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The Huxu Au-dominated polymetallic deposit is a hydrothermal deposit located in the Dongxiang volcanic basin in the middle section of the Gan-Hang tectonic belt in South China. The orebodies primarily occur within the Jurassic-Cretaceous quartz diorite porphyry, while the genesis of this deposit is unclear. This study focused on geological and mineralogical characteristics, in-situ trace elements and S-Pb isotopes of three generations of pyrite of the Huxu deposit to clarify the distribution of trace elements in pyrite, ore-forming fluid and material sources, and genetic types of the deposit. The mineralization stage of the deposit can be divided into quartz-pyrite stage (S1), quartz-pyrite-hematite stage (S2), quartz-polymetallic sulfide stage (S3) and quartz-hematite stage (S4), with the corresponding pyrite being divided into three generations (Py1–Py3). in-situ trace element data of pyrite show that Au in pyrite mainly exists in the form of solid solution (Au+), and the content is relatively low at all stages (0.18 ppm for Py1, 0.32 ppm for Py2, 0.68 ppm for Py3), while Pb and Zn mainly exist as sulfide inclusions in the pyrite. S-Pb isotopes show that the sulfur and ore-forming material of this deposit are mainly sourced from magma. The mineral association, mineral textures and trace elements in different stages of pyrite indicate that fluid boiling and fluid mixing are the key factors of native gold precipitation in S2 and S4, respectively, while water-rock interaction controlled the precipitation of Pb-Zn sulfides. These integrating with geological characteristics suggests that the deposit should be an intermediate sulfidation epithermal deposit. [ABSTRACT FROM AUTHOR]

The Songshugang deposit is a large Ta–Nb deposit in South China, with Ta–Nb mineralization associated genetically with the granite and pegmatite. A diversity of quartz from topaz–albite granite, quartz–mica pegmatite, quartz–feldspar pegmatite, and quartz–fluorite pegmatite at Songshugang was studied by CL and LA–ICP–MS in order to constrain enrichment mechanisms of Nb and Ta and to find geochemical indicators of quartz for rare metal deposits. Cathodoluminescence image illuminates a canvas of complexity, the quartz from topaz–albite granite, quartz–mica pegmatite, quartz–feldspar pegmatite, and quartz–fluorite pegmatite, exhibits numerous dark CL streaks, patches, and a series of healed fractures. These textures suggest that the rocks were fractured because of deep crustal pressure, and underwent later hydrothermal metasomatism and quartz filling. The quartz from quartz–fluorite pegmatite present limited patches or fractures but distinct growth bands, indicating that the melt fluid composition during the formation of quartz at this stage varies greatly and is less affected by mechanical fragmentation. The LA–ICP–MS analysis of quartz shows that there is a positive correlation between Al and Li in the quartz from topaz–albite granite, quartz–mica pegmatite, quartz–feldspar pegmatite, to quartz–fluorite pegmatite, indicating that Al mainly enters the quartz lattice through charge compensation substitution mechanism with Li. However, our data deviate from the theoretical Li:Al mass ratio of ~ 1:3.89 in quartz, indicating that there may be competition between H+ and Li in a water-rich magmatic environment. The quartz from topaz–albite granite is enriched in K and Na elements, and the quartz from quartz–fluorite pegmatite is enriched in fluorite with a low Ca content in quartz, further elucidating that these rocks were subjected to hydrothermal metasomatism. From topaz–albitite granite to quartz–fluorite pegmatite, Al, Li and Ge content and Al/Ti, Ge/Ti, Sb/Ti ratios in quartz gradually increased, but Ti content gradually decreased, reflecting the high evolution of magma, which can enrich rare metal elements. Based on the characteristics of quartz CL textures and trace elements in topaz–albite granite, quartz–mica pegmatite, quartz–feldspar pegmatite, and quartz–fluorite pegmatite, combined with the albitization and K-feldspathization of rocks, it is suggested that the Nb–Ta mineralization in Songshugang may be influenced by the combined action of magmatic crystallization differentiation and fluid metasomatism. By comparing the quartz in the Songshugang pluton with the quartz in the granite type and pegmatite type rare metal deposits recognized in the world, the Songshugang pegmatite share similarities with the LCT-type pegmatite. Combined with previous studies, the Ge/Ti > 0.1 and Ti < 10 ppm, as well as Al, Li, Ge, Sb, K, Na contents and Al/Ti, Sb/Ti ratios in quartz have the potential to be a powerful exploration marker for identifying granite-like pegmatitic Nb–Ta deposits in other places. [ABSTRACT FROM AUTHOR]

The world-class Huize deposit hosts significant germanium (Ge) resources in the Sichuan–Yunan–Guizhou (SYG) Mississippi Valley-type (MVT) Pb–Zn province of China. The distribution and enrichment mechanism of Ge is still poorly understood. In the main ore-forming stage of Huize, we identified six sphalerite colors from C1 (black) to C6 (white) in transmitted light. Two color sequences are confirmed, including C1 → C2 → C3 → C6 and C1 → C2 → C4 → C5 → C6. We used multiple analytical methods to reveal the Ge distribution and incorporation mechanism into sphalerite and the possible enrichment factors. Our results show that Ge occurs as argutite (GeO2), and in the sphalerite crystal lattice, C1 and C3 sphalerite has up to 593 ppm Ge. Two substitution mechanisms, i.e., Ge4+ + □(vacancy) → 2Zn2+ (e.g., C1 and C2) and Ge4+ + 2Cu+ → 3Zn2+ (e.g., C2, C3, C4, and C5), are inferred from the Huize sphalerite. They show different spatial structures of sphalerite and a weak shift of the white line observed by high-resolution X-ray absorption near-edge structure (XANES) spectroscopy. The trace-element composition of sphalerite suggests that reduced sulfur content of the ore-forming fluid contributes to Ge enrichment, followed by high temperature (> 300 °C). [ABSTRACT FROM AUTHOR]

The Xingluokeng deposit is the largest granite-related tungsten deposit within the Wuyi metallogenic belt in South China. The Xingluokeng intrusion primarily consists of porphyritic biotite granite, biotite granite, and fine-grained granite. The deposit is represented by veinlet-disseminated mineralization with K-feldspathization and biotitization, alongside quartz-vein mineralization with greisenization and sericitization. This study investigates in-situ analyses of quartz compositions from both the intrusion and hydrothermal veinlets and veins. Trace element correlations indicate that trivalent Al3+ and Fe3+ replace Si4+ within the quartz lattice, with monovalent cations (such as Li+, Na+, and K+) primarily serving as charge compensators. Low Ge/Al ratios (< 0.013) of quartz from granites suggest a magmatic origin. The low Al/Ti and Ge/Ti ratios, accompanied by high Ti contents in quartz, suggest that the porphyritic biotite granite and biotite granite are characterized by relatively low levels of differentiation and high crystallization temperatures. In contrast, the fine-grained granite exhibits a higher degree of fractionation, lower crystallization temperatures, and a closer association with tungsten mineralization. Ti contents in quartz from quartz veins indicate Qz-I formed at temperatures above 400 °C, while Qz-II to Qz-V formed at temperatures below 350 °C. Variations in different generations of quartz, as indicated by Al content and (Al + Fe)/(Li + Na + K) ratio, suggest that Qz-I precipitated from a less acidic fluid with a stable pH, whereas Qz-II to Qz-V originated from a more acidic fluid with notable pH variations. Consequently, alkaline alteration and acidic alteration supplied the essential Ca and Fe for the precipitation of scheelite and wolframite, respectively, highlighting a critical mechanism in tungsten mineralization at the Xingluokeng deposit. [ABSTRACT FROM AUTHOR]

The Yangla Cu skarn deposit is located in the central part of the Jinshajiang Suture Zone, southwest China, with a total reserve of 150 Mt Cu @ 1.03%. The newly discovered antimony orebodies at the depth of Yangla are strictly controlled by the stratum, structure, and lithology, which are lenticular and vein-like within the marble fracture zone, which can provide a window into multistage mineralization and ore genesis at Yangla. Mineralization can be divided into three types, Cu–Pb–Zn (skarn) pyrite, galena, and sphalerite, Cu (porphyry) chalcopyrite and pyrite, and Sb (hydrothermal) stibnite and pyrite. The mineral assemblages were stibnite + pyrite + calcite + quartz ± minor scheelite in antimony ores. This study presents quantitative measurements of the trace element compositions of pyrite and stibnite from the Yangla antimony ores. Analysis of pyrite with electron probe microanalysis (EPMA) showed enrichment in Co, Ni, Sb, As, and Mo, and deficit in its S and Fe contents when compared to the stoichiometric concentrations of S and Fe in pyrite. The Sb-related pyrite may belong to sedimentary-reworked genesis and may be modified by hydrothermal fluids, thereby presenting a certain difference (i.e., crystal morphology, texture, and chemical composition) compared to the skarn and porphyry Cu-related pyrite in the Yangla Cu skarn deposit. Analysis of stibnite with EPMA and inductively coupled plasma-mass spectrometry showed enrichment in As, Pb, Sn, Pb, Cu, and Zn, and presented much higher Sb contents and slightly lower S contents when compared to the stoichiometric concentrations of Sb and S in stibnite. Statistical analysis of the stibnite trace elements showed correlations for the elemental pairs Cu–Pb, As–Sb, and Sn–Pb, and the coupled substitution equations Sb3+ ↔ Cu+ + Pb2+, Sb3+ ↔ As3+, and Sn2+ ↔ Pb2+ may be the major factors governed the incorporating Cu, Pb, As and Sn within the stibnite. Moreover, this study preliminary shows that the antimony mineralization may belong to a carbonate replacement hydrothermal genesis at Yangla. [ABSTRACT FROM AUTHOR]

The Gangdese belt in Xizang has experienced both Jurassic subduction and Cenozoic continental collision processes, making it a globally renowned region for magmatic rocks and porphyry copper deposits. Numerous Jurassic intrusions have been identified in the belt. Apart from the quartz diorite porphyry in the large Xietongmen deposit, the Cu mineralization potential of other Jurassic intrusions in this belt remains unclear. This study presents zircon U–Pb dating and trace elements, apatite major and trace elements as well as published whole-rock geochemical and isotopic data of the Dongga tonalite in the central part of the Gangdese belt, aiming to reveal the petrogenesis, oxidation state, volatile content, and Cu mineralization potential of this intrusion. The Dongga tonalite has a zircon U–Pb age of 179.4 ± 0.9 Ma. It exhibits high whole-rock V/Sc values (8.76–14.6), relatively low apatite CeN/CeN* ratios (1.04–1.28), elevated zircon (Eu/Eu*)N values (an average of 0.44), high Ce4+/Ce3+ values (205–1896), and high ∆FMQ values (1.3–3.7), collectively suggesting a high magmatic oxygen fugacity. The Dongga tonalite features amphibole phenocrysts, relatively high whole-rock Sr/Y ratios (20.3–58.9), and lower zircon Ti temperatures (502–740 °C), reflecting a high magmatic water content. Estimation of magmatic sulfur content (0.002–0.024 wt%) based on apatite SO3 contents indicates an enriched magma sulfur content. Combined with previous studies and the collected Sr–Nd–Hf isotopes, the Dongga tonalite is derived from juvenile lower crust related with subduction of the NeoTethys oceanic slab. When compared with Xietongmen ore-bearing porphyries, the Dongga tonalite exhibits remarkable similarities with the Xietongmen ore-bearing porphyries in terms of magma source, tectonic background, magmatic redox state, and volatile components, which indicates that the Dongga tonalite has a high porphyry Cu mineralization potential, and therefore, provides important guidance for the future mineralization exploration. [ABSTRACT FROM AUTHOR]

We use Sr-Nd isotopes of apatite and trace element compositions of apatite-zircon pairs from a major ore layer in each of three selected magmatic Fe-Ti-V oxide ore deposits (Hongge, Panzhihua, and Taihe) in the Emeishan large igneous province (LIP) in southwestern China to contrast the magmatic controls on ore formation. The average contents of REEs in apatite from a representative ore zone/layer in each of these deposits are higher than the predicted values of apatite crystallizing from a melt with REE contents assumed to be the same as the average values of high-Ti basalts in the Emeishan LIP, confirming that the ore-forming magmas all experienced higher degrees of fractional crystallization by major silicate minerals than the average basalt. The apatites Sm/Yb and Sr/Y indicate that the Panzhihua magma was generated at a shallower depth and experienced higher degree of plagioclase fractional crystallization than Taihe and Hongge. The apatite Sr-Nd isotopes can be reproduced by ~ 8 wt% contamination with Precambrian gneiss-schist in the parental magma for Hongge and by ~ 10 wt% and ~ 25 wt% contamination with marbles in the parental magmas for Panzhihua and Taihe, respectively. A recycled, high-T altered oceanic gabbroic component in the mantle source is a viable alternative to the marble contamination model for Taihe. Coexisting zircon trace element compositions reveal that the parental magma for Taihe (ΔFMQ+4.0) is more oxidized than those for Hongge (ΔFMQ−0.4) and Panzhihua (ΔFMQ−0.7), questioning that magma oxidation played a critical role in the genesis of Fe-Ti-V oxide ore deposits in the Emeishan LIP. [ABSTRACT FROM AUTHOR]

The Huashandong W deposit (7.7 Mt @ 0.26% WO3) is a newly discovered Neoproterozoic scheelite-dominated deposit in the world-class Jiangnan tungsten belt, South China. It occurs largely in metasedimentary rocks near the western margin of the Neoproterozoic Jiuling batholith and mainly consists of W-bearing exogreisen, hydrothermal breccias, and quartz veins. Two episodes of Neoproterozoic granite magmatism are identified with zircon U-Pb ages of ca. 830–823 and 807–804 Ma, respectively. According to cross-cutting relationships and mineral assemblages, two periods of hydrothermal alteration and W mineralization, corresponding to the two episodes of granite magmatism, are recognized in the Huashandong deposit. The early period is dominated by greisenization and associated scheelite mineralization whereas the late period is characterized by sericitization, hydrothermal brecciation, quartz veining, and associated scheelite and minor wolframite mineralization. Molybdenite Re-Os dating indicates that the early- and late-period W mineralization took place at ca. 828 and 800 Ma, respectively. Zircon trace element characteristics suggest that the Jiuling granite crystallized from reduced granitic magmas and has the potential for W mineralization. The petrologic and geochemical features of the Jiuling granite, coupled with the zircon U-Pb ages and Hf isotopic signatures and molybdenite Re-Os ages, imply that the Huashandong W deposit is genetically related to two phases of evolved granodiorites in the Jiuling batholith. The magmatic-hydrothermal nature of both metallogenic events is confirmed by H-O isotopes on hydrothermal quartz. [ABSTRACT FROM AUTHOR]

The Dongping gold deposit, located near the northern margin of the North China Craton, contains ore bodies spatially associated with the Devonian Shuiquangou syenite, Cretaceous Shangshuiquan granite, and Archean metamorphic rocks. Major and trace elements and S–Pb isotopes of pyrite from two stages of gold-quartz veins and wall rocks were used to constrain the composition of hydrothermal fluids and metal sources. Stage-1 (early) pyrites are euhedral to subhedral, medium- to coarse-grained, and have low gold contents. Py1a is homogeneous with few fractures, whereas Py1b, which occurs on the edges of Py1a, is porous and has higher metal contents. Stage-2 (late) pyrites are mostly anhedral to subhedral and have smaller grain sizes and higher gold contents than Stage 1. Py2a occurs with sulfide minerals such as galena and chalcopyrite, and Py2b is porous and has the highest gold content (up to 1839 ppm) and smallest grain size. All pyrite samples yield negative δ34S values (− 7.5 to − 3.5‰), reflecting oxidized conditions during mineralization. The ~ 2‰ decrease in δ34S values from Stage 1 (− 4.3‰, − 4.9‰) to Stage 2 (− 7.0‰, − 6.4‰) may reflect a change in the fluid source and/or an increase in fO2. The Pb isotope composition of Stage-1 pyrite is suggestive of a mantle source similar to that of the Shuiquangou syenite, whereas Stage-2 pyrite has more radiogenic Pb isotopic compositions suggestive of an Archean metamorphic source. Combined with previous studies, our trace element and isotopic results indicate that the two stages of pyrite had different sources, with Stage-2 pyrite being more strongly influenced by metasedimentary rocks. We propose that the early stage of low-grade gold mineralization was related to emplacement of the Devonian Shuiquangou syenite, whereas the late stage of high-grade gold mineralization was related to emplacement of the Cretaceous Shangshuiquan granite and leaching of gold from Archean metamorphic rocks. [ABSTRACT FROM AUTHOR]

Carbonate-hosted Pb–Zn deposits frequently contain significant amounts of critical metals such as germanium in sphalerite. However, the textural and chemical controls leading to Ge enrichment remain poorly constrained. Based on textural observations and laser-ablation (multi-collector) inductively coupled plasma mass spectrometry analysis, we investigate the origin, textural control, and incorporation of Ge in the Zhulingou carbonate-hosted Zn(-Ge) deposit, South China, which contains > 400t Ge at 97.9 ppm. Two hydrothermal stages (I and II) and three textural types of sphalerite (Sp1, Sp2, and Sp3) are recognized in stratabound and stockwork Zn(-Ge) orebodies. Acicular colloform Sp1 formed in stage I, whereas euhedral sector-zoned Sp3 is related to stage II. In acicular-euhedral Sp2, both Sp1 and Sp3 are observed. A large variation of Ge concentrations is observed with an average Ge of 1013 ppm in Sp1, decreasing to 621 ppm in Sp2 and to 492 ppm in Sp3. In the three types of sphalerite, Ge concentrations are not correlated to monovalent cations (Cu and Ag), indicative of unusual substitution mechanisms coupled to divalent cations such as Mn, Pb, or Cd. Trace element distribution, sulfur, and lead isotopes suggest that the deeply circulating brines interacted with Ge-rich basement rocks and mixed with shallow biogenic sulfur: This mixing process was certainly the main factor controlling the Ge endowment. The precipitation of acicular sphalerite was likely controlled by a combination of specific fluid conditions (i.e., low T and pH, and rapid mineral growth rate) and fluid mixing. These conditions leading to the formation of acicular sphalerite were favorable for Ge enrichment, compared to co-existing euhedral grains generally less rich in Ge. [ABSTRACT FROM AUTHOR]

Early Cambrian black shales on the Yangtze Platform host a regionally distributed highly metalliferous sulfide-rich carbonaceous unit which has been the subject of extensive debate. This marker unit, with a few centimeters or tens of centimeters in thickness, displays extreme enrichment in Mo and Ni (wt% range), and in a broad spectrum of other metals such as As, Au, PGE, Re, Cu, Zn, Cd, Ag, Sb, Se, Tl, and Hg, and occurs discontinuously along the western passive margin of the Yangtze Platform. It grades laterally in stratigraphically equivalent meter-thick vanadium-rich shale and tens-of-meter-thick sapropelite (combustible shale). New Cu and Zn isotope data, combined with existing Cd, Cr, Ni, Mo, Hg, and Se isotope and other chemical data, allow to attempt an integrated view on the formation of this intriguing unit of hyper-enriched metalliferous black shale. The authigenic Cu enrichment in the 1000-ppm range has produced no or little Cu isotope fractionation (0.03 ± 0.26 ‰ δ65Cu) beyond the lithogenic background. Heavy zinc and cadmium isotope enrichment in the sulfidic samples (1.11 ± 0.18 ‰ δ66Zn, 0.31 ± 0.10 ‰ δ114Cd) is controlled by sulfide fractionation and contrasts with V-rich and barren shale (0.60 ± 0.18 ‰ δ66Zn, 0.00 ± 0.14 ‰ δ114Cd). The distinctly negative Ni isotope composition of the metalliferous unit (−0.84 ± 0.05 ‰ δ60Ni) with Ni in the percent range has been interpreted as due to hydrothermal activity related to the leaching of mafic rocks and their sulfides. Sorption processes (Fe-oxyhydroxides) and redox cycling in the water column and the bottom sediment with microbial activity could be an alternative interpretation. The extreme metal enrichment can be understood as due to a process chain, from high biological productivity in the oxic photic zone to sulfate reduction in the deeper sulfidic water column and upper sediment layer. Key to the metal enrichment seems to be extremely low clastic sedimentation and advanced carbon destruction by anaerobic oxidation. Hydrothermal input of basinal brines along the rifted margin of the Yangtze Platform was likely a part of this scenario. [ABSTRACT FROM AUTHOR]

The textures and compositions of hydrothermal apatite grains have been reported in many iron oxide-apatite (IOA), porphyry, and rare-earth elements (REE) polymetallic deposits. However, such information for apatite in hydrothermal gold deposit is not available. In this study, we present integrated textural, elemental, and in situ oxygen isotopic data of hydrothermal apatite grains from the Hatu gold deposit (56t Au, average grade: 5 g/t) in the West Junggar, Northwest China, to investigate the detailed mineralization processes and nature of ore-forming fluids. Hydrothermal apatite is present within the quartz-sulfide ores at the Hatu gold deposit. Apatite grains of the Hatu gold ores contain abundant fluid inclusions and fine sulfide crystals, indicating that they are closely related to gold mineralization. Three types of hydrothermal fluorapatite (Ap1, Ap2, and Ap3) were revealed by Cathodoluminescence (CL) imaging. The Ap1 and Ap2 formed in the auriferous ore-forming stage, whereas the Ap3 formed in the post-ore stage. The three types of apatite have distinct total REE concentrations (216–751 ppm for Ap1, 14–120 ppm for Ap2, and 914–1422 ppm for Ap3) as well as chondrite-normalized REE distribution patterns. The textures and compositions of different apatites are inconsistent with dissolution–re-precipitation processes but instead point to three episodes of apatite formation in the Hatu hydrothermal system. The Ap3 has different REE and lower Eu/Eu* values (0.97–1.72) than Ap1 (1.34–4.50) and Ap2 (1.69–4.95), indicating a change of fluid compositions and a decrease of oxygen fugacity from the auriferous ore-forming stage to post-ore stage. All three types of apatite (Ap1, Ap2, and Ap3) show relatively high and consistent oxygen isotope compositions ranging from 14.2 ± 0.3‰ to 15.2 ± 0.2‰, from 14.5 ± 0.2‰ to 15.0 ± 0.3‰, and from 13.8 ± 0.3‰ to 15.4 ± 0.2‰, respectively. Their calculated δ18Ofluid values are higher than magmatic–hydrothermal fluids but consistent with those from metamorphic fluids derived from meta-basalts. The near-zero δ34S values of hydrothermal pyrite grains in the gold ores are much higher than those of pyrite framboid grains in the ore-hosted sedimentary rocks (− 41.1 to − 24.3‰), suggesting the sulfur may be derived from meta-basalts rather than sedimentary rocks in the mining area. Taken together, we suggest that Hatu is an orogenic gold deposit formed by fluids and metals derived from metamorphic de-volatilization of meta-basalts at depth. Our study highlights that a combination of CL imaging, in situ trace elements, and oxygen isotope compositions of hydrothermal apatite can be a novel and powerful tool to trace the nature of ore-forming fluids in the hydrothermal gold deposits. [ABSTRACT FROM AUTHOR]

The Guanting Pb–Zn deposits in the Jianshui area, southern Yunnan Province, SW China, are located in the conjunction of the Yangtze Block, Cathaysian Block and Sanjiang Block, and they belong to part of the Sichuan-Yunnan-Guizhou (SYG) Pb–Zn metallogenic province. The Pb–Zn orebodies occur in basaltic and limestone breccia at the interfaces between the Maokou limestone and Emeishan basalt. Here, we use zircon U–Pb dating, Rb–Sr dating, trace elements and S isotope data of sulfides to constrain the ages and genesis of deposits. Petrological investigations reveal two main stages of mineralization. Early-stage sphalerites yield a Rb–Sr age of 251.1 ± 8.5 Ma, and it is contemporaneous with the Guanting basalt within the range of error, which has a concordant age of 247.3 ± 4.2 Ma. This metallogenic age indicates that early-stage mineralization may be related to Emeishan volcanic hydrothermal activity. Initial value of 87Sr/86Sr (0.709) and rare earth elements (REE) patterns of minerals suggest that ore-forming materials were likely derived from mixed mantle-crust sources, and paleo-seawater participated in deposition of Pb–Zn ore. There are two peaks of sulfur isotope (δ34S) in the Huangtian and Xinzhai deposits. The δ34S of early-stage sulfide is concentrated at + 1.1‰ VCDT to + 3.9‰ VCDT, suggesting that the sulfur was directly supplied by basaltic volcanic activity. Late-stage colloidal sulfides have δ34S ranging from + 6‰ VCDT to + 9‰ VCDT, suggesting marine sulfur origin, and that reduced sulfur derived from carbonate strata by thermochemical sulfate reduction (TSR). According to the geochemical characteristics, geochronology and regional geodynamic setting, we assume that early-stage mineralization in the Guanting Pb–Zn deposits is Emeishan volcanic hydrothermal mineralization, and late-stage mineralization is similar with Mississippi Valley-type (MVT) deposit. Our results provide new evidence for understanding hydrothermal mineralization associated with the Emeishan flood basalts in the SYG area. [ABSTRACT FROM AUTHOR]

The Dachang Sn-polymetallic ore district in South China is the second largest tin district in the world with a tin reserve of over one million tonnes. Zn-Cu skarn and stratiform, massive, and vein Sn-Pb-Zn ores are all present in this district. This has led to a debate as to whether the Sn orebodies were formed by Cretaceous magmatic-hydrothermal replacement or Devonian submarine exhalative-hydrothermal sedimentation. Here, we present a systematic investigation of the major, trace element, and boron isotopic compositions of different types of tourmaline in the Dachang ore district. Tourmaline disseminated in the Longxianggai granite and pegmatite veins belongs to the schorl series and has high contents of Li, Zn, and Ga. The δ11B value of primary magma of the Longxianggai granite is estimated to be about −13‰, close to the global average δ11B value (−11‰) for S-type granites. Tourmaline from quartz-tourmaline veins in the Longxianggai granite has similar chemical composition to the magmatic tourmaline and likely formed from hydrothermal fluids exsolved from the evolved granitic melt. The δ11B value of the initial hydrothermal fluids is also calculated to be about −13‰. Tourmalines from the skarn and sulfide ores in the Lamo deposit have higher Mg/(Mg+Fe) and lower Na/(Na+Ca) ratios and higher contents of Be, Ge, Sr, and Sn than magmatic tourmaline. These patterns likely reflect input of elements derived from the host Devonian limestone. The δ11B values of the hydrothermal fluids are estimated to be between −13 and −10‰, suggesting evolved magmatic-hydrothermal fluids related to the Longxianggai granite. Tourmalines from the stratiform and vein ores in the Changpo-Tongkeng deposit are extremely Mg-rich and mostly belong to the dravite series. They have high contents of Sc, V, Cr, Sr, and Sn and show positive Eu anomalies. The δ11B values of these B- and Sn-rich fluids are estimated to be between −15 and −10‰, suggesting that the fluids also have a magmatic-hydrothermal origin. These fluids are most likely derived from the same granitic magma source, but may have interacted with the Devonian volcanic rocks. [ABSTRACT FROM AUTHOR]

The lower Cambrian black rock series in eastern Yunnan province is a high-quality shale gas reservoir with great prospect for oil-gas exploration. However, the depositional conditions and mechanisms of organic matter enrichment are not well understood. In this study, geochemical characteristics of total organic carbon (TOC) and major and trace elements of fourteen black rock series samples from Dahai outcrop in eastern Yunnan province are systematically investigated to analyze the paleoenvironment and their effects on organic matter enrichment and established the accumulation model of organic matter. Results show that TOC contents of the four lithologic units of Qiongzhusi Formation black rock series are 0.70, 0.34, 1.77, and 0.27, respectively, which suggests that TOC content is generally low (mean = 0.51%). The main elements show that P2O5, CaO, and MgO are relatively rich, whereas other elements depleted. The enrichment factors (EFs) of trace elements showed that Pb and Zn are highly enriched in all samples, and Cu, Sr, Ba, U, Mo, V, Be, and Mo are also enriched in different lithofacies units. The elemental anomalies may be related to hydrothermal activities, which may lead to the distortion of some paleoenvironmental indicators to some extent. The Rb/Sr and Sr/Cu values show that the palaeoclimate gradually changed from dry to humid. Al concentrations indicate a gradual increase in terrigenous detritus supply. The hydrodynamic conditions and sedimentation rates implied by Zr/Al and Ti/Al values correspond well with lithology and grain size. Based on the comprehensive analysis of B/Ga and Sr/Ba ratios, it is considered that the black rock series in Qiongzhusi Formation was mainly formed in brachial water. Multiple paleoredox indicators (e.g., Ni/Co, V/Cr, U/Th, and V/(V+Ni) ratios) suggest that the sedimentary environment is mainly oxidized, which is usually considered unfavorable for organic matter preservation, and it also forms carbonaceous shale (unit 3) in a dysoxic environment. The Mo/TOC ratios suggest that the sedimentation during Qiongzhusi Formation period was under restricted conditions. The paleoproductivity indicated by P/Ti, Ni/Al and Babio values decreased gradually from medium level to low level. In summary, relatively high paleoproductivity is a prerequisite for organic matter accumulation and less terrigenous debris supply, and relatively arid climate and reductive conditions are favorable for the preservation of organic matter. [ABSTRACT FROM AUTHOR]

The Youjiang Basin is characterized by a wide distribution of Au and Sb deposits. These deposits are mainly hosted by sedimentary rocks from Cambrian to Triassic and are structurally controlled by faults and folds. Three types of Sb mineralization can be distinguished based on geologic characteristics, economic metals, and mineral associations. The first type is dominated by Sb mineralization but contains minor or little Au, similar to the large Qinglong deposit. The second type has a spatial association with the gold deposit but formed independent Sb mineralization, reminiscent of the Badu deposit. In the third type, Sb generally formed as an accompanying element in the Carlin-type gold deposit, and stibnite occurred as euhedral crystals filling the open space and faults in the late stage of gold mineralization, analogous to the Yata deposit. Trace element concentrations and sulfur isotopic ratio of stibnite, and oxygen isotope of stibnite bearing quartz were analyzed to infer the ore source(s) for Sb mineralization and genesis. To distinguish the various types of stibnite mineralization between the deposits, Cu, Pb, and As have recognized most diagnostic, with an elevated concentration in Au and Au-Sb deposits and depleted in Sb deposit. The δ34S isotopic composition of stibnite samples from three deposits show a wide variation, ranging from −6.6 ‰ to + 17.45 ‰. Such isotopic values may indicate the sedimentary sulfur source, introduced by fluid–rock interaction. On the other hand, fluid mixing of several end members cannot be excluded. The calculated δ18O isotopic data of Sb-bearing quartz show the initial ore fluid in Au and Au-Sb deposits most likely have a magmatic or metamorphic origin that enriched during fluid–rock interaction, and Sb deposit characterized by initial meteoric water. From these data, we proposed that different lithologies, fluid–rock interaction, fluid pathways, and different ore fluids controlled the compositional evolution of fluids, which might be the main reason for the diversity of Au or Sb mineralization. [ABSTRACT FROM AUTHOR]

Mafic lava is generally used to study the oxygen fugacity of lithospheric mantle. However, some studies confirmed that the high oxygen fugacity of mafic lava from lithospheric mantle may be result of auto-oxidation during the late magma evolution. Whether mafic lava reflects the oxygen fugacity of source area remains controversial. The major and trace element compositions of biotite, amphibole, and plagioclase as well as the Sr isotopes of plagioclase were in-situ examined aim to evaluate the variation in oxygen fugacity of mafic magma during transportation from depth to current location. Mineralogical characteristics show that the dikes originate from an enriched lithospheric mantle source and experienced very little or no crustal contamination during the magma transfer process. Clinopyroxene, plagioclase, Al-rich amphibole, biotite, and Mg-rich amphibole crystallized successively as the depth of magma reduced from 75.9 to 0.8 km. Fayalite-magnetite-quartz (△FMQ) and Ni-NiO (△NNO) are used as reference oxygen fugacity buffers in this study. The average oxygen fugacity of mafic magma gradually increases from △NNO-1.50 (lithospheric mantle source) to △NNO + 2.74 (near the surface) during magma evolution. Calculation results from clinopyroxene, amphibole and biotite show that the oxygen fugacity of magma increases during fractionation of clinopyroxene, plagioclase, amphibole, and biotite. However, the above fractionation cannot generate such a wide variation in oxygen fugacity. Moreover, it is not caused by degassing in terms of the low carbonate mineral content and increasing S6+/Stot ratios during fractionation. Previous studies have shown a rapid cooling and a high H2O content of the Jiaodong mafic magma. Combine with the garnet-spinel transition zone of mantle lithosphere and magnetite observed in petrography, we tend to propose that the variation in oxygen fugacity of mafic magma were caused by magnetite-spinel fractional crystallization at depth. Low-pressure metamorphic amphibole and the country rocks of Late Mesozoic monzodiorite, which has a much higher oxygen fugacity than the stable range of magnetite-spinel, indicated that the secondary alteration in last stage of magma evolution may cause additional variation in oxygen fugacity. In that case, mafic lava cannot be used to determine the oxygen fugacity of source rock. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Qi191 Au deposit is a newly discovered granite-hosted Au deposit in the Qiyugou Au orefield, located in the southern margin of the North China Craton (NCC). Gold ore bodies are hosted by both the Qi191 hornblende monzogranite and the Taihua Complex and are composed of disseminations and sparse veins. K-feldspar, quartz-sericite, and sericite-chlorite alteration formed outward from the center to the periphery of the mineralized granite. Principal ore minerals include galena, pyrite, and chalcopyrite, with minor sphalerite, hematite, pyrrhotite, gold, famatinite, and hessite. The Qi191 Au deposit formed over four successive stages of hydrothermal mineralization: a quartz stage (I), a quartz-pyrite-galena stage (II), an economic quartz-calcite-galena-pyrite stage (III), and a quartz-calcite stage (IV). The Qi191 hornblende monzogranite yields a SIMS zircon U–Pb age of 131.3 ± 1.0 Ma. Hydrothermal sericite yields a plateau 40Ar–39Ar age of 132.9 ± 1.4 Ma, which is consistent with the zircon U–Pb age, suggesting that the Qi191 Au deposit is generically related to the hornblende monzogranite. Trace element contents and S isotopic compositions of sulfides indicate that metals and S entered the hydrothermal fluid as pulses. The equilibrium temperature of S and the isotopic compositions of S–Pb reflect a magmatic source. Gold mainly precipitated as native gold in a relatively acidic and reducing environment. This work suggests that further exploration for magmatic hydrothermal gold deposits in the Qiyugou and more widely in the southern margin of the NCC should target hornblende monzogranites such as the Qi191 and Qi189 granitoids. [ABSTRACT FROM AUTHOR]

Dongguashan is one of the largest porphyry-skarn Cu-Au deposits in eastern China and titanite is found in the ore system. Five types of both magmatic and hydrothermal titanites are distinguished, based on their textural and chemical characteristics. Types 1 and 2 titanites are magmatic in origin whereas types 3, 4, and 5 are hydrothermal. Magmatic titanites are wedge-shaped and display concentric and sector zoning, whereas hydrothermal titanites show a wide range of textures that vary with different alteration stages. REE, Sn, Mo, and Cu are enriched in magmatic titanites (types 1 and 2). In contrast, vanadium and HFSE are enriched in hydrothermal titanites, especially in type 4 titanite from the propylitic alteration zone. Magmatic titanite (type 1) coexists with magnetite and K-feldspar and crystallized in oxidized and H2O-rich magma at 730–760 °C. Type 2 titanite contains ilmenite inclusions reflecting changes in the fO2 of the magma chamber, possibly caused by input of mafic magma. The mobility and enrichment of HFSE and association with fluorapatite reflect the F-rich composition of the magmatic-hydrothermal fluid at Dongguashan. The relationship between titanite textures and chemistry indicates that titanite can serve as a recorder of magmatic-hydrothermal processes in porphyry copper systems. U-Pb dating of type 4 titanite from the propylitic alteration zone and type 5 titanite from skarn yielded ages of 139.0 ± 2.6 Ma and 137.0 ± 2.0 Ma, respectively, indicating that it formed synchronously with the associated quartz monzodiorite. [ABSTRACT FROM AUTHOR]

The Yangla Cu deposit is the largest ore deposit in the Jinshajiang polymetallic metallogenic belt, northwest Yunnan, China. There is no consensus on the genesis of the ore deposit owing to the limited studies on the chemical compositions of sulfides. This study used an electron probe micro-analyzer to constrain the chemical compositions of pyrite, chalcopyrite, molybdenite, and sphalerite in the porphyry Cu ore of the Yangla Cu deposit and compared them with the chemical compositions of sulfides in the skarn Cu ore. The trace element contents and their occurrences were used to estimate the metallogenic temperature and infer the genesis of the Yangla deposit. The results show that the sulfides in the porphyry Cu ores have variations of ore element concentrations relative to their theoretical values. Pyrite is depleted in S but elevated in Fe; chalcopyrite is depleted in Cu, Fe, and S; and molybdenite and sphalerite are enriched in S whilst depleted in Mo and Zn. The concentrations of the main metallogenic elements Cu, Fe, Mo, Zn, and S in the porphyry are generally lower than those in skarn, suggesting that the porphyry ore was formed in a moderate to moderate-high temperature metallogenic environment. The formation time may also be slightly later than that of the skarn Cu ore. Elements such as As, Co, Cu, Pb, Zn, Mo, Cd, and Ni mainly exist as isomorphic replacements and mineral inclusions in the sulfides of both porphyry and skarn Cu ores. The trace element features of sulfides in the two ore bodies show that the Yangla Cu deposit may be a composite super imposed ore deposit, and its formation has undergone the process of exhalative-sedimentary to skarn-porphyry mineralization. [ABSTRACT FROM AUTHOR]

This work reports an important episode of extensional, mafic magmatism that impacted the North China Craton (NCC) during the Permo-Triassic and influenced the evolution of this Craton. We sampled 30 representative mafic dykes cropping out in eastern NCC, within the Hebei Province, China. New zircon LA-ICP-MS U–Pb ages, geochemical, and Sr–Nd–Pb isotopic data for these mafic dykes identified them as typical dolerites formed between 211.9 ± 1.3 and 263.9 ± 2.6 Ma. The mafic rocks fall into the alkaline and calc-alkaline series. They are enriched in light rare earth elements, some large ion lithophile elements (e.g., Rb, Ba, and Sr), K, and Pb, and depleted in Nb, Ta, and Ti. The dykes have high initial 87Sr/86Sr ratios (0.7034–0.7178), negative εNd (t) values (−2.2 to −5.9), and relatively constant initial Pb isotopic ratios, that are EM1-like: (206Pb/204Pb)i = 16.39–16.74, (207Pb/204Pb)i = 15.22–15.24, and (208Pb/204Pb)i = 36.66–36.86, respectively. Our results indicate that the Hebei Province dolerites were likely derived from magma generated through low-medium degree partial melting (3.0–20%) of an EM1-like garnet-lherzolite mantle source. The parental magmas fractionated olivine, clinopyroxene, and Ti-bearing phases with obvious crustal contamination during rapid ascent and dyke emplacement. Since the possible influence of subduction of the Yangtze Plate has been excluded, we propose a model for the origin of the investigated mafic rocks, involving the Permian collision between the Siberian Block and the NCC. The mafic dykes of eastern NCC within Hebei Province formed during a period of crustal thinning in response to extension after the early Permian collision. [ABSTRACT FROM AUTHOR]

The Shuiyindong Carlin-like gold deposit, the largest one of this type in China, is located in the Late Paleozoic–Early Mesozoic Youjiang basin. The pyrites in the studied ore bodies (No. I to V) can be divided into four main types plus several sub-types: (1) As-poor pyrites include Py1 (Py1a and Py1b), Py2, and Py3; and (2) As-rich pyrite Py4 (Py4a and Py4b). In situ LA-ICP-MS analyses show that the As-rich pyrite also contains higher Au, Cu, Sb, and Tl than the other pyrite types. In situ NanoSIMS analyses show the δ34S variation of Py1 (48.1~67.5‰), Py2 (2.4~7.6‰), Py3 (9.2~14.2‰), and Py4 (− 3.0~6.6‰), with the average values of 58.1‰, 5.1‰, 11.4‰, and 3.1‰, respectively. The large δ34S variations of As-poor pyrites may reflect a sedimentary source. However, the narrow ranges of δ34S values for the As-rich pyrite (Py4) may not reflect a sedimentary but a magmatic or metamorphic origin. A metamorphic sulfur source of Py4 is favored due to paucity of coeval magmatism in the region and decreasing variations of δ34S values from Py1 to Py4. Integrated transmission electron microscope (TEM) and NanoSIMS element mapping show that the distribution and concentration of Au are discordant with As and Cu at the submicron scale, also implied by the occurrence of some of Au as nano-submicron particles in Py4. Overall, our new data indicate that the ore fluids were not only enriched in Au but also in As, Cu, and S. Taking an alternative of fluid oxidation probably resulting in the decreasing δ34S values of Py4, our result of I to V orebodies indicates the mixing between the underlying metamorphic fluid and meteoric water. Integrated variations in δ34S and As-Au-Cu correlations across individual pyrite grains infer the physicochemical changes of aqueous and/or aqueous-carbonic fluids along migration paths. [ABSTRACT FROM AUTHOR]

The Yamansu iron deposit is hosted in submarine volcanic rocks in the Aqishan–Yamansu belt of Eastern Tianshan, NW China. A geological cross-section for the Carboniferous strata in the ore district shows that ore bodies in the Yamansu deposit are hosted in andesitic crystal tuff of the third cycle of the Carboniferous Yamansu Formation. This indicates an association between mineralization and volcanism. The orebodies are strata bound and lensoid and generally share the occurrence state of the host rocks. Magnetite mineralization mainly occurs asbreccia ores, ores in the mineralized volcanic rocks, massive ores, and sulfide-rich ores according to their structures and sequences of formation. Trace element compositions of magnetite from various types of ores were determined by LA-ICP-MS. The dataset indicates thatdifferent types of magnetite havedistinct trace element contents correlated to their formation environments. Magnetite crystals from breccia ores have high Ti, Ni, V, Cr, and Co and low Si, Al, Ca, and Mg contents, indicating crystallization from a volcanic magmatic eruption, which is consistent with field evidence of coexisting altered volcanic breccia. Magnetite crystals from ores in the mineralized volcanic rocks have moderate Ti, Ni, V, Cr, and Co contents. In contrast, magnetite from massive ores and sulfide-rich ores have low concentrations of Ti, Cr, Ni, and V, high concentrations of Si, Al, Ca, and Mg, and evidence of hydrothermal magnetite. In-situ magnetite compositions imply a magmatic-hydrothermal process. Although δ18O values for magnetite grains fromYamansu vary (+ 1.3 to + 7.0‰), they all plot in the range field of volcanic iron deposits, and they also record a magmatic-hydrothermal process. The compositions of Yamansu magnetites are interpreted as controlled mainly by temperature, fluid, host rock buffering, oxygen fugacity, and sulfur fugacity. The metallogenic conditions of the Yamansu deposit changed from high temperature and low oxygen fugacity to low temperature and high oxygen fugacity. However, more fluid-rock reactions and higher sulfur fugacity were involved during the deposition of massive ores and sulfide-rich ores. [ABSTRACT FROM AUTHOR]

The Xiasai–Lianlong metallogenic belt in the central Yidun Terrane (China) hosts several Sn–Ag and (Sn–) Ag–Pb–Zn deposits, which are spatially associated with Cretaceous granites. The Xiasai Ag–Pb–Zn deposit (about 0.27 Mt Pb+Zn, 1028 t Ag, and 20,000 t Sn) is the largest deposit in the belt and is related to a monzogranite intrusion. The deposit consists of sulfides in hydrothermal veins, resulting from three successive mineralization stages (I–III). A Rb–Sr isochron of sphalerite samples yielded an age of 99 ± 3 Ma, and zircon U–Pb laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) dating of the Xiasai monzogranite gave ages between 102 ± 1 and 101 ± 1 Ma. The Xiasai monzogranite has a weakly peraluminous A-type granite composition, with high SiO2, alkali, and FeOt contents and low CaO, MgO, and TiO2 contents. It is marked by enrichments in Rb, Th, and U, with depletions in Ba, Nb, Sr, P, and Ti relative to the primitive mantle. The REE patterns show a negative slope due to LREE enrichment with negative Eu anomalies (Eu/Eu* = 0.1–0.3). The Xiasai monzogranite, with variable εHf(t) values (− 2.7 to 0.6) and Meso- to Neoproterozoic two-stages Hf model ages (TDM2 = 925–1095 Ma), was probably derived from mixing of melts derived from partial melting of the Paleoproterozoic crustal basement and the Early Cretaceous mantle in an extensional tectonic setting. Hydrothermal fluids are characterized by high temperatures (423–481 °C) and salinities (14.9–19.0 wt% NaCl) for Sn mineralization (stage I), moderate temperatures (285–386 °C) and salinities (3.5–8.0 wt% NaCl) for the Cu–Zn mineralization (substage II-2), and low temperatures (158–242 °C) and salinities (3.4–5.7 wt% NaCl) for the Ag–Pb mineralization (substage II-3). The H–O isotopes indicate that the hydrothermal fluid likely has a magmatic component that mixed over time with infiltrating meteoric water and organic matter during fluid–rock interactions. The δ34S values of sphalerite range from − 9.7 to − 3.1‰ and those from galena from − 10.5 to − 4.9‰. The estimated δ34S value of the hydrothermal fluid is − 8.5‰, using the sulfur isotopic fractionation of sphalerite–galena pairs that are interpreted to be in equilibrium. Sulfides from substages II-2 and II-3 have relatively homogeneous Pb isotopic compositions, which are similar with those of K-feldspars from the Xiasai monzogranite. Geochronological and isotope data support a magmatic–hydrothermal origin for the Xiasai Ag–Pb–Zn deposit. [ABSTRACT FROM AUTHOR]

The Sanjiu uranium ore field, located in the central of Zhuguangshan granitic batholith, is a newly discovered granite-related uranium ore field in South China. The main sulfide in the ore field is pyrite, which is closely related to uranium mineralization. The textures, major and trace elements, S–He–Ar isotopes compositions of pyrites in ores of different grade were observed and/or analyzed by optical microscope, scanning electron microscope, electron microprobe, laser ablation inductively coupled plasma mass spectrometry, and noble gas mass spectrometer (Helix-SFT). It is observed that these U-related pyrites are generally euhedral–subhedral with dissolution textures, anhedral variety with colloform texture, veinlet and fine particles, and the color of the associated minerals is mostly dark hue, such as purple–black fluorite, dark-red hematite, and dark-green chlorite, etc. The analytical results show that the average compositions of major elements in pyrite are FeS1.944. Pyrites are characterized by S-deficiency, low content of Co and Th, and Co/Ni > 1, which indicate that these ores are of low-temperature hydrothermal origin. We found that the higher the grade of ore, the more deficient in S, the more obvious negative δ34S, and the higher REE content (close to U-rich granitic pluton) of pyrite. The S–He–Ar isotopic compositions of various varieties of pyrites indicate that the ore-forming fluids mainly come from crust-derived fluids and mixed with mantle-derived fluids. [ABSTRACT FROM AUTHOR]

We report U–Pb dating of zircon, as well as geochemical and Hf isotope data, in order to constrain the formation time, magma source, and tectonic setting of granite porphyry dykes in the Xicha gold–(silver) district in southern Jilin Province, Northeast China. The zircon grains are euhedral–subhedral, display oscillatory growth zoning and have Th/U ratios varying between 0.11 and 0.78, which together imply a magmatic origin. The dating results indicate the porphyry formed in the Early Cretaceous (122 ± 1 Ma), and it contains SiO2 = 70.64–72.31 wt%, Al2O3 = 13.99–14.64 wt%, K2O + Na2O = 6.96–7.81 wt%, K2O/Na2O = 1.24–2.10, and A/CNK = 1.11–1.41. Chemically, the porphyry belongs to a high-K calc-alkaline S-type granite. Chondrite-normalized rare earth elements (REE) patterns show LREE enrichment, light rare earth elements (LREE)/heavy rare earth elements (HREE) = 9.93–11.97, (La/Yb)N = 11.08–15.16, and δEu = 0.69–0.95. On the trace element spider diagram, large ion lithophile elements such as Rb, Ba, K, Th, and U are enriched, whereas the high field strength elements Ti and P are depleted. The εHf(t) values of zircon from the granite porphyry vary between − 17.1 and − 13.2, and their Hf two-stage model ages vary from 2.01 to 2.26 Ga, implying that the magma was derived from partial melting of old lower crust. The granite porphyry dykes and many A-type granites in the region formed at the same time, suggesting an extensional environment. The combination of the occurrence of strong magmatism, large-scale mineralization, and extensional tectonics throughout much of Eastern China indicate that the Early Cretaceous was a period of significant lithospheric thinning. The southern Jilin Province, therefore, experienced lithospheric thinning during the Early Cretaceous. [ABSTRACT FROM AUTHOR]

The Axi gold deposit is one of the largest epithermal deposits in northwestern China and is characterized by multistage generations of pyrite associated with gold mineralization. Genetic models for superjacent epithermal Au and porphyry Cu systems involve either contemporaneous or episodic mineralization, implying different metal sources and ore-forming events. Nine pyrite separates from disseminated ores associated with pyrite-sericite-quartz alteration in the Axi deposit yield a Re–Os isochron age of 350 ± 10 Ma (MSWD = 5.1, initial 187Os/188Os (IOs) = 0.20 ± 0.11). This age likely reflects a mixed contribution of two subtypes of disseminated pyrite (Py1) based on zoned pyrite crystals. The isochron age of 353 ± 6 Ma (MSWD = 1.6, IOs = 0.107 ± 0.021, n = 6), excluding samples with pyrite cores, overlaps previous ages for andesite from the Dahalajunshan Formation (ca. 356 Ma), indicating that the early mineralization event occurred shortly after the formation of host rocks (ca. 353 Ma). Pyrite from disseminated ores shows little variation of sulfur isotopic compositions (+ 2.9 to + 4.0‰) and has high Cu, Co, Ni, and V contents, which favors a magmatic-hydrothermal origin. Pyrite grains from gray quartz veins yield a younger Re–Os isochron age of 332 ± 8 Ma (MSWD = 0.22, n = 4). Vein-hosted pyrite shows characteristics of a mantle-derived magma source (IOs: 0.171 ± 0.024; δ34S: − 0.10~+ 3.10‰), which result from the intrusion-driven convective hydrothermal circulation accompanying fluid exsolution and metal remobilization from basement and wallrocks. Our data demonstrate that the Axi gold deposit was formed during two temporally separated hydrothermal events. This model of ore formation may apply to other epithermal-porphyry deposits within the Axi–Tawuerbieke district: disseminated Au and porphyry-style Au ± Cu mineralization occurred shortly after magmatic activity (356–353 Ma) whereas epithermal-style Au mineralization occurred at ca. 332 Ma. [ABSTRACT FROM AUTHOR]

The Ekomedion two-mica granite, southwestern Cameroon, has potential for uranium and molybdenum mineralization. Here, we present LA-ICP-MS U–Pb ages, Lu–Hf isotope characteristics, trace element concentrations and Ti-geothermometry of zircon from this granite hosting U–Mo mineralization in pegmatitic pods. The majority of zircon are CL-dark though some CL-bright cores were also identified. U–Pb zircon age data range from 121 ± 3 to 743 ± 11 Ma with only 5 of 34 ages being near concordant. The concordant mean age of 603 ± 12 Ma is similar to ages of granitic intrusions along the Central African Shear Zone in Cameroon. Apparent ages with mean of 261 ± 6 Ma reveal open system behavior with respect to Pb and/or U. Zircon εHfi values range from − 20.3 to − 0.3. This implies that U–Mo was remobilized during partial melting of the surrounding gneiss. Zircon Th/U > 0.1 as well as an increasing Hf with decreasing Th/U indicates that fractional crystallization was the main factor that controlled U–Mo mineralization in pegmatitic pods. Y and Y/Ho ratios cluster from 29 to 33 close to the chondritic ratio of 28 and indicate fractionation of Y and Ho with low F contents during the earliest stages of crystallization. Late stage accumulation of F-rich magmatic-hydrothermal fluids impacted U–Mo mineralization as a ligand. Zircon contains a prominent negative Eu anomaly pointing to a fractionating system rich in plagioclase. Calculated Ti-in-zircon temperatures span 672 °C to 1232 °C with the temperatures at the high end reflecting interference from mineral inclusions in the zircon grains while the lower temperature values are linked to crystallization. [ABSTRACT FROM AUTHOR]

The Muli antimony deposit is located in the Au–Sb polymetallic metallogenic belt in south-eastern Yunnan, China. In this paper, we investigated the concentrations of trace elements in gangue minerals, mainly calcite, quartz, and pyrite, which were formed at different metallogenic stages. Meanwhile, the host rocks, predominantly composed of limestone, are also analysed for comparison. The calcite from the Nadan ore section is enriched with medium-heavy rare earth elements (M-HREEs), likely due to the presence of a high concentration of Fe and Mn impurities, which results in the preferential enrichment of M-HREEs in the calcite. Alternatively, the calcite may be precipitated from the M-HREE-rich granitic leaching fluid. In the Muli ore section, both quartz and pyrite in the metallogenic period show enrichment with light rare earth elements (LREEs), and the wall rock is also enriched with LREEs, which indicates that the wall rock material was involved in the metallogenic process. The W-shaped tetrad effect of quartz in the late metallogenic stage was interpreted to determine extensive fluid–rock interactions in highly fractionated Si-rich systems. Fe and Mn impurities cause M-HREE to be preferentially enriched with calcite to some extent. Whether mineralization is related to granite deserves further study. Eu and Ce anomalies of different types of gangue minerals indicate that the temperature and the fO2 were constantly changing during mineralization, and the temperature of the main ore-stage was higher than 200 °C in an oxidized state. The various REE patterns, LREE/HREE and (La/Yb)N values, reveal that there may be multi-sources and multi-stage hydrothermal activities in the Muli antimony deposit. The REE distribution patterns of minerals are likely interfered with by many internal and external factors. Studies on REE characteristics of calcite, quartz, pyrite and limestone in the Muli antimony deposit have greatly improved the understanding of ore-forming fluids. When we traced the origin and evolution of ore-forming fluids by means of mineral REE distribution patterns, in addition to the determination of inclusions of ore minerals related to mineralization and the in situ analysis methods performed by LA-ICP-MS, we should also combine the REE characteristics of various minerals or trace the ore-forming fluids with multiple methods. [ABSTRACT FROM AUTHOR]

The Zhonggu orefield is located within the southern Ningwu volcanic basin and is one of the largest iron ore districts within the Middle–Lower Yangtze River Metallogenic Belt (MLYRMB) of eastern China. The area hosts the Gushan iron oxide–apatite (IOA) deposit and the Baixiangshan, Longshan, Hemushan, Zhongjiu, and Taipingshan skarn-type iron deposits. Here, we employ laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) to determine trace element concentrations in magnetite from these deposits. Combining these new data with geological information from these deposits indicates that the iron ore within the Gushan deposit has V and Ti compositions that are strongly suggestive of a Kiruna-type IOA origin. Specifically, the V and Ti chemistry of magnetite in iron ore breccias from the Gushan deposit suggests that this style of mineralization formed at a high temperature and as a result of magmatic magnetite precipitation. This was followed by precipitation of lower temperature magmatic–hydrothermal massive magnetite. Both types of magnetite host exsolved ilmenite. Elemental mapping also indicates that Gushan breccia-hosted magnetite records hydrothermal fluid activity that formed late-stage vein mineralization. In comparison, other deposits within the Zhonggu orefield all contain magnetite with compositions that are indicative of skarn mineralization. This implies that these deposits formed as a result of magmatic–hydrothermal rather than purely magmatic or purely hydrothermal activity, contrasting with the Gushan deposit. Finally, the geochemistry of magnetite within thick anhydrite units in the Longshan deposit indicates the formation by low-temperature sedimentary processes, and this magnetite was subsequently overprinted as a result of hydrothermal activity during the formation of the main Longshan deposit. Overall, this study indicates that the IOA, skarn-type, and sedimentary anhydrite-type iron mineralization in the Zhonggu iron ore field record evolving metallogenic processes from initially orthomagmatic mineralizing systems to high- to moderate-temperature magmatic–hydrothermal systems and finally to low-temperature hydrothermal mineralization. [ABSTRACT FROM AUTHOR]

The fault-controlled Nibao Carlin-type gold deposit, together with the strata-bound Shuiyindong deposit, comprise a significant amount of the disseminated gold deposits in southwestern Guizhou Province, China. Five main types and two sub-types of pyrite at the Nibao deposit (Py1a/Py1b, Py2, Py3, Py4, Py5) were distinguished based on detailed mineralogical work. Py1, Py2 and Py3 are Au-poor, whereas Py4 and Py5 are Au-rich, corresponding to a sedimentary and hydrothermal origin, respectively. Through systematic in situ analyses of NanoSIMS sulfur isotopes, the framboid pyrite Py1a with negative δ34S values (− 53.3 to − 14.9‰) from the Nibao deposit were found to originate from bacterial sulfate reduction (BSR) processes in an open and sulfate-sufficient condition while the superheavy pyrite Py1b (73.7–114.8‰) is probably due to the potential influence of closed-system Rayleigh fractionation or the lack of preservation of deep-sea sediments. Data of Py2 and Py3 plot within the area of S isotope compositions from biogenic and abiogenic sulfate reduction. In view of few coeval magmatic rocks in the mining district, the near zero δ34S values of the Au-rich pyrites (Py4 and Py5) may discount the potential involvement of magmatic but metamorphic or sedimentary origin. LA-ICP-MS and TEM work show that Au in ore-related pyrite is present as both nanoparticles and structurally bound. LA-ICP-MS analyses show that the Au-rich pyrite also contains higher As, Cu, Sb, Tl and S than other types of pyrite, which inferred a distal manifestation of deep hydrothermal mineralization systems. [ABSTRACT FROM AUTHOR]

The Nanling Range in South China is well known for its rich granite-related W–Sn deposits. To elucidate the controls of different granite-related W–Sn metallogenesis in the region, we chose five representative ore-related granites (Yanbei, Mikengshan, Tieshanlong, Qianlishan, and Yaogangxian intrusions) in the Hunan–Jiangxi region, and studied their magmatic zircon ages and trace element geochemistry. Our new zircon data showed the differences in ages, temperatures and oxygen fugacity of the ore-forming magmas. Zircon U–Pb ages of the Yanbei and Mikengshan intrusions are characterized by 142.4 ± 2.4 and 143.0 ± 2.3 Ma, respectively, whereas the Tieshanlong and Qianlishan intrusions are 159.5 ± 2.3 and 153.2 ± 3.3 Ma, respectively. The Sn-related intrusions were younger than the W-related intrusions. The Ti-in-zircon thermometry showed that there was no systematic difference between the Sn-related Yanbei (680–744 °C) and Mikengshan (697–763 °C) intrusions and the W-related Tieshanlong (730–800 °C), Qianlishan (690–755 °C) and Yaogangxian (686–751 °C) intrusions. However, the zircon Ce4+/Ce3+ ratios of the Yanbei (averaged at 18.3) and Mikengshan (averaged at 18.8) intrusions are lower than those of the Tieshanlong (averaged at 36.9), Qianlishan (averaged at 38.4) and Yaogangxian (averaged at 37) intrusions, indicating that the Sn-related granitic magmas might have lower oxygen fugacities than those of the W-related. This can be explained by that, in more reduced magmas, Sn is more soluble than W and thus is more enriched in the residual melt to form Sn mineralization. The difference in source materials between the Sn-related and the W-related granites seems to have contributed to the different redox conditions of the melts. [ABSTRACT FROM AUTHOR]

The Pingchuan iron deposit, located in the Yanyuan region of Sichuan Province, SW China, has an ore reserve of 40 Mt with ~ 60 wt% Fe. Its genesis is still poorly understood. The Pingchuan iron deposit has a paragenetic sequence of an early Fe-oxide–Pyrite stage (I) and a late Fe-oxide–pyrrhotite stage (II). Stage I magnetite grains are generally fragmented, euhedral–subhedral, large-sized crystals accompanying with slightly postdated pyrite. Stage II magnetite grains are mostly unfragmented, anhedral, relatively small-sized grains that co-exist with pyrrhotite. Combined with micro-textural features and previously-obtained geochronological data, we consider that these two stages of iron mineralization in the Pingchuan deposit correspond to the Permian ELIP magmatism and Cenozoic fault activity event. Both the Stage I and II magnetites are characterized with overall lower contents of trace elements (including Cr, Ti, V, and Ni) than the ELIP magmatic magnetite, which suggests a hydrothermal origin for them. "Skarn-like" enrichment in Sn, Mn, and Zn in the Stage I magnetite grains indicate significant material contributions from carbonate wall-rocks due to water–rock interaction in ore-forming processes. Stage II magnetite grains contain higher Mn concentrations than Stage I magnetite grains, which possibly implies more contribution from carbonate rocks. In multiple-element diagrams, the Stage I magnetite shows systematic similarities to Kiruna-type magnetite rather than those from other types of deposits. Combined with geological features and previous studies on oxygen isotopes, we conclude that hydrothermal fluids have played a key role in the generation of the Pingchuan low-Ti iron deposit. [ABSTRACT FROM AUTHOR]

The Huize Zn–Pb–Ag deposit in SW China has an ore reserve in excess of 5 Mt. with an ore grade of ≥25 wt% Zn + Pb and 46–100 g/t Ag. This deposit is hosted in Carboniferous dolostone and limestone. Sulfide mineralization is dominated by sphalerite, galena, and pyrite. Four types of pyrite (Py1 to Py4) are temporally and spatially related to mineralization distinguished on the basis of textural features and mineral associations. Pyrite 1 to 3 corresponds to the pyrite-sphalerite sub-stage, whereas Py4 corresponds to sphalerite-galena-pyrite sub-stage. Pyrite 1 shows zoned texture composed of an inclusion-rich core and an inclusion-free rim, whereas Py2, Py3, and Py4 show replacement relic or overgrowth textures. The zoned texture in Py1 was formed by multiple stages of ore fluids, whereas replacement relic texture in Py2 to Py4 was formed by replacement of pyrite by late Pb-Zn-rich fluids. Trace element variation in pyrite results from a combination of mineral inclusions, co-precipitating minerals, and various fluid compositions. Sphalerite, pyrite, and galena have δ34S values of 10.4–23.5‰, suggesting that sulfur was probably derived from the thermochemical reduction of marine sulfates. The Huize pyrite has Co and Ni concentrations (0.02–9.5 ppm and 0.08–143 ppm, respectively) and Co/Ni ratios (~0.01–2.63) similar to pyrite from sedimentary exhalative deposits, submarine hydrothermal vents, and sedimentary pyrite, which may be due to pyrite precipitation from low-temperature (<~250 °C), basin brines or seawater. The Co/Ni ratios of the Huize pyrite are lower than those (~0.2–7.2) of pyrite from Mississippi Valley-type Zn-Pb deposits. The Huize pyrite has Co and Ni contents lower than those associated with volcanogenic massive sulfide, iron oxide copper gold, and porphyry Cu deposits, arguing against the involvement of a magmatic/volcanic component and a direct genetic link between Permian Emeishan basalts and Pb-Zn mineralization. Combining with fluid inclusion temperatures and silver grade, we define the Huize deposit as a transitional type between Mississippi Valley-type and high-temperature carbonate-replacement Zn-Pb deposits. [ABSTRACT FROM AUTHOR]

The Zhuxi W (Cu) skarn deposit is the largest W deposit in the Jiangnan porphyry–skarn tungsten belt in South China, and is also among the largest deposit of this type in the world. Titanite is a common mineral in the Zhuxi deposit, and occurs in three textural settings: titanite I associated with retrograde-altered exoskarn with weak mineralization; titanite II in retrograde-altered endoskarn with disseminated Cu ore; and titanite III from altered granite with disseminated W ore. Here, we present LA-ICP-MS U–Pb data on the three types of titanite which show 207Pb-corrected weighted mean 206Pb/238U ages of 148.1 ± 7.4 Ma (n = 25, MSWD = 0.22), 148.9 ± 1.5 Ma (n = 28, MSWD = 0.37), and 149.9 ± 1.3 Ma (n = 31, MSWD = 0.28), respectively. These ages are consistent with the previously reported ages of the ore-related granite. The coeval nature of the W and Cu ores suggests that the W and Cu ores formed synchronously, and are associated with the granitoids. The Ce and Eu anomalies in the three types of titanite record redox fluctuation during the mineralization process, and suggest variable contamination of the magmatic-hydrothermal system by reduced carbonate wall-rock that contains abundant carbonaceous matter. Our study demonstrates that hydrothermal titanite commonly occurring in reduced-type W skarn deposits has potential for isotopic dating and in constraining the redox conditions for the mineralization process. [ABSTRACT FROM AUTHOR]

The Gutaishan deposit is a slate-hosted lode Au–Sb deposit in the Xiangzhong Sb–Au metallogenic province, South China. The deposit has a proven reserve of ca. 9 -t gold at an average grade of 13-g/t and contains 2500-t Sb. The deposit represents the product of a complex ore-forming process, comprising four different stages, of which the third stage is the main gold–stibnite bearing stage. Scanning electron microscopy, electron probe microanalysis, and laser ablation inductively coupled plasma-mass spectrometry were used to investigate the occurrence of visible gold and the distribution of invisible gold in pyrite and arsenopyrite. Visible gold displays textural complexity with four distinct categories defined and assumed to have formed directly precipitated from ore-forming fluid and remobilized from pyrite and arsenopyrite. Pyrite and arsenopyrite occur as ten and four texturally distinct subtypes; all host invisible gold, which is lattice-bound. Trace element mapping of selected pyrite and arsenopyrite grains reveals a marked compositional zoning with respect to Au and other elements in both minerals. Observed decoupled behavior between Au and As in some grains contradicts the paradigm of coupled Au and As substitution. Evidence suggests that the Gutaishan deposit likely represents an evolving Au–Sb mineralization event recorded by the complex texture and geochemical signatures of visible gold, sulfides, and sulfosalts. [ABSTRACT FROM AUTHOR]

The Ningzhen region of China is located in the easternmost part of the middle-lower Yangtze River Cu-Fe polymetallic metallogenic belt. From west to east, it comprises five main intermediate-acidic intrusive complexes: the Qilinmen, Anjishan, Xiashu-Gaozi, Shima, and Jianbi complexes. Geochemical investigations show that these five intrusive complexes exhibit high contents of SiO2, at 64.74-73.40 wt%, Al2O3, at 14.15-17.37 wt%, and K2O + Na2O, at 6.49-8.68 wt%. The majority of the samples belong to the high-K calc-alkaline series, with a few samples plotting in the calc-alkaline and tholeiitic series. Trace element analysis shows that the samples are enriched in large ion lithophile elements (LILE) and are depleted in high field strength elements (HFSE). The chondrite-normalized rare earth element (REE) patterns are characterized by right-inclined curves, showing light rare earth element (LREE) enrichment. In addition, the (La/Yb)N ratios are high at 15.02-37.28, with an average of 29.13, and slightly negative or none Eu anomalies are present. In the (La/Yb)N-δEu diagram, the samples plot within the crust-mantle type field. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) zircon U-Pb dating yielded ages of 122.0 ± 1.0 Ma, 106.1 ± 0.8 Ma, 108.7 ± 1.4 Ma, 103.5 ± 1.9 Ma, and 96.8 ± 1.7 Ma for the Qilinmen, Anjishan, Xiashu-Gaozi, Shima, and Jianbi complexes, respectively. On the basis of this research and knowledge of several known metal deposits related to these complexes, we suggest that the Mesozoic large-scale diagenesis and metallogenesis in the Ningzhen region may have ceased at 100 Ma or about 95 Ma. [ABSTRACT FROM AUTHOR]

The Huajian gold deposit is one of the largest hydrothermal intrusion-related gold deposits in eastern Hebei Province, located in the northern margin of the North China Craton (NCC). The mineralization in this district displays a close spatial association with the shoshonitic Niuxinshan intrusive complex (NIC), which contributes to the characterization of the metallogeny associated with convergent margin magmatism. In the current study, new geochronological and geochemical data are combined with previously published isotopic data, obtained from the granitic rocks in the NIC, to constrain the timing of the district’s tectonic setting transformation and determine its bearing on regional metallogeny. The new geochronological data constrain the timing of the tectonic transformation between 155 and 185 Ma. The NIC’s granitic rocks can be geochemically subdivided into two groups. One group’s geochemical signature exhibits steep rare earth element (REE) patterns with negligible Eu anomalies, lower Yb, higher Sr, and negative Nb–Ta–Ti (NTT) anomalies, which indicate a volcanic-arc environment with a thickened crust in a convergent setting. The other group exhibits flat REE patterns with obvious negative Eu anomalies, higher Yb, lower Sr, and weak NTT anomalies, which indicate an intra-plate extensional environment with a thinning crust. Combining geochronologic and isotopic data, the mineralization is Late Jurassic (~155 Ma). This is interpreted to be genetically related to the crystallization of the shallow crustal-sourced portions of this complex. Additionally, a tectonic model is presented that provides a plausible explanation for the abundant polymetallic mineralization that occurs in the northern margin of the NCC after 155 Ma. [ABSTRACT FROM AUTHOR]

There is a dearth of information about the distribution of trace elements in kerogen from shale rocks despite several reports on trace element composition in many shale samples. In this study, trace elements in shale rocks and their residual kerogens were determined by inductively coupled plasma-mass spectrometry. The results from this study show redox-sensitive elements relatively concentrated in the kerogens as compared to the shales. This may be primarily due to the adsorption and complexation ability of kerogen, which enables enrichment in Ni, Co, Cu, and Zn. For the rare earth elements (REEs), distinct distribution characteristics were observed for shales dominated by terrigenous minerals and their kerogen counterparts. However, shales with less input of terrigenous minerals showed similar REE distribution patterns to their residual kerogen. It is speculated that the distribution patterns of the REEs in shales and kerogens may be source-related. [ABSTRACT FROM AUTHOR]

The Yamansu Fe deposit (32 Mt at 51% Fe) in the Eastern Tianshan Orogenic Belt of NW China is hosted in early Carboniferous volcano-sedimentary rocks and spatially associated with skarn. The paragenetic sequence includes garnet-diopside (I), magnetite (II), hydrous silicate-sulfide (III), and calcite-quartz (IV) stages. Pyrite associated with magnetite has a Re-Os isochron age of 322 ± 7 Ma, which represents the timing of pyrite and, by inference, magnetite mineralization. Pyrite has δ34SVCDT values of − 2.2 to + 2.9‰, yielding δ34SH2S values of − 3.1 to 2‰, indicating the derivation of sulfur from a magmatic source. Calcite from stages II and IV has δ13CVPDB values from − 2.5 to − 1.2‰, and − 1.1 to 1.1‰, and δ18OVSMOW values from 11.8 to 12.0‰ and − 7.7 to − 5.2‰, respectively. Calculated δ13C values of fluid CO2 and water δ18O values indicate that stage II hydrothermal fluids were derived from magmatic rocks and that meteoric water mixed with the hydrothermal fluids in stage IV. Some ores contain magnetite with obvious chemical zoning composed of dark and light domains in BSE images. Dark domains have higher Mg, Al, Ca, Mn, and Ti but lower Fe and Cr contents than light domains. The chemical zoning resulted from a fluctuating fluid composition and/or physicochemical conditions (oscillatory zoning), or dissolution-precipitation (irregular zoning) via infiltration of magmatic-hydrothermal fluids diluted by late meteoric water. Iron was mainly derived from fluids similar to that in skarn deposits. [ABSTRACT FROM AUTHOR]

Uranium-lead isotopes and trace elements of titanite from the Chengchao iron skarn deposit (Daye district, Eastern China), located along the contact zones between Triassic marine carbonates and an early Cretaceous intrusive complex consisting of granite and quartz diorite, were analyzed using laser ablation inductively coupled plasma mass spectrometry to provide temporal constraints on iron mineralization and to evaluate its potential as a reference material for titanite U-Pb geochronology. Titanite grains from mineralized endoskarn have simple growth zoning patterns, exhibit intergrowth with magnetite, diopside, K-feldspar, albite and actinolite, and typically contain abundant primary two-phase fluid inclusions. These paragenetic and textural features suggest that these titanite grains are of hydrothermal origin. Hydrothermal titanite is distinct from the magmatic variety from the ore-related granitic intrusion in that it contains unusually high concentrations of U (up to 2995 ppm), low levels of Th (12.5-453 ppm), and virtually no common Pb. The REE concentrations are much lower, as are the Th/U and Lu/Hf ratios. The hydrothermal titanite grains yield reproducible uncorrected U-Pb ages ranging from 129.7 ± 0.7 to 132.1 ± 2.7 Ma (2σ), with a weighted mean of 131.2 ± 0.2 Ma [mean standard weighted deviation (MSWD) = 1.7] that is interpreted as the timing of iron skarn mineralization. This age closely corresponds to the zircon U-Pb age of 130.9 ± 0.7 Ma (MSWD = 0.7) determined for the quartz diorite, and the U-Pb ages for zircon and titanite (130.1 ± 1.0 Ma and 131.3 ± 0.3 Ma) in the granite, confirming a close temporal and likely genetic relationship between granitic magmatism and iron mineralization. Different hydrothermal titanite grains have virtually identical uncorrected U-Pb ratios suggestive of negligible common Pb in the mineral. The homogeneous textures and U-Pb characteristics of Chengchao hydrothermal titanite suggest that the mineral might be a suitable internal reference material for U-Pb dating. [ABSTRACT FROM AUTHOR]

Highly metalliferous black shales (HMBS) are enriched in organic carbon and a suite of metals, including Ni, Se, Mo, Ag, Au, Zn, Cu, Pb, V, As, Sb, Se, P, Cr, and U ± PGE, compared to common black shales, and are distributed at particular times through Earth history. They constitute an important future source of metals. HMBS are relatively thin units within thicker packages of regionally extensive, continental margin or intra-continental marine shales that are rich in organic matter and bio-essential trace elements. Accumulation and preservation of black shales, and the metals contained within them, usually require low-oxygen or euxinic bottom waters. However, whole-rock redox proxies, particularly Mo, suggest that HMBS may have formed during periods of elevated atmosphere pO. This interpretation is supported by high levels of nutrient trace elements within these rocks and secular patterns of Se and Se/Co ratios in sedimentary pyrite through Earth history, with peaks occurring in the middle Paleoproterozoic, Early Cambrian to Early Ordovician, Middle Devonian, Middle to late Carboniferous, Middle Permian, and Middle to Late Cretaceous, all corresponding with time periods of HMBS deposition. This counter-intuitive relationship of strongly anoxic to euxinic, localized seafloor conditions forming under an atmosphere of peak oxygen concentrations is proposed as key to the genesis of HMBS. The secular peaks and shoulders of enriched Se in sedimentary pyrite through time correlate with periods of tectonic plate collision, which resulted in high nutrient supply to the oceans and consequently maximum productivity accompanying severe drawdown into seafloor muds of C, S, P, and nutrient trace metals. The focused burial of C and S over extensive areas of the seafloor, during these anoxic to euxinic periods, likely resulted in an O increase in the atmosphere, causing short-lived peaks in pO that coincide with the deposition of HMBS. As metals become scarce, particularly Mo, Ni, Se, Ag, and U, the geological times of these narrow HMBS horizons will become a future focus for exploration. [ABSTRACT FROM AUTHOR]

The Pengshan Sn and Pb-Zn polymetallic deposits are located in the south margin of the Jiujiang-Ruichang (Jiurui) district of the Middle-Lower Yangtze River Metallogenic Belt in South China. Four large deposits include Huangjinwa, Zengjialong, Jianfengpo, and Zhangshiba, the former three are Sn-dominant deposits which occur as stratiform orebodies in the contact zones of the Pengshan granites and within the country rock strata, whereas Zhangshiba consists of stratiform Pb-Zn orebodies within the Precambrian metasedimentary strata. In this study, we present results on zircon U-Pb ages, major and trace elements, and mineral chemistry as well as Sr-Nd-Hf isotope data of the granites, Pb and S isotopes of both the Sn-dominant and Pb-Zn dominant deposits, and U-Pb dating of cassiterite from the Pengshan district. SHRIMP and LA-ICP-MS zircon U-Pb dating shows that the Pengshan granites were emplaced in the Early Cretaceous (129-128 Ma), which is in good agreement with the U-Pb dating (130-128 Ma) of cassiterite from the Jianfengpo Sn deposit. The Pengshan granites consist mainly of weakly peraluminous highly fractionated I-type affinity granitic rocks. Detailed elemental and isotopic data suggest that the granites formed by partial melting of Mesoproterozoic metamorphic basement materials with minor input of mantle-derived melts. The mineral chemistry of biotite demonstrates that the Pengshan granitic magma had a low oxygen fugacity, thereby precluding the tin dominantly partitioning into the rock-forming silicate minerals and favoring accumulation in the exsolved residual liquid during magma crystallization stages. Sulfur isotopes show a relatively heavy sulfur isotopic composition from 5.8 to 17.6 ‰, and no difference for sulfur isotopes between the Sn deposits (5.8-13.4 ‰, Huangjinwa, Zengjialong, Jianfengpo) and the Pb-Zn deposit (mostly 7.1-13.0 ‰, except for one 17.6 ‰, Zhangshiba). The sulfur isotope data of pyrite from the host sedimentary rocks show relatively higher δS values of 22.7-28.7 ‰. Lead isotopes indicate that the granites have higher Pb/Pb, Pb/Pb, and Pb/Pb ratios than the host Precambrian metasedimentary rocks, and the sulfide minerals from the orebodies fall in between them. Again, there is no difference for Pb isotopes between the Sn deposits (Huangjinwa, Zengjialong, Jianfengpo) and the Zhangshiba Pb-Zn deposit. The coincidence in S and Pb isotope compositions for Sn and Pb-Zn deposits suggests that similar sources for these mineralization, possibly derived from a mixed source of the granitic magmas and the Precambrian metasedimentary rocks. These data therefore favor of a magmatic-hydrothermal origin for both the Sn and Pb-Zn polymetallic mineralization in the Pengshan district. [ABSTRACT FROM AUTHOR]

Sphalerite is a common sulphide and is the dominant ore mineral in Zn-Pb sulphide deposits. Precise determination of minor and trace element concentrations in sulphides, including sphalerite, by Laser-Ablation Inductively-Coupled-Plasma Mass-Spectrometry (LA-ICP-MS) is a potentially valuable petrogenetic tool. In this study, LA-ICP-MS is used to analyse 19 sphalerite samples from metamorphosed, sphalerite-bearing volcanic-associated and sedimentary exhalative massive sulphide deposits in Norway and Australia. The distributions of Mn, Fe, Co, Cu, Ga, Se, Ag, Cd, In, Sn, Sb, Hg, Tl, Pb and Bi are addressed with emphasis on how concentrations of these elements vary with metamorphic grade of the deposit and the extent of sulphide recrystallization. Results show that the concentrations of a group of trace elements which are believed to be present in sphalerite as micro- to nano-scale inclusions (Pb, Bi, and to some degree Cu and Ag) diminish with increasing metamorphic grade. This is interpreted as due to release of these elements during sphalerite recrystallization and subsequent remobilization to form discrete minerals elsewhere. The concentrations of lattice-bound elements (Mn, Fe, Cd, In and Hg) show no correlation with metamorphic grade. Primary metal sources, physico-chemical conditions during initial deposition, and element partitioning between sphalerite and co-existing sulphides are dominant in defining the concentrations of these elements and they appear to be readily re-incorporated into recrystallized sphalerite, offering potential insights into ore genesis. Given that sphalerite accommodates a variety of trace elements that can be precisely determined by contemporary microanalytical techniques, the mineral has considerable potential as a geothermometer, providing that element partitioning between sphalerite and coexisting minerals (galena, chalcopyrite etc.) can be quantified in samples for which the crystallization temperature can be independently constrained. [ABSTRACT FROM AUTHOR]

The geochemistry of major and trace elements (including heavy metals and rare earth elements) of the fresh and weathered black shales, and the soils derived from black shales in the Ganziping mine area in western Hunan province (China) were studied using the following techniques: X-ray fluorescence (XRF), inductively coupled plasma mass spectrometer (ICP-MS) and X-ray diffraction (XRD). The results show that the black-shale soils are significantly enriched with AlO and FeO, and depleted of mobile elements CaO, NaO and KO. The soils are also highly enriched with heavy metals U, V, Ni, Ba, Cu, Zn and Pb, that may cause potential heavy-metal contamination of the soils. Composition of the soils is homogeneous compared to the weathered black shales, for which the concentrations of major elements except CaO and NaO, and trace elements except heavy metals (U, V, Ni, Ba, Cu, Zn and Pb) as well as the mobile Sr, show lower variations than in the weathered black shales. Ratios of Zr/Hf, Ta/Nb, Y/Ho, Nd/Sm, and Ti/(Ti + Zr), of the soils are also less variable, with values constantly similar to that of the fresh and weathered black shales correspondingly. Thus, components of the soils are believed to be contributed from the parent black shales through weathering and pedogenesis. It is concluded that the soils were formed by at least two stages of geochemical processes: the early stage of chemical differentiation and the later stage of chemical homogenization. The chemical differentiation that was taken during black-shale weathering might have caused the depletion of CaO and NaO, and the enrichment of AlO and FeO; while the chemical homogenization that was taken during pedogenesis led to the depletion of SiO and KO, and to the further enrichment of AlO and FeO. The heavy-metal enrichment (contamination) of the soils was then genetically related to the enrichment of AlO and FeO in the soils. [ABSTRACT FROM AUTHOR]

Olivine phenocrysts in ugandite and leucite basanite from the western branch of the East African Rift have been analysed for up to 34 trace elements by Laser-ICP-MS with detection limits as low as 1 ppb. A combination of point analyses with varying ablation crater diameters and line scans allow the identification of subtle zonations from core to rim, as well as characterization of the chemical effects of contamination along cracks. Trace element concentrations are remarkably uniform between large and small phenocrysts; fractionated leucite basanites (Mg# 59) have higher D and D, and less fractionated LREE/HREE than MgO-rich ugandites (Mg# 75-80). Minor zonation is seen in elements with cation charges from 5+ to 2+ (P, Ti, Zr, Cr, Al, Sc, V, Cu, Mn, Ni) and show correlation between Ti and Al, but not P. Early phenocryst cores with high Li or Ni, low Mn, or enrichments in many trace elements can be identified, whereas xenocrysts have exceptionally low Na, Cr, Ti, V and Co. Partition coefficients for Ni are 31-35, less than in lamproites, with which they demonstrate an approximately linear correlation with KO content, KO/AlO and KO/NaO of the melt, but none with SiO content or Mg#. D-values for Cr, Mn and Co overlap with those of basalts, whereas those for Sc (0.011-0.018), Zn (0.44-0.49) and Ga (0.006-0.007) are lower. D of various potassic rocks (0.015 in the Ugandan rocks) confirms the dependence on fO calibrated by the Fe/(Fe+Fe) of spinels; the Ugandan potassic rocks crystallized at fO = FMQ to FMQ + 1. The ugandite olivines have some trace element characteristics reminiscent of those in metasomatized Kaapvaal peridotites, but not ocean islands. Line scan analyses are contaminated in Al, Ca, Cu, Ga, Sr, Zr, Nb, La and Ce, elements that are also concentrated in microcracks between subgrains, indicating smearing out during polishing, and demonstrating that large spot analyses produce the best results. [ABSTRACT FROM AUTHOR]

This paper presents detailed mineral chemical, element geochemical and Sr-Nd-Hf isotopic data for the Late Jurassic (155 ± 4 Ma) lamprophyre dikes in the Liaodong Peninsula, NE China. The lamprophyres are shoshonitic and geochemically fall into three groups: Group I has relatively high SiO (52.5-57.0 wt.%), low MgO (5.5-8.3 wt.%) and compatible trace element (e.g. Cr = 128-470 ppm) contents, high initial Sr/Sr ratios (0.7093-0.7117), and low ε (T) values (−9.6 to −12.1); Group II has relatively low SiO (44.8-50.0 wt.%), high MgO (10.8-14.2 wt.%) and compatible trace element (e.g. Cr = 456-1,041 ppm) contents, low initial Sr/Sr ratios (0.7073-0.7087), and high ε (T) values (−1.4 to −2.9); Group III is transitional between the two in all elemental and isotopic compositions. Interpretation of the elemental and isotopic data suggests that the lamprophyric melts were derived by partial melting of subcontinental lithospheric mantle (SCLM) at a depth of 60-80 km (group I), decompression melting of upwelling asthenosphere at 60-100 km (group II), and mixing between the SCLM-derived and asthenosphere-derived melts (group III). It is assumed that the local SCLM was detached at a depth of 60-80 km by the 155 Ma ago. A continental arc-rifting related to the Palaeo-Pacific plate subduction is favored as a geodynamic force for such a cratonic lithosphere detachment. [ABSTRACT FROM AUTHOR]