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An editorial focuses on the discovery and significance of layered chromite mineralization within mafic-ultramafic rocks in the Gayahe area of the East Kunlun Orogenic Belt, Northwestern China. It highlights the identification of chromitite layers with high ore grades, marking a significant find in an area previously lacking economically valuable chromite deposits.

An editorial focuses on the newly discovered Jinshui tin deposit located in the middle section of the East Kunlun Orogenic Belt in northwestern China. It highlights the mineralization age of the deposit, determined through U-Pb dating of zircon and cassiterite, and discusses its implications for exploration in this region. It reports that the Jinshui deposit represents a significant addition to the known tin deposits in the area, with the ages of mineralization and magmatic activity.

Two types of turquoise, including homogeneous Cu-rich turquoise and oscillatory zoned turquoiseplanerite series, are recognized in association with quartz-barite veins hosted by Cambrian carbonaceous slates from western Hubei Province of China. Combined fluid inclusion and Raman micro-spectroscopic data reveal that turquoise-bearing barite-quartz veins contain three types of fluid inclusions (pure CH4-N2, carbonic-aqueous, and aqueous), suggesting the responsible fluid is of carbonic-aqueous composition with low oxygen fugacity. Pressure-corrected homogenization temperatures in quartz and barite show a range from 325 to 485 °C and 186 to 391 °C, respectively. Carbon, oxygen, and hydrogen isotopic data suggest that the mineral-forming fluids have a mixed metamorphic-organic affinity, in which the fluids have δ18O and δD values of 15.0 to 18.8‰ and –111 to –93‰, respectively. Generally, the formation of quartz-barite-turquoise veins could be triggered by prior metamorphic devolatilization, followed by the interaction of fluids with country rocks enriched in carbonaceous material, which resulted in the leaching of Cu, Fe, P, and Al from chalcopyrite, pyrite, magnetite, monazite, xenotime, apatite, feldspar, and muscovite in the wall rocks. Decomposition of the organic matter in the carbonaceous slates, caused by regional metamorphism and deformation, could also promote the concentration and transportation of necessary metals for the turquoise. Thus, we propose a new model and suggest that the turquoise gem deposits in western Hubei Province of China belong to the non-magmatic hydrothermal vein type deposit, not the previously proposed supergene origin. The turquoise-forming fluids were characterized by the coexistence of two immiscible fluids of non-magmatic affinity (i.e., moderate to high-temperature and low-salinity aqueous fluid and pure CH4-N2 fluid formed by interaction with carbonaceous slates). The bluish green homogeneous turquoise in the metamorphic quartz-barite-turquoise veins evolved toward the turquoise-planerite solid solution series as the metal-leaching capability of the aqueous fluids decreased. [ABSTRACT FROM AUTHOR]

An internal standard as ablation yield is required to calibrate raw data by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) technology. In this study, we established a new calibration method based on the mica (muscovite and biotite) structure formula-based normalization procedure, achieving high precision determination of major and trace element concentrations of mica (muscovite and biotite) by LA-ICP-MS without using an internal standard. Since the volatile components (F, Cl and OH) cannot be effectively and directly determined by ICP-MS, and the potassium concentration determined by LA technology in mica shows systematic deviation, we theoretically calculated the concentrations of volatile components and potassium, and corrected the influence of these elements on the summed normalization procedure. Applying multiple external standards plus the above modified normalization procedure, we determined the major and trace element contents of muscovite and biotite from a pegmatite dyke by this new method. The results are identical to the major element contents obtained by EPMA (Electron Probe Microanalyzer) and to the trace element contents determined by traditional internal standard-used LA-ICP-MS within ±5%. The new analytical procedure by LA-ICP-MS is low-cost and time-saving compared to the traditional method that needs combining both EPMA and LA-ICP-MS. [ABSTRACT FROM AUTHOR]

Geothermal systems in Tibet, a crucial geothermal region in China, belong to the Mediterranean-Himalayan geothermal belt and are characterized by a broad distribution of cesium (Cs) bearing geyserite deposits. Targejia, one of the largest Cs-bearing geyserites in southern-western Tibet, contains 1.446 × 104 tons of Cs. The highest ore grade reaches 2.89 wt%, and the ore-forming process can be subdivided into mineralization stages I to V. Cs is heterogeneously distributed in geyserites. Herein, two Cs-bearing ores are investigated, with distinct characteristics of (1) low-Cs-bearing ore (amorphous silica opal-A and opal-CT type) with low Cs (average of ~0.2 wt%), Na, K, Al, and Ca contents, and (2) high-Cs-bearing ore (clay type) with high-Cs (average of ~1.40 wt%), -Na, -K, -Al, and -Ca contents. It is reported for the first time that Cs primarily exists in clay rather than in amorphous silica opal. The Cs-enrichment mechanisms are diferent for the above two Cs-bearing geyserite types: (1) The deprotonated –OH, surrounded by water molecules, controls the amount of Cs absorbed on the geyserite surface (Si–OH) in the low-Cs-bearing ore. (2) The variable Cs content depends on the Al content because Al substitutes Si, yielding more negative charges to absorb Cs in the high-Cs-bearing ore. Geothermal fluid loading-mass elements, such as Cs and SiO2, precipitate as amorphous silica (opal) with clay minerals. Mineral saturation index modeling was used to predict the most applicable physical parameters for ore formation. The results confirm that the ore forms at ~85 °C and a pH of ~8.5 in the Na-Cl system at stage V. The degree of Cs enrichment reduces from the latest stage V (0–4 ka) to the early stage IV (4–17 ka), and is controlled by clay dissolution, which might further relate to the climate change in Tibet's Holocene. Fluid-rock interaction modeling shows that dissolution–reprecipitation induces a higher order of amorphous silica formation and clay dissolution at >40 °C and pH of 5–9 at stages V and III, excluding Cs from the ore. [ABSTRACT FROM AUTHOR]

The Wangjiadashan area in Suizhou-Zaoyang region of Hubei Province in the Tongbai-Dabie orogenic belt hosts important copper-gold deposits and contains a large number of quartz syenite porphyry dykes, occurring mostly along the NEE-trend faults. In this study, we used LA-ICP-MS zircon U-Pb dating method and obtained an age of 143.6 ± 1.4 Ma, which represents the emplacement of these quartz syenite porphyry dykes was at the Yanshanian, but it was slightly earlier than the previously reported ages (139–135 Ma) for granites widespreading in Suizao area. The geochemical data of the Wangjiadashan quartz syenite porphyry show high K2O, CaO, Na2O and Al2O3 contents but extremely low MgO contents (0.01 wt.%–0.46 wt.%). The geochemical characteristics indicate that these quartz syenite porphyry dykes belong to the typical C-type adakite and were possibly formed in the post-collisional environment. Multi-isotopic (Sr-Nd-Pb-Hf) analyses indicate that these quartz syenite porphyry dykes were originated from crust without distinct mantle materials involved. It is suggested that the Wangjiadashan quartz syenite porphyry was generated from partial melting of the thickened lower continental crust, and garnet but no plagioclase was left as residual phase. Compared with the widespread granites of the Tongbai area, the Wangjiadashan quartz syenite porphyry formed earlier and derived from more juvenile and K-rich lower crust, while they all belong to intensive magmatism concentrated during the Early Cretaceous epoch in the Tongbai area. [ABSTRACT FROM AUTHOR]

Although an extensive continental arc magmatism was recorded in the northern North China Craton (NCC) during the Carboniferous, a general geodynamic model has not been constructed, and associated crust–mantle processes are not fully understood. Here, we carried out systematic geochronological and geochemical investigations on the alkali‐feldspar granite pluton in the Zhaojinggou area, northern NCC. U–Pb dating of high‐U–Th zircons failed to obtain concordant ages due to severe metamictization, while apatite U–Pb dating yielded a perfect age of 327.6 ± 4.1 Ma, indicating the emplacement of granites in the Early Carboniferous. The granites have high SiO2 (74.99–76.88 wt%) and K2O (5.73–6.43 wt%) contents and exhibit enriched LREEs, K, Rb, Th, U, and Pb, and depleted Nb, Ta, P, and Ti contents, which are typical of highly fractionated, I‐type high‐K granites formed under a continental arc setting. Moreover, the high‐K granites show highly enriched Nd isotopic compositions (with whole‐rock and apatite εNd(t) of −33.6 to −16.3) that are distinctly lower than other Carboniferous continental arc rocks in the northern NCC (εNd(t) from −18.5 to −9.9). These geochemical characteristics indicate that the high‐K granites possibly originated by partial melting of the Archean TTG gneisses and mafic rocks in the lower crust. Involvement of mantle‐derived fluids is crucial to induce the low‐temperature melting, and sufficient fractional crystallization was reached during subsequent magmatic evolution. Previous studies suggest that the Carboniferous continental arc rocks in the northern NCC have mantle‐derived or crust–mantle mixed sources. Our study, however, indicates that there also exist coeval crust‐derived magmatic rocks in this area. In combination with previous work and this study, we support the hypothesis that the widespread Carboniferous continental arc magmatism in the northern NCC is related to the southward subduction of the Palaeo‐Asian Ocean (PAO), and the different magma sources and extensive crust–mantle interactions are responsible for the formation of diverse types of magmatic rocks with contrasting isotopic compositions. We also draw attention to the fact that phosphate minerals such as apatite may be a preferable chronometer relative to high‐U–Th zircon in a highly fractionated igneous system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co and Ni occur mainly in sulfides through isomorphic substitution in the Yindongshan ultramafic–mafic intrusions. • Magmatic iron deposits hosted by ultramafic–mafic intrusions with sulfide mineralization are promising targets for Co and Ni exploration. The Yindongshan iron deposit in western Hubei Province of China is hosted within Ordovician ultramafic–mafic intrusions. Recent field geological surveys have detected cobalt (Co) and nickel (Ni) enrichment within the Yindongshan clinopyroxenite, suggesting good potential for subeconomic Co-Ni mineralization. This study investigated the occurrence modes and enrichment processes of Co and Ni in the Yindongshan deposit through field geology and in situ analysis of the rock texture, geochronology, and geochemistry of sulfides, Fe-Ti oxides, and silicate minerals. The Yindongshan clinopyroxenites were emplaced at 440.2 ± 7.2 Ma via titanite LA-ICP-MS U-Pb dating, and underwent extensive post-magmatic metamorphism at 401.2 ± 8.6 Ma via apatite U-Pb dating. This metamorphism led to the widespread formation of amphibole via the replacement of clinopyroxene. Subsequently, hydrothermal epidote-albite veins, calcite-pyrite veins, and later actinolite veins developed. Pyrites from both clinopyroxenites and calcite veins show limited δ34S variations from −5.4 ‰ to −1.2 ‰, suggesting a magmatic sulfur source. Late-vein actinolites display geochemical characteristics distinct from those of amphiboles, indicating possible involvement of external fluids. LA–ICP–MS trace element results reveal a general increase in Co and Ni contents from silicate minerals and Fe-Ti oxides to pyrite and from earlier-crystallized coarse-grained clinopyroxenite to later medium- to fine-grained clinopyroxenite. The highest Co and Ni contents observed in pyrite from coarse-grained clinopyroxenite suggest their preferential incorporation into early sulfide minerals and then progressively depleted through magmatic evolution such as fractional crystallization. The positive correlation between Co and Ni with Fe in pyrite, along with the consistent parallel time-resolved LA–ICP–MS depth profiles among different mineral phases, indicates that isomorphic substitution occurred in pyrite. In silicate minerals, the Co and Ni contents increase from pyroxene, amphibole, to actinolite, with almost no Co or Ni present in epidote. The elevated Co and Ni contents in metamorphic amphiboles are attributed to their remobilization from magmatic pyrite to newly formed amphiboles. During the late hydrothermal phase, external fluids might transport additional Co and Ni, contributing to higher concentrations in late actinolite veins. In general, Co and Ni in the Yindongshan iron deposit are primarily hosted in sulfide minerals and can be remobilized during regional metamorphism and metasomatism. Thus, magmatic iron or iron–titanium oxide deposits hosted by mafic–ultramafic intrusions with sulfide mineralization may serve as promising targets for further Co-Ni exploration. [ABSTRACT FROM AUTHOR]

The Huangling gold deposits belong to orogenic gold deposits, forming during the tectonic transformation period at ca. 830–800 Ma. [Display omitted] • Gold mineralization in the Huangling region occurred ca. 830-800 Ma. • The timing of gold mineralization coincided with the tectonic transformation period. • The Huangling gold deposits belong to orogenic gold deposits. The Huangling region of northwestern Hubei Province, which contains 76 gold deposits with more than 310 gold-quartz veins, is located in the northern part of the Yangtze Craton, South China Block. Despite several geological and geochronological studies conducted on gold deposits in this region, the timing and origin of gold mineralization remain controversial. This study utilizes in situ U–Pb dating of apatite and monazite from representative ores from the Banchanghe, Hongwucun, and Sunjiahe gold deposits to determine the timing of gold mineralization. The results indicate that gold mineralization occurred ca. 830–800 Ma, which is consistent with the period of tectonic transformation in the region. This study proposes that the gold deposits in the Huangling region represent typical orogenic gold deposits. These findings indicate a rare example of a well-preserved early Neoproterozoic orogenic gold system, suggesting the existence of orogenic gold deposits during the growth of the Rodinia supercontinent. This study highlights the significant potential for further exploration in the deep of the Huangling region to uncover additional gold veins. These findings also suggest that the Neoproterozoic orogenic belts of the Yangtze Craton may serve as important targets for gold deposit exploration in the future. [ABSTRACT FROM AUTHOR]

It has long been debated whether the India-Eurasia collision was a single-stage event that began 60-55 million years ago, or whether it was a two-stage process that involved a collision between India and the Trans-Tethyan Arc before the early Paleocene, and the collision of India with Eurasia during the middle Eocene. Here, we report a late Paleogene angular unconformity (ca. 40-28 Ma) in western Myanmar. This angular unconformity developed around the same time as the Assam unconformity (NE India) but is younger than those found in northern Myanmar. Development of these unconformities indicates that an oblique convergence margin in western Myanmar formed before the middle Eocene, with a major dextral strike-slip fault (proto-Sagaing/Shan Scarp Fault) in the backarc. We interpret this oblique convergence margin to be partial continental collision between the West Myanmar Terrane (WMT) and NE India. In backarc regions, syn-rift successions of the Shwebo sub-basin have formed as a consequence of transtensional tectonics along the proto-Sagaing/Shan Scarp Fault since at least the late Paleocene. The syn-rift successions consist of Asian-derived materials that were not identified in the forearc because of the Wuntho-Popa Arc served as a geographical barrier. The presence of the unconformities and tectonic configuration of the Myanmar backarc sub-basins are inconsistent with the scenario inferred from paleomagnetic data, in which the WMT was part of an intra-oceanic arc at near-equatorial latitudes before the late Oligocene. Instead, we propose that the WMT has been part of continental SE Asia since at least the Paleocene (ca. 60-58 Ma). We reconsider the paleomagnetic data and suggest that the Mawgyi Arc, rather than the WMT, is the oceanic fragment that rifted from the northern Gondwana margin during the Late Jurassic. The Mawgyi Arc collided with continental SE Asia (WMT) during the Late Cretaceous, and then with India during the early Eocene (ca. 51-49 Ma). Our results support the collision between India and Eurasia is a multistage event. • Our findings support a two-stage India-Asia collision scenario. • The unconformities propagated from north to south over western Myanmar during the Paleogene. • Syn-Rift sequences of the Shwebo basin were produced by transtensional faulting. • The West Myanmar Terrane was anchored on SE Asia before the late Paleocene (60-58 Ma). [ABSTRACT FROM AUTHOR]

The diagenetic sequence from opal-A to opal-CT has been observed in geothermal systems worldwide. Xizang, a unique geothermal region in the world, has experienced several large-scale geothermal activities since 0.5 million years ago. The Targejia and Gulu geothermal systems were investigated in this study. The time for transformation from opal-A to opal-CT varies, indicating that the rates of silica phase transformation depend on specific conditions; however, their silicon isotopic compositions are not significantly different, ranging from −1.0‰ to −0.3‰ in Targejia and from −1.1‰ to −0.1‰ in Gulu. Additionally, silica sinters undergo varying degrees of diagenesis, as supported by different time periods and varying degrees of ordering. The δ30Si values of different phases, opal-A and opal-CT, also did not significantly change, ranging from −1.1‰ to −0.3‰ for opal-A and from −1.0‰ to −0.1‰ for opal-CT. Due to the lower dissolution rates of sediments, high aluminum content, and reduced reactivity of silica sinters, the δ30Si values of silica sinters are less susceptible to secondary modifications, and the initial information after the silica sinters formation is well preserved. Hence, the isotopic signatures of silica sinters reflect various depositional environments and can be used to reconstruct paleo-geothermal activity. The narrow range and slightly negative isotopic values of silica sinters suggest that large-scale high-temperature geothermal activity has occurred in different regions since 0.5 Ma. The diagenesis of silica sinters may have been influenced by postlarge-scale high-temperature geothermal activity. Such large-scale, high-temperature and long-term natural eruptions in geothermal fields are typically associated with magmatic activity, possibly caused by crustal remelting processes. • The rates of silica phase transformation depend on specific conditions. • δ30Si values of silica sinters are less susceptible to secondary modifications during diagenesis. • Large-scale high temperatures geothermal activities occurred in Xizang. • They are typically associated with magmatic activity caused by crustal remelting processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three types of cobalt minerals and four types of nickel minerals are identified in Dulenggou Cu-Co deposit. • In-situ U-Pb dating of monazite yielded an age of 467 ± 17 Ma for mineralization. • Dulenggou deposit is a SEDEX-type Cu-Co deposit in the East Kunlun orogenic belt. The East Kunlun region in western China stands out as an important polymetallic metallogenic belt hosting economically significant Au, Cu, Fe, Pb, Zn, Sn, Co, Ni and Cr resources. Within this belt lies the Dulenggou deposit, a notable Cu-Co deposit. Three cobalt minerals (cobaltine, siegenite, and glaucodot) and four nickel minerals (ullmannite, gerdorffite, violarite, and millerite) coexisting with chalcopyrite and pyrite were identified in the Dulenggou deposit. The mineralization of Co and Ni primarily occurs in the form of sulfarsenides (cobaltine and gersdorffite) rather than sulfides (siegenite and ullmannite). Sulfides are commonly associated with chalcopyrite, whereas sulfarsenides coexist with chalcopyrite occasionally within the host rocks. The presence of organic-rich surrounding sedimentary rocks reduces oxygen fugacity, and the increase in arsenic content may influence the paragenetic association of minerals. The sequence of mineral formation is Py0 (host rocks) → PyI + Ccp + Co-Ni minerals (the major mineralization stage) → PyII. The mineralization age of the Dulenggou deposit has been determined by in situ U–Pb dating of hydrothermal monazite in closely association with chalcopyrite and Co–Ni minerals, yielding an age of 467 ± 17 Ma. The δ34S values of sulfides (pyrite and chalcopyrite) from ores and host rocks range widely from 1.9 ‰ to 22.1 ‰. From Py0 to PyI to PyII to chalcopyrite, the δ34S values change from 17.6 ‰ to 22.1 ‰, from 9.1 ‰ to 14.6 ‰, from 1.9 ‰ to 7.7 ‰, and from 9.6 ‰ to 13.4 ‰, respectively. The positive δ34S values suggest that the primary sulfur source possibly originated from seawater and/or the host rocks. Based on the geological and geochemical characteristics, the Dulenggou copper-cobalt deposit is identified as a syngenetic sea floor sedimentary exhalative deposit. [ABSTRACT FROM AUTHOR]

Lithium is one of the important strategic energy metals, which is in short supply in China. There are three major types of lithium deposits: brine and salt lake type, highly differentiated granite or pegmatite type, and carbonate-clay type. In recent years, some new types of lithium deposits have also begun to receive great attention and subject recent research. There are many crypto-explosive breccia pipe type deposits in the world, including copper, gold, lead, zinc, tungsten and tin deposits, but little is known about this type of lithium deposit. This paper introduces the latest research results of the Weilasituo Sn−Li−Rb polymetallic deposit in Inner Mongolia (NE China), which occurs in the middle-southern section of the Great Xing'an Range metallogenic belt. A remarkable feature of this deposit is the coexistence of various mineralization types, including granite type Rb and Sn−Zn, hydrothermal crypto-explosive breccia pipe type Li−Rb, quartz vein type Sn−Zn and sulfide vein type Pb−Zn−Ag mineralization. Among them, hydrothermal crypto-explosive breccia pipe type Li-Rb deposit is currently very rare at home and abroad, which is likely a new type of rare metal deposit that worthy of our attention. This paper systematically summarizes the geology, alteration and mineralization, geochemistry, isotopes and geochronology of the Weilasituo deposit, and establishes a new petrogenic and metallogenic model. [ABSTRACT FROM AUTHOR]

During in situ determination of major and trace element concentrations of minerals by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), an internal standard is needed. In this study, we present a new modified calibration strategy without using an internal standard but still able to achieve accurate major and trace element determination of fluorapatite by LA-ICP-MS. Reference materials and normalization to bulk metal-oxide components as 100% were used to correct absolute amount differences of materials and sensitivity drift during each ablation process. Because F and P have high first ionization energy with low sensitivity in ICP-MS and may not be accurately measured by quadrupole ICP-MS, we determined the concentrations of these elements based on the calculation of the mineral unit formula to remove the disturbance of F and P to total normalization. We used the calibration with reference standards plus the above modified calibration strategy to determine the compositions of the standard reference material Durango and two types (magmatic and hydrothermal) of fluorapatite samples. The data of major and trace element compositions obtained by our new method without an internal standard are identical to those of the previous traditional internal standard-dependent calibration method within 1%. Overall, our new calibration method can achieve the same accuracy but lower cost and less time compared to the previous method. [ABSTRACT FROM AUTHOR]

Keywords: Pyrite formation and replacement; sulfur isotopes; gold remobilization; epithermal gold mineralization EN Pyrite formation and replacement sulfur isotopes gold remobilization epithermal gold mineralization 1133 1148 16 06/01/22 20220601 NES 220601 Introduction Large gold deposits may form by multiple gold enrichment events, but it is often hard to clarify whether the last of these events represents remobilized gold from pre-existing mineralization or relates to new gold introduction during a distinct epigenetic event ([23]; [14]). In many gold deposits, gold shows a bimodal distribution in which refractory gold within pyrite was overprinted by later visible gold as distinct inclusions or filling fractures within the pyrite. The formation of visible gold by hydrothermal alteration of refractory gold-bearing pyrite may provide new insights into the formation of high-grade gold ores in epithermal deposits, although the direct introduction of gold by later auriferous fluids cannot be ruled out. For example, at Sunrise Dam, Australia, textural evidence exists that is consistent with the replacement of arsenian pyrite, whereby remobilized gold was deposited as native gold inclusions oriented parallel to crystal faces or in fractures, inferring the partial replacement of parent arsenian pyrite via fluid-mediated CDR reactions ([45]). Furthermore, oscillatory- and sector-zoned pyrite from Jerome and Kenty deposits in Canada record textures, such as porosity development coincident with the presence of native gold and accessory sulfide phases, that are suggestive of CDR reactions that liberated gold and associated elements from earlier auriferous pyrite ([15]). [Extracted from the article]

Despite their relatively rare occurrence, lepidolite-subtype pegmatites host abundant Li–Nb–Ta–Cs–Sn mineralization and represent a high-flux pegmatitic system with abnormally high F and Li activity. Characterization of highly fluxed melts and the impact of fluxes and exsolved fluids on fractionation of peraluminous melts have mainly been studied in experimental systems, with natural system correlations remaining poorly understood. Consequently, we conducted a systematic mineralogical study of a lepidolite-subtype pegmatite in the North Qinling orogenic belt, Central China. An abnormal "concave downward" fractionation trend for primary columbite-group minerals on the quadrilateral diagram is identified, and irregularly zoned columbite crystals coexist with F-rich minerals in one of the core zones have the highest Ta contents (normally 50.17–63.13 wt% Ta 2 O 5) and Ta/(Nb + Ta) ratios (up to 0.65). Despite the consistently Ta-dominated B-site in the crystal lattice of microlite-group minerals, extreme compositional variations at the A- and Y-sites are observed. Compared with microlites in intermediate zones, the abrupt increase in U in microlite crystals in core zones and late units (up to 20.16 wt% UO 2), is ascribed to the melt-fluid interaction with exsolved U-rich aqueous fluids. In addition, the fractional crystallization of F-bearing minerals resulted in a gradual decrease in F contents in microlite-group minerals from extremely F-rich (2.68–4.84 wt% F) in intermediate zones to low F species (mainly 0.82–1.71 wt% F) in core and late zones. Moreover, autometasomatism by a late fluxed melt and hydrothermal metasomatism by late aqueous fluids are identified in columbite- and microlite-group minerals. This work highlights that these non-typical fractionation behaviors related to the activity of fluxes (especially F) and the exsolution of aqueous fluids during the internal evolution of pegmatitic melts, are critical for the generation of lepidolite-subtype pegmatites. Fluorine was gradually enriched in the pegmatitic melt, and reached its highest level during crystallization of the (inner) intermediate and core zones. Non-equilibrium crystallization occurred throughout pegmatite evolution, and late units were most probably formed from aqueous fluid-enriched residual melts, rather than by hydrothermal replacement. [Display omitted] • Columbite-group minerals define an abnormal "concave downward" fractionation trend. • Microlite-group minerals display extreme A- and Y-site compositional variations. • Both autometasomatism and hydrothermal metasomatism are identified. • Non-typical fractionation behaviors are critical for the generation of lepidolite-subtype pegmatites. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Galinge Co-bearing skarn iron deposit formed at 237.1 ± 0.3 Ma. • Occurrence of Co includes independent Co minerals skutterudite and cobaltite. • Factors controlling Co-minerals precipitation include increase in pH and decrease in the As/S ratio. Skarn iron deposits, as representative examples of Co-rich magmatic-hydrothermal deposits, are attracting increasing attention due to rising cobalt demand worldwide. However, the specific Co enrichment mechanisms and metallogenic processes in skarn deposits remain elusive. This study presents high-precision in situ U–Pb geochronological data for garnet from skarns, major and trace element analyses of sulfarsenides and sulfides, and X-ray mapping in the Galinge deposit. The Galinge skarn iron deposit formed at 237.1 ± 0.3 Ma (garnet U–Pb dating), during which time the region was in the post-collisional stage. During this period, the crust was thickened, causing delamination of the lithospheric mantle, which further led to the upwelling of asthenospheric materials and partial melting of the lower crust. As the resultant mixed magma ascended, it reacted with carbonate strata to form skarn deposits. Cobalt shows two occurrence modes in the Galinge deposit: independent cobalt minerals such as skutterudite and cobaltite, and isomorphic substitution of Co with other metals in ore minerals (arsenopyrite, pyrrhotite, sphalerite, pyrite, magnetite, and chalcopyrite). Our results revealed that arsenopyrite is the most cobalt-enriched ore mineral in the Galinge deposit, with an average Co content of 34,077 ppm. Other minerals generally contain insignificant Co contents of less than 500 ppm, including sphalerite (471 ppm) > pyrite (194 ppm) > pyrrhotite (145 ppm) > alabandite (∼100 ppm) > magnetite (7 ppm) > chalcopyrite (2 ppm). In arsenopyrite, cobalt and nickel replace iron in accordance with the inverse correlation between the concentrations of cobalt and nickel (wt%) and that of iron. In pyrite and chalcopyrite, a portion of the isomorphic cobalt substitutes for Fe or Cu. The weak correlation between Co (ppm) and Cu or Fe (wt%) indicates that only isomorphic cobalt is carried out by substituting Fe or Cu. The negative correlation between Co + Fe and Zn or Mn suggests that cobalt and iron replace Zn or Mn in sphalerite and alabandite. No evidence of element substitution was observed in pyrrhotite. Our study highlights that during the early mineralization stage, cobalt in the magmatic-hydrothermal fluids migrated in the form of CoCl 4 2 -. Subsequently, under the influence of an increase in pH, CoCl 4 2 - reacts with H 3 A s O 3 0 to form Co As 3 (skutterudite). With the continuous precipitation of arsenides and sulfarsenides, the As/S (reduced) ratio decreased, leading to the Co As 3 (skutterudite) changing to CoAsS (cobaltite). [ABSTRACT FROM AUTHOR]

[Display omitted] • A new type clay-Li deposit is found in southern Hubei Province, China. • This deposit was formed by fault-controlled hydrothermal alteration. • Hydrothermal apatite U-Pb dating indicates an age of 135.2 ± 13.9 Ma. • The Li enrichment is related to the Mufushan granitic magmatism. Clay-Li deposits are among the major Li deposits in the world and occur mainly in sedimentary and/or volcanic-sedimentary strata. The Li orebodies are generally stratiform and stratibound, and Li is mainly hosted in various clay minerals. Here, we report a new type of clay-Li deposit that occurs along fault zones developed in metasedimentary rocks with significant alteration, and Li is also hosted in clay minerals in the Jinyinshan area in Xianning, southern Hubei Province, China. The study area has no granitic rock outcrops, but approximately 15 km south is the Mufushan granite batholith, where large-scale rare metal mineralization, such as Li, Be, Nb and Ta granitic pegmatites, developed in the internal and outer contact zones of the granite batholith. In this study, high-Li clay minerals, including chlorite, kaolinite and smectite, were identified. The enrichment of Li is closely related to hydrothermal activity along the F9 fault in the region. Hydrothermal apatite coexisting with Li-clay in the orebody along the fault zone yielded an in situ U–Pb age of 135.2 ± 13.9 Ma, which is in good agreement with the ages of granites and Li-pegmatites around the Mufushan batholith. Petrographic, geochemical, and chronological evidence suggests that the ore-forming fluids and Li were likely sourced from the Mufushan granite batholith or a similar blind granite at the depth of the study area; that is, the granite-derived ore-forming fluids can travel long distances along fault zones, and during this pathway, Li from the metasedimentary rocks (i.e., the Lengjiaxi Group) may also have been leached by the fluids and contributed to the Li mineralization in the Jinyinshan clay-Li deposit. The close spatial relationships among different clay minerals indicate that fluid physical–chemical conditions (changes in temperature) may play a crucial role in controlling the formation of Li-rich clay minerals. Our study indicates that the Mufushan area has great potential for hydrothermal clay-Li mineralization occurring in the Lengjiaxi Group metasedimentary rocks around the Mufushan batholith. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three types of pyrite were identified in the Maoping MVT Pb-Zn deposit. • Sulfur for Py1 and Py2 originated from sulfates by thermochemical reduction. • Sulfur for Py3 originated from bacterial sulfate reduction. • Fluid mixing of metal-bearing basin brine and fluid containing reduced sulfur was responsible for ore formation. The SYG (Sichuan–Yunnan–Guizhou) area is one of the most economically significant Mississippi Valley Type (MVT) ore provinces, providing approximately 27 % of the Pb–Zn resources in China. The Pb-Zn deposits in this region are renowned for their high grade, and the Maoping deposit with 20.3 % Pb-Zn grade is one prime example. However, the mechanism of such high-grade mineralization remains unclear, and pyrite may record valuable ore-forming information before and during Pb-Zn mineralization. Based on field geology and petrography, three hydrothermal stages were identified in the Maoping deposit: dolomite–pyrite vein (stage I), dolomite–sphalerite–galena vein (stage II), and calcite vein (stage III). Three types of pyrite are recognized: Py1 and Py2 occur in stage I, and Py3 is closely associated with sphalerite and galena in stage II. Py1 exhibits the highest concentrations of S, Pb, Sb, Cu, Co, Ni, V, Ag, Mn, Se, and Mo, and Py3 shows the highest Fe and As contents but the lowest levels of S, Pb, Sb, Cr, Ti, Co, Ni, Mn, and Mo. The element composition of Py2 shows transitional characteristics between those of Py1 and Py3. The Co and Ni contents gradually decrease from Py1 through Py2 to Py3, while their ratios remain within the range of 0.1–1.0. Compared with Py1 and Py2, Py3 exhibits suddenly elevated As levels and apparent acicular structures, indicating that a rapidly precipitating environment was likely triggered by an abrupt temperature decrease. Py1 exhibits δ34S values of 19.7–21.5 ‰, followed by Py2 between 18.6 and 21.1 ‰; both indicate that the sulfur was sourced from sulfates by thermochemical sulfate reduction (TSR). In contrast, Py3 exhibits lower δ34S values ranging from 7.5 to 11.0 ‰, potentially attributed to bacterial sulfate reduction (BSR). The differences in mineral structure, element composition, and sulfur isotopes among the three pyrite types indicate the involvement of two distinct fluids: metal-bearing basin brine and fluid containing reduced sulfur. The former was derived from basin brine that extracted ore metals (Pb2+ and Zn2+) from host sedimentary piles. The latter originated from carbonate strata in the Maoping area containing reduced sulfur formed by BSR. We propose that the ore-bearing basin brine reacted with organic matter in the wallrock through TSR to generate Py1 and Py2 in stage I and then mixed with the positioned fluid containing reduced sulfur via BSR to precipitate Py3, sphalerite, and galena in stage II. Hence, fluid mixing is the primary ore-forming mechanism and effectively accounts for the high-grade Pb–Zn ores in the Maoping deposit. [ABSTRACT FROM AUTHOR]

The Early Cretaceous peralkaline Baerzhe pluton hosts a potentially large REE-Nb-Zr-Be deposit in inner Mongolia, northeastern China. The mechanism responsible for the extreme enrichment of rare metals and rare earth elements in the pluton is still ambiguous. This study presents new evidence for silicate melt immiscibility as the key mechanism at Baerzhe using amphibole-group minerals from spherulite granite, which contains spherulites with abundant REE- and HFSE-bearing minerals. The spherulite from the transsolvus granite is composed of two distinct zones, i.e., a dark-colored core consisting of arfvedsonite aggregates and a light-colored rim consisting mostly of quartz and feldspar, rare amphibole, and abundant HFSE- and REE-bearing minerals. Four types of amphibole (Amp I, Amp-IIa, Amp-IIb and Amp-III) from the transsolvus granite and one type (Amp-IV) from the subsolvus granite are recognized, and all of them are magmatic fluoro-arfvedsonite. The earliest phase consists of euhedral inclusions of Amp-I within quartz or feldspar. They show an enrichment in HREEs relative to LREEs and a depletion in medium REEs, consistent with the REE pattern controlled by the mineral lattice. This implies that Amp-I likely formed in an initial homogeneous mel relatively depleted in REEs; thus, the mineral structure played a dominant role in REE partitioning. Compared with other types of amphiboles, Amp-IIa and Amp-IIb from the spherulite phase display the highest REE contents, with flat LREEs and MREEs and a slight upward HREE pattern. Combined with the significant accumulation of REE- and HFSE-bearing minerals in the rim zone, differences in REE patterns among different amphibole types imply that the spherulite crystallized in a volatile-rich silicate melt and was probably the product of silicate melt immiscibility. Interstitial Amp-III with lower REE contents from the matrix phase crystallized in the separate volatile-poor silicate melt. The Amp-IV from the subsolvus granite has the lowest CaO content, with strong depletion in LREEs relative to HREEs, suggesting a more evolved melt composition. It is concluded that silicate melt immiscibility may serve as an important key mechanism that occurred in the early stage of magmatic evolution, resulting in the enrichment of REEs and HFSEs, which played a critical role in the formation of large to giant ore deposits such as the Baerzhe deposit. [Display omitted] • Both transsolvus spherulite granite and subsolvus granite in the Baerzhe deposit. • Amphibole textures and compositions indicate the silicate melt immiscibility. • REE and HFSE minerals associated in the rims of spherulite granite. • Large-scale silicate melt immiscibility occurred in the early magma stage. [ABSTRACT FROM AUTHOR]

The Mufushan area, which has abundant rare-metal pegmatites within and around the Mufushan Granite Complex, has become a major target for Ta-Nb-(Li-Be) exploration in South China. The age and origin of the pegmatites and associated rare-metal mineralization are still under debate. Here, we report the in situ U-Pb ages and geochemical characteristics of granites and pegmatites in the Guanyuan and Duanfengshan districts, which are located in the central and northern parts of the Mufushan Complex. Combined zircon, apatite and monazite U-(Th)-Pb dating revealed that biotite, two-mica, and muscovite granites from the Guanyuan and Duanfengshan districts were emplaced at 143–139 Ma, which overlaps with the U-Pb ages of columbite-group minerals (CGM) from different internal zones of the Duanfengshan pegmatites (142–140 Ma). Whole-rock major and trace element compositions and Sr-Nd-Hf isotope data reveal that the granites and pegmatites experienced continuous evolution from biotite, two-mica, and muscovite granites to pegmatite and that the magma originated from the partial melting of mica schists that are abundant in the Mufushan area. Temporal, chemical and mineralogical evidence indicates a genetic link between muscovite granite and Ta-Nb pegmatites. The textures and chemical compositions of CGM from different pegmatites exhibit features typical of magmatic CGM, indicating that fractional crystallization was the driving force that promoted Ta-Nb enrichment. The increasing alumina saturation index [ASI: molar Al/(Ca–1.67P + Na + K)] of pegmatitic melt due to albite crystallization may have been the main factor controlling CGM deposition, explaining why major Ta-Nb mineralization is bound to albite pegmatites. The Duanfengshan and other rare-metal pegmatites in the Mufushan area are derivatives of the most evolved granitic facies (i.e., muscovite granite) of the Mufushan Complex. The Duanfengshan and Renli pegmatite fields indicate that the Early Cretaceous (∼140 Ma) may have been an important, underappreciated epoch for the formation of pegmatite-related rare-metal resources in the Mufushan area and beyond in South China. [Display omitted] • The rare metal pegmatites have genetic relationship with the muscovite granite in the Mufushan area. • In-situ U-Pb dating of columbite-group minerals indicate the rare metal mineralization occurred at 142–140 Ma. • Prolonged fractional crystallization is the driving force to promote rare metal mineralization in granite-pegmatite system. • Early Cretaceous is an important epoch for the formation of pegmatite rare-metal resources in South China. [ABSTRACT FROM AUTHOR]

A comprehensive study of zircon U–Pb ages, major and trace elements, whole‐rock Sr–Nd–Pb isotopes and zircon Hf isotopes of the gneissic granite and quartz monzonite in the Tongbai Complex is conducted in an attempt to unravel their petrogenesis and shed new light on the tectonic evolution and crust thickening process of the Tongbai orogen. Zircon U–Pb dating indicates that the emplacement of gneissic granite was early at 144.2 ± 1.3 Ma, whereas the quartz monzonite formed later at 130.2 ± 1.7 Ma. Both the gneissic granite and quartz monzonite samples share many chemical similarities, such as high Al2O3, K2O, Sr contents and low MgO contents, together with high Sr/Y, high La/Yb ratios, suggesting an C‐adakitic affinity and possibly derived from partial melting of the thickened lower crust. The later quartz monzonites may have involvement of much more proportion of mantle‐derived materials (such as the metamorphosed mafic rocks, ecologite) in the lower crust during partial melting for its petrogenesis, due to its higher MgO, Cr, Ni, and V contents than the gneissic granites. The formation of the gneissic granite and quartz monzonite records the evolution history for the lower crust thickening beneath the Tongbai orogen at the Cretaceous. Nearly all granitoids in the Tongbai orogen currently found have an emplacement age of >130 Ma and have higher Sr/Y ratios and lower MgO, Cr, Ni, and V contents with respect to the granitoids in the Dabie orogen which occurs in two stages of granitic magmatism of >130 Ma and <130 Ma. The Tongbai orogen lacks the granitoids formed by significant crust–mantle mixing that occurred in the Dabei area at <130 Ma. These results indicate that the lower crust was continuing thickening but probably not delaminated beneath the Tongbai orogeny during the Early Cretaceous. [ABSTRACT FROM AUTHOR]

Qinzhou-Hangzhou metallogenic belt is an important polymetallic (Cu, Mo, W, Sn, Pb, Zn, Au, and Ag) belt in South China. The Xinmin polymetallic deposit is located in the southwestern segment of this belt, which ore bodies hosted in the contact zone of granite and Lower Devonian sedimentary strata and in the structure fractured zone within the strata. Three hydrothermal stages can be distinguished: quartz+tourmaline+pyrite (early stage), tourmaline+pyrite+galena+bismuthinite+sphalerite+chalcopyrite+pyrrhotite (main stage), and quartz+calcite+dolomite (late stage). The mineralizing fluid system can be described as aqueous with medium-high salinity (2.7-50.7 wt.‰ NaCl equiv. in the main stage and 0.18-8.81 wt.‰ NaCl equiv. in the late stage) and medium-high temperature of 485°C to 205°C (main stage) and 300°C to 116°C (late stage). The trapping pressures varied from 2 MPa to 30 MPa (main stage) and 0.4 MPa to 9 MPa (late stage). The δ 18 O values of quartz range from 6.7‰ to 8.5‰, and the δ D values for fluid inclusions in quartz range from -45‰ to -52‰. The calcite has C-isotopes ranging from -5.8‰ to +0.7‰ and O-isotopes from +12.7‰ to 21.4‰. H-O-C isotope data are consistent with a hydrothermal fluid derived from the Cretaceous granitoid magma. The δ 34 S values of sulfides are -3.3‰ to +1.9‰. Sulfides have 206Pb/204Pb ratios of 18.377 to 18.473, 207Pb/204Pb ratios of 15.606 to 16.684, and 208Pb/204Pb ratios of 38.613 to 38.902. The S-Pb isotope data suggest derivation of S and Pb mainly from the Cretaceous granitic magma. It is concluded that the Xinmin deposit is a medium-high temperature, medium-high salinity hydrothermal polymetallic deposit, related to the granitic magmatism and strictly controlled by the fault and shattered zones. [ABSTRACT FROM AUTHOR]

Early Cretaceous mafic rocks are first reported in the northern Guangxi region from the western Qin-Hang belt in the interior South China Block. A systematic investigation of zircon U–Pb dating, whole-rock geochemistry, Sm–Nd isotopes and zircon Hf–O isotopes for these mafic rocks reveals their petrogenesis and the mantle composition as well as a new window to reconstruct lithospheric evolution in interior South China Block during Late Mesozoic. Zircon U–Pb dating yielded ages of 131 ± 2 Ma to 136 ± 2 Ma for diabase and gabbro from Baotan area, indicating the first data for Early Cretaceous mafic magmatism in the western Qing-Hang belt. These mafic rocks show calc-alkaline compositions, arc-like trace element distribution patterns, low zircon εHf(t) of − 9.45 to − 6.17 and high δ18O values of + 5.72 to + 8.09‰, as well as low whole-rock εNd(t) values of − 14.27 to − 9.53. These data suggest that the studied mafic rocks are derived from an ancient lithospheric mantle source that was metasomatized during Neoproterozoic subduction. Thus, the occurrence of these mafic rocks indicates a reactivation of Neoproterozoic subducted materials during an extension setting at Late Mesozoic in the western Qin-Hang belt, an old suture zone that amalgamates the Yangtze and Cathaysia blocks. [ABSTRACT FROM AUTHOR]

[Display omitted] • Protracted fractional crystallization and subsolidus processes formed the Arskartor granite-pegmatite system with Be-polymetallic mineralization. • Nonequilibrium crystallization of a fluxed late granitic melt generated the Be-mineralized granite. • The undercooled pegmatitic melt with varying amounts of aqueous fluids at different fractions caused variable amounts of beryl in different internal zones. The Arskartor Be-Nb-Mo deposit is the second largest Be deposit in the Chinese Altai, NW China, which hosts over 11,000 tons of BeO resource. The muscovite-albite granite and rare-metal pegmatite in the ore district are spatially and temporally coexisted and both are beryllium mineralized. The muscovite-albite granitic stock can be divided into a barren zone and a Be-mineralized zone. The pegmatite shows an well-developed internal zone including the layered muscovite-quartz-albite zone, (lower) beryl-muscovite-quartz zone, quartz core, (hanging) beryl-muscovite-quartz zone, and muscovite-quartz-microcline zone. Beryl is the dominant Be-bearing mineral and mainly occurs in the Be-mineralized granite, the layered muscovite-quartz-albite and the beryl-muscovite-quartz zones of the pegmatite. Subhedral to euhedral beryl in the Be-mineralized granite is interstitial to or intergrown with rock-forming minerals. In contrast, beryl crystals in the pegmatite are coarser in grain size and more euhedral in shape, and mainly coexist with coarse "booked" muscovite and blocky quartz. Concentrations of Li, Cs and Na/Li ratios of beryl are 184–760 ppm, 218–1996 ppm, and 2.13–21.3, respectively. The progressive variations of incompatible elements compositions and Na/Li ratios are consistent with the fractional crystallization mechanism of the granite-pegmatite system. Paragenesis and internal structure of beryl suggest nonequilibrium crystallization of a relatively incompatible elements and fluxes-enriched late granitic melt, generated the coarse-grained Be-mineralized granite. With the progressive enrichment of incompatible and fluxing elements and decreasing temperature, liquidus overcooling was achieved and generated the aplite and immediate zoned pegmatite that hosts abundant beryl. Moreover, the differentiating pegmatitic melt with varying amounts of aqueous fluids at different melt fractions, likely resulted in heterogeneous distribution of beryllium and subsequent variable amounts of beryl crystallization in different internal zones. The exsolution of aqueous fluids from the residual pegmatitic melt resulted in Mo-mineralization and related hydrothermal alteration. Consequently, both protracted fractional crystallization and subsolidus processes contributed the formation of the Arskartor granite-pegmatite system with Be-polymetallic mineralization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two stages of Cretaceous basalt erupted in the Jiurui district of the Yangtze Block. • The older basalts are Island arc basalt-like, forming from melts derived from an enriched lithospheric mantle. • The younger basalts are Oceanic island basalt-like, forming from melts derived from a depleted asthenospheric mantle. • The Cretaceous lithospheric mantle underneath the Yangtze Block was similar to EM I. The Cretaceous volcanic-sedimentary succession in the Jiurui district of the Yangtze Block contains basalts that are interlayered with fine clastic rocks, conglomerate and breccia strata. Here, we present data of whole-rock 40Ar–39Ar dating, major and trace elements, Sr–Nd–Pb isotopes, zircon U–Pb dating and Hf isotopes, and plagioclase trace element analyses to constrain the petrogenesis and tectonic background of these basaltic rocks,. Two episodic eruptions (ca. 126 Ma and ca. 91 Ma) are recognized, and the early basalts display evident enriched source characteristics such as high incompatible and low compatible elements, negative Nb, Ta, and Ti, slightly positive Pb anomaly, negative ε Nd (t) and ε Hf (t) values, higher (87Sr/86Sr) i , and high incompatible elements in plagioclase, indicating an island arc basalt-like nature. The younger basalts show low incompatible and high compatible elements, negative Rb, Pb, Nb, and Ta, positive Sr anomaly, positive ε Nd (t) values, lower (87Sr/86Sr) i , and low incompatible elements in the plagioclase, indicating an oceanic island basalt-like characteristic. The early ca. 126 Ma basalts were probably derived from a deeper and older enriched lithospheric mantle consisting of rutile-bearing garnet pyroxenite or eclogite, whereas the younger ca. 91 Ma basalts were derived from a shallower and younger depleted asthenospheric mantle constituting peridotite, with limited amounts of enriched lithospheric mantle component. The retreat and rollback of the paleo-Pacific slab and related lithospheric thinning and mantle composition transition processes probably occurred at ca. 126 Ma and ca. 91 Ma in this inland region of the Yangtze Block in northwestern Jiangxi province. [ABSTRACT FROM AUTHOR]

Fluid-flow within tectonic belts and fault-fluid interaction are fundamental and controlling factors of large thrust belt evolutions, formation of mineral deposits in the upper crust and the ductile shear deformation in the middle crust. In central South China, a large Chuandong-Xiangexi fold-and-thrust belt and long-distance displaced thrust faulting are developed, but their formation mechanism is still in debate. In particular, the evolution of fluid-flow and fault-fluid interactions in this fold-and-thrust belt is still not well constrained. In this study, through detailed structural and microstructural observations together with stable isotope and fluid inclusion analyses, we aim to unravel the deformation characteristics and syn-tectonic fluid-flow along the detachment in the frontal zone of this fold-and-thrust belt. One approximately 30–60 m thick, NW-verging detachment thrust with brittle-ductile deformation and alternating the strongly and weakly deformed zones is identified in the Lower Permian bioclastic and argillaceous limestones. The strongly deformed zone is characterized by tectonic lenses, fault gouge, calcite veins, S–C fabric, and foliated fault rocks/gouge, while the weak deformation zone is marked by scattered fractures without calcite veins and weakly deformed tectonic lenses. The fluids within the thrust faults originate from formation waters (saline fluids or brines) in a closed system, evidenced by the δ18O values, the 87Sr/86Sr ratios, the hydrocarbon-bearing fluid inclusions characterized by moderate salinity (10–14 wt% NaClequiv.) and moderate-high homogenization temperatures (∼160–350 °C). In the hanging wall of the Huangyingshan fault, the fluids involved in the thrusting processes are most likely brines derived from Middle and Lower Triassic carbonate aquifers. While in the footwall, the fluids are likely brines derived from Cambrian evaporitic aquifers. These findings on the detachment thrust fault zone could provide valuable constraints on the conduit and distance of hydrocarbon secondary migration for exploring the potential of large-scale hydrocarbon accumulation in the Chuandong-Xiangexi fold-and-thrust belt. [Display omitted] • One NW-verging detachment thrust is identified in the Chuandong-Xiangexi fold-and-thrust belt in central South China. • The syn-tectonic high-temperature fluids circulating along the thrust faults, originate from saline formation waters. • The fluids involved in the hanging wall are brines from Middle and Lower Triassic carbonate aquifers. • The fluids in the footwall are brines from Cambrian evaporitic aquifers. • The Lower Permian detachment thrust fault zone provide constraints on the conduit and distance of hydrocarbon migration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Textural and chemical features of beryl can trace magmatic-hydrothermal evolution. • Cs in beryl is an ideal trace element to monitor the magmatic evolution. • Fluid exsolution can promote the remobilization of Ta and Rb. In the large Shihuiyao Rb-Nb-Ta-Be deposit, a beryl-bearing granite was identified with three texturally different zones that show an increasing degree of fractionation, including the albite granite (bottom zone), albite granite with pegmatite pockets (intermediate zone), and intercalation of granite and pegmatite layers (top zone). Beryl occurs both in the intermediate and top zones. Microtextural (SEM), Raman spectra, and trace-element (LA-ICP-MS) data on beryl from these zones shed new light on the behavior of trace elements during magmatic-hydrothermal evolution. In the intermediate zone, magmatic beryl (Brl-1) has a homogeneous texture, while beryl in the top zone (Brl-2) can be divided into magmatic (Brl-2a) and metasomatic subtypes (Brl-2b). The magmatic Brl-2a shows oscillatory zonation, whereas the metasomatic Brl-2b is darker in BSE images and highly porous. Fractional crystallization led to an increase in Na, Sc, Fe, Rb, and Cs contents from Brl-1 to Brl-2a. Comparing these data with those of beryl in other pegmatites worldwide reveals that Cs in beryl is an ideal trace element to monitor the magmatic evolution of the pegmatite host. Distinct textural and chemical features of Brl-2a and Brl-2b reflect metasomatic alteration by a dissolution-reprecipitation process for Brl-2b. In combination with published experimental and fluid inclusion data, we propose that metasomatic fluids exsolved from the magma during late-magmatic stages could transport large amounts of rare metals, such as Ta and Rb. The higher content of Ta in Brl-2b compared to Brl-2a suggests that metasomatic fluids exsolved from the magma play a favorable role in Ta mineralization. In contrast, decreasing Rb contents in Brl-2b is attributed to the high mobility of Rb in the fluid. Such Rb-rich fluids are expected to generate Rb orebodies of economic value surrounding the ore-bearing granite, implying that more investigation into hydrothermal Rb mineralization in the Shihuiyao district is warranted. [ABSTRACT FROM AUTHOR]

• At Luiswishi Cu-Co deposit, the quartz-, dolomite-, and magnesite-(sulfide) veins occur in silicic, dolomitic, and magnesitic host rocks, respectively. • U-Pb dating of hydrothermal monazites from main ore vein and post-ore pyrite yielded ages of 523 Ma and 506 Ma. • Pyrite from different stages show distinct trace elements and sulfur isotope characteristics. • A two-stage model is proposed by Neoproterozoic syn -sedimentary-diagenetic overprinted by Pan-Afriacn orogenic mineralization events. The Central African Copperbelt (CACB) hosts the majority of the Co resources in the world, however, whether these Cu-Co deposits were formed during the syn -sedimentary-diagenetic stage or by later hydrothermal processes at the orogenic stage is a matter of debate. The Luiswishi deposit, hosted in the least deformed and metamorphosed host rocks of the Katanga Supergroup within the CACB, was selected in this study to explore this issue. Petrographic observations indicate a certain correlation between the mineralogical compositions of the veins and their host rocks, with quartz-, dolomite-, and magnesite-(sulfide) veins occurring in silicic, dolomitic, and magnesitic host rocks, respectively. Four paragenetic stages were identified, i.e., the pre-ore stage with pyrite (Py0), syn -sedimentary-diagenetic Cu-Co stage with chalcopyrite (Ccp1), syn -orogenic Cu-Co stage with pyrite (Py2) and chalcopyrite (Ccp2), and post-ore stage with pyrite (Py3) as the dominant sulfides. U-Pb dating of hydrothermal monazites associated with the main vein-type mineralization and post-ore pyrite yielded ages of 523 Ma and 506 Ma, respectively, coinciding with the peak metamorphism of the Lufilian orogeny. Py0 exhibits elevated contents of Co and As but low Cu and Ni, with variable δ34S V-CDT values from −9.1 ‰ to + 12.0 ‰. The δ34S V-CDT values for Ccp1 vary with the lithology of the host rocks (avg. −1.3 ‰ for quartz siltstone; avg. 3.6 ‰ for dolomitic sandstone/dolostone; avg. 5.6 ‰ for magnesite rock). The coarse-grained Ccp2 from the discordant veins shows higher Sn and In contents than Ccp1, indicating that Ccp2 formed in a hydrothermal fluid with increased temperature. Py2 shows a gradual decrease in Co and As from the early phase (Py2a) to later phase (Py2c), reflecting the gradual depletion of these elements in the hydrothermal fluid. The sulfides in syn -orogenic vein-type ores show similar δ34S values as their corresponding syn -sedimentary-diagenetic sulfides disseminated in the stratiform ores, indicating that the sulfur for orogenic mineralization was mainly derived from the syn -sedimentary-diagenetic sulfides. Overall, the current study supports a model in which the sediment-hosted Cu-Co deposits in the CACB formed from Neoproterozoic syn -sedimentary-diagenetic processes overprinted by Pan-African orogenic mineralization events. The bulk of the metals and sulfur in the deposits were introduced in the syn -sedimentary-diagenetic stage, and the orogenic mineralization process mainly played the role of remobilization and upgrading of the syn -sedimentary-diagenetic mineralization. [ABSTRACT FROM AUTHOR]

The Wangjiadashan Cu–Au deposit is a vein‐type deposit controlled by the secondary faults of the Wushan Fault zone in the Suizao area of Hubei Province. Three hydrothermal stages are identified, namely, (I) barren quartz stage, (II) the quartz‐sulphide stage, and (III) quartz‐carbonate stage. Six types of fluid inclusions occur in quartz: (a) liquid‐rich aqueous fluid inclusions (L + V), (b) vapour‐rich aqueous‐carbonic fluid inclusions (V + L), (c) water‐rich aqueous‐carbonic fluid inclusions (L + V + CO2), (d) CO2‐rich aqueous‐carbonic fluid inclusions (V + L + CO2), (e) pure carbonic fluid inclusions (pure CO2), and (f) daughter mineral‐bearing multiphase inclusions (S‐type) with three subclasses (S1, S2, and S3 subtype). Two types of fluid inclusions occur in calcite: (a) liquid‐rich aqueous fluid inclusions (L + V) and (b) pure carbonic fluid inclusions (pure CO2). The S‐type fluid inclusions include halite (NaCl), calcite (CaCO3), and chalcopyrite (CuFeS2). The fluid system is composed of CO2–NaCl–H2O. The homogenization temperatures of the three stages are 295°C to 390°C, 245°C to 280°C, and 200°C to 241°C, with salinities of 7.3–19.8 wt% NaCl equiv. (except for several high values of 33.8 to 44.3 wt% NaCl equiv.), 7.7–13.7 wt% NaCl equiv., and 5.6–10.1 wt% NaCl equiv., respectively. Fluid immiscibility occurred in stage I that accounts for the high‐salinity fluids, but the dominant ore precipitation occurred afterward during temperature drop. In situ sulphur isotope analysis indicates a δ34S value around 0 (+1.1% to +2.2%) for the chalcopyrite, suggesting that the sulphur likely derived from the deep‐seated magma. Pyrites show δ34S values from −0.5‰ to +6.5‰ in stage II, from +0.7‰ to +6.6‰ in country rock of marble, but significantly higher from +12.8‰ to +21.7‰ in country rock of greenschist. These results indicate the sulphur for pyrite in stage II likely derived from the mixing of deep‐seated magma and country rocks. From stages I to II, a slightly increase of δD (from −86‰ and −73‰ to −59‰ and −56‰) and a decrease of δ18O (from 8.9‰ and 7.1‰ to 1.3‰ and 3.4‰) indicate that an increasing involvement of meteoric water. The carbon isotopes of fluid inclusions CO2 in quartz of stage I (−11.0‰ to −13.0‰) indicate a major magmatic or metamorphic carbon source mixed with minor sedimentary sourced carbon, but a major organic carbon source (−32.0‰ to −35.0‰) for stage II fluids. In conclusion, the Wangjiadashan Cu–Au deposit belongs to the orogenic type. [ABSTRACT FROM AUTHOR]

Gypsum often occurs in marine sediments as an authigenic mineral, but it may also be produced artificially through oxidation of sulfide during sample storage and preparation. Therefore, the origin of the gypsum should be carefully checked, especially for those DSDP, ODP and IODP samples that have stored for a long time. It is nearly impossible to distinguish between gypsum formed by these two processes based on the mineral morphology or the sulfur and oxygen isotope methods currently used. In this study, we proposed a simple, quantitative scheme based on chemical extractions of iron and sulfur to distinguish whether the gypsum in marine sediment samples is an authigenic mineral or an artificial product formed after sample collection. The new method was tested on two suites of deep-water sediment cores sampled from Hydrate Ridge and Kaoping Slope, in which the origins of gypsum were known beforehand, and was successfully validated. Finally, the potential influence of artificial productions of elemental sulfur and jarosite on the application of this new method was evaluated and the corresponding solutions were given. • A quantitative method to distinguish artificial from authigenic gypsum in marine sediments. • The plotting scheme has been validated by two case studies. • This method will benefit future researches on marine sedimentary environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Calc-alkaline magma can exsolve high REE fluid. • High F content can facilitate the transportation of REE from magma into fluid. • The assimilation of evaporates enhances REE transportation. Hydrothermal fluids associated with carbonatites and peralkaline silicate rocks typically exhibit high REE content, but this is generally not the case for calc-alkaline rocks. However, the Tieshan skarn Fe-Cu deposit in the Edong district of Hubei Province in China demonstrates economic REE mineralization potential linked to calc-alkaline rocks. To investigate the presence of REE enrichment in the fluid, we present textural and compositional data of rock-forming mineral amphibole from the quartz diorite in the Tieshan deposit. Three distinct types of amphibole are identified in the Tieshan quartz diorite, namely Early amphibole , Main-stage amphibol e, and Late amphibole , following the crystallization sequence. Early amphibole (813–864 °C, 115–152 MPa) crystallized when the magma was emplaced at a depth of approximately 4.8 km. Main-stage amphibol e (741–806 °C, 58–103 MPa) crystallized at a depth of roughly 3 km. Between the early and main-stage amphibole crystallization, the magma experienced fractional crystallization of pyroxene, amphibole, and plagioclase, resulting in a REE enrichment in the residual melt. Late amphibole crystallized subsequent to the transition from lithostatic to hydrostatic stress states (656–729 °C, 27–52 MPa). Significantly, the transport of REE from the magma system initiated towards the end of Main-stage amphibol e crystallization. A comparison with the Tonglvshan granitic rocks in the same district indicates an elevated F content and extended fractional crystallization history in the Tieshan magma, contributing to REE enrichment in its melt. Furthermore, the high F content lowered the solidus temperature of the Tieshan magma, thereby facilitating the more efficient removal of REE into the fluid. The assimilation of evaporate into the magma possibly led to heightened sulfur and chlorine levels in the fluid, enabling the transport of a significant amount of REE. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) isotopes are an emerging proxy for biological controlled metal and nutrient cycling in the modern oceans, but its potential as a geochemical proxy in ancient environments is still uncertain yet. Sequential leaching experiments of organic matter (OM)-rich shales from the early Cambrian Niutitang Formation (Fm.) were performed in order to understand the cycling of bioessential metals short after the Cambrian animal evolution. Carbonate, OM, sulphide and silicate leachates of OM-rich shales show an overall Cd isotope variation of 6 ε112Cd/110Cd (ε112Cd) units, indicating preferential incorporation of light Cd isotopes in the order sulphide > OM > carbonate > silicate. Carbonate leachates not only show negative correlations of ε112Cd with bulk-rock total organic carbon (TOC) and δ13C org but also show co-variations with redox-sensitive elements and bioessential metal concentrations, indicating a combined redox and primary productivity evolution of the early Cambrian Nanhua Basin on the Yangtze. Together with increased Cd/Zn ratios and decreasing total organic carbon (TOC) and redox-sensitive elements (RSE) concentrations in the upper Niutitang, this argues for an increase in essential metal availability for primary producers. Coinciding with the transition from a highly unstable ecosystem shortly after the Precambrian/Cambrian boundary to a more habitable environment increased nutrient uptake, oxygen availability and enhanced dissolved organic carbon (DOC) recycling match with the diversification of early metazoan fossil findings at the studied local. Our findings demonstrate that Cd isotopes in combination with trace metals can be used to infer changes in biogeochemical metal cycling in paleoenvironments and further allow establishing Cd isotope systematics as a reliable paleoproductivity proxy in the search for Earth's earliest phototrophic life. [ABSTRACT FROM AUTHOR]

The Wushan copper polymetallic deposit is located in the Tongbai-Dabie orogenic belt in central China. Two small granitoid stocks (Donggushan and Xigushan) occur in the deposit, which is next to the largest Qijianfeng Granite Complex in the Suizao area. The mineralization of Wushan copper polymetallic deposit is mainly composed of ore-bearing quartz veins and quartz stockworks. Two hydrothermal stages are identified as the quartz-sulfide stage (early stage) and the barren quartz stage (late stage). A detailed petrographic study shows four types of fluid inclusions in quartz, including the aqueous fluid inclusions (L+V/V+L), the aqueous-carbonic fluid inclusions (L+V+CO2), the pure carbon dioxide fluid inclusions (pure CO2), and the daughter mineral-bearing multiphase fluid inclusions (S). The daughter mineral-bearing multiphase fluid inclusions (S) are further divided into three subclasses according to their different solid mineral assemblages, including (1) S1: L+V+Hal, (2) S2: L+V+CO2+S (chalcopyrite), and (3) S3: L+V+S (calcite, chalcopyrite, and hematite)±Hal. A laser Raman spectroscopic analysis shows that the main components of fluid inclusions are water and carbon dioxide. The solid minerals of the S-type fluid inclusions include halite, calcite, chalcopyrite, and hematite. The homogenization temperatures of fluid inclusions are 377 to 468°C for the early stage, with a salinity of 11.1 to 34.1 wt.% NaCl equivalent (11.1 to 17.4 wt.% NaCl equivalent and 28.4 to 34.1 wt.% NaCl equivalent, respectively) and an estimated pressure of 89 to 137 MPa. The homogenization temperatures of fluid inclusions in the late stage are 267 to 380°C with salinity of 7.0 to 12.1 wt.% NaCl equivalent and an estimated pressure of 46 to 115 MPa. Therefore, the temperature, salinity, and pressure of the fluid show a decreasing trend from the early to the late stage. In the early stage, the fluid is immiscible, which leads to the precipitation of sulfides. Pyrite shows a δ34S of approximately 0 (-1.8 to +3.4‰), and chalcopyrite also shows a similar δ34S of approximately 0 (+1.5 to +2.4‰), which indicates that the sulfur in the ore-forming fluid is mainly derived from deep-seated magma. Combined with C-H-O isotopic compositions, the initial ore-forming fluid is likely magmatic water, but with the addition of meteoric water in the late stage. By comparing with the typical characteristics of magmatic hydrothermal vein deposit and orogenic deposit related to shear zones, we suggest that the Wushan copper polymetallic deposit is most likely a magmatic hydrothermal vein deposit, which is of great significance for the further exploration work in the Wushan and surrounding areas. This new finding also fills the gap that no magmatic hydrothermal vein type Cu deposits have been found in the Suizao area or even in the Qinling-Dabie orogenic belt in central China. [ABSTRACT FROM AUTHOR]

The Hermyingyi W-Sn deposit, situated in southern Myanmar, SE Asia, is a typical quartz-vein type W-Sn deposit. The ore-bearing quartz veins are mainly hosted by the Hermyingyi monzogranite which intruded into the Carboniferous metasedimentary rocks of Mergui Series. According to mineral assemblages and crosscutting relationships, four ore-forming stages are recognized: (1) silicate-oxide stage; (2) quartz-sulfide stage; (3) barren quartz vein stage; (4) supergene stage. Five molybdenite samples from the deposit yield Re-Os model ages ranging from 67.8±1.6 to 69.2±1.6 Ma (weighted mean age of 68.7±1.2 Ma), and a well-defined isochron age of 68.4±2.5 Ma (MSWD=0.18, 2σ). This Re-Os age is consistent with the previously published zircon U-Pb age of the Hermyingyi monzogranite (70.0±0.4 Ma) (MSWD=0.9, 2σ) within errors, which indicates a genetic link between the monzogranitic magmatism and W-Sn mineralization. The new high-precision geochronological data reveal that the granitic magmatism and associated W-Sn mineralization in southern Myanmar took place during the Late Cretaceous (70-68 Ma). The extremely low Re contents (22.9 ppb to 299 ppb) in molybdenite, coupled with sulfide δ34S values in the range of +1.9‰ to +5.6‰ suggest that ore-forming metals were predominately sourced from the crustal-derived granitic magma. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Gold occurs as 'visible gold' and the extremely low Au concentration feature in pyrite. • In situ lead isotope analyses indicate a similar source for the sulfides to the granite porphyry. • Microscopic δ34S variation is related to the (f O 2) and pH reduced from multi-stage mineralization. Abstract The Qiyugou district is one of the most important gold deposit distribution areas in the Xiong'ershan region, North China Craton. These deposits are hosted in Archean Taihua Supergroup rocks as gold-bearing breccia pipes. Here, we report a detailed in situ analysis of trace elements and S-Pb isotopes in sulfides from different ore stages, in combination with electron probe microanalysis of ore minerals from the gold-bearing J4 breccia pipe in the Qiyugou district, to unravel the gold distribution and their textural relationships to pyrite, the metal sources and S-Pb isotopic composition variations during the ore-forming processes. The Qiyugou breccia pipes hosted gold ore (over 70 t Au, average grade of 2–5 g/t) that formed in four mineralization stages, i.e., an early K-feldspar-biotite-magnetite-quartz-pyrite (Py-1) stage (I) that can be further divided into two substages, namely the Ia K-feldspar-biotite-magnetite stage and the Ib quartz-pyrite stage; a gold-pyrite (Py-2)-quartz stage (II); a gold-quartz-polymetallic sulfide (Py-3) stage (III); and a late quartz-carbonate stage (IV). The visible native gold and electrum grains occur as small inclusions and disseminations in the fractures within Py-2 and Py-3. Tellurides and Bi-Pb-minerals are widespread in the stage II stockworks and veins, as is intergrowth with visible native gold and Py-2. In situ LA-ICP-MS trace element analysis reveals the presence of invisible gold hosted in three types of pyrite with extremely low Au content (Py-1 ≤ 0.05 ppm; Py-2 ≤ 0.03 ppm; Py-3 ≤ 0.02 ppm). Concentrations of Te, Bi, and Pb in pyrite are high and correlate well with Au concentrations, but As content is low. Therefore, the Te, Bi and Pb played a significant role in gold mineralization in As-deficient ore fluids in the J4 gold-bearing breccia pipe from the Qiyugou district. High-precision in situ laser ablation multiple collector inductively coupled mass spectrometry (LA-MC-ICP-MS) lead isotope analyses indicate that the sulfides have 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios from 17.250 to 17.629, from 15.401 to 15.621, and from 37.649 to 38.290, respectively, which are similar to the granite porphyry in the district and indicative of their similar lead sources. High-precision in situ LA-MC-ICP-MS sulfur isotope analyses of pyrite show a large δ34S variation (e.g., from −18.1 to −11.1 per mil for Py-1, from −12.2 to − 6.6 per mil for Py-2, and from −4.9 to −1.6 per mil for Py-3) with a remarkable increasing trend from stage I, stage IIto stage III. This trend may record a decreasing oxygen fugacity of the ore-forming fluids during mineralization. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Fluid cooling and fluid-rock interaction are the major factors resulting in the ore precipitation. • C-H-O-S isotopes suggest a magmatic source of the ore-forming fluids. • Zhaiping deposit is a typical mesothermal deposit that formed in an early Cretaceous extensional environment in SE China. Abstract The Zhaiping Ag-Pb-Zn deposit (204 t Ag, average grade: 221.8 g/t) is located in the coastal area of the Cathaysia Block, Southeast China. Vein-type Ag-Pb-Zn orebodies are mainly hosted in the early Cretaceous volcanic and subvolcanic rocks, and structurally controlled by a group of NW-trending extensional faults. Ore-related hydrothermal alteration is well developed on both sides of the veins, dominated by silicic, phyllic, propylitic, and carbonate alteration. Mineralization can be divided into three stages: (1) the pre-ore quartz-pyrite stage, (2) syn-ore quartz-Ag-base metal stage, and (3) post-ore quartz-calcite stage. Microthermometric measurements of fluid inclusion assemblages in quartz, fluorite, sphalerite, and calcite from various hydrothermal stages reveal that from the pre-ore, syn-ore to post-ore stages, the homogenization temperatures range from 365 to 319 °C, from 317 to 222 °C, and from 233 to 172 °C, respectively. Fluid salinities range from 1.7 to 10.8 wt% NaCl equivalent. The microthermometric data indicate that the fluid cooling and fluid-rock interaction are two important mechanisms for ore precipitation. The δ34S V-CDT values of sulfide minerals (pyrite, sphalerite, galena, pyrrhotite and tetrahedrite) range from −1.9 to 6.2‰, and mostly between 1.0 and 4.5‰, consistent with a deep-seated magmatic sulfur source. Hydrogen and oxygen isotopic compositions of quartz indicate a primarily magmatic origin for the ore-forming fluids, and the proportion of meteoric water increased during the ore-forming processes. Post-ore stage calcite has δ13C V-PDB values of −2.8 to −0.8‰ and δ18O V-SMOW values of 4.2–6.4‰, corresponding to calculated values of fluids of −3.2 to −1.1‰, and −4.9 to −2.8‰, respectively. The carbon isotopes indicate a magmatic source for carbon but the oxygen isotopes indicate a significant contribution of meteoric water during calcite precipitation. We therefore proposed that the Zhaiping deposit is a typical mesothermal deposit that formed in an extensional environment related to the early Cretaceous subduction of the paleo-Pacific plate. [ABSTRACT FROM AUTHOR]

Highlights • Positive Ce anomalies were found in post-Marinoan cap carbonates. • Positive Ce anomalies were produced by reductive dissolution of Mn- (oxyhydr) oxides. • A dysoxic manganous wedge sandwiched between oxic surface water and anoxic ferruginous deep water. • Positive Ce anomaly indicates the transitional oxygen recovery in the aftermath of Marinoan glaciation. Abstract Oxygenation exerted an important control on the emergence and diversification of metazoans in the aftermath of the Marinoan glaciation. However, the relationship between the oceanic dissolved O 2 (DO) levels and early metazoan evolution remains equivocal. To provide a temporal and spatial reconstruction of the redox conditions for this critical interval, this study investigates the early Ediacaran cap carbonate deposits within intra shelf facies at three localities in the Three Gorges area, the Yangtze platform, South China. Trace and rare earth elements are sequentially extracted from the carbonate fraction for pristine temporal seawater signals. The Member II dolostones of the Duoshantuo Formation, which overlies the cap carbonates, show a negative Ce anomaly. No Ce anomaly is observed in the lower units of the cap carbonates. In contrast, positive Ce anomalies (Ce/Ce* > 1.3) in the uppermost part of the cap carbonates are observed in all studied sections. These positive Ce anomalies are accompanied by high Mn/Fe ratios (ranging from 5.04 to 14.96) and slightly positive MREE anomalies, suggesting that a Fe-Mn-(oxyhydro) oxide coparticipation occurred during the cap carbonate deposition. The positive Ce anomalies may result from the reductive dissolution of the Ce-enriched Mn-(oxyhydro) oxides across a Mn(IV)/Mn(II) redoxcline, in a distinct manganous water wedge that was sandwiched between well-oxygenated and anoxic ferruginous deep water layers. This wedge may have exhibited low oxygen conditions, with approximately 10 µM DO (dissolved oxygen), in comparison to the >90 µM DO expected in an oxic setting and 0 µM DO in an anoxic setting. Therefore, the presence of a positive Ce anomaly in the uppermost part of the cap carbonates indicates a new intermediate manganous condition and further elucidates the water column redox structure that existed following the end of the Marinoan glaciation. Early Ediacaran metazoans were possibly restricted to fully oxygenated conditions and were absent in the manganous or ferruginous-rich environments. [ABSTRACT FROM AUTHOR]

Highlights • Detrital zircons from Mayuan and Mimianshan Group metasedimentary rocks indicate two styles of age spectra. • The Daling, Longbeixi, Dikou and Dajinshan formations show a Cambrian depositional age, not previously thought Precambrian. • The Nanshan Formation is likely deposited during Cryogenian-Ediacaran. • The Cathaysia Block is mostly likely geographically close to west and central India-Himalaya during Cambrian. Abstract Pre-Palaeozoic metasedimentary rocks are widespread in the Cathaysia Block but their accurate depositional ages are poorly constrained. Here we report a detailed study on U–Pb dating for zircons from the metasedimentary rocks in both Mamianshan and Mayuan groups from NW Fujian Province. The data show two models of age spectrum, i.e. multimodal and unimodal. Multimodal samples include detrital zircons from Daling and Longbeixi Formations of Mamianshan Group, Dajinshan Formation of Mayuan Group and Dikou Formation. Their age spectra are characterized by two prominent age groups of 1.3–0.9 Ga and 0.9–0.7 Ga, and two minor age groups of 0.7–0.5 Ga and 2.7–2.4 Ga. They all have the youngest age group of Ediacaran-Cambrian (ca. 0.61–0.53 Ga). Their age spectra resemble those of early Cambrian strata in Nanling and Yunkai regions of the Cathaysia Block, indicating that their depositional age is most likely Cambrian rather than previously proposed mid-Neoproterozoic or Paleoproterozoic. Therefore it is suggested that the originally named Mamianshan Group, Mayuan Group and Dikou Formation metamorphic strata are probably not anymore a traditional lithostratigraphic unit but a "complex" with rocks of multiple ages. The unimodal samples are all from Nanshan Formation of Mayuan Group, which show age spectra characterized by the dominating age cluster of mid-Neoproterozoic (ca. 0.88–0.74 Ga). The age spectra are very similar to those of the Cryogenian strata in Nanhua rift basin of the South China Block. Therefore, we suggest that the depositional age of those unimodal samples from Nanshan Formation is likely Cryogenian. In addition, detrital zircons from our Cryogenian samples are mostly euhedral-subhedral and they could be derived mainly from the South China Block itself. In contrast those Cambrian samples may have exotic East Gondwana derived detrital zircon compositions. Comparing age spectra of detrital zircons from different terranes, our studied Cambrian strata in the Cathaysia Block show a similarity to those of western and central North India-Himalaya. It is suggested that the Cathaysia Block should be more close to west and central India-Himalaya during Cambrian. [ABSTRACT FROM AUTHOR]

The Fuzishan Cu-Mo deposit is located in the Edong district of the Middle-Lower Yangtze River Metallogenic Belt, China. The orebodies mainly occurred as lenticular and bedded shapes in the skarn zone between the Lower Permian Qixia Formation carbonate rocks and the quartz diorite. Four paragenetic stages have been recognized based on petrographic observations: (1) prograde skarn stage, (2) retrograde skarn stage, (3) quartz-sulfide stage, and (4) carbonate stage. Six fluid inclusion types were recognized: S1 (vapor + liquid + halite ± other daughter minerals), S2 (vapor + liquid + daughter minerals except halite), LV (rich liquid + vapor), VL (rich vapor + liquid), V (vapor), and L (liquid) types. Fluid inclusion studies show distinct variations in composition, final homogenization temperature, and salinity in four stages. Daughter minerals of the primary fluid inclusions include chalcopyrite, molybdenite, hematite, anhydrite, calcite, and halite in the prograde skarn stage and hematite, calcite, and sulfide (?) in the retrograde skarn stage. No daughter minerals occurred in the quartz-sulfide and carbonate stages. Final homogenization temperatures recorded in these stages are from 405 to >550°C, from 212 to 498°C, from 150 to 485°C, and from 89 to 223°C, respectively, while salinities are from 3.7 to 42.5, from 2.6 to 18.5, from 2.2 to 17.9, and from 0.2 to 11.5 wt.% NaCl equivalent, respectively. The coexisting VL and S1 type fluid inclusions show similar homogenization temperature of 550 to about 650°C in the prograde skarn stage, indicating that immiscibility occurred at lithostatic pressure of 700 bars to perhaps 1000 bars, corresponding to a depth of 2.6 km to about 3.7 km. The coeval VL and LV types fluid inclusions with homogenization temperature of 350 to 400°C in the late retrograde skarn and quartz-sulfide stages suggest that boiling occurred under hydrostatic pressure of 150 to 280 bars, equivalent to a depth of 1.5 to 2.8 km. Mo mineralization in the retrograde stage predated Cu mineralization which mainly occurred in the quartz-sulfide stage. Fluid compositions indicate that ore-forming fluid has high fO2 and rich Cu and Mo concentration in the early stage, while relatively lower fO2 and poor Cu and Mo concentration in the middle to late stages. Microthermometric data show a decreasing trend in temperature and salinity in the fluid evolution process. Decreasing temperature and boiling event may be the main factors that control the ore precipitation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Weiling granitic pegmatite is a super-large LCT-type pegmatite in South China. • Pegmatitic muscovite yielded an Ar-Ar age of 405.33 ± 3.38 Ma, indicating an Early Devonian emplacement age. • Weiling pegmatite most likely evolved from anatectic melts that did not experience significant fractionation. • Origin by low degrees of muscovite dehydration partial melting of crustal lithologies rich in fluxing metals is proposed. The Weiling granitic pegmatite is a super-large (ca. 9.20 million tons) LCT-type pegmatite body in the Northern Wuyi area of South China, with the typical mineral assemblage quartz, plagioclase, K-feldspar and muscovite as well as tourmaline (schorl-dravite), garnet (almandine-spessartine) and beryl. This overall unzoned pegmatite with locally layered texture has economic amounts of the rare metal mineral beryl and ultrapure quartz, and porcelain clay in its uppermost weathering parts. The 40Ar/39Ar dating of pegmatitic muscovite yielded a precise age of 405.33 ± 3.38 Ma, indicating this beryl-bearing pegmatite body was formed in the Early Devonian rather than in the Jurassic-Cretaceous as previously thought. Boron and Nd isotope data demonstrate that the pegmatitic melts have solely crustal sources and are most likely derived from partial melting of the ambient metasedimentary rocks from the Zhoutan Formation. Geochemical characteristics of pegmatitic minerals muscovite, beryl, tourmaline, garnet and K-feldspar and the absence of coeval fertile granites around this pegmatite suggest that the Weiling pegmatite most likely evolved from anatectic melts that did not experience significant fractionation. The pegmatitic melts were generated by low degrees of muscovite dehydration partial melting of local metasedimentary rocks rich in fluxing elements and rare metals. These melts experienced limited differentiation during ascent in the crust. The beryl mineralization formed in the medium-temperature (222–357 ℃), low-salinity (3.3–10.9 wt% NaCl equiv.) and high-density (0.62–0.86 g/cm3) H 2 O-NaCl-KCl-CO 2 -N 2 system. These temperatures are much lower than typical granitic pegmatites, possibly reflecting late fluids derived from the pegmatitic magma and experienced post-crystallization alteration. The Weiling pegmatite represents a Be-bearing pegmatite that formed by partial melting of local metasedimentary rocks. [ABSTRACT FROM AUTHOR]

Lithium (Li) isotopes have been used as a sensitive proxy to trace water-rock interaction, but its behavior during this process in geothermal system is still unclear. In this study, we use Rehai geothermal system in Tengchong, China, as a natural lab to investigate the behavior of Li isotopes in different pH conditions (acid and alkaline fluids). Alkaline fluids are characterized by high Li contents of 5–10 ppm compared to 0.3–1.5 ppm in acid fluids. Mineral formation path was modeled by PHREEQC and WATCH program. Acid fluids are far-from equilibrium that inhibits the formation of secondary minerals, and the δ7Li data are from −7.8‰ to −0.8‰, lower than the host rock (−0.4‰). In the absence of evidence for secondary mineral formation along the flow path, the negative correlation of δ7Li versus Li/Na ratio is explained by different degrees of dissolution, i.e., incongruent dissolution, resulting in a wide variable δ7Li. For alkaline fluids, clay minerals such as chlorite and smectite are formed during water-rock interaction and fluid boiling process. These samples have uniform δ7Li value of 0.4–0.9 ‰ (with a mean of +0.6‰), slightly higher than the host rock (−0.4‰). Intensive water-rock interaction drives the system to reach equilibrium with host rock, causing the congruent dissolution of host rock. Thus, the fluids show the geochemical characteristics of host rock, and conceal the role of clay minerals. This study enhances our understanding for the controlling factors of Li isotopes in hydrosphere, which highly depends on system characteristic (pH, temperature, water-rock ratio and duration time etc.), the fluxes of dissolution and precipitation, and the critical role of these parameters needs to be considered carefully when interpreting δ7Li values, especially judging whether the system is in equilibrium with surrounding rock. [Display omitted] • Evolution path of geothermal system is modeled by PHREEQC and WATCH programs. • Dissolution is the dominant path in acid fluids, causing δ7Li as function of dissolution degree. • The δ7Li of alkaline fluids is controlled by host rock that overwhelms the role of clay formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A carbonate U-Pb age of 565.0 ± 5.5 Ma was obtained from the Dengying Formation. • New age is consistent with regional Ediacaran successions in the Yangtze Block. • New age aids in re-evaluating the chronostratigraphic framework of the Ediacaran successions. • New age leaves us hope of dating other Precambrian carbonates worldwide. Precambrian sedimentary carbonate succession ages are challenging due to the lack of suitable fossil records and mineral chronometers and techniques. Here we present the first result for in situ LA-ICP-MS U–Pb dolomite dating from the Dengying Formation in the Mayuan area, Shaanxi Province, South China. The sample yields a date of 565.0 ± 5.5 Ma (2σ, MSWD = 2.8, n = 47). This age agrees well with regional Ediacaran successions in the Yangtze Block. The new ages are considered alongside regional correlations of Ediacaran successions in South China and help to re-evaluate the chronostratigraphic framework of the Dengying and Doushantuo Formation. It also opens a new window for dating those blind sedimentary carbonate strata, particularly during the Precambrian era. [ABSTRACT FROM AUTHOR]

The Shirenzhang tungsten deposit is a classic wolframite-quartz vein-type deposit located in northern Guangdong Province, eastern segment of the Nanling W-Sn polymetallic belt. The ore veins, controlled by the NW-striking fault system, are mainly hosted in the Ordovician metasedimentary rocks and can also be found with less amount in the cupola of the concealed granitic stock, displaying a typical five-floor vertical zonation proposed by the Chinese geologists. The concealed granitic stock mainly comprises two intrusive facies, the porphyritic biotite granite (G1) in the outer zone and the medium- to fine-grained monzogranite (G2) in the inner zone. In this paper, we report new cassiterite U-Pb ages and Pb isotopes of sulfides for the Shirenzhang tungsten deposit, combined with new zircon U-Pb ages and Hf isotopes, elemental geochemistry and Sr-Nd-Pb isotopes of the concealed granitic rocks, with aims to elucidate the origin of the ore-related granites and the link between the tungsten mineralization and granitic magmatism. LA-ICP-MS zircon U-Pb dating gives the weighted mean ages of 164 ± 2 Ma for G1 and 162 ± 4 Ma for G2, respectively. Cassiterite from the wolframite-bearing quartz vein and the drusy quartz vein yield the weighted mean ages of 164 ± 2 Ma and 160 ± 2 Ma, respectively. These ages suggest that both the granitic intrusion and related W-(Sn) mineralization in the Shirenzhang deposit were initiated during the late Jurassic (ca. 160 Ma). The Shirenzhang granitic rocks are weakly peraluminous highly fractionated I-type granites. Detailed elemental and isotopic data demonstrate that the granitic rocks were derived from partial melting of the Paleoproterozoic basement rocks at a relatively shallow depth of ~30 km triggered by underplating of basaltic magma, and underwent extensive fractional crystallization of hornblende, biotite, feldspar, and monazite and/or allanite. A continental arc setting induced by northwesterly subduction of the paleo-Pacific plate is suggested for the genesis of the Shirenzhang I-type granites. The comparable Pb isotopic compositions of feldspar and sulfides imply that the lead in the ore veins was of magmatic origin. Integrating the spatial-temporal relationship between the ore veins and the concealed granitic rocks with the Pb isotopes from the sulfides and granites, we suggest that the tungsten mineralization is genetically linked with the concealed granitic rocks in the Shirenzhang deposit. Fractional crystallization and melt-fluid interaction may play an important role on the formation of the granite-related tungsten mineralization. [ABSTRACT FROM AUTHOR]

In order to find criteria to discriminate the synchronous ore-associated and barren granitoid rocks, we have determined apatite chemistry associated with ore-associated (Cu-Au) and barren granitoid rocks in the Edong district of the Middle and Lower Yangtze River metallogenic belt, South China. Both rock types give zircon U-Pb ages between 135.0 and 138.7 Ma. Apatite has a higher volatile and Li content (Cl: 0.19–0.57 wt%, average 0.35 wt%, SO 3 : 0.08–0.71 wt%, average 0.32 wt%, Li: 0.49–7.99 ppm, average 3.23 ppm) in ore-associated rocks than those in barren rocks (Cl: 0.09–0.31 wt%, average 0.16 wt%, SO 3 : 0.06–0.28 wt%, average 0.16 wt%, Li: 0.15–0.89 ppm, average 0.36 ppm). Apatite (La/Yb) N ratios and Eu/Eu ⁎ values are relatively high and show wider variation in ore-associated rocks than those in barren rocks. Apatite (La/Sm) N and (Yb/Sm) N show positive correlation in ore-associated rocks but negative in barren rocks. The higher volatile content occurs in ore-associated magma, favoring Cu-Au transportation and deposition. Furthermore, amphibole fractional crystallization in ore-associated magma further enriched the ore elements in the residual melt. Barren rocks may have undergone fluid exsolution before emplacement, which makes it barren in Cl, S and ore elements (Cu, S). These signatures emphases the significance of volatile and magma evolution in mineralization and indicate that analyses of magmatic apatite can serve to distinguish ore-associated from barren intrusions. [ABSTRACT FROM AUTHOR]

The Kuh-Pang copper deposit (2.8 Mt @ 1.65% Cu, 0.52 g/t Au, 34 g/t Ag) is a volcanic-hosted epithermal deposit in the central part of the Late Eocene-Oligocene Urmia-Dokhtar Magmatic Arc of Iran. Three stages of fluid evolution are identified at the Kuh-Pang deposit: (i) early pre-ore stage: with homogenization temperature of 205–372 °C (298 ± 45 °C), salinity of 11.3 ± 2.9 wt% NaCl equiv., fluid trapped at ∼200 bars, (ii) main-ore stage: with homogenization temperature of 175–310 °C (253 ± 43 °C), salinity of 2.1–12.5 wt% NaCl equiv. at ∼150 bars, and (iii) late post-ore stage: with homogenization temperatures of 148 to 231 °C (199 ± 24 °C), and salinity of 1.1–9.8 wt% NaCl equiv. These data record an evolution of mineral precipitation from deeper (>2 km) to shallower environments (<500 m). Fluids trapped in the early (quartz I) and main-ore stages (quartz II) yielded δ 18 O fluid values of +5.7 to +5.9‰ and +3.2 to +3.8‰, and δD fluid values of  −77 to −41‰ and −84 to −60‰, respectively. These data indicate a major magmatic fluid source, with slightly increasing mixing of meteoric waters. Calcite in the late post-ore stage has δ 13 C V–PDB values of −5.8 to −5.6‰ and δ 18 O V–SMOW values of 8.2–8.6‰, with calculated δ 18 O fluid and δ 13 C fluid values of −1.0 to −1.4‰ and −5.4 to −5.2‰ respectively, that are also consistent with a predominantly magmatic carbon source and a significant fluid mixing by meteoric waters. [ABSTRACT FROM AUTHOR]

Mechanisms for Fe isotope fractionation in hydrothermal mineral deposits and in zones of associated K-feldspar alteration remain poorly constrained. We have analyzed a suite of bulk samples consisting of granite displaying K-feldspar alteration, Precambrian metamorphic rocks, and pyrite from gold deposits of the Jiaodong Peninsula, East China, by multi-collector inductively-coupled plasma mass spectrometry. Pyrites from disseminated (J-type) ores show a δ 56 Fe variation from +0.01 to +0.64‰, overlapping with the signature of the host granites (+0.08 to +0.39‰). In contrast, pyrites from quartz veins (L-type ores) show a wide range of Fe-isotopic composition from −0.78 to +0.79‰. Negative values are never seen in the J-type pyrites. The Fe isotope signature of the host granite with K-feldspar alteration is significantly heavier than that of the bulk silicate Earth. The Fe isotopic compositions of Precambrian metamorphic rocks across the district display a narrow range between −0.16‰ and +0.19‰, which is similar to most terrestrial rocks. Concentrations of major and trace elements in bulk samples were also determined, so as to evaluate any correlation between Fe isotope composition and degree of alteration. We note that during progressive K-feldspar alteration to rocks containing >70 wt% SiO 2 , >75 ppm Rb, and <1.2 wt% total Fe 2 O 3 , the Fe isotope composition of the granite changes systematically. The Fe isotope signature becomes heavier as the degree of alteration increases. The extremely light Fe isotopic compositions in L-type gold deposits may be explained by Rayleigh fractionation during pyrite precipitation in an open fracture system. We note that the sulfur isotopic compositions of pyrite in the two types of ores are also different. Pyrite from J-type ores has a systematically 3.5‰-higher δ 34 S value (11.2‰) than those of pyrite from the L-type ores (7.7‰). There is, however, no correlation between Fe and S isotope signatures. The isotopic fractionation of sulfur is used to constrain a change in the f O 2 of the hydrothermal fluids from which pyrite precipitated. This work demonstrates that the Fe isotope composition of pyrite displays a significant response to the process of pyrite precipitation in hydrothermal systems, and that systematic fractionation of iron isotopes occurs during fluid/rock reaction in the K-feldspar alteration zone of the Linglong granite. The implications of the results are that processes of mineralization and associated fluid-rock interaction, which are ubiquitously observed in porphyry-style Cu-Au-Mo and other hydrothermal deposits, may be readily traceable using Fe isotopes. [ABSTRACT FROM AUTHOR]

The Liyuan lode gold deposit is located in the Shanxi province, central North China Craton. Gold orebodies are mainly hosted in Archean metamorphic rocks and structurally controlled by the NNE-trending faults. Gold occurs in disseminated and auriferous quartz-sulfide veins and veinlets within hydrothermally altered rocks. Mineralization can be divided into three intervals: (1) quartz-pyrite stage, (2) quartz-polymetallic sulfides stage, and (3) quartz-carbonate stage. Gold formed mainly in the middle stage. Sericite sample associated with the middle stage pyrite from phyllic alteration zones yields an well-defined 40 Ar/ 39 Ar plateau age of 133.3 ± 1.2 Ma, which is remarkably consistent with zircon U-Pb age (133.4 ± 1.1 Ma) of the quartz porphyry dikes in the Liyuan mine, indicating a close relationship between gold mineralization and granitic magmatism in the area. The sulfur isotopic compositions of pyrite (Py1-2) from the early stage have a narrow range from −0.3 to 4.1‰, indicating a deep-seated magmatic source. However, the sulfides (Py3-5, sphalerite, galena) from the middle stage have lower δ 34 S V-CDT values of −7.2 to 3.0‰, which is thought to be a result of fluid oxidation during gold mineralization. The Pb isotopic compositions of sulfides from Liyuan ores have 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, and 208 Pb/ 204 Pb ratios of 16.671–16.860, 15.236–15.255, and 41.452–44.159, respectively, indicting a high-thorium lower continental crust source of ore-forming materials. The δ 13 C VPDB and δ 18 O VSMOW values of late stage calcite ranging from −7.1 to −5.8‰ and 12.2 to 13.7‰, respectively, illustrating a deep-seated magmatic source of carbon-bearing portion. Given the absence of granite bodies at the present mining levels, we speculate that the ore-forming fluids may have been exsolved from a concealed granite pluton at greater depth. Based on the regional tectono-magmatic events, ore geology, geochronologic and isotopic data obtained in this study together with the previous published fluid inclusion data, we suggest that the Liyuan deposit is an orogenic gold deposit that is probably related to the early Cretaceous granite magmatism in the interior of the North China Craton. [ABSTRACT FROM AUTHOR]