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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.

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

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]

The Miaoya carbonatite complex in the South Qinling Orogen hosts one of the largest REE-Nb deposits in China. The origin and evolution of REE enrichment in this Silurian intrusion have been extensively studied, whereas Nb mineralization remains less well understood. Here, we report detailed mineralogical and geochemical data on diverse Nb-bearing minerals from the Miaoya carbonatite to explain the development of Nb mineralization in these rocks. Ferrocolumbite is the dominant Nb mineral, which occurs principally as an alteration product of the earlier-crystallized Nb phases (uranopyrochlore, betafite, and fersmite). The ferrocolumbite varieties (Clb-1, Clb-2, Clb-3) inherited some compositional characteristics of its precursors, in particular a trend of decreasing Ta2O5 and UO2 from Clb-1 to Clb-3, which mimics the Ta-U depletion trend from uranopyrochlore to betafite and fersmite. Varieties Clb-1 and Clb-2 and associated calcite and altered uranopyrochlore show evidence of hydrothermal overprint such as positive Eu anomaly. Ferrocolumbite Clb-2 shows slightly higher Eu/Eu* and Zr/Hf ratios and contains fewer relicts of its precursor mineral in comparison with Clb-1, possibly indicating local enrichment of F in the hydrothermal system. Calcite associated with Clb-3 and fersmite shows a trace element signature characteristic of igneous carbonates, suggesting that this mineral paragenesis is least affected by metasomatic overprint with no contribution from external fluids. The study of the Miaoya REE-Nb deposit shows that late-stage metasomatism of carbonatites does not significantly enhance Nb grade in contrast to that of REE mineralization and leads to the formation of a secondary Nb paragenesis with specific trace element characteristics. [ABSTRACT FROM AUTHOR]

The Maogongdong deposit is located in the giant Dahutang W-Cu-(Mo) ore field, northern Jiangxi Province, South China. It is mainly a vein-type deposit, characterized by early W and late Cu-Mo mineralization, and temporally and spatially associated with Late Mesozoic S-type muscovite granites emplaced into a Neoproterozoic granodiorite batholith and the Shuangqiaoshan Group metasedimentary rocks. Fluid inclusions and H–O isotopes suggest that the early ore-forming fluids of the Maogongdong deposit are mainly magmatic water with relatively high temperature (270–410 °C) and moderate-to-low salinity, while the late ore-forming fluids are mixed with meteoric water, with medium-to-low temperature (160–270 °C) and low salinity. Infrared and conventional microthermometric studies of fluid inclusions of the main tungsten mineralization stage show that the homogenization temperatures of primary fluid inclusion assemblages in wolframite (325 to 355 °C) are about 20 °C higher than those of coexisting scheelite and generally 40 °C higher than those in quartz. The δ34S values of sulfides (− 5.2 to − 1.3 ‰) in the sulfide stage are slightly lower than the magmatic sulfur (− 1.7 to 0.6 ‰) in the pre-ore stage, most likely due to an increase in oxygen fugacity. The low carbon isotope values (− 26.2 to − 15.5 ‰) of fluid inclusions in the tungsten mineralization stage show that a large amount of organic carbon was added before mineralization. Fluid cooling and pressure decrease are the main factors of tungsten ore precipitation, while local boiling may also make a contribution. Mixing of the different fluids led to the formation of copper and molybdenum ores. [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]

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]

[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]

The Zhaiping Ag–Pb–Zn vein deposit in the Coastal Volcanic Belt of southeastern China, which resulted from subduction of the paleo-Pacific oceanic lithosphere beneath the South China Block, is hosted by Early Cretaceous sub-volcanic rocks (rhyolite porphyry) and younger granite porphyry and quartz porphyry. Three generations of veins have been recognized: (i) pre-ore quartz + pyrite, (ii) syn-ore silver + pyrite + pyrrhotite + base metal sulfides + quartz + sericite, and (iii) post-ore quartz + calcite + fluorite veins. Rubidium–Sr dating of syn-ore pyrite yielded an isochron age of 132.2 ± 2.1 Ma (2σ, MSWD = 2.0, n = 4), which is roughly coincidental with the age of the granite porphyry and quartz porphyry (zircon U–Pb age: ca. 133 Ma). The age data, together with Pb, S, H, and O isotopic compositions, indicate a close temporal and possibly genetic relationship between mineralization and porphyry magmatism at Zhaiping. Geochemical and isotope data demonstrate that the Zhaiping sub-volcanic rocks were derived from partial melting of Proterozoic crustal sources and underwent fractionation of feldspars, monazite, and/or allanite. The 87Sr/86Sr ratios of pre-ore (Aph1) and syn-ore (Aph2) stage apatite are in the ranges of 0.71350 to 0.71441 and 0.71260 to 0.71328, respectively, which are distinct from those of the sub-volcanic intrusive rocks (0.7119–0.7125). The Sr isotope signature, together with lower fluid temperatures (< 360 °C) relative to typical magmatic fluid, points at addition of an external fluid. It is suggested that the sub-volcanic intrusion acted as a heat source that drove the dehydration of, and subsequent fluid circulation within, the host rocks. Lower 87Sr/86Sr ratio but higher Sr content of Aph2 relative to Aph1 possibly indicates continuous fluid–rock interaction and progressive decomposition of feldspar in the host rocks, thus supplying large amounts of Sr and probably Pb to the ore fluid. [ABSTRACT FROM AUTHOR]

The Daye district represents one of the largest concentrations of skarn deposits in eastern China. There are two major types of skarn deposits (Fe skarn vs. Cu skarn) within this district, both genetically related to late Mesozoic high-K calc-alkaline granitoids. In this study, we present in situ compositional and Sr–Nd isotopic investigations of apatite from granitoids associated with Fe skarn and Cu skarn deposits to put constraints on the magma source, evolution, and volatile composition, which provide significant new insights into the genesis of the two contrasting mineralization styles in the Daye district. Apatite from granitoids related to Cu skarns and Lingxiang Fe skarn has εNd(t) values of − 8 to − 4, similar to that of the contemporaneous mafic rocks in the Daye district, which were dominantly derived from an enriched lithospheric mantle source. Apatite in granitoids associated with the Chengchao Fe skarn has lower εNd(t) values of − 15 to − 9, suggesting larger degrees of contaminations from ancient lower crust materials. Fractionation models based on apatite Sr/Y and Eu/Eu* ratios, suggest that magmas related with the Cu skarns have experienced amphibole-dominated fractionation under high pressure and hydrous conditions, whereas those associated with Fe skarns have undergone plagioclase-dominated fractionation at relatively low pressure and dry conditions. Based on results of apatite compositional analysis and apatite-melt partitioning data, the estimated magma Cl contents for the Fe skarn range from 3260 to 13,940 ppm, significantly higher than those for the Cu skarn (Cl = 430–5990 ppm). Apatite from Fe skarn-related intrusions has (87Sr/86Sr)t ranging from 0.7073 to 0.7082, whereas the variety from Cu skarn-related intrusions displays lower (87Sr/86Sr)t of 0.7054–0.7061. These Sr isotope data, combined with whole-rock S isotopes of this study and previous investigations suggest that the Fe skarn-related intrusions have assimilated larger amount of evaporite-bearing carbonate during magma ascent and emplacement. The assimilation process may have not only promoted magmatic water exsolution but also provided sufficient amount of Cl− and SO 4 2 - , which facilitated effective complexation and transportation of Fe2+ and subsequent oxidization of ferrous Fe to precipitate magnetite, respectively. We suggest that evaporite assimilation into the granitoid magmas has played a crucial role in the large-scaled Fe skarn mineralization in the Daye district. This study highlights that apatite is a sensitive petrogenetic-metallogenic indicator for granitoids and thus can be useful in mineral exploration. [ABSTRACT FROM AUTHOR]

The large Hebaoshan gold deposit (41.5 t Au, average grade: 3.5 g/t) is located in a hitherto poorly documented gold province in the northeastern part of the South China Block. It is hosted by Precambrian metasedimentary rocks that experienced Triassic greenschist- to amphibolite-facies metamorphism. Three hydrothermal stages can be distinguished: quartz + sericite + pyrite + pyrrhotite (stage I), quartz + magnetite + sulfide (stage II), and quartz + carbonate + pyrite + hematite (stage III). Auriferous pyrite samples yielded a Rb-Sr isochron age of 234 ± 3 Ma (2σ, MSWD = 0.24), and ore-related hydrothermal sericite yielded a 40Ar-39Ar plateau age of 226.4 ± 2.0 Ma (2σ, MSWD = 1.01), which are distinctly younger than ca. 430 Ma granitic rocks in the mining district and older than 170–130 Ma granites in the region, ruling out any genetic link between granite emplacement and gold mineralization. The mineralizing fluid system can be described as carbonic-aqueous with low to moderate salinity (2.2–10.1 wt% NaCl equiv.) and medium temperature of 290 to 350 °C (stage I) and 230 to 280 °C (stage II). The δ18O quartz ranges from 13.3 to 15.4 ‰, and the δD values for fluid inclusions in quartz range from − 97 to − 60 ‰. The calcite has C-isotopes ranging from − 6.1 to − 3.8 ‰ and O-isotopes from 2.8 to 13.6 ‰. H-O-C isotope data are consistent with a metamorphic fluid derived from devolatilization of Neoproterozoic basement rocks during regional metamorphism in the Late Triassic Indosinian period. The δ34S values of sulfides for stages I, II, and III are 0.1 to 7.8 ‰, − 10.6 to 5.1 ‰, and − 18.9 to − 14.1 ‰, respectively, indicating an increase in oxygen fugacity during fluid ascent which resulted in more negative sulfur isotope values of sulfides and precipitation of gold. Pyrite separates have 206Pb/204Pb ratios of 17.340 to 17.687, 207Pb/204Pb ratios of 15.539 to 15.604, and 208Pb/204Pb ratios of 37.749 to 38.094. The S-Pb isotope data suggest derivation of S and Pb from the Precambrian metasedimentary country rocks. Auriferous pyrite yielded elevated 3He/4He ratios (0.78–1.46 Ra), which suggest a mantle component as can be expected from fluids derived from a subduction setting. It is concluded that Hebaoshan is an orogenic gold deposit that formed during Triassic flat-slab subduction of the paleo-Pacific plate beneath the South China Block and thus constitutes the first Triassic deposit of this type recognized in the coastal area of Southeast China. [ABSTRACT FROM AUTHOR]

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

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] • 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]

Unlike classic skarn-type scheelite deposits directly acquiring sufficient Ca2+ from surrounding limestones, all of the scheelite orebodies of the Shangfang tungsten (W) deposit occur mainly in amphibolite, and this provides a new perspective on the mineralization mechanism of W deposits. The ability of hydrothermal scheelite (CaWO4) to bind REE3+ in their Ca2+ crystal lattices makes it a useful mineral for tracing fluid-rock interactions in hydrothermal mineralization systems. In this study, the REE compositions of scheelite and some silicate minerals were measured systematically in-situ by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to assess the extent of fluid-rock interactions for the Late Mesozoic quartz-vein-type Shangfang W deposits. According to the variations in CaO and REE among scheelite and silicate minerals, the amphibole and actinolite in amphibolite may be able to release large amounts of Ca2+ and REE3+ into the ore-forming fluids during chlorite alteration, which is critical for scheelite precipitation. Furthermore, an improved batch crystallization model was adopted for simulating the process of scheelite precipitation and fluid evolution. The results of both the in-situ measurements and model calculations demonstrate that the precipitation of early-stage scheelite with medium rare-earth elements (MREE)-rich and [Eu/Eu*]N<1. The early-stage scheelite would consume more MREE than LREE and HREE of fluid, which will gradually produce residual fluids with strong MREE-depletion and [Eu/Eu*]N>1. Even though the partition coefficient of REE is constant, the later-stage scheelite will also inherit a certain degree of MREE-depletion and [Eu/Eu*]N future from the residual fluids. As a common mineral, sheelite forms in various types of hydrothermal ore deposits (e.g., tungsten and gold deposits). Hence, the improved batch crystallization model is also possible for obtaining detailed information regarding fluid evolution for other types of hydrothermal deposits. The results from model calculations also illustrate that the Eu anomalies of scheelite are not an effective index correlated to oxygen fugacity of fluids but rather are dominantly controlled by the continuous precipitation of scheelite. [ABSTRACT FROM AUTHOR]

The North Wuyi area is an important metallogenic belt in South China and hosts many Pb–Zn–Ag deposits within the Jurassic–Cretaceous volcanic basins. These deposits are mostly genetically associated with Late Jurassic magmatism. The Cretaceous granitic rocks in the Lizikeng basin, at the eastern part of the North Wuyi area, were investigated for their mineralogical and geochemical characteristics in this study. Three types of granitic rocks, quartz monzonite, granite porphyry, and monzogranite, occur, and zircon U–Pb dating reveals that they all formed during the short period of 133–129 Ma, corresponding to the early Cretaceous volcanic-intrusive activities in South China. The whole-rock geochemistry indicates that all three granitic rocks have I-type affinity. The quartz monzonite and granite porphyry have consistently low whole-rock εNd(t) values of − 10.4 to − 9.6 and zircon εHf(t) values of − 14.2 to − 8.2, and they were likely derived from Proterozoic crustal sources without any significant contribution of mantle-derived material. The monzogranite, which shows also negative but slightly higher εNd(t) and εHf(t) values of − 7.6 to − 7.1 and − 9.3 to − 7.0, respectively, might also be derived from a major Proterozoic crustal source but with some input of mantle magma. The geochemical data show that the monzogranite belongs to tungsten-bearing granite with highly evolved characteristics, and with high Nb and W contents similar to the typical rare-metal and W-bearing granites in South China. A large number of typical hydrothermal rare-metal minerals are identified in the monzogranite, such as W-bearing rutile, niobian rutile, and columbite-group minerals as well as ferberite. The discovery of the early Cretaceous granitic rocks with tungsten mineralization potential indicates that the North Wuyi area is prospective for rare-metal mineralization, which opens a new window for rare-metal prospecting in the volcanic basins, as this type of ore deposit was previously thought to occur in granites from mountain range areas in South China, such as the Nanling Range. [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]

[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]

[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]

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]

[Display omitted] • Hydrothermal titanite U-Pb dating reveals Shanhou Pb-Zn deposit formed at ca. 145 Ma. • C-O-S isotopes indicate a magmatic fluid source. • Pb isotopes indicate a Neoproterozoic metamorphic rock source for ore materials. • Shanhou Pb-Zn deposit belongs to skarn type associated with a concealed granitic intrusion. Stratabound base metal sulfide deposits within Neoproterozoic metavolcanic rocks and skarns in the Fujian Province are important Zn-Pb producers in China. To date, the inability to determine absolute ages and proper sources of Pb-Zn mineralization has led to conflicting ore genetic models. These include the metamorphosed volcanogenic massive sulfide (VMS) model, which predicts that the Pb-Zn mineralization was synchronous with submarine volcanic activity, and the Early Cretaceous magmatic-hydrothermal skarn model. The Shanhou deposit (2.56 Mt ore @ 6.8 % Pb + Zn) in the central Fujian Province, the southeastern coastal area of China, consists of twelve stratabound massive Pb-Zn sulfide orebodies hosted in hydrothermally altered metavolcanic rocks of the Neoproterozoic Dongyan Formation. No intrusive body that could have contributed to the formation of the calc-silicate mineral-dominated wall rocks and Pb-Zn ores has been found spatially associated with the Shanhou deposit, and the origin of the mineralizing fluids, sulfur, and metals has not yet been identified previously. Here we present in-situ U-Pb ages of hydrothermal titanite and C-O-S-Pb isotopes of gangue and ore minerals to constrain the timing and origin of the Pb-Zn mineralization. Three hydrothermal stages can be identified: pyroxene (prograde stage I), epidote + chlorite + titanite (retrograde stage II), and quartz + calcite + polymetallic sulfides (quartz-calcite-sulfide stage III). In-situ LA-ICP-MS U-Pb isotopic analyses of hydrothermal titanites coexisting with sulfides in two massive ore samples yield indistinguishable ages of 145 ± 13 Ma and 144 ± 9 Ma, overlapping the 152 to 145 Ma emplacement age of granitic rocks in the central Fujian area. The results show that the Shanhou Pb-Zn deposit is significantly younger than the Neoproterozoic host (meta)volcanic rocks, arguing against a Neoproterozoic VMS genetic model as suggested by some previous researchers. The δ34S (V-CDT) values of pyrrhotite, pyrite, marcasite, chalcopyrite, sphalerite, and galena in the massive sulfide ores range from −2.9 to 6.9 ‰, indicating that the sulfur at Shanhou is mainly of magmatic origin. Sphalerite separates have 206Pb/204Pb ratios of 17.782 to 17.782, 207Pb/204Pb ratios of 15.585 to 15.593, and 208Pb/204Pb ratios of 38.376 to 38.407, which are similar to those of the host rocks, indicating that the ore-forming materials were derived from the host rocks. Calcite in sulfide ores has δ13C V-PDB values of −7.8 to −4.3 ‰ and δ18O V-SMOW values of 6.1 to 9.5 ‰, suggesting a magmatic origin for the ore-forming fluids. It is concluded that the Shanhou stratabound Pb-Zn deposit is a metasomatic skarn-like deposit associated with a possible hidden Early Cretaceous felsic intrusion at depth, rather than a metamorphosed VMS deposit. [ABSTRACT FROM AUTHOR]

[Display omitted] • Various colors of sphalerite are found in the Maoping Pb-Zn deposit. • Germanium incorporates into sphalerite via 2Cu+ + Ge4+ → 3Zn2+. • Sulfur fugacity places a dominant control on Ge enrichment in sphalerite. • The reduced sulfur sources varied for the two-stage Ge enrichment processes. The Maoping Pb-Zn deposit is one of the largest deposits in the Sichuan-Yunnan-Guizhou (SYG) MVT province in southwest China, which is also one of the biggest germanium producers in China. The hydrothermal mineralization process in this deposit can be divided into: (I) dolomite-pyrite stage, (II) sphalerite-galena stage, and (III) calcite stage. Five colors of sphalerites are recognized, including (C1) black, (C2) red brown, (C3) deep brown, (C4) light brown, and (C5) light red sphalerite. Pure colored C1, C2, C3 and C4 are dominanting in the entire sphalerite sequence, and there are also few rhythmic zonal sphalerites (e.g., Z1, Z2) composed of above four colored sphalerites. The C5 sphalerite precipitates last, and often cross-cuts other colored sphalerites in fine veins. Galena usually postdates than multicolor sphalerites. Based on μ-XRF and LA-ICP-MS mapping analysis, the Fe and Cu respectively dominate the variations of many other trace elements (e.g., Mn, Ag, Cd, Ga, Ge). The C5 and C1 sphalerites show the highest germanium contents (geometric mean 49 ppm for C5; 22 ppm for C1), followed by C4 (geometric mean 13 ppm). The contents of germanium and copper show a strong linear correlation for all colored sphalerites, in which germanium incorporates into sphalerite by the mechanism of 2Cu+ + Ge4+ → 3Zn2+, while the nano-inclusion of Cu(Ag)-As(Ga)-S sulfosalt may evenly distribute in C5 sphalerite, resulting in its higher (Cu/Ge) mol ratios. According to the temperature and sulfur fugacity deduced from element compositions of sphalerite, the higher sulfur fugacity is more beneficial to the enrichment of germanium, relative to temperature. The sulfur isotope data suggest that the sulfur in C1, C2, C3 and C4 sphalerites originated from the Zaige and Baizuo Formations via bacterial sulfide reduction (BSR), in contrast to the sulfur in C5 sphalerite that mainly derived from the Datang Formation, with significantly higher sulfur fugacity and lower temperature. It is concluded that the fluids with germanium and reduced-sulfur derived from the Zaige and Baizuo Formations, mixed with the metal-bearing (e.g., Pb, Zn, Ag) basin brine, and caused the first-stage germanium enrichment in C1, C2, C3 and C4 sphalerites. Then the second-stage enrichment of germanium in C5 sphalerite was due to the involvement of fluid with germanium and reduced-sulfur derived from the Datang Formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Huangjiagou Paleoproterozoic pegmatites underwent ca. 1.75 Ga high-temperature metamorphism and ca. 130 Ma metasomatism. • The Cretaceous fluids provide additional REEs and redistribute REE and U to form economic minerals. • Primary allanite from pegmatite shows three zones with different U-Pb ages but a reliable Sm-Nd age at 1.8 Ga. • Hydrothermal overprinting caused Sm-Nd systems from incomplete equilibration to equilibration. Sm-Nd and U-Pb isotope systems are widely used to dating various magmatism and tracing geological processes, but their behaviors during post-magmatic metamorphic and/or hydrothermal disturbances remain unclear. Here, we investigated the trace elements, U-Pb and Sm-Nd isotope systems of accessory minerals (allanite, titanite, and apatite) from the Huangjiagou Paleoproterozoic rare-earth pegmatite, to determine the timing of magmatism and also the overprinted metamorphic and hydrothermal events, with a particular emphasis on the isotopic behavior of these accessory minerals under metamorphic event and fluid-rock reaction. Two-period accessory minerals are identified: Group I allanite, crystallized in the magmatic period but was modified by high-temperature metamorphism and hydrothermal metasomatism; and Group II allanite, titanite and apatite, which newly precipitated in the late hydrothermal event. In-situ U-Pb dating of the Group I allanite (type Ia) yielded a magmatic age of ca. 1.82 Ga, whereas the type Ib allanite record the high-temperature anhydrous thermal metamorphism at ca. 1.75 Ga. Group II allanite and titanite yielded U-Pb ages of ca. 131 Ma, indicating a Mesozoic hydrothermal metasomatism overprinting, due to the emplacement of neighboring granites. Group I allanite exhibits different zones and inconsistent U-Pb ages, but they exhibit an identical Sm-Nd isochron age (∼1.83 Ga) broadly consistent with the pegmatite age, indicating immobility nature of the Sm-Nd system. Group II titanite and allanite exhibit a Sm-Nd isochron age of ∼130 Ma with initial ε Nd (t) values of −27.5 to −29.8, consistent with the whole-rock ε Nd (t = 130 Ma) values of granitic rocks, implying a total redistribution of the REEs. While, Group II apatite and coexisting allanite did not produce geologic meaningful Sm-Nd ages with a wider initial ε Nd (t) range of −15.8 to –23.7, indicating the fluid has incompletely equilibrated Sm-Nd isotopic system due to various fluid-rock reaction. Our study provides a typical example to illustrate the robustness of the Sm-Nd isotopic system of magmatic allanite under the disturbance of later metamorphism and metasomatism, and shows the different degree equilibration of Sm-Nd isotopes in hydrothermal systems under various fluid-rock reactions. [ABSTRACT FROM AUTHOR]

The Lingshan granite batholith (Jiangxi province, southeast China) is a rather unique example of Nb-Ta-rich rare-metal granite, and three different types of tourmalines have been identified in the marginal granite zone, including (i) quartz-tourmaline nodules (Tur-N type) in the fine-grained biotite granite, (ii) tourmaline segregations and/or tourmaline-filled cavities (Tur-P type) and (iii) tourmaline veins (Tur-PV type) in pegmatite dykes. The extensive fractional crystallization process from the fine-grained biotite granite to pegmatite has been revealed by the geochemical and boron isotope compositions from the Tur-N to the Tur-P and/or Tur-PV type tourmalines, such as increasing Fe contents, decreasing Nb/Ta and Zr/Hf ratios, as well as restricted boron isotopes (δ11B, −12.0 to −9.0‰). Particularly, the Nb and Ta contents increase from the Tur-N to the core of the Tur-P type tourmaline, and then decrease towards the rim of the Tur-P type tourmaline. It is, therefore, possible that the decreasing variations of Nb and Ta from the core to the rim within the Tur-P type tourmaline more likely record the compositional and environmental evolution from the late boron-rich magma to the exsolved hydrothermal fluids. The late-stage Tur-PV type tourmaline as the hydrothermal product contains the lowest F contents. Thus, we suggest that the Nb Ta mineralization in the Lingshan granite batholith dominantly occurs in the highly-evolved granitic melt rather than during the post-magmatic aqueous fluid. Furthermore, the Nb and Ta contents of Lingshan tourmaline overlap with previous reported tourmaline data from W Sn rare-metal deposits instead of Au deposit. This signature is comparable to the fact that small volumes of W Sn mineralization occur in the Songshugang Ta-Nb-(W Sn) deposit. Hence, the Nb and Ta contents in tourmaline can be used as potential parameter to explore the Nb-Ta-(W Sn) mineralization not only in the Lingshan granite and pegmatite but also in similar granite batholith elsewhere in the world. [Display omitted] • Three types of tourmalines are identified in the Lingshan granite batholith. • Tourmaline formed either by magmatic or hydrothermal processes. • Nb/Ta and Zr/Hf in tourmaline demonstrate a fractional crystallization trend. • Volatile increase of tourmaline is consistent with the Nb Ta enrichment processes. • Tourmaline Nb Ta contents can indicate the Nb-Ta-(W Sn) mineralization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nb-Ta minerals in the Shihuiyao deposit include columbite-group minerals and ixiolite. • Nb-Ta minerals formed during multiple stages from magmatic to hydrothermal. • A coupled dissolution-reprecipitation mechanism is proposed for columbite-group minerals. • The ixiolite is most likely formed during water–rock reaction. The Nb-Ta ore body in the Shihuiyao Rb-Nb-Ta-(Be-Li) deposit comprises muscovite-albite granite (MAG) and greisen (GR), with the dominant Nb-Ta minerals of columbite-group minerals (CGM) and ixiolite. The petrographic and chemical data suggest that the Nb-Ta oxides well record the magmatic-hydrothermal evolution process. The magmatic CGM are generally homogenous crystals or with oscillatory zoning patterns, while the CGM formed during the magmatic-hydrothermal transition stage overprints the early CGM crystals in the MAG or shows a normal zoning pattern (decreasing Nb/Ta ratios from the core to rim) in the GR, and possesses higher contents of Sc and Ti. The hydrothermal Nb-Ta oxides in both the MAG and GR share the same origin, i.e., the hydrothermal fluids exsolved from the magma at the late stage of magmatic evolution. However, distinct chemical differences between them indicate that a single fluid activity did not pervade the entire system; instead, two different hydrothermal processes were present: fluid metasomatism and water–rock reaction. The hydrothermal CGM generally occurs in the GR and metasomatizes the primary crystals by a coupled dissolution-reprecipitation mechanism. The chemical compositions of these CGM grains were significantly modified during this process, which was manifested by the increasing Sn and W contents in the reprecipitated phases. The ixiolite is most likely formed by another hydrothermal mechanism, i.e., water–rock reaction, during which the hydrothermal fluids can extract a large amount of Sn, Sc, U, and REE from the wall rocks or earlier formed magmatic phases and finally controlled the formation and chemical distribution of the ixiolite. [ABSTRACT FROM AUTHOR]

The Miao'ershan uranium ore district is one of the most important granite-hosted uranium producers in South China. There are several Triassic granite plutons in the Miao'ershan batholith, but uranium ore deposits mainly occur within the Douzhashan granitic body. Precise zircon U–Pb dating indicated that these Triassic granite plutons were emplaced during 204 to 215 Ma. The Douzhashan U-bearing granite lies in the central part of the Miao'ershan batholith, and has higher U contents (8.0 to 26.1 ppm, average 17.0 ppm) than the nearby Xiangcaoping granite (5.0 to 9.3 ppm, average 7.0 ppm) and the Yangqiaoling granite (6.4 to 18.3 ppm, average 11.5 ppm) in the south part of the batholith. The Douzhashan granite is composed of medium-grained two-mica granite, whereas the Xiangcaoping and Yangqiaoling granites are composed of porphyritic biotite granite. Both the Xiangcaoping and Douzhashan granites have high A/CNK ratios (> 1.10), high ( 87 Sr/ 86 Sr) i ratios (> 0.720) and low ε Nd (t) values (− 11.3 to − 10.4), suggesting that they belong to strongly peraluminous S-type granites. The Douzhashan granite has low CaO/Na 2 O ratios, high Rb/Sr and Rb/Ba ratios, indicating a partial melting origin of clay-rich pelitic rocks. In contrast, the Xiangcaoping granite formed from clay-poor psammite-derived melt. The Yangqiaoling granite shows different geochemical characteristics with the Douzhashan and Xiangcaoping granites, indicating a different magma source. The Yangqiaoling granite has higher ε Nd (t) of − 9.4 to − 8.3 and variable A/CNK values from 0.98 to 1.19, suggesting a mixture source of meta-sedimentary rocks and meta-igneous rocks. Crystallization fractionation is not the main mechanism for U enrichment in the Douzhashan granite. We suggest that U-rich pelitic rock sources may be the key factor to generate peraluminous U-bearing granites in South China. Searching for those granites which are reduced, strongly peraluminous and were derived from U-rich pelitic rocks, is the most effective way for exploring granite-hosted U deposits. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluid mixing triggered the Zn-Pb precipitation. • C O S-Pb isotopes favor a magmatic-hydrothermal origin for ore fluids and metals. • Pyrite texture and chemistry record the ore-forming processes. • Fengyan represents a stratabound distal Zn-Pb skarn deposit. The Fengyan stratabound Zn-Pb deposit (total resources: 24.7 Mt of ore @ 4.09 % Zn and 1.92 % Pb) is hosted by Neoproterozoic marble and metavolcanic rocks in the Meixian ore field of southeastern China. Hitherto, the genesis of this deposit has been a matter of debate, including a Neoproterozoic volcanogenic massive sulfide genesis (VMS) or an Early Cretaceous magmatic-hydrothermal origin. Based on fluid inclusion data from various hydrothermal stages, stable isotope data of hydrothermal minerals, and in-situ trace element analyses of poly-stage pyrite (Py1-3), the deposit can be classified as a distal skarn-type. A complex paragenesis reflects four hydrothermal stages: stage I (pyroxene + garnet + Py1), stage II (epidote + hematite + magnetite + Py2), stage III (quartz + sphalerite + galena + Py3a + Py3b), and stage IV (calcite). The prograde skarn comprises andradite-rich garnet (on average Ad 57 Gr 34 Py 9) and pyroxene (on average Hd 58 Di 10 Jo 32) with high Mn contents. Fluid inclusion data reveal salinity and temperature ranges for the prograde and retrograde skarn fluids as 11.5 to 14.6 wt% NaCl equiv. at 278 to 338℃ and 7.5 to 11.2 wt% NaCl equiv. at 235 to 275℃, respectively. The entrapment pressure is calculated as 130 bars. The sulfide ore minerals of stage III were precipitated at lower temperatures (186 to 259℃) from aqueous fluids with lower salinities (<6.6 wt% NaCl equiv.). Late-stage calcite was deposited from a more dilute (<2.2 wt% NaCl equiv.) and cooler (<200℃) fluid with extremely depleted δ18O fluid values of −10.1 to −2.0 ‰ (V-SMOW), consistent with a meteoric origin. A mean δ34S V-CDT of 1.7 ± 0.9 ‰ of sulfide minerals points to a magmatic sulfur source. Lead isotopic compositions of sphalerite separates (206Pb/204Pb = 18.295–18.381, 207Pb/204Pb = 15.644–15.662, and 208Pb/204Pb = 38.494–38.724) are similar to those of the Yanshanian granitic bodies in the region but different from those of the ore-hosting marble and metavolcanic rocks. Calcite in the late stage has δ13C V-PDB values of −5.4 to −1.5 ‰, consistent with a predominant magmatic origin. Variations of Co, Ni, Se, and As in pyrite of different generations are interpreted to reflect changes in temperature during hydrothermal evolution. The Co/Ni ratios in all generations of pyrite, mainly between 1 and 10, indicate a magmatic-hydrothermal source. Overall, our new data indicate progressive mixing of a granite-derived magmatic fluid with meteoric waters, as is expected in a distal skarn deposit. [ABSTRACT FROM AUTHOR]

[Display omitted] • Textural features and in situ trace elements of fluorite are studied. • Water-rock reaction plays a dominant role for fluorite mineralization. • Variation in pH and temperature caused the precipitation of fluorite. • A dissolution-reprecipitation-recrystallization process is proposed. The Wujianfang fluorite deposit shows a four-stage mineralization history: (1) pre-ore stage of disseminated fluorites, (2) early-ore stage of fluorite-muscovite-pyrophyllite, (3) main-ore stage of fluorite-pyrophyllite, and (4) late-ore stage of fluorite-albite-quartz. Detailed cathodoluminescence imaging, fluid inclusion study, and in-situ LA-ICP-MS trace element analysis of fluorite in different stages or mineral assemblages were applied to reveal the fluorite mineralization and metasomatic history of this deposit. These data show that water-rock reaction between hydrothermal fluids and wall rocks not only provides the dominant ore-forming materials for fluorite mineralization, but also promotes the precipitation of fluorite by changing the pH of ore-forming fluids. Temperature change also plays an important role in fluorite precipitation. Fluorite grains from the pre-, early-, and main-ore stages have been variably metasomatized by a coupled dissolution-reprecipitation-recrystallization mechanism, which is characterized by complex petrographic and chemical zones. During this process, many trace elements were leached from the primary fluorite grains or other accompanied minerals, and parts of these elements were immediately reprecipitated into the new phases. Then, the recrystallized phases were formed from the leachate solutions of primary minerals. Our study highlights that fluorite generally has a complex growth history due to metasomatic alteration by hydrothermal fluids during the ore-forming process. Thus, in-situ microanalysis is essential and necessary to obtain effective and accurate constraints on hydrothermal evolution, and most of the interpretations based on bulk analysis of fluorites crystals should be cautioned. [ABSTRACT FROM AUTHOR]

As a world-class tin–tungsten province, South China is well known for its extensive Mesozoic granitic magmatism. The Dulong district, located in the western Cathaysia Block of the South China tin–tungsten province, is characterized by widespread Mesozoic granitoids and accompanying Sn-polymetallic ore deposit (~ 30 Mt of Sn). It is one of the most important polymetallic tin ore districts in China. In this study, three mineralization-related granite types were identified in the Dulong district, including the Dulong coarse-grained granite (DCG), the Dulong fine-grained granite (DFG), and the Dulong porphyritic granite (DPG). Detailed studies are presented on zircon U–Pb ages, major and trace elements, mineral chemical and Nd–Hf isotopic compositions of the tin-bearing granites from the Dulong district. LA-ICP-MS U–Pb dating of zircon grains from these three granite bodies yields ages of 90.1 ± 0.7 Ma, 89.7 ± 0.8 Ma and 86.0 ± 0.5 Ma, respectively. Geochemically, the granites are strongly peraluminous, with high contents of alkalis, enrichment in P, Li, Rb, Cs, Ta, Sn, W and U, depletion in Ti, Mg, Co, Ni, Sr, Ba, Zr, Hf, Th and rare earth elements. Fractional crystallization of plagioclase and K-feldspar was the principal process of magmatic differentiation that controlled Rb, Sr, Ba and Eu concentrations, whereas rare earth elements were fractionated by accessory minerals, such as apatite and monazite. The geochemical data suggest that the rocks are highly fractionated S-type granites. The granites show bulk rock ε Nd (t) values in the range of − 12.2 to − 10.8 and zircon ε Hf (t) values from − 15.5 to − 2.5, with Meso-Paleoproterozoic T DM C ages for both Nd and Hf isotopes. Geochemical and isotopic data suggest that these highly fractionated S-type granites DCG, DFG and DPG were originated from the same episode of partial melting of the protolith, which have analogous components of metamorphosed pelitic rocks from the Meso-Paleoproterozoic continental crust. Extreme fractional crystallization resulted in enrichment of tin in the evolved granitic magma, and the reduced magmas (fO 2 below NNO) would efficiently remove Sn into a hydrothermal fluid, and lead to deposition of Sn-rich mineral phases. The association of Dulong and Gejiu magmatism in the western Cathaysia Block may be likely to mark the onset of back-arc extension or intra-arc rift in the region during Late Cretaceous. The upwelling of asthenospheric mantle may have triggered partial melting of metasedimentary rocks in the overlying crust to generate the S-type granitic magmas. [ABSTRACT FROM AUTHOR]

Granite-hosted uranium ore deposits are the most important commercial U-producers in South China. These U-bearing granites generally contain high-U-concentration zircons. Zircons in the U-bearing Douzhashan Granite show black rims in cathodoluminescence images, which have very high U concentrations of up to > 25,000 ppm. The high-U black rim domains of zircons show similar REE patterns to those of low-U mantle domains with oscillatory zoning, but have higher REE concentrations and weaker positive Ce anomalies. The high-U black rim domains of zircons may have formed from late-stage evolved U-rich and H 2 O-rich magma. We carried out a SHRIMP U-Pb dating for these zircons and the results show that the high-U (12,007–26,706 ppm) rim domains of the zircons always yield older 206 Pb/ 238 U ages (268 ± 9 Ma, n = 5, MSWD = 2.7) than the low-U (558–3667 ppm) mantle domains (228 ± 11 Ma, n = 4, MSWD = 3.1), and both of these ages are older than the emplacement age (211 ± 3 Ma) of the U-barren Xiangchaoping Granite, which was intruded by the Douzhashan Granite. Hence, these results demonstrate a matrix effect associated with SHRIMP U-Pb analyses of high-U zircons. The reverse discordance for SHRIMP results of high-U zircons was produced by analytical artifact. However, our LA-ICP-MS analyses show that the black rim domains (12,840–26,018 ppm U) of the zircons have the same U-Pb ages as the low-U mantle domains (1215–4075 ppm U). Both domains yield a weighted mean 206 Pb/ 238 U age of 203 ± 4 Ma (n = 13, MSWD = 1.4), which is consistent with the 40 Ar- 39 Ar age (207 ± 4 Ma) of muscovite from this granite. It thus indicates that LA-ICP-MS U-Pb analyses for high-U zircons (up to 26,000 ppm U) show an insignificant matrix effect and likely yield more reliable U-Pb ages for the high-U zircons than SHRIMP analyses. In order to get reliable U-Pb ages using the LA-ICP-MS method for the high-U zircons, a pulse-analog cross calibration for the ICP-MS collector should be performed. Our precise U-Pb dating and geochemical studies indicate that the U-bearing Douzhashan Granite was emplaced during the late Indosinian stage and formed in a post-collisional setting of the Indosinian Orogeny. It is distinct from most U-bearing Granites in South China, which were largely emplaced during the early Indosinian stage and formed in a syn-collisional setting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Huangjiagou NYF pegmatites contain abundant magmatic allanite-(Ce). • The allanite U-Th-Pb dating yields age of 1829 ± 23 Ma. • Allanite Nd isotopes suggest the pegmatite originated from dehydrated Taihua Group. U-Th-Pb dating and Sm-Nd isotopes of magmatic allanite from the Huangjiagou NYF pegmatites (lesser Qinling orogenic belt, China) were precisely measured and compared with zircon U-Pb dating and Lu-Hf isotopes to demonstrate the suitability and robustness of the U-Th-Pb and Sm-Nd system in allanite as a note-taker of formation age and magma sources for pegmatites. Allanite crystals from the Huangjiagou NYF pegmatites exhibit complex chemical zoning with a homogeneous primary internal domain, which has a typical magmatic origin with high La/Sm, Th/U, and low Eu/Eu*. The allanite has low La/Ce ratios (0.48–0.62) and thus is classified as allanite-(Ce). We used time-depended element fractionation and the changing of NAI with ablating different matrices to test the matrix differences between allanite and zircon standard 91500, and achieved excellent allanite U-Th-Pb date using zircon 91500 as external standard. Magmatic allanite-(Ce) yields a lower-intercept age of 1829 ± 23 Ma on the Tera-Wasserburg plot and a 208Pb/232Th weighted average age of 1840 ± 17 Ma, both of which are consistent with the zircon 207Pb/206Pb weighted mean age (1826 ± 11 Ma) within uncertainty, supporting the reliability and accuracy of non-matrix matched allanite U-Th-Pb dating. We used titanite standard (MKED1) to correct the time-drift in allanite Nd isotope analysis. And by integrating the zircon Lu-Hf isotopes and allanite Sm-Nd isotopes, together with field investigation and mineralogy, we suggest that the Huangjiagou NYF pegmatites belong to an abyssal class, formed in the late Paleoproterozoic, and likely related to the partial melting of the dehydrated Taihua Group (amphibolite and TTG granites) in the post-collisional tectonic setting between the Eastern and Western blocks along the trans-North China Orogen (TNCO). This study confirms the talent of allanite serving as a good indicator for the crystallization age and magma sources of NYF pegmatites using non-matrix matched U-Th-Pb dating and in situ Sm-Nd isotope analysis. [ABSTRACT FROM AUTHOR]

Abstract: Large-scale Cu–Au mineralization is associated with the Late Mesozoic granitoids in the Jiurui district of the Middle–Lower Yangtze Mineralization Belt in Eastern China. To constrain the petrogenesis of these granitoids and coeval mafic rocks, a detailed geochemical and Sr–Nd–Pb–Hf isotopic study was performed. The Jiurui granitoids are made up primarily of granodiorite porphyry and quartz diorite porphyry. These granitoids are characterized by SiO2 and K2O contents of 58.8wt.% to 68.6wt.% and 1.9wt.% to 5.7wt.%, respectively. These granitoids show relatively high MgO contents (1.0wt.% to 3.1wt.%, average 2.1wt.%) and high Mg# values (39 to 70, average 54). The Jiurui granitoids are enriched in light rare earth elements (LREE), large ion lithophile elements (LILE), and compatible trace elements (Cr, Ni and V) but are relatively depleted in Nb, Ta, Y and Yb. These rocks show a negligible negative Eu anomaly (Eu/Eu⁎ =0.76–1.13, average 0.91) and nearly no negative Sr anomaly. The whole-rock initial 87Sr/86Sr ratios range from 0.7060 to 0.7092, and the εNd(t) values vary from −5.4 to −2.0. The granitoids show radiogenic Pb isotopic ratios with values of 206Pb/204Pb (17.93–18.21), 207Pb/204Pb (15.55–15.58), and 208Pb/204Pb (38.16–38.56) for the plagioclases. The zircon Hf isotopic compositions show εHf(t) values from −11.8 to 2.4. The coeval mafic rocks consist of lamprophyre, diabase and fine-grained mafic dyke. These rocks are characterized by SiO2 contents ranging from 47.6wt.% to 54.8wt.%, with a negative Eu anomaly and a positive to negative Sr anomaly. The whole-rock initial 87Sr/86Sr ratios range from 0.7059 to 0.7071, and the εNd(t) values vary from −3.8 to −1.4. By comparing the geochemical and isotopic compositions of the Jiurui granitoids and the coeval mafic rocks, we conclude that the granitoids are similar to adakites that were likely related to the delamination processes, and the coeval mafic rocks may have originated directly from enriched lithospheric mantle. The thickened lower continental crust and underlying enriched lithospheric mantle may have been simultaneously delaminated into the asthenospheric mantle. This process led to the partial melting of the thickened lower crust and the enriched lithospheric mantle, and the melts experienced an interaction with the asthenospheric mantle during ascension. Mafic melts could be generated from the enriched lithospheric mantle, which was heated by the upwelling asthenospheric mantle. The geochemical and isotopic compositions of mafic rocks were most likely controlled by the AFC process. A geochemical and isotopic comparison of the granitoids in the Jiurui district with those of two other districts (e.g., Angui and Tongling) in the same mineralization belt indicates that a significant crust–mantle interaction played a crucial role in their petrogeneses and metallogeneses. From the southwest to northeast in this metallogenic belt, the proportion of mantle component that was involved in the granitic magma shows a decreasing trend from the Jiurui to the Angui and Tongling districts. It is suggested that the Juirui district has the highest potential for a significant amount of Cu–Au accumulation because the mantle is an important supply for these metals. [Copyright &y& Elsevier]

Abstract: Lithospheric thinning and destruction of the North China Craton have been topics of active discussion throughout the last two decades, but the specific processes associated with lithospheric thinning remains controversial. Here we report co-occurrence of low-Ti (TiO2 <1.1wt.%, Ti/Y<270) and high-Ti (TiO2 >2wt.%, Ti/Y>370) types of lamprophyres in the Jiaodong Peninsula, eastern North China Craton in order to address this issue. Low-Ti lamprophyres are depleted in HFSE and enriched in Pb, both typical subduction signatures. We suggest they were derived from partial melting of an ancient and enriched lithospheric mantle, which was previously modified by slab-derived hydrous fluids. In contrast, the high-Ti lamprophyre has trace element patterns similar to many oceanic basalts with depletion of Pb but little or no HFSE depletion. We infer that they originated from partial melting of a convective asthenospheric mantle. Zircon U–Pb dating shows that both types of lamprophyres intruded the eastern North China Craton about 121Myr ago. Their indistinguishable ages thus appear to record a rapid transition from lithospheric to asthenospheric mantle source, suggesting further that the lithosphere beneath the eastern North China Craton was removed, potentially delaminated ca. 121Myr ago beneath Jiaodong Peninsula. The detachment of cratonic lithosphere is likely related to continental arc-rifting which resulted from Palaeo-Pacific plate subduction in the Mesozoic. [Copyright &y& Elsevier]

The Dachang gold deposit is located in the Late Triassic Songpan-Ganzi Fold Belt, NE Tibetan Plateau. Gold ore is concentrated as veins along secondary faults and fracture zones in the Bayan Har Group metaturbidites. No exposed felsic plutons are present in the vicinity of the deposit. The auriferous veins contain <15% sulphide minerals, mainly arsenopyrite, pyrite, and stibnite. Gold is commonly enclosed within arsenopyrite and pyrite. Typical alteration around the ore bodies includes silicification, sericitization, and weak carbonatization. Gold-bearing quartz samples have δ18O values of 16.9–21.2‰ (V-SMOW) from which δ18OH2Ovalues of 6.2–9.6‰ can be calculated from the fluid inclusion temperatures (or 10.0 to 12.7‰ if we used the average arsenopyrite geothermometer temperature of 301°C). The δD values of fluid inclusions in quartz range from –90‰ to –72‰. δ34S values of gold-bearing sulphides mainly range from –5.9‰ to –2.8‰ (V-CDT). Pyrite and arsenopyrite in ores have206Pb/204Pb ratios of 18.2888 to 18.4702,207Pb/204Pb ratios of 15.5763 to 15.6712, and208Pb/204Pb ratios of 38.2298 to 38.8212. These isotopic compositions indicate that the ore-forming fluids were of metamorphic origin, and the S and Pb may have been derived from the host metaturbidites of the Bayan Har Group. The Dachang Au deposit has geological and geochemical features similar to orogenic gold deposits. We propose that the ores formed when the Songpan-Ganzi Fold Belt was intensely deformed by Late Triassic folding and thrusting. Large-scale thrusting resulted in regional allochthons of different scales, followed by secondary faults or fracture zones that controlled the ore bodies. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Lingshan complex a ring-like multiphase batholith all formed at ca. 133 Ma. • They formed from discrete source process rather than fractional crystallization of a single magma. • The marginal units formed after rejuvenation and extraction from the crystal mush reservoirs. • The Nb-Ta enrichment is related to the extensive fractional crystallization of granitic magma. The Lingshan granite complex, located in the northeast part of the Qin-Hang Belt, Jiangxi Province, southeast China, has produced the largest Ta-Nb deposits in China, i.e., the Huangshan Nb-Ta and Songshugang Ta-Nb-(W-Sn) deposits. This complex is spatially a ring-like multiphase batholith, and comprises a series of granitic rocks from the central to marginal units. Mafic microgranular enclaves (MMEs) occur only in the central unit. Geochronologic results show that the magmatic activities at Lingshan district took place at Early Cretaceous, with similar emplacement ages (133–134 Ma) between the central and marginal units. The Lingshan granites are metaluminous to weakly peraluminous (most A/CNK < 1.1), and display typical A-type affinity. However, the whole-rock REE contents and Zr/Hf and (La/Yb) N ratios exhibit an abnormal increase from the central to marginal units. The Li, Rb and Cs elements of biotite as well as the Zr/Hf ratios of zircon do not exhibit a continuous enrichment trend from the central towards marginal granites. All these features suggest that the generation of Lingshan granites is more complex than the fractional crystallization from a single parental magma. Alternatively, a crystal mush model could be applied to better interpret the geochemical and isotopic contrasts between different granite phases. The marginal granites were likely formed by later crystallization events after the rejuvenation and extraction from the crystal mush reservoirs, while the central granites were formed from the residual crystal-rich mush with a relatively low terminal porosity. Moreover, the Nb and Ta contents of biotite exhibit a gradual enrichment with increasing fluorine contents in the marginal granites. The enrichment of lithium and fluorine in the granitic melt can significantly promote the proportion of non-bridging oxygens (NBOs) for coordinating Nb and Ta in the melt, further enhancing the solubility of columbite and tantalite, and eventually causing the Nb and Ta elements either incorporate into the mineral lattice of micas in the early marginal granites or form columbite-group minerals in the pegmatite/altered granite. In summary, we propose that the Ta-Nb enrichment event in the Lingshan district is spatially and genetically related to the extensive fractionation evolution from central to marginal units. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrothermal apatite and zircon U-Pb geochronology record the Qiucun gold mineralization occurred at ca. 161 Ma. • Fluid inclusion and C-H-O isotope data indicate a meteroic fluid source. • S-Pb isotope suggest derivation of them from the volcanic host rocks and deeper-seated crustal materials. • Qiucun represent a Late Jurassic low-sulfidation epithermal gold deposit in SE China. On the basis of zircon and apatite U-Pb dating, H-O-C-Pb isotopes, and fluid inclusion data, a metallogenic model is established for the Qiucun gold deposit (gold resource > 10 t, average grade: 4.9 g/t) in the Dehua goldfield in the Mesozoic Coastal Volcanic Belt (southeastern China). Three hydrothermal stages can be distinguished within the Late Jurassic volcanic host rocks: Stage I, dominated by quartz-pyrite, Stage II with a quartz-sulfide assemblage, and Stage III reflected by quartz-calcite. The ore-hosting volcanic rocks were formed at 170.2 ± 0.9 Ma. Distinctly younger U-Pb ages of 162.5 ± 1.0 Ma and 160.5 ± 6.0 Ma obtained on syn -ore hydrothermal zircon and apatite, respectively, clearly indicate that gold mineralization postdates the volcanic host rocks. Fluid inclusion data reveal that the ores were precipitated from low-temperature (275 to 170 °C), low-pressure (<55 bar), and low-salinity (<5 wt% NaCl equiv.) solutions, with a systematic decrease in temperature and pressure from stages I to III. The δ34S V-CDT ratios for gold ores vary between −3.2 and 0.6 ‰. Sulfide separates yielded 206Pb/204Pb ratios of 18.368 to 18.504, 207Pb/204Pb ratios of 15.685 to 15.718, and 208Pb/204Pb ratios of 38.792 to 39.063. These data suggest S and Pb derivation from the host volcanic rocks and perhaps deeper-seated crustal materials. Calcite from Stage III has δ13C V-PDB values of −2.9 to −2.7 ‰ and δ18O V-SMOW values of 8.2 to 10.8 ‰. Calculated δ18O fluid (−7.6 to −2.7‰) and δD fluid (−119 to −49‰) values document a largely meteoric nature of the mineralizing fluid. All data together point at a Late Jurassic low-sulfidation epithermal gold mineralization with metal remobilization from host volcanic rocks and basement. [ABSTRACT FROM AUTHOR]

Titanite, as one significant petrogenetic tracer, occurs in the ore-bearing alkaline unit (syenite and aegirine-augite syenite dikes) and in the barren calc-alkaline unit (monzodiorite) and metamorphosed strata (called as leptynite) in the recently found large Yushishan Nb-Ta deposit from South Qilian, NW China. Most titanite grains in the alkaline unit display obvious shape-preferred orientation and zonation, coexisting with allanite, zircon and alkali feldspar. Some titanite grains from the alkaline unit have been partially or completely altered into fine-grained euxenite and/or Nb-rich rutile, but retained their original crystal shapes. Although some titanite grains in the igneous rocks show obvious core-rim textures, both of them yield almost the same U-Pb ages. Combined with U-Pb dating of zircon from these different rock units, the complex magmatic-metamorphic events in the Yushishan district can be subdivided into two different periods: the first one occurring in the Neoproterozoic (ca. 834–790 Ma, zircon U-Pb ages) that are related to the regional volcanism and metamorphic activities and the formation of leptynite during the metamorphism, while the second one occurring in the early Paleozoic (ca. 490–470 Ma, titanite and zircon U-Pb ages) that are related to the formation of granitic intrusions and subsequent metamorphic process and Nb-Ta mineralization. Geochemically, titanite from these igneous rocks is consistent with the typical features of igneous titanite, such as high Fe and REE contents, and negative Eu anomalies. The zoned titanite in both alkaline (mainly syenite) and calc-alkaline units uniformly displays a core-to-rim decreasing trend for the Fe, REE, Nb and Ta contents and Th/U ratios, corresponding to a secular variation from the magmatic to metamorphic evolution. Titanite from the leptynite is interpreted to be of metamorphic origin, with low Fe and REE contents, weakly positively sloping REE patterns, along with positive Eu anomalies. It is suggested that the titanite can be used as an indicator of metal fertility and ore potential for the host rocks/fluids. The high Nb and Ta features in titanite from the alkaline unit suggest a genetic relationship between the alkaline granitic magmatism and Nb-Ta mineralization in the Yushishan deposit. In addition, the high and variable Nb and Ta contents in titanite from the leptynites reveal an inherited signature of the metamorphic fluids. Considering the absence of titanite in the ore-bearing leptynites, we speculate that titanites with high and variable Nb and Ta contents of titanite in the barren leptynites have the potential to provide abundant metals for the precipitation of Nb-Ta-bearing minerals to form economic orebodies. • Paleozoic magmatic-metamorphic events and Nb-Ta mineralization occur at Yushishan. • Zoned titanites from Yushishan intrusive rocks record evolution of magmatic to metamorphic process. • High Nb-Ta contents in titanite can be used as good indicator for Nb-Ta mineralization. [ABSTRACT FROM AUTHOR]

The Miao’ershan–Yuechengling batholith (MYB) is one of the largest granitic batholiths in South China. At least five individual phases have been identified for the Paleozoic granites in the MYB. SHRIMP and LA–ICP–MS zircon U–Pb dating results imply that these granites were emplaced at 435±4Ma, 427±3Ma, 417±6Ma, 404±6Ma and 382±2Ma, respectively. The ages gradually decreased from the southeast to the northwest, implying that the MYB was incrementally emplaced from the southeast to the northwest lasting from early Silurian to late Devonian. Most granites are metaluminous to weakly peraluminous, and contain low P2O5 contents (<0.15%). These granites show enrichment of Rb, Th, U and depletion of Ba, Sr, Eu, Ti. They show relatively high (87Sr/86Sr)i ratios (>0.715), low ε Nd(t) values (−8.9 to −6.7), and low zircon ε Hf(t) values (−9.5 to −4.0). These geochemical and isotopic characteristics indicate that these granites may have formed from partial melting of Paleoproterozoic basement rocks. Slight geochemical differences between different phases can be interpreted as resulting from partial melting of heterogeneous sources or different proportion mixing of meta-igneous and meta-sedimentary rocks. Zircon Hf isotope model ages vary from 1.77 to 1.93Ga, with an average value of 1.84±0.07Ga. These data indicate that crust growth in this region took place mainly during the Paleoproterozoic (ca. 1.84Ga), and the basement in the MYB should belong to the Cathaysia Block. The formation of the Paleozoic granites in the MYB was suggested to be related to the late orogenic magmatism of the Wuyi–Yunkai orogeny. Thus, the late orogenic magmatism in the northwestern part of the Wuyi–Yunkai orogeny must have lasted until ca. 381Ma and took place also to the east of the Anhua–Luocheng Fault. [ABSTRACT FROM AUTHOR]

The Xiangshan volcanic-intrusive complex is composed of rhyolitic crystal tuffs, welded tuffs, rhyodacite, porphyroclastic rhyolitic lava, subvolcanic rocks such as granite porphyry, and late quartz monzonitic porphyry and lamprophyre dikes. We report the first occurrence of a quartz–amphibole schist (QAS) xenolith enclosed within a mafic microgranular enclave (MME) in the Xiangshan volcanic-intrusive complex. The mineralogy of this xenolith consists of amphibole, biotite, quartz, and minor plagioclase. Petrographic and mineral composition studies indicate that the protolith of this xenolith likely originated from the metamorphic basement beneath Xiangshan. The amphibole (actinolite and magnesiohorblende) has been partially replaced by orthopyroxene at 800–1000°C and by diopside at <700°C, according to mineral thermometers; this replacement process may have taken place after the xenolith was trapped by the mafic magma host (now an MME). Studies of the QAS xenolith provide new information on the emplacement history of the mafic magma. The peak metamorphic temperature for amphibole replaced by pyroxene is higher than the crystallization temperature of the subvolcanic magma, which indicates that the heat of pyroxene formation must have been provided by the engulfing mafic melt. This magma must have emplaced to crustal level and trapped the QAS as a xenolith and then injected into the felsic magma. We suggested that the hybridization processes for the major elements of the pristine mafic magma may have been contaminated by crustal rocks to form its present composition of MME before mafic magma injection. However, the hybridization process appears not to have been formed via a single-stage process because various types of MMEs are presented in the Mesozoic magmatic rocks of SE China. [ABSTRACT FROM AUTHOR]

Abstract: The Linglong granite is one of the most important Mesozoic plutons in the Shandong Peninsula, eastern China, and its petrogenesis has long been controversial, particularly with regard to the nature of source region and geodynamic setting. Our new precise zircon U–Pb dating results reveal that the Linglong granite was emplaced in the Late Jurassic (157–160Ma). In addition, abundant inherited zircons are identified in the granite with four groups of age peaked at ~208, ~750, ~1800 and ~2450Ma. Geochemical studies indicate that the Linglong granite is weakly peraluminous I–type granite, and is characterized by high SiO2, Sr and La, but low MgO, Y and Yb contents, strongly fractionated REE pattern and high Sr/Y and La/Yb ratios. It also exhibits high initial 87Sr/86Sr ratios (0.7097 to 0.7125), low εNd(t) (−17.7 to −20.3) and variable zircon εHf(t) (−22.2 to −8.7) values. Calculation of the zircon saturation temperature (TZr) reveals that the magma temperatures are 760±20°C, and the lowest TZr value of 740°C may be close to initial magma temperature of this inheritance-rich rock. Interpretation of the elemental and isotopic data suggests that the Linglong granite has some affinities with the adakite, and was most likely derived from partial melting of thickened lower crust without any significant contribution of mantle components. The presence of a large number of inherited zircons and variable Sr–Nd–Hf isotopic compositions reveal that the Linglong granite probably has multiple sources consisting of the lower crust of both South China Block and North China Block, as well as the collision-related alkaline rocks and UHP metamorphic rocks. The continental arc-rifting related to the Izanagi plate subduction was the most likely geodynamic force for formation of the Jurassic Linglong adakatic granite in the Shandong Peninsula. [Copyright &y& Elsevier]

Abstract: A detailed study utilizing zircon U–Pb dating, major and trace element geochemistry, and Sr–Nd–Hf isotope geochemistry has been carried out for the Caijiang granite in Jiangxi Province and the Gaoxi granite in Fujian Province, South China. The new data indicate that the Caijiang and Gaoxi granites are Triassic (228–230Ma) and have the petrographic and geochemical characteristics of A-type granites. In both granites, biotite occurs along the boundary of euhedral plagioclase and quartz, which implies that the primary magma could have been anhydrous. The two granites show high contents of total alkalis (Na2O+K2O=7.81–12.15%), high field strength elements (e.g. Zr=240–458ppm, Y=16.8–38.0ppm, Nb=13.5–33.8ppm and Zr+Nb+Ce+Y=382–604ppm) and rare earth elements (total REE=211–373ppm) as well as high Ga/Al ratios (10000×Ga/Al=2.41–3.53). The lowest magmatic temperatures estimated from zircon saturation thermometer were 800–840°C for the Caijiang granite and 820–850°C for the Gaoxi granite, respectively. The Caijiang granite has relatively high (87Sr/86Sr)i ratios of 0.71288 to 0.72009, low ε Nd(t) values of −9.9 to −9.3, and low zircon ε Hf(t) values (peak value of −7.5). Whole-rock Nd isotopic model ages and zircon Hf isotopic model ages mostly vary from 1.65Ga to 1.80Ga. The Gaoxi granite has also high (87Sr/86Sr)i ratios of 0.71252 to 0.71356, low ε Nd(t) value of −13.8 and low zircon ε Hf(t) values (peak value of −12.0). Whole-rock Nd isotopic model ages and zircon Hf isotopic model ages mostly vary from 1.95Ga to 2.10Ga. According to these data, we suggest that the two granites might have been derived from partial melting of Precambrian crustal rocks that had been granulitized during an earlier thermal event. Our study of the Caijiang and Gaoxi granites, together with previous studies on two Triassic alkaline syenites (Tieshan and Yangfang) in Fujian Province and one A-type granite (Wengshan) in Zhejiang Province in South China, indicate a wide transtensional tectonic environment in the Cathaysia Block that lasted at least from 254Ma to 225Ma. Combined with extant data for the Indosinian granites and tectonic evolution in South China, we suggest that the formation of A-type granites was related to the local NE-trending extensional faults probably caused by collision between the South China Block and the Indochina Block or the North China Block. [Copyright &y& Elsevier]