polymetallic deposit, this indicates that the hydrothermal fluids responsible for the W–Mo–Pb–Zn mineralization were derived from mixed sources.

Garnet and scheelite as indicators of multi-stage tungsten mineralization in the Huangshaping deposit, southern Hunan province, China

The Huangshaping W–Mo–Pb–Zn deposit in southern Hunan province, south China, contains multiple generations of garnet and scheelite in skarn and sulfide–carbonate altered rocks. Optical characteristics and chondrite-normalized rare earth element (REEN) patterns obtained by in situ laser ablation–inductively coupled plasma–mass spectrometry analysis were used to distinguish different generations of garnet and scheelite. These data show a clear correspondence of garnet REEN patterns to major element zonation, with HREEs (e.g., Gd–Lu) being depleted overall. Coarse-grained garnets in the Huangshaping deposit have extreme HREE depletions and significant LREE (e.g., La–Eu) enrichment, particularly for Ce, Pr, and Nd. This indicates that REEs in these garnets are the result of coupled substitutions: [Ca2+]VIII− 1[REE3+]VIII+1 and [Fe2+]IV +1[Al3+]IV − 1. Medium-grained garnets have REEN patterns showing significant LREE enrichment and depleted HREEs, with high Sn contents. This suggests that substitution of REEs in these garnets occurs as [Ca2+]VIII−1[REE3+]VIII+1[Sn4+]IV−1[Al3+]IV+1. The fact that medium-grained garnets have high Sn contents indicates mineralizing fluids were oxidizing, which is consistent with significant positive Eu anomalies. However, hump-shaped REEN patterns for garnet rims suggest substitution by: [Ca2+]VIII−2[Na+]VIII+1[REE3+]VIII+1, where Nd–Tb are preferentially incorporated into the garnet lattice over other REEs.Group-1a scheelite has black cores in cathodoluminescence images, and REEN patterns showing extreme LREE enrichment and HREE depletion. Group-1b scheelite has cores with fine oscillatory zoning and enriched LREEs with depleted HREEs, similar to the REEN patterns of Group-2a scheelite that occur as rims with bright CL surrounding both Group-1a and 1b scheelite. The substitution mechanism for REEs in these three types of scheelite is: [Ca2+]VIII−3[ ]VIII+1[REE3+]VIII+2, with [ ] being a Ca site vacancy. The influence of REE speciation in the hydrothermal fluid dominates the REEN patterns of these types of scheelite. However, for Group-2b bright rims of scheelite, REEs are incorporated as: [Ca2+]VIII−2[Na+]VIII+1[REE3+]VIII+1, similar to the garnet rims. Finally, scheelite Mo contents and δEu values that decrease from Group-1a to 2b support a temporal decrease in oxygen fugacity of the mineralizing fluids.Ratios of Y/Ho and Mo contents that decrease from Group-1a and 1b to Group-2a and 2b scheelites are similar to those in porphyry-related skarn W (Mo) and quartz vein Au–W deposits, respectively. Our studies also suggest that all these scheelites in this deposit formed from magmatic fluids. At the Huangshaping deposit, medium-grained garnets associated with Group-1a scheelite precipitated from evolved magmatic fluids during prograde metamorphism, as indicated by their complementary Y/Ho ratios. Paragentically younger scheelite, particularly Group-2b, may have formed from dilute magmatic fluids that underwent large-scale hydrothermal circulation. The characteristics of Group-1b and 2a scheelite likely reflect a transitional environment and fluid mixing during tungsten mineralization in the polymetallic Huangshaping deposit.

Jurassic magmatism related Pb-Zn-W-Mo polymetallic mineralization in the central Nanling Range, South China: Geochronologic, geochemical, and isotopic evidence from the Huangshaping deposit

The Nanling Range in South China is characterized by extensive Mesozoic magmatism and coeval nonferrous and rare metal mineralization. Huangshaping is a world-class Pb-Zn-W-Mo polymetallic skarn deposit in the central Nanling Range. Magmatic rocks occurring in this ore district include quartz porphyry, granite porphyry, granophyre, dacite porphyry, and aplite, with only the first three granitoids genetically associated with polymetallic mineralization. Most of the orebodies are constrained within the contact zones as skarn and veins between these granitic stocks and the carbonate wall rocks.Since the age of the quartz porphyry is still controversial, and studies of the dacite porphyry and aplite are absent, we focus on these magmatic rocks first. LA-ICP-MS zircon U-Pb dating suggests that the crystallization ages of the quartz porphyry, dacite porphyry, and aplite are 154.3±1.9Ma, 158.1±0.8Ma, and 148.4±3.4Ma, respectively. Combined with previously published age data, we infer the evolutionary sequence of magmatic rocks should be dacite porphyry→quartz porphyry→granite porphyry (granophyre)→aplite. The quartz porphyry, dacite porphyry, and aplite yield high contents of high field strength elements (Zr+Nb+Ce+Y=255–440ppm), high ratios of 10,000×Ga/Al (2.6–3.2), and prominent depletions in Ba, Sr, Eu, P, and Ti, indicating their crustal affinities to A-type granites. They have negative εNd(t) values (−9.4 to −7.0) and high initial Pb isotopic ratios (206Pb/204Pbi=18.307–18.644, 207Pb/204Pbi=15.689–15.742, 208Pb/204Pbi=38.589–38.986), suggesting that they were probably derived by partial melting of ancient granulitic crustal materials.The sulfide minerals exhibit a wide range of δ34SV-CDT values from −22.6 to 24.2‰, with 206Pb/204Pb of 17.669–19.708, 207Pb/204Pb of 15.492–15.714, and 208Pb/204Pb of 37.880–39.789, indicating that sulfur, lead, and other associated metals were derived from a mixture of magmatic components and the Carboniferous wall rocks. Fluid inclusions in pyrrhotite, sphalerite, and marmatite samples have 3He/4He ratios of 0.12 to 1.53 Ra, with calculated mantle helium proportions of 1.3 to 18.9%, indicating a predominantly crustal origin for the ore fluids, with minor inputs from the mantle. The Huangshaping deposit is a typical example of the genetic relationship both spatially and temporally between Jurassic magmatism and polymetallic metallogeny in the Nanling Range.

Fluid origin and migration of the Huangshaping W–Mo polymetallic deposit, South China: Geochemistry and 40Ar/39Ar geochronology of hydrothermal K-feldspars

The Huangshaping deposit is a world-class W–Mo–Pb–Zn–Cu polymetallic deposit that formed during the Jurassic magmatic event in the central Nanling region, South China. In order to reveal the three-dimensional development of mineralization and alteration in this complicated fluid-rock system, four typical hydrothermal K-feldspar samples were collected from potassic alteration zones at different elevation levels around main W–Mo ore bodies, followed by precise trace element analysis and 40Ar/39Ar dating. The results show that these K-feldspars have a pronounced lanthanide tetrad effect with high contents of Ga, Ta, Nb, U, Y and HREE but low concentrations of Ba, Sr, Eu and Zr, suggesting a hydrothermal origin. Additionally, correlation between the Ca/Cl/K ratios and the apparent ages suggest that metasomatic fluids played an important role in the formation of the hydrothermal K-feldspars. The plateau 40Ar/39Ar ages which represent the timing of potassic alteration vary from 152.9±0.5 to 154.3±0.6Ma, spatially showing younger trends from north to south and from shallow to deep. These dates correspond to the previous published molybdenite Re–Os data variations in different elevation levels, which record the mineralization event with relatively older ages ranging from 153.8 to 159.4Ma. Combined with the spatial relation analysis among samples, the fluid migration rates associated with the mineralization and alteration are calculated at 10–100mMa−1. Thus, we propose a fluid downward migration model for the Huangshaping polymetallic deposit.

Petrogenesis of Late Jurassic granitoids and relationship to polymetallic deposits in southern China: The Huangshaping example

ABSTRACTSouthern Hunan Province, located in the Cathaysia Block where the Shi–Hang zone and Nanling belt meet, is characterized by extensive Mesozoic magmatism and coeval polymetallic mineralization. The Huangshaping W–Mo–Pb–Zn–(Cu) deposit is representative in this area. However, the petrogenesis of the granitoids associated with the Huangshaping deposit, and their relationships with mineralization, remain undetermined. In this paper we focus on zircon U–Pb dating, whole-rock geochemistry, and Sr–Nd–Pb–Hf isotopic compositions in order to further our understanding of these issues, as well as their regional implications. The Huangshaping granitoids are characterized by two pulses of intrusive activity: a first-stage quartz porphyry and a second-stage felsite and granite porphyry, our new data show that the quartz porphyry and felsite formed at 160.5 ± 1.3 and 156.6 ± 1.4 Ma, respectively, representing a period of Late Jurassic magmatism. Granitic enclaves within the quartz porphyry crystallized at 160.2 ± 1.6 Ma, and zircons and apatites from the enclaves exhibit Hf isotopic and geochemical compositions that suggest a Palaeoproterozoic lower crustal melt as one end-member of the magma that formed the quartz porphyry, whereas another likely end-member was coeval mantle-derived magma, as indicated by the geochemistry and Sr–Nd–Pb–Hf isotopes. However, both the felsite and granite porphyry were probably derived from the melting of metamorphic basement rocks in the upper crust. The felsite clearly formed as a result of the rapid ascent and cooling of magma, whereas the granite porphyry underwent fractional crystallization. The magma sources and evolution of the granitoids, as well as their association with the Huangshaping mineralization, suggest that melting of upper crustal components controlled the W–Mo and Pb–Zn mineralization, whereas dehydration of a subducted slab provided the Cu mineralization in southern Hunan Province.

Genesis of the Huangshaping W–Mo–Cu–Pb–Zn polymetallic deposit in Southeastern Hunan Province, China: Constraints from fluid inclusions, trace elements, and isotopes

The Huangshaping polymetallic deposit is located in southeastern Hunan Province, China. It is a world-class W–Mo–Pb–Zn–Cu skarn deposit in the Nanling Range Metallogenic Belt, with estimated reserves of 74.31Mt of W–Mo ore at 0.28% WO3 and 0.07% Mo, 22.43Mt of Pb–Zn ore at 3.6% Pb and 8.00% Zn, and 20.35Mt of Cu ore at 1.12% Cu. The ore district is predominantly underlained by carbonate formations of the Lower Carboniferous period, with stocks of quartz porphyry, granite porphyry, and granophyre. Skarns occurred in contact zones between stocks and their carbonate wall rocks, which are spatially associated with the above-mentioned three types of ores (i.e., W–Mo, Pb–Zn, and Cu ores).Three types of fluid inclusions have been identified in the ores of the Huangshaping deposit: aqueous liquid–vapor inclusions (Type I), daughter-mineral-bearing aqueous inclusions (Type II), and H2O–CO2 inclusions (Type III). Systematic microthermometrical, laser Raman spectroscopic, and salinity analyses indicate that high-temperature and high-salinity immiscible magmatic fluid is responsible for the W–Mo mineralization, whereas low-temperature and low-salinity magmatic-meteoric mixed fluid is responsible for the subsequent Pb–Zn mineralization. Another magmatic fluid derived from deep-rooted magma is responsible for Cu mineralization.Chondrite-normalized rare earth element patterns and trace element features of calcites from W–Mo, Pb–Zn, and Cu ores are different from one another. Calcite from Cu ores is rich in heavy rare earth elements (187.4–190.5ppm), Na (0.17%–0.19%), Bi (1.96–64.60ppm), Y (113–135ppm), and As (9.1–29.7ppm), whereas calcite from W–Mo and Pb–Zn ores is rich in Mn (>10.000ppm) and Sr (178–248ppm) with higher Sr/Y ratios (53.94–72.94). δ18O values also differ between W–Mo/Pb–Zn ores (δ18O=8.10‰–8.41‰) and Cu ores (δ18O=4.34‰–4.96‰), indicating that two sources of fluids were, respectively, involved in the W–Mo, Pb–Zn, and Cu mineralization.Sulfur isotopes from sulfides also reveal that the large variation (4‰–19‰) within the Huangshaping deposit is likely due to a magmatic sulfur source with a contribution of reduced sulfate sulfur host in the Carboniferous limestone/dolomite and more magmatic sulfur involved in the Cu mineralization than that in W–Mo and Pb–Zn mineralization. The lead isotopic data for sulfide (galena: 206Pb/204Pb=18.48–19.19, 207/204Pb=15.45–15.91, 208/204Pb=38.95–39.78; sphalerite: 206Pb/204Pb=18.54–19.03, 207/204Pb=15.60–16.28, 208/204Pb=38.62–40.27; molybdenite: 206Pb/204Pb=18.45–19.21, 207/204Pb=15.53–15.95, 208/204Pb=38.77–39.58 chalcopyrite: 206Pb/204Pb=18.67–19.38, 207/204Pb=15.76–19.90, and 208/204Pb=39.13–39.56) and oxide (scheelite: 206Pb/204Pb=18.57–19.46, 207/204Pb=15.71–15.77, 208/204Pb=38.95–39.13) are different from those of the wall rock limestone (206Pb/204Pb=18.34–18.60, 207/204Pb=15.49–15.69, 208/204Pb=38.57–38.88) and porphyries (206Pb/204Pb=17.88–18.66, 207/204Pb=15.59–15.69, 208/204Pb=38.22–38.83), suggesting Pb206-, U238-, and Th 232-rich material are involved in the mineralization. The Sm–Nd isotopes of scheelite (εNd(t)=−6.1 to −2.9), garnet (εNd(t)=−6.8 to −6.1), and calcite (εNd(t)=−6.3) from W–Mo ores as well as calcite (εNd(t)=−5.4 to −5.3) and scheelite (εNd(t)=−2.9) from the Cu ores demonstrate suggest more mantle-derived materials involved in the Cu mineralization.In the present study we conclude that two sources of ore-forming fluids were involved in production of the Huangshaping W–Mo–Pb–Zn–Cu deposit. One is associated with the granite porphyry magmas responsible for the W–Mo and then Pb–Zn mineralization during which its fluid evolved from magmatic immiscible to a magmatic–meteoritic mixing, and the other is derived from deep-rooted magma, which is related to Cu-related mineralization.

S, Pb, and Sr isotope geochemistry and genesis of Pb–Zn mineralization in the Huangshaping polymetallic ore deposit of southern Hunan Province, China

The Huangshaping Pb–Zn–W–Mo polymetallic deposit, located in southern Hunan Province, China, is one of the largest deposits in the region and is unique for its metals combination of Pb–Zn–W–Mo and the occurrence of significant reserves of all these metals. The deposit contains disseminated scheelite and molybdenite within a skarn zone located between Jurassic granitoids and Carboniferous sedimentary carbonate, and sulfide ores located within distal carbonate-hosted stratiform orebodies. The metals and fluids that formed the W–Mo mineralization were derived from granitoids, as indicated by their close spatial and temporal relationships. However, the source of the Pb–Zn mineralization in this deposit remains controversial.Here, we present new sulfur, lead, and strontium isotope data of sulfide minerals (pyrrhotite, sphalerite, galena, and pyrite) from the Pb–Zn mineralization within the deposit, and these data are compared with those of granitoids and sedimentary carbonate in the Huangshaping deposit, thereby providing insights into the genesis of the Pb–Zn mineralization. These data indicate that the sulfide ores from deep levels in the Huangshaping deposit have lower and more consistent δ34S values (−96m level: +4.4‰ to +6.6‰, n=13) than sulfides within the shallow part of the deposit (20m level: +8.3‰ to +16.3‰, n=19). The δ34S values of deep sulfides are compositionally similar to those of magmatic sulfur within southern Hunan Province, whereas the shallower sulfides most likely contain reduced sulfur derived from evaporite sediments. The sulfide ores in the Huangshaping deposit have initial 87Sr/86Sr ratios (0.707662–0.709846) that lie between the values of granitoids (0.709654–0.718271) and sedimentary carbonate (0.707484–0.708034) in the Huangshaping deposit, but the ratios decreased with time, indicating that the ore-forming fluids were a combination of magmatic and formation-derived fluids, with the influence of the latter increasing over time. The lead isotopic compositions of sulfide ores do not correlate with sulfide type and define a linear trend in a 207Pb/204Pb vs. 206Pb/204Pb diagram that is distinct from the composition of the disseminated pyrite within sedimentary carbonates and granitoids in the Huangshaping deposit, but is similar to the lead isotopic composition of sulfides within coeval skarn Pb–Zn deposits in southern Hunan Province. In addition, the sulfide ores have old signatures with relative high 207Pb/206Pb ratios, suggesting that the underlying Paleoproterozoic basement within southern Hunan Province may be the source of metals within the Huangshaping deposit.The isotope geochemistry of sulfide ores in the Huangshaping deposit shows a remarkable mixed source of sulfur and ore-forming fluids, and the metals were derived from the basement. These features are not found in representative skarn-type Pb–Zn mineralization located elsewhere. The ore-forming elements (S, Pb, and Zn) from the granitoids made an insignificant contribution to sulfide precipitation in this deposit. However, the emplacement of granitoids did provide large amounts of heat and fluids to the hydrothermal system in this area and extracted metals from the basement rocks, indicating that the Jurassic magmatism associated with the Huangshaping deposit was crucial to the Pb–Zn mineralization.

Photocatalytic Reduction of CrVI by Natural Sphalerite Suspensions under Visible Light Irradiation

Abstract The photocatalytic reductive capability of a natural semiconducting mineral, sphalerite has been studied for the first time. The sphalerite from the Huangshaping deposit of Hunan Province performed great photoreductive capability that 91.95% of the Cr6+ was reduced under 9 h visible light irradiation, higher than the 70.58% under 9.5 h UV light irradiation. The highly reductive ability results from its super negative potential of electrons in the conduction band. Furthermore, Fe substitution for Zn introduces donor states, and the oxidation process of Fe2+ to Fe3+ makes it an effective hole-scavenger. Cd and Cu substitute for Zn also reduce the bandgap and help broaden the absorbing edge towards the visible light. These substituting metal ions in natural sphalerite make it a hyper-active photocatalyst and very attractive for solar energy utilization.