Source Of Ore-forming Materials Research Articles

Ore-forming material sources of the Pb–Zn–(Ag–Fe–Cu) deposits in the northern Gangdese belt, Lhasa terrane: Constraints from geology, geochronology and S–Pb isotopes

Many new skarn Pb–Zn–(Ag–Fe–Cu) deposits have been identified in the northern Gangdese polymetallic belt (NGPB). The NGPB comprises skarn deposits with different metal associations: Pb–Zn–(Ag), Pb–Zn–Fe–Cu, and Fe–Cu. The sources of ore-forming materials and whether intrusions contribute materials to these deposits, remain debated subjects. This study focused on zircon U–Pb dating and S–Pb isotopes of metal sulfides, ore-forming rocks, and wall rocks from the typical deposits in the three systems. Zircon U–Pb dating indicates that the biotite granite in the Longmala deposit was emplaced at 54.6 ± 0.6 Ma, which is consistent with its metallogenic age. The δ34S values of sulfides from the Pb–Zn–(Ag) deposits (Yaguila: −2.1‰ to + 6.0‰, Mengya’a: −0.8 ‰ to + 4.6 ‰) are similar to those from Pb–Zn–Fe–Cu deposits (Longmala: +1.6‰ to + 3.6‰, Lietinggang–Leqingla: −8.3 ‰ to + 2.0 ‰), suggesting a magmatic source of sulfur. The Pb isotopes of sulfides in Pb–Zn–(Ag) deposits (206Pb/204Pb = 18.4804–18.6935, 207Pb/204Pb = 15.6637–15.7331, and 208Pb/204Pb = 38. 0164–39.2612) are similar to those of the contemporaneous intrusions, as are those of Pb–Zn–Fe–Cu and Fe–Cu deposits, suggesting that the intrusions provided metals for the three systems. In comparison, the sulfides from the Pb–Zn–(Ag) deposits have higher 207Pb/204Pb values (15.6637 to 15.7331, mostly > 15.70) than the Fe–(Cu) deposits (15.6186 to 15.6848) and the Pb–Zn–Fe–Cu deposits (15.6163 to 15.7197), indicating that the metals of Pb–Zn–(Ag) deposits were derived from the upper-crust magma, whereas the metals of Fe–(Cu) and Pb–Zn–Fe–Cu deposits originated from the deep magma that required the involvement of mantle-derived components. Combined with previous research, we propose that the metals of Pb–Zn–(Ag) deposits originated from S-type granites, whereas those of Pb–Zn–Fe–Cu and Fe–(Cu) deposits were derived from I-type granites in the NGPB.

Fluid evolution and ore genesis of the A'gui Cu deposit in southern Great Xing'an Range, Northeast China: Evidence from fluid inclusion and C–H–O–S–Pb isotopes

The A'gui Cu deposit is located in the eastern slope of the southern Great Xing'an Range (SGXR), and it is a vein-type Cu deposit spatially and temporally related to the Cretaceous monzogranite which intruded Pingshan Formation. Vein-type Cu orebodies are mainly hosted in the NE and nearly EW faults. Previous studies on the A'gui deposit mainly focused on geological exploration, and there was no study on its fluid evolution and genesis. Therefore, we carried out conducted fluid inclusion and stable isotope (C–H–O–S–Pb) analysis to study the fluid evolution, fluid and ore-forming material sources and genesis of the A'gui deposit. According to the field investigations and mineral crosscutting relationships, four paragenetic stages were identified: quartz–pyrite–chalcopyrite–pyrrhotite–arsenopyrite ± magnetite (Stage I), quartz–pyrite–chalcopyrite (Stage II), quartz–chalcopyrite ± pyrite–sphalerite–galena (Stage III) and carbonate ± quartz (Stage IV). From Stage I to Stage II, the assemblage of fluid inclusions (FIs) in quartz is characterized by the development of daughter mineral–bearing three–phase FIs (SL–type), vapour FIs (V–type), vapour–rich two–phase aqueous FIs (LV–type) and liquid–rich two–phase aqueous FIs (VL–type). Only VL–type FIs appeared in the Stage III quartz and Stage IV calcite. The homogenization temperatures of FIs in stages I, II, III and IV are 329–390 °C, 255–336 °C, 166–244 °C and 120–157 °C, with salinities of 3.37–45.33 wt%, 3.53–39.76 wt%, 4.17–7.86 wt% and 3.37–7.15 wt% NaCl eqv., respectively. The fluid inclusion type assemblage suggested that obvious fluid boiling occurred in the Stage I and Stage II. Fluid boiling may be the reason for the precipitation of useful minerals. According to the HO isotope analysis of stages I–II quartz (δ18OH2O = −2.1 to 3.2 ‰, δDV–SMOW = −128.4 ‰ to −110.6 ‰), the fluid was originally magmatic water. From Stage III to Stage IV (δ18OH2O = −12.3 to −2.3 ‰, δDV–SMOW = −129.6 ‰ to −104.2 ‰), the HO isotope value is obviously close to the meteoric water line, indicating that meteoric water is mixed with evolved magmatic solutions. The ore–forming fluid of the A'gui deposit represents a medium–high temperature NaCl-H2O magmatic hydrothermal system. The C isotope compositions (δCV–PDB = −5.74 ‰ to −4.76 ‰) in stage IV indicate that the C in the fluid was derived from a magmatic source and was affected by meteoric water. In addition, the measured S isotope compositions in stages I–III of the hydrothermal fluids (δ34SV–CDT = 2.2 to 3.7 ‰) indicate that S mainly comes from granitic magma. Further, the Pb isotope (206Pb/204Pb = 18.276–18.367, 207Pb/204Pb = 15.52–15.556, 208Pb/204Pb = 38.157–38.193) in stages I–III indicate that the ore-forming materials are derived from the mixture of mantle and orogenic material. In summary, this study showed the A'gui is a typical magmatic hydrothermal vein-type Cu deposit that related to Cretaceous monzogranite formed under the joint constraints of Mongolia-Okhotsk Ocean and Paleo-Pacific Ocean tectonic system. Fluid boiling and mixing are the main ore-forming mechanism.

Serpentinization and its implications for ultramafic-hosted sulfide mineralization: A case study at the Tianzuo hydrothermal field, 63.5°E, Southwest Indian Ridge

Reaction of ultramafic rocks with seawater and subsequent serpentinization has been considered one of the most important factors controlling the formation of ultramafic-hosted seafloor massive sulfide (UM-SMS) deposits. However, the mineralization processes responsible for these deposits remain poorly understood, in particular because they are less abundant as compared with their basaltic counterparts. In this work, serpentinites with different alteration grades collected at the Tianzuo hydrothermal field (THF), Southwest Indian Ridge, were studied. Mineralogical and chemical analyses were performed in the secondary opaque minerals resulting from serpentinization to understand the role of this process during the formation of UM-SMS deposits. Our results show that these opaque minerals mainly consist of magnetite, hematite, pentlandite, and minor pyrite, suggestive of high but varying oxygen and sulfur fugacities. The hematite is characterized by an enrichment in Mg, Si, Ni, and Co as compared with magnetite. Pentlandite associated with hematite has elevated and consistent Ni contents as compared with that associated with magnetite. These results indicate that breakdown and decomposition of primary silicate and sulfide minerals during serpentinization has controlled the sources of ore-forming materials. Concentrations of Te are variable and show a positive correlation with Ni in pentlandite associated with magnetite or hematite, suggesting that gabbroic intrusions provided additional material to the hydrothermal system. Oxidation and sulfidation conditions are ideal for the formation of trisulfur ion S3− in THF, which can significantly improve the capability of hydrothermal fluids for leaching ore-forming metals from the wall rocks, promoting the formation of THF. In addition of reduced systems, hydrothermal fluids with high oxygen and sulfur fugacities triggered by extensive seawater infiltration can most likely also develop in ultramafic-hosted systems. These results suggest that the areas with well-developed fractures are promising candidates for further exploration of UM-SMS deposits along mid-oceanic ridges.

Metallogenic Material Source and Genesis of the Jilinbaolige Pb-Zn-Ag Deposit, the Great Xing’an Range, China: Constraints from Mineralogical, S Isotopic, and Pb Isotopic Studies of Sulfide Ores

The Jilinbaolige Pb-Zn-Ag polymetallic deposit is located in the eastern part of Inner Mongolia and in the central-southern part of the Great Xing’an Range, in which several large-sized Pb-Zn-Ag deposits have been found. The Jilinbaolige deposit, which occurs mainly at the contact zone between Yanshanian granite intrusion and sedimentary strata, shows strong NE-to-NNE structural control. The deposit includes three ore-forming stages: (1) the arsenopyrite–pyrite–chalcopyrite–sphalerite stage, (2) the galena–sphalerite–quartz stage, and (3) the pyrite–calcite–quartz stage. In this study, we present a systematic study on the mineralogical and geochemical characteristics (including major elements, S isotopes, and Pb isotopes) of the main sulfide ore minerals in the Jilinbaolige Pb-Zn-Ag deposit in order to evaluate the metallogenic environment, ore-forming material source, and genesis of this polymetallic deposit. The sulfide typomorphic characteristics, ore fabric, and thermometry suggest that the genesis of sulfides in the deposit is closely related to magmatic-hydrothermal activity. The early stage of mineralization might have evolved from a high-temperature hydrothermal environment. The sulfur isotopic results show that the δ34S values in the Jilinbaolige deposit range from 2.3‰ to 6.1‰, with an average value of 3.98‰, indicating that the sulfur originated from magmas with both mantle and crustal components. The Pb isotopic compositions (206Pb/204Pb = 18.214–18.330, 207Pb/204Pb = 15.478–15.615, 208Pb/204Pb = 37.957–38.292, μ = 9.24–9.50, ω = 34.49–36.49) of the sulfide ores suggest that that the lead is of crust-mantle mixed origin. The comparison between the S and Pb isotopic compositions of the Jilinbaolige deposit and the polymetallic deposits from the central-southern parts of the Great Xing’an Range suggests that these deposits have a similar metallogenic source, which is closely related to the Yanshanian granite and medium-temperature hydrothermal fluids. These ore-bearing hydrothermal fluids that evolved from deep magmatic sources migrated along the contact and fracture zones and during the subsequent gradual decrease in temperature, and the metallogenic components were deposited in the relatively open fracture and fissure space. Our results provide insights for further mineral prospecting in the south-central part of the Great Xing’an Range.

Trace Elements and Pb-O Isotopes of Scheelite: Metallogenic Implications for the Shimensi W-Polymetallic Deposit in South China

The world-class Shimensi tungsten (W)-polymetallic deposit is located in Jiangnan Orogen, with an estimated reserve of 742.5 kt WO3 @ 0.195% W, 403.6 kt Cu and 28 kt Mo. In this paper, the trace elements and Pb-O isotopes of scheelite (the main ore mineral) are presented to study the ore-forming material source and ore-forming fluid evolution. The results show that the REE distribution in scheelite is mainly controlled by the substitution mechanism of 3Ca2+ = 2REE3+ + □Ca (where □Ca is the Ca-site vacancy). Oxygen isotope data indicate that the scheelite mineralization occurred under high-temperature oxygen isotope equilibrium conditions, and that the ore-forming fluid has a magmatic–hydrothermal origin. The variation in scheelite Eu anomalies and the wide range of scheelite Y/Ho ratio indicate that the ore-forming fluid evolves from reducing to oxidizing, and the early-stage and late-stage ore-forming fluid may have been relatively rich in F− and HCO3−, respectively. The significant Mo decrease in scheelite from the early to late stage that are opposite to the influence of fO2 variation may have resulted from the crystallization of molybdenite and Mo-rich scheelite. Lead isotopes of the ore minerals of scheelite, wolframite, molybdenite and chalcopyrite can be divided into three groups, similar to these of feldspars in different granites. Both the Mesozoic porphyritic and fine-grained biotite granites have Pb isotope ratios similar to the ores, which suggests that the former two are the main ore material source.

Material Source and Genesis of the Daocaowan Sb Deposit in the Xikuangshan Ore Field: LA-ICP-MS Trace Elements and Sulfur Isotope Evidence from Stibnite

The Daocaowan antimony (Sb) deposit is a newly discovered Sb deposit located outside the northeast Xikuangshan ore field. In the absence of geochemical data, the metallogenic mechanism of the Daocaowan Sb deposit and its relationship with the Xikuangshan ore field remains unclear. Using high-resolution LA-ICP-MS technique, this study quantitatively determined the in-situ S isotope values and trace element composition of stibnite from the Daocaowan Sb deposit in South China to investigate the source of ore-forming materials and genesis of this deposit. The trace element compositions of stibnite from the Daocaowan Sb deposit revealed the form of occurrence and substitution mechanism of trace elements in stibnite, providing new constraints for explaining the genesis of Sb deposits. The relatively smooth LA-ICP-MS profiles indicate that As, Cu, Hg, and Pb primarily occur as solid solutions in stibnite. Therefore, we speculate that the substitution 3Sb3+↔As3+ + 2Cu+ + Hg2+ + Pb2+ may be the reason for the enrichment of As, Cu, Hg, and Pb in stibnite. A comparison with the Xikuangshan Sb deposit reveals the metallogenic mechanism of the Daocaowan Sb deposit, and the relationship between the two. With the exception of higher content of Fe in Stibnite from the Daocaowan deposit as compared to the Xikuangshan deposit, other trace elements are similar between the two deposits. The results show that the Daocaowan and Xikuangshan Sb deposits may have the same source of ore-forming fluids. We propose that the ore-forming fluid flowed through the Xikuangshan Sb deposit along the F75 fault and dissolved pyrite in the wall rock. Subsequently this fluid containing a high concentration of Fe precipitated and mineralized at Daocaowan. Meanwhile, the S isotope value of the Daocaowan Sb deposit (+6.65 to +9.29‰) is consistent with that of the Xikuangshan, proving that the ore-forming materials of the two deposits are from the same source, probably the basement strata. We propose that the Daocaowan Sb deposit is part of the Xikuangshan ore field, indicating a great prospecting potential in the northeast of the Xikuangshan ore field.

Crystallization processes and genesis of scheelite in a quartz vein-type W deposit (Xianghuapu, South China)

Scheelite is widely developed in quartz vein-type tungsten (W) polymetallic deposits, and CL images, REE patterns and SrO isotope distributions of this mineral provide important constraints regarding its precipitation mechanism. We undertook a systematic investigation of the geochemistry (using in-situ SrO isotopes, EPMA, and LA-(MC)-ICP-MS), CL images, and fluid inclusions along core-to-rim transects of single scheelite grains from the Xianghuapu W deposit (South China) to constrain the source of ore-forming materials and reconstruct the crystallization history of the deposit. The scheelite grains show heterogeneous signatures in CL images recording a three-stage (core–mantle–rim) crystallization history. The scheelites also show decreasing concentrations of REEs from core to rim (core mean = 20.1 ppm, SD = 13.2; mantle mean = 18.7 ppm, SD = 17.8; rim mean = 5.80 ppm, SD = 5.27), as well as contrasting REE patterns and MREE distributions. There are significant variations in concentration, from core to rim of the scheelite, of MREEs (core mean = 10.0 ppm, SD = 6.43; mantle mean = 4.89 ppm, SD = 5.33; rim mean = 0.79 ppm, SD = 0.68) and HREEs (core mean = 39.4 ppm, SD = 23.4; mantle mean = 22.3 ppm, SD = 20.3; rim mean = 4.74 ppm, SD = 4.07). The 87Sr/86Sr ratios and δ18Oscheelite values decrease from core (87Sr/86Sr = 0.740817–0.743807; mean 18Oscheelite = −6.2‰) and mantle (87Sr/86Sr = 0.740048–0.745267; mean δ18Oscheelite = −7.0 ‰) to rim (87Sr/86Sr = 0.733809–0.738398; mean δ18Oscheelite = −7.9 ‰). In addition, the homogenization temperatures of fluid inclusions from the scheelite grains also decrease from core (225–236 °C, mean = 230 °C, SD = 8.20) and mantle (184–217 °C, mean = 201 °C, SD = 11.2) to rim (153–178 °C, mean = 166 °C, SD = 7.04), but the salinity of fluid inclusions changes less (mean = 1.48 wt%, 0.84 wt%, and 0.75 wt%, respectively). The low salinity and δ18OH2O values of the fluid suggest a large amount of meteoric water was mixed into the metallogenic system, resulting in a pH increase and triggering scheelite precipitation. The high Sr contents and change in 87Sr/86Sr ratios reveal that W mineralization was mainly related to Jurassic granitic magmatism, and extensive fluid-rock interaction occurred during the scheelite crystallization process. From core to rim, the magmatic Sr decreased, while the proportion of Sr derived from the limestone wall rock increased. The inhomogeneous REE and SrO isotope distributions may be a ubiquitous feature of quartz vein-type W deposits in magmatic settings globally, and in situ LA-(MC)-ICP-MS analysis can assist in revealing the complex crystallization processes of scheelite in such deposits.

Formation of the Miaoan Au-Polymetallic Deposit in the Northern Taihang Mountain, North China Craton: Ore Geology, Geochronological and Geochemical Perspectives

Several gold ore-concentrated areas have been recognized in the destruction zone of the North China Craton (NCC). However, the deposits in the western part of the destruction zone have received less attention. Miaoan, a typical Au-polymetallic deposit in the northern Taihang Mountain, provides a good sample for deepening our understanding of the genesis of gold deposits in the western destruction zone. In this study, detailed ore geology, pyrite Rb-Sr age, trace element and S-C-O isotopes of Au-bearing ores were conducted to constrain the source of ore-forming materials and their tectonic setting. The pyrites obtain an Rb-Sr isochron age of 129.5 ± 2.5 Ma, consistent with those of magmatic rocks in this deposit, suggesting their genetic relationship. The δ34S values ranging from −5.5‰ to 1.6‰ and the high Co/Ni and Y/Ho ratios of pyrites indicate the mantle-crust mixing characteristics of ore-forming fluids. The δ13C (−6.3‰ to −2.0‰) and δ18O (9.3‰ to 17.6‰) values of Au-bearing ores and calcites suggest mixing characteristics as well. Geochronologically, the Miaoan Au-polymetallic deposit was formed during the destruction of the NCC. We propose that the Miaoan Au-polymetallic deposit is a decratonic gold deposit and that its ore-forming materials have a mixed source of mantle and crust.

Hydrothermal evolution and origin of the Suixian molybdenum deposit in the Tongbai orogenic belt, China: Constraints from geology, fluid inclusions and multiple isotopes (H[sbnd]O[sbnd]C[sbnd]S[sbnd]Pb)

The Suixian Mo deposit is a recently discovered deposit in the northern Hubei Province, Tongbai orogen. The Mo orebodies of this deposit are all hosted in the metamorphic rocks (leuco-gneiss, amphibolite and marble) of the Neoproterozoic Tianwangzhai Group, and these orebodies have no direct contact with the granite surrounding the host rocks. The mineralization types are dominated by disseminated ore and fine Mo-bearing quartz-sulfide veins. Hydrothermal alteration consists of abundant feldspathization, epidotization and chloritization, together with less garnetization, tremolitization, and muscovitization. A detailed study on fluid inclusions and multiple isotope (CHOSPb) analyses, together with geologic features, are carried out to investigate the fluid composition, fluid origin and evolution, the source of ore-forming materials, and the ore genetic type. In line with microthermometric measurements and laser Raman analysis on fluid inclusions from three hydrothermal stages, the ore-forming fluid in this deposit is characterized by medium–high temperatures and salinities, as well as richness in CO2 and CH4. Three hydrothermal stages are identified in this deposit, including (I) feldspar-quartz-amphibole-muscovite stage, (II) quartz-sulfides stage, and (III) quartz-calcite-scheelite-fluorite stage. From stages I, II to III, the temperatures change from 290 to 354 °C, through 229–312 °C, to 173–269 °C, with decreasing salinities of 12.6 to 16.3 wt% NaCl equiv., 4.5 to 13.4 wt% NaCl equiv., and 0.2 to 6.9 wt% NaCl equiv., respectively. Most of sulfur isotope data of sulfides (chalcopyrite, pyrite, pyrrhotite and molybdenite) show a narrow δ34S range from −2.0 to 3.0 ‰, suggesting a dominant magmatic source, but some data show either positive or negative values (δ34S: −13.3 to −10.6 ‰ and 9.8 to 11.2 ‰) which may indicate small contribution from the restricted wall rocks. The Pb isotope data (molybdenite, pyrite and pyrrhotite: 206Pb/204Pb: 17.239 to 18.483; 207Pb/204Pb: 15.378 to 15.717; 208Pb/204Pb: 37.889 to 38.850) imply that the lead of sulfides pertains to a mixture of magma (derived from the lower crust) and upper crustal materials (host metamorphic rocks). Based on evident CO2 and CH4 in fluid inclusions, the gradually depleted carbon isotopic compositions (δ13C: −5.4 to −9.9 ‰ at stage I, −14.8 to −19.7 ‰ at stage II, and −17.0 to −24.2 ‰ at stage III) and the HO isotope data, it is suggested that the ore-forming fluids were mainly magmatic fluids with mixture of some organic-containing water, and the thermochemical reaction between the fluids and organic matters (e.g., CH4) from host metamorphic rocks and fluid immiscibility are two important mechanisms for Mo mineralization. Compared with typical Mo deposits in the same orogen, the Suixian Mo deposit belongs to the magmatic hydrothermal vein-type deposit associated with intrusions rather than porphyry or skarn type deposit.

Composition and Geochemical Characteristics of Pyrite and Quartz: Constraints on the Origin of the Xinjiazui Gold Deposit, Northwestern Margin of the Yangtze Block, China

The Xinjiazui gold deposit, a newly discovered deposit, is situated in the northwestern margin of the Yangtze Block, China. The source and genesis of gold mineralization are poorly understood. It is urgent to use the H–O isotopic composition of quartz and geochemistry of pyrite to evaluate the origins of the Au and ore-forming fluids of this deposit. Three types of pyrite were identified, including synsedimentary framboidal pyrites (Py0), the directional arrangement of pyrites in pre-mineralization stage (Py1), and euhedral coarse-grain pyrites in the quartz–sulfide veins of the mineralization stage (Py2). The As content in Py2 is relatively higher than Py0 and Py1, indicating that the ore-forming fluids are strongly enriched in As. The δ34S values of Py2 (+5.50–+13.34‰) overlap with the S1–2M phyllite (+7.25‰–+8.70‰). This result is consistent with the Pb isotopic composition of Py2, showing that the source of ore-forming materials was derived from the S1–2M phyllite. Meanwhile, the variations in quartz’s H and O isotopic composition suggest that the ore-forming fluids were derived originally from metamorphic fluid. Additionally, the Au mineralization is strictly controlled by the shear zone. Above all, we would like to classify the Xinjiazui deposit as an orogenic gold deposit.

The mineralization of Daxiao carbonate-hosted Pb-Zn deposit, northeast Yunnan province, SW China: Constraints from Rb-Sr isotopic dating and H[sbnd]O[sbnd]S-Pb isotopes

The Sichuan-Yunnan-Guizhou (SYG) Pb-Zn metallogenic province located in western Yangtze Block contains more than 400 carbonate-hosted Pb-Zn deposits. Uncertain mineralization age and ore-forming material source causing debates on the genesis of these carbonate-hosted Pb-Zn deposits. To address this issue, the Daxiao Pb-Zn deposit was chosen as a case study. The orebodies of Daxiao deposit are hosted in Mesoproterozoic Heishan formation argillaceous dolomite interbedded with slate. Three main mineralization stages have been identified, including syn-sedimentary stage, hydrothermal stage and supergene stage. The ore minerals consist of galena, sphalerite, chalcopyrite, argentite, smithsonite, anglesite and cerussite in the deposit. The early hydrothermal stage sphalerite yielded a Rb-Sr isochron age of 223.5 ± 2.9 Ma, consistent with the spike of Pb-Zn mineralization in SYG metallogenic province. Quartz in hydrothermal stage yields δDSMOW values of −69.6 to −65.8 ‰ and calculated δ18OFluid values of + 3.4 – +5.6 ‰, showing an affinity of metamorphic water. While the quartz in supergene stage yields δDSMOW values of −68.3 to −65.8 ‰ and calculated δ18OFluid values of −4.1 to −1.7 ‰, indicating abundant basinal brine or meteoric water had mixed into ore-forming fluid during its evolution from hydrothermal stage to supergene stage. Sulfur isotopic composition (δ34S = +6.3 – +19.1 ‰) of different stage sulfides reveal that the ore-forming sulfur originated from sulfates within the wall rocks, and mainly reduced by Thermal-chemical reduction (TSR). Moreover, the 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of early hydrothermal stage sphalerite are 18.282 – 18.312, 15.603 – 15.681and 38.287 – 38.311, respectively. Those of late hydrothermal stage galena are 18.315 – 18.491, 15.676 – 15.721 and 38.314 – 38.326, respectively. All of them plot in the overlapping area of Emeishan flood basalts, Kunyang and Huili groups and Sinian to Triassic strata, indicating that these wall rocks jointly contributed the ore-forming metals for these Pb-Zn deposits in SYG metallogenic province. Hence, a metallogenic model for Daxiao and other carbonate-hosted Pb-Zn deposit in SYG metallogenic province was proposed: In the thrustfold systems caused by the subduction of Paleo-Pacific and the closure of Jinshajiang-Ailaoshan Paleo-Tethys ocean in Late Triassic to Early Jurassic. The fluids originated from metamorphic water migrated along deep faults and extracted ore-forming materials from wall rocks (including Proterozoic basement rocks, Sinian to Triassic sedimentary wall rocks and Permian Emeishan flood basalts), and then precipitated ores in the secondary thrust faults or interlayered fractures within these thrustfold systems.

Sediment-hosted disseminated gold deposits in orogenic belts: An example from the giant Jiagantan gold deposit in the West Qinling orogen, China

Sediment-hosted disseminated gold deposits in orogenic belts share many similarities to both epizonal orogenic and Carlin-type gold deposits, leading to a lot of difficulties in their genetic classification. The giant Jiagantan gold deposit was newly discovered in the West Qinling orogen, central China, and was selected to provide a better understanding of this issue. Gold mineralization at Jiagantan is hosted within sandstone and silty slate, and the gold is intimately associated to disseminated pyrite and arsenopyrite. Three generations of pyrite (Py0, Py1, and Py2) and two generations of arsenopyrite (Apy1 and Apy2) are recognized and used to perform in situ textural, chemical, and sulfur isotopic analyses.The diagenetic Py0 is framboidal and porous, and contains elevated concentrations of As, Sb, Co, Ni, Cu, Ti, and V. The early mineralization stage Py1 and Apy1 are disseminated within sandstone and silty slate, and have the highest average Au concentrations of 7.7 ppm and 12.6 ppm, respectively. The intermediate mineralization stage Py2 and Apy2 are hosted by quartz veins and veinlets, coexisting with stibnite, chalcopyrite, and minor amounts of other sulfides. Gold mineralization mainly took place during the early mineralization stage. Microscopic observations and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) output graphs confirm the majority of gold may reside in the crystallographic structures of Py1 and Apy1.The diagenetic Py0 grains show negative δ34S values of −25.2 to −20.1‰, implying the derivation of sulfur by bacterial reduction of marine sulfate. The hydrothermal Py1, Py2, Apy1, and Apy2 have higher but still negative δ34S values ranging from −16.4 to −5.0‰, suggesting an origin of sulfur from metamorphism of the underlying Devonian sedimentary rocks.The Jiagantan gold deposit can best be classified as an epizonal orogenic gold deposit owing to the possible metamorphic origin of Au, As, S, and other associated elements. The source of ore-forming materials is the key to discriminating orogenic gold deposits from Carlin-type gold deposits, while the type of host rocks, the style of mineralization, and the occurrence state of gold may not be the effective indicators.

Tourmaline and zircon trace the nature and timing of magmatic-hydrothermal episodes in granite-related Sn mineralization: Insights from the Libata Sn ore field

AbstractThe Bin Yauri-Libata polymetallic ore district is a Sn and Au ore-bearing district in the Zuru schist belt, Northwestern Nigeria. The Libata Sn ore field is characterized by a set of cassiterite-bearing hydrothermal veins associated with Neoproterozoic Pan-African granites affected by deformation and low-grade metamorphism. The hydrothermal alteration associated with cassiterite-bearing quartz veins in the Libata deposit includes silicification, albitization, chloritization, and potassic alteration. In this study, geochemical and geochronological data from tourmalines and zircons from Sn-bearing lodes, unmineralized and altered granites is applied to reveal the timing, fluid composition, and source of ore-forming materials for tin mineralization in the Libata ore field. Zircon trace element and Hf isotopes [εHf(t) = +4.37 to +10.85] reveal a mantle-derived source with some crustal contribution for the melts forming the Libata Sn-bearing granites. LA-ICP-MS zircon U-Pb dating constrains the magmatic and hydrothermal ages to 650–646 and 649–646 Ma for the Libata granites. Overlapping zircon εHf(t) and 176Hf/177Hf but distinct 176Lu/177Hf and 176Yb/177Hf ratios from magmatic and hydrothermally altered zircons reveal a magmatic source for the hydrothermal fluids which triggered cassiterite deposition in the Libata ore field. Major element chemistry constrain tourmalines from the Libata ore field as schorls that show high alkalis, low-Ca contents, and moderate ☐ values (where ☐ is x-site vacancy). High Li, Zn, and Sn concentrations in tourmaline as well as Li/Sr and Ca-Fe-Mg ratios demonstrate that the tourmaline formed from granite-sourced fluid likely derived from the host Libata granites. Measured δ11B values from the Libata tourmaline range from –15.7‰ to –14.1‰. The δ11B of the mineralizing fluid is estimated to be –13.1 to –11.9‰ for the Libata tourmalines at 400–500 °C and overlaps with averages from fractionated granites worldwide. Therefore, our data show that tourmaline and zircon are useful tracers of magmatic-hydrothermal evolution in rare-metal-bearing granite systems.

The fractionation of iron isotope and its constraints on the sources of ore-forming materials in the Jinchanghe skarn polymetallic deposit in Sanjiang region, Southwest China

金厂河矿床是西南三江成矿省保山地块最具代表性的远端矽卡岩型多金属矿床之一，查明其成矿金属来源对理解该类矿床成因以及区域成矿规律具有重要意义。本文通过分析不同成矿阶段代表性含铁矿物的铁同位素组成，探讨其在成矿过程中的分馏机制，从而示踪成矿金属的源区特征。金厂河矽卡岩型矿床中成矿前阶段未蚀变的石榴子石和氧化物成矿阶段的磁铁矿均相对富集铁的重同位素，其δ⁵⁶Fe值分别为0.05‰~0.16‰和0.07‰~0.18‰，而硫化物成矿阶段的黄铁矿和黄铜矿则相对富集铁的轻同位素，其δ⁵⁶Fe值分别为-0.12‰~0.17‰和-0.54‰~-0.38‰，整体显示出从高氧逸度的成矿前阶段向低氧逸度的硫化物成矿阶段演化过程中矿物δ⁵⁶Fe值逐渐降低的趋势，指示Fe³⁺富集铁的重同位素，Fe²⁺富集铁的轻同位素。同时，金厂河矿床各阶段矿物的δ⁵⁶Fe值均显著低于碳酸盐围岩，而接近全球花岗岩的δ⁵⁶Fe值，表明成矿的铁不是由围岩贡献，而是来自于隐伏的中酸性岩体。;Jinchanghe is a representative distal skarn polymetallic deposit in Baoshan block in the Sanjiang metallogenic province, finding out the sources of ore-forming metals is of great significance to understand the genesis of deposit and regional metallogeny. In this study, we analyzed the iron isotopic compositions of Fe-bearing minerals from different stages, to investigate the fractionation mechanism of iron in ore-forming process, and to trace the sources of ore-forming metals. The unaltered garnet from pre-ore stage and magnetite from oxide-ore stage in Jinchanghe skarn deposit are relatively rich in heavy isotopes of iron, with δ⁵⁶Fe values of 0.05‰~0.16‰ and 0.07‰~0.18‰, respectively. Whereas, the pyrite and chalcopyrite from sulfide-ore stage are relatively rich in light isotope, with δ⁵⁶Fe values of -0.12‰~0.17‰ and -0.54‰~-0.38‰, respectively. All results show that, from pre-ore stage of high oxygen fugacity to sulfide-ore stage of low oxygen fugacity, the δ⁵⁶Fe values of minerals gradually decrease, indicating that the heavy isotope of iron is enriched in Fe³⁺, but the light isotope of iron is enriched in Fe²⁺. Furthermore, the iron isotopes of minerals from different stages in Jinchanghe are significantly lower than that of carbonate wall rock, and close to that of global granite, implying that the ore-forming iron are not contributed by wall rock, but from the concealed granitic rocks.

Genesis of the Weizigou Au Deposit, Heilongjiang Province, NE China: Constraints from LA-ICP-MS Trace Element Analysis of Magnetite, Pyrite and Pyrrhotite, Pyrite Re-Os Dating and S-Pb Isotopes

The Weizigou Au deposit in Heilongjiang Province, NE China, located in the southern Jiamusi Massif, shows similarities to IOCG deposits. To determine the mineralization age, sources of ore-forming materials and genetic type, pyrite Re-Os dating, S-Pb isotopic analysis, in situ sulfur analysis and LA-ICP-MS analysis of trace elements in magnetite, pyrite and pyrrhotite were conducted. Four pyrite samples yielded a Re-Os isochron age of 197 ± 11 Ma, implying the occurrence a metallogenic event in the Early Jurassic. The δ34S values of sulfides display a relatively narrow range from 4.70‰ to 12.83‰ (mainly 9.90‰ to 12.83‰), which may be accounted for the extensively exposed granitic gneiss and meta-gabbro, with δ34S values of 7.44‰ to 8.44‰ and 4.37‰ to 10.54‰, respectively. Sulfide lead isotopic compositions have 206Pb/204Pb = 18.605–20.136, 207Pb/204Pb = 15.637–15.710 and 208Pb/204Pb = 38.534–39.129, indicating that the lead was derived from a mixed source. Magnetite has the characteristics of a lower Ti content and higher Zn content, indicating that it should be of hydrothermal origin, which may be related to IOCG-type mineralization. Pyrite and pyrrhotite have a Co/Ni ratio greater than 1 and a lower As content, indicating that they are of magmatic hydrothermal origin. Integrating the above analysis results, we inferred that the Weizigou Au deposit experienced the IOCG-type mineralization in the Middle-Late Permian, associated with magmatic-hydrothermal mineralization in the Early Jurassic.

Genesis of the Longkou–Tudui gold deposit, Jiaodong Peninsula, eastern China: Constraints from zircon U-Pb dating, fluid inclusion studies and C–H–O–S stable isotopes

The Jiaodong Peninsula in eastern China hosts numerous large and giant gold deposits. Recently, a set of gold deposits distributed along the Guocheng Fault have been identified as a new gold mineralization type, of which the Longkou–Tudui gold deposit is spatially associated with the Muniushan monzogranite whereas its genesis is poorly constrained. A systematic study including zircon U-Pb dating, fluid inclusions, C–H–O–S stable isotopes was carried out in order to determine the genesis of the Longkou–Tudui gold deposit. Zircon dating results indicate that the Muniushan monzogranite and dioritic porphyrite were emplaced at 2089–2066 Ma (with a metamorphism probably occurring at 1860 ± 27 Ma, MSWD = 0.98) and 115.6 ± 1.4 Ma, respectively. Combined with cross-cutting relationships of the Muniushan monzogranite, dioritic porphyrite, and gold orebodies, it is inferred that the gold mineralization occurred in the early Cretaceous. Fluid inclusion study demonstrates a H2O–NaCl ± CO2 system, with a progressive decrease in average values of homogenization temperature and salinity from pre-ore to post-ore stages but a slight increase in bulk density. The ore-forming fluid is characterized by reductive, acidic, high to middle temperature, low salinity, and low density as revealed by a combined study on fluid inclusion and stable isotopes. H–O–C–S isotopic compositions indicate that the ore-forming materials have multiple sources including an inherited S source from the Jingshan Group, a mantle-derived C source, and a mixed H–O source induced by the addition of meteoric water. Compared with other Jiaodong gold deposits, the Longkou–Tudui deposit does not differ in mineralization age, nature and evolution of ore-forming fluid, and source of ore-forming materials except for orebody occurrence and heavier δ34S values inherited from the Jingshan Group, and this deposit was a byproduct of oceanic subduction of the Paleo Pacific Ocean.

Genesis of the Erdaohe skarn Pb-Zn-Ag deposit in the Great Hinggan Range, NE China: Evidence from geology, fluid inclusions, and H–O–S isotope systematics

The large Erdaohe Pb-Zn-Ag deposit is an important and representative skarn deposit in the middle segment of the Great Hinggan Range. The Pb-Zn ore bodies are mainly hosted in and among different lithological layers of volcaniclastic and carbonate rocks. The Si–Ca interface with abrupt changes in rock chemical properties and the bedding detachment faults played important roles in controlling mineralization. The mineralization of the deposit can be divided into three stages: (1) pre-ore skarn stage (I); (2) syn-ore quartz–sulfide stage (II); and (3) post-ore quartz–carbonate stage (III). Here, we present a combined study of geology, fluid inclusions (FIs), laser Raman analysis and H–O–S isotopes to constrain the origin and evolution of ore-forming fluids and the source of ore-forming materials. Four types of FIs are identified in the Erdaohe deposit, including liquid-rich (L-type), vapor-rich (V-type), CO2 (C-type) and daughter mineral-bearing (S-type) FIs. The L-type, V-type, C-type and S-type FIs appear simultaneously in stages I and II, and their homogenization temperatures (Th) are similar, indicating that boiling of the ore-forming fluids occurred. From stages I to III, Th varies from 338 to 475 °C, 194 to 383 °C and 157 to 323 °C, with salinities ranging from 3.87 to 50.72 wt% NaCl equiv., 0.35 to 39.05 wt% NaCl equiv. and 0.18 to 6.88 wt% NaCl equiv., respectively. The main ore-forming fluid was a H2O–NaCl ± CO2 system. From stages I to III, the variations in δ18Ofluid range from −2.3 to 7.2‰, −8.8 to 1.0‰, and −13.6 to −3.8‰; the ranges of δD are −141 to −208‰, −133 to −161‰, and −126 to −142‰, respectively. H–O isotope studies reveal that the initial ore-forming fluid was mainly derived from magma and underwent intense degassing, followed by mixing with meteoric water. The δ34S values of sulfide minerals vary in a small range, are concentrated from 5.2 to 10.0‰, and are characteristic of deep-sourced magmatic sulfur. The high δ34S values in the Erdaohe deposit are probably the result of magmatic sulfur mixing with sulfur from the surrounding Duobaoshan Formation. The alteration style related to mineralization, combined with FIs, laser Raman analysis, and H–O–S isotopes, suggests that the Erdaohe Pb-Zn deposit is a typical skarn deposit associated with magmatic activity. The boiling of ore-forming fluids and mixing with meteoric water played crucial roles in ore precipitation.

Genesis of the Yanghuidongzi Cu deposit, NE China: Constraints from H-O-Pb isotopic compositions and geochronological study

• The Yanghuidongzi Cu deposit classified as a porphyry type Cu deposit. • H-O isotopes indicate a mixing of magmatic water and meteoric water for ore fluids. • Pb-Re isotopes indicated a deep seated magma mixed with crustal materials for ore metals. • The Yanghuidongzi Cu deposit formed during Early Jurassic . The newly-discovered Yanghuidongzi porphyry Cu deposit is located in the southeastern part of Heilongjiang Province in NE China and represents one of the rare Jurassic porphyry Cu deposits within the easternmost segment of the Central Asian Orogenic Belt (CAOB). The Cu mineralization occurs as veins and disseminations hosted by granodiorite porphyry, associated with typical porphyry copper deposit alteration zoning, which is characterized by from an inner K-silicate zone through to a quartz–sericite zone to an outer propylitic zone, the K-silicate alteration and quartz–sericite alteration are closely related to mineralization. LA-ICP-MS zircon U-Pb data, sericite Ar-Ar and Molybdenite Re-Os data, and H-O and Pb isotopic compositions are used to constrain the ore-forming age and genesis of the Yanghuidongzi Cu deposit. LA-ICP-MS U-Pb dating of zircons from three granodiorite porphyry samples yielded weighted mean 206 Pb/ 238 U ages of 194.3 ± 1.2 Ma, 192.0 ± 2.0 Ma, and 194.6 ± 2.1 Ma respectively, whereas zircon U-Pb age of granodiorite in the study area yielded weighted mean 206 Pb/ 238 U age of 199.5 ± 1.5 Ma that are interpreted to be the emplacement age of these intrusions. 40 Ar- 39 Ar dating of sericite from a quartz-pyrite vein and a quartz-polymetallic sulfide vein yielded plateau ages of 193.9 ± 2.1 Ma and 193.6 ± 1.9 Ma, respectively, whereas five molybdenite samples yielded a Re-Os isochron age of 194.8 ± 2.1 Ma, with a weighted mean model age of 193.6 ± 1.2 Ma. Mineralization ages are consistent with the emplaced ages of the granodiorite porphyry within the analytical uncertainties, indicating that the Cu mineralization is genetically related to the granodiorite porphyry. The fluid δ 18 O fluid and δ 18 D fluid values range from −4.22‰ to 6.5‰ and from −92.8‰ to −65.7‰, respectively, indicating that the ore fluids were mixtures of magmatic and meteoric water. The 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, and 208 Pb/ 204 Pb values of the pyrite and chalcopyrite are 17.547–18.327, 15.446–15.505, and 37.408–38.113, respectively, suggesting a common, magmatic source for the sulfur. Taking Re (6.75–29.53 ppm) data into consideration, the sources of ore-forming materials may be from a mixture of crustal and mantle sources. Combining our new data with the Jurassic regional tectonic setting, the Yanghuidongzi Cu deposit and the related granitoids formed in a compressional tectonic setting are associated with the subduction of the Paleo-Pacific Plate beneath the Eurasian continent.

Geochronology and Isotope Geochemistry of the Yingfang Pb-Zn-Ag Deposit: Implications for Large-Scale Metallogeny along the Northern Flank of the North China Craton

The northern flank of the North China Craton (NCC) hosts a linear zone of gold, molybdenum, silver, lead, and zinc polymetallic ore deposits. Among these, the Yingfang Pb-Zn-Ag deposit is located in the central part of the Yanshan–Liaoxi metallogenic belt (YLMB) which extends for approximately 1000 km and forms part of the major mineralized zone. In this study, we characterize the mineralization and trace the ore genesis based on new sulfur and lead isotopic geochemistry and evaluate the timing of mineralization from Rb-Sr isotope dating of sulfides. The pyrite δ34S values range from +3.2‰ to +5.8‰ with a mean at +4.07‰, close to the values of mantle and meteorite sulfur. The 206Pb/204Pb values range from 16.833 to 18.956, 207Pb/204Pb from 15.374 to 15.522, and 208Pb/204Pb from 37.448 to 37.928. Five samples of sulfide, from the Yingfang deposit, yield a Rb-Sr isochron age of 135.7 ± 4.1 Ma. This age is close to the age of the adjacent Niujuan Ag-Au deposit and the associated Er’daogou granite, suggesting a close relationship between magmatism and metallogeny in this region. The S and Pb isotopes of the regional silver polymetallic deposits show similar sources of ore-forming materials. According to a compilation of the available age data on the Mesozoic ore deposits in the northern flank of the NCC, we divide the mineralization into the following four periods: 240–205 Ma, 190–160 Ma, 155–135 Ma, and 135–100 Ma. Mesozoic magmatism and mineralization in the Yingfang deposit mainly took place at 245 Ma and 145–135 Ma. We correlate the Pb-Zn-Ag mineralization to metallogeny associated with large-scale inhomogeneous lithosphere thinning beneath the NCC.

Trace element geochemistry and O-S-Pb-He-Ar isotopic systematics of the Lishan Pb-Zn-Cu hydrothermal deposit, NE Hunan, South China

The Jiangnan Orogenic Belt, as an important polymetallic metallogenic belt in South China, hosts numerous Au-Sb, W, Cu, Co, and Pb-Zn deposits. The newly discovered Lishan Pb-Zn-Cu deposit (> 0.64 Mt at 1.64% Pb, 2.54% Zn, and 0.42% Cu) in the northeastern Hunan Province is mainly accommodated by the Late Jurassic to Early Cretaceous Mufushan pluton, with vein-type Pb-Zn-Cu orebodies controlled by nearly N-S-trending faults. However, ore genesis, mineralization process, and the contribution of magmatism are unclear despite its closely spatial association with the Mufushan pluton. In this contribution, in-situ trace element, O and S isotopic analyses, as well as Pb, He and Ar isotopic analyses were conducted to determine the sources of ore-forming materials and fluids and potential mineralization process in the Lishan Pb-Zn-Cu deposit. Four stages of hydrothermal processes, from early to late, are recognized: (1) quartz; (2) quartz + fluorite + chlorite + chalcopyrite + pyrite; (3) quartz + fluorite + chlorite + sphalerite + galena + chalcopyrite + pyrite; and (4) quartz + calcite + chalcopyrite + pyrite. The trace element compositions reveal several important substitutions, including 4Zn2+ ↔ 2Sb3+ + Pb2+ + □ (vacancy) in sphalerite, and Ag+ + Sb3+ ↔ 2Pb2+ and (Ag, Cu, Tl)+ + (Bi, Sb)3+ ↔ 2Pb2+ in galena. The Lishan sphalerite is characterized by high contents of Mn (44.3–244 ppm), Fe (5379–19037 ppm), Co (30.0–186 ppm), and Ga (3.81–381 ppm) and low contents of Ag (1.04–20.7 ppm) and Sb (0.03–1.88 ppm). The sphalerite geothermometer combined with Ga/In (1.32–9716) ratios suggest moderate to low mineralization temperatures of 174–251 °C. The δ34S values of sphalerite, galena, chalcopyrite, and pyrite vary between −5.1 and −0.4‰, consistent with those of the magmatic sulfur source. The Pb isotopic compositions (206Pb/204Pb = 18.140–18.378, 207Pb/204Pb = 15.666–15.819 and 208Pb/204Pb = 38.574–39.207) of sulfides demonstrate that the ore metals were most likely derived from the Mufushan granitoids, but contaminated by the Lengjiaxi Group rocks. The oxygen isotopic values of quartz and noble gas isotopic compositions of sulfides indicate that the ore-forming fluids were mainly formed by the mixture of crust-derived magmatic hydrothermal fluid and meteoric water. Combined with principal component analysis, the Lishan sphalerite is different from the trace element characteristics of sphalerite in other types of deposits. In combination with the available data, we propose that the Lishan deposit belongs to a moderate to low temperature hydrothermal vein-type deposit.