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[Display omitted] • Amphibolites are Neoproterozoic subduction-related mafic rocks formed at 959 Ma. • Amphibolites were metamorphosed at 430 Ma in the north Qaidam UHPM belt. • The 918–875 Ma and 454–368 Ma magmatism correlated to associated tectonic processes. In order to better understand the Neoproterozoic and Paleozoic magmatism, metamorphism and tectonic evolution of the whole Tibetan Plateau, here we report the field observations, LA-ICP-MS zircon U-Pb dating, whole-rock geochemistry, Sr-Nd isotopes, and LA-MC-ICP-MS zircon Lu-Hf isotopes of the amphibolites, volcanic rocks, and granitoids from the north Qaidam UHPM belt of the northeastern Tibetan Plateau. The Neoproterozoic mafic rocks (protolith of amphibolites) with zircon U-Pb age of 959 Ma are subduction-related magmatic rocks formed in a failed continental back arc rift above an oceanic-continental subduction zone by melting of an enriched mantle. These mafic rocks underwent Paleozoic metamorphism as revealed by metamorphic zircons that crystallized at 430 Ma during the retrogression from eclogite to amphibolite facies metamorphism. The Neoproterozoic granitoids are strongly peraluminous muscovite granites with LA-ICP-MS zircon U-Pb ages of 918–875 Ma. The formation of these granitoids occurred at high to low temperatures and low oxygen fugacities, and was possibly derived by partial melting of Paleo- to Meso-Proterozoic crustal rocks during the orogenic collapse. The Paleozoic magmatism, including 454 Ma arc-type dacites, 412 Ma collisional muscovite granite, and the post-collisional 370 Ma biotite monzogranite and 368 Ma diorite, records a detailed tectonic evolution history from oceanic subduction, through continental collision, to post-collision in the north Qaidam UHPM belt. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porphyry Mo and lode Au mineralization coexist at the Laowan district. • Multiple geochronological constraints reveal two separate mineralization events. • Mo mineralization at 141 Ma is simultaneous with the porphyry intrusion. • Au mineralization at 124–128 Ma is coincident with the monzogranite intrusion. The Laowan super-large (208 t Au) gold deposit is located in the Tongbai orogenic belt, along with a newly-discovered molybdenite deposit at its depth in the northern periphery. The gold deposit is a fault-controlled lode gold deposit featuring sulfide quartz vein-type and altered rock-type mineralization hosted within the metamorphic rocks, whereas the molybdenum deposit is a typical porphyry-type deposit. These two deposits have their respective paragenetic sequences and mineralization types without spatial overlapping in the ore field. Here, we present U–Pb dating of zircon, hydrothermal rutile, and REE phosphates, and Re–Os dating of molybdenite to constrain the relationship between the Au and Mo mineralization, and their relation to Mesozoic granitic magmatism. Textural features indicate that rutiles and associated phosphate minerals are of hydrothermal origin, generated by re-precipitation and dissolution of titanite crystals hosted in the metamorphic host rocks due to hydrothermal alteration during Au and Mo mineralization. LA-ICP-MS U–Pb dating of rutile from the auriferous altered rocks yields a 206Pb/238U age of 120.0 ± 6.7 Ma (MSWD = 1.4), consistent with the ages of the associated monazite (125.0 ± 2.4 Ma) and xenotime (126.3 ± 2.0 Ma), representing the timing of the gold mineralization, coeval with Laowan monzogranite (zircon U–Pb: 128.8 ± 0.7 Ma). Rutile from the molybdenum deposit show an older 206Pb/238U age of 141.0 ± 11 Ma (MSWD = 1.1), consistent with the molybdenite Re–Os age (141.5 ± 1.7 Ma; MSWD = 0.27) and the zircon U-Pb age (141.6 ± 0.8 Ma; MSWD = 1.5) of the Songpa porphyry. Hence, the Au and Mo mineralization in the Laowan district represent two episodic mineralization events related to the late Mesozoic granitic magmatism. Our study also suggested that multiple isotopic dating is helpful to precisely constraint the ages for complex hydrothermal deposits. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Burma Terrane was a Western Pacific-type margin before the late Eocene. • Sediments at the Burmese margin were locally derived in the Cretaceous-Eocene. • Provenance divergence was induced by the tectonic evolution of the Burmese margin. The evolution of large fluvial drainages in SE Tibet and adjacent areas reflects the degree of coupling between tectonics, erosion, and climate. Reconstruction of their spatio-temporal development provides significant constraints for our understanding of the palaeogeographic evolution of numerous blocks in this domain. The Burmese continental margin drained by the Irrawaddy River and its tributaries includes blocks of the Burma Terrane and the Mount Victoria Land (Eastern Belt of the Indo-Burman Ranges). To investigate how was this margin developed from the amalgamation of the two blocks since the mid-Cretaceous, we present seismic profiles, sedimentary budget, sandstone petrography, bulk-rock geochemistry, and detrital apatite U-Pb ages from the margin. Our results show that provenance of the Burmese Forearc and Backarc depressions shifted from the proximal Western Myanmar Arc and equivalents within northern Burma Terrane to the northern Mogok Metamorphic Belt and Dianxi-Burman batholiths within SE Tibet during the late Paleogene. The provenance transition is synchronous with tectonic evolution of the Burma Terrane from an(a) oceanic/continental island arc setting to an active continental margin. We propose an evolved Western Pacific-type margin for the Burma Terrane, which is dominated by typical accretionary wedge, calc-alkaline island arc, and extensional forearc/backarc basins. An increase in sediment accumulation rates (SARs) in the Burmese Forearc indicates that the input from basement rocks within northern Burma Terrane (Tagaung–Myitkyina Belt) became more prominent and the Eastern Belt of the northern Indo-Burman Ranges were totally exposed in the Middle-Late Eocene. This result corroborates the Burma Terrane assembled with SE Asia (Sibumasu Terrane) before the Middle Eocene. The first presence of SE Tibet-like detritus and the diversification of SARs in the Burmese Forearc and Backarc in the Oligocene are compatible with dextral motion on the Sagaing Fault, which may have triggered the birth of the palaeo-Irrawaddy river and fluvial drainage reorganization in its upper reaches. Higher sedimentary fluxes recorded in the Burmese Forearc and Backarc depressions and the Andaman Sea during the Neogene are compatible with enhanced rock erosion within SE Tibet and thus, can be explained by rapid tectonic uplift and an intensified Asia monsoon in this region. [ABSTRACT FROM AUTHOR]

The Shuangqishan gold deposit (>20t gold) is located in a hitherto poorly-documented gold province in the southeastern Cathaysia Block, South China. It is hosted by Neoproterozoic amphibolite-facies metamorphic rocks and consists of quartz-sulfide veins with distinct alteration haloes. Three stages of hydrothermal activity have been identified, and gold is mainly associated with veins of Stage II (quartz-pyrite±chalcopyrite). Gold occurs both as refractory gold hosted by pyrite and free gold enclosed in, or filling, microfractures of pyrite and quartz. U-Pb isotope dating of hydrothermal apatite from the Substage IIa veins yielded an age of 436.8 ± 7.6 Ma. The ore fluid was of carbonic-aqueous composition and low oxygen fugacity. Total homogenization temperatures in Substage IIa and IIb range from 270° to 310°C and 250° to 295°C, respectively. Variable CO 2 /H 2 O ratios indicate fluid unmixing under fluctuating pressures. Stage I quartz veins show evidence of ductile deformation and have δ18O fluid and δD values of 10.3 to 11.2‰ and −67to −66‰, respectively, consistent with a metamorphic fluid. Stage II veins have slightly higher δ18O values of 10.9 to 13.7‰, with calculated δ18O fluid values of 4.8 to 8.0‰. The 3He/4He ratios of pyrite are elevated (0.06–0.23 Ra) relative to crustal He reservoirs (<0.01 Ra). Fluid inclusions in quartz yielded δ13C CO2 values of −23.0to −11.4‰ (V-PDB), reflecting variable contributions of organic carbon. The sulfide δ34S V-CDT values range from −4.7to −1.0‰, consistent with a deep-seated sulfur source. The Pb isotope compositions of pyrite (206Pb/204Pb=17.141–17.871, 207Pb/204Pb=15.484–15.570) are more radiogenic than those of unaltered host rocks. All available data demonstrate that the Shuangqishan deposit is the first report orogenic gold deposit formed during the late Wuyi-Yunkai intracontinental orogeny in the Cathaysia Block. Unlabelled Image • Hydrothermal apatite U-Th-Pb geochronology record the Shuangqishan gold mineralization occurred at 437 Ma. • Fluid inclusion and isotope data indicate a sub-crustal origin for the mineralizing fluids, sulfur, and metals. • The Shuangqishan gold deposit formed as a result of reactivation of metasomatized mantle. • The Shuangqishan gold deposit is the first identified Early Paleozoic orogenic gold deposit in the Cathaysia Block. [ABSTRACT FROM AUTHOR]

Abstract Reconstructing the environmental conditions that supported early life on Earth relies on well-preserved geochemical archives in the rock record. However, many geochemical tracers either lack specificity or they are affected by post-depositional alteration. We present a data set of major and trace element abundances and Cd isotope compositions of dome-shaped and conophyton-type stromatolites of the Late Mesoproterozoic Paranoá Group (Brazil), showing distinct values with unprecedented resolution at the lamina scale. The studied stromatolites consist of dolomite with a high purity and a negligible content of immobile elements (e.g., <0.66 ppm Zr), indicating that elemental compositions are not influenced by detrital contamination. Even though the carbonates have experienced different extent of recrystallization, the measured elemental and isotopic compositions do not correlate with fluid mobile elements. The stromatolites thus represent prime archives for geochemical proxies to reconstruct paleo-environmental conditions. Two endmember compositions can be distinguished by multiple proxy analysis, reflecting the contrasting depositional environments of the two types of stromatolites: Shale-normalized rare earth elements including yttrium (REY SN) patterns of domal stromatolites show a light REY SN (LREY) enrichment (Yb SN /Pr SN < 0.84), slightly super-chondritic Y/Ho ratios (33.6–39.3) and unfractionated Cd isotopes relative to upper continental crust. This indicates that the stromatolites formed in a shallow-water environment that was episodically influenced by seawater. Their REY and Cd compositions are dominated by dissolved elements that were delivered via weathering and erosion processes from the ambient continent. In contrast, REY SN patterns of the conophyta are parallel those of modern seawater with an LREY SN depletion relative to HREY SN (Yb SN /Pr SN = 2.1 to 3.9), positive Gd SN anomalies (1.1 to 1.4) and strong super-chondritic Y/Ho ratios (37.9 to 46.2), suggesting a microbial habitat that was dominated by seawater. Cd isotopes correlate negatively with Cd and U, but positively with Mn and Ce concentrations, reflecting authigenic carbonate formation at different depths within a redox gradient of the ancient microbial mat. ε112/110Cd dol values increase from −3.52 at the mat surface to +3.46 in the interior of the mat, due to the effect of kinetic fractionation during Cd-uptake, e.g. by adsorption onto organic matter or by precipitation of sulfides, in addition to incorporation into carbonate minerals. Hence, our multi-proxy approach including Cd isotopes bears a high potential to shed light on environmental conditions in ancient microbial habitats and the activity of microbial life on Early Earth. Graphical abstract Unlabelled Image Highlights • Petrography, trace elements & stable C, O and Cd isotopes of ~1 Ga old stromatolites. • No detrital or post-depositional alteration of the REE and Cd carbonate inventories. • REE signatures indicate two distinct contemporaneous stromatolite habitats. • Cd isotopes show biological activity and metal cycling in Late Mesoproterozoic oceans. • Characterization of ancient microbial mats on highest resolution. [ABSTRACT FROM AUTHOR]

Late Mesozoic magmatic rocks that range in composition from mafic to felsic are widespread in the Jiurui district of the Middle-Lower Yangtze River belt in eastern Yangtze Craton of southeastern China. Among which the lamprophyre dikes represent mantle-derived magma and record deep mantle magmatic processes in the region. In this paper, we report a detailed study of geochronology, mineral chemistry, petrochemistry and Sr-Nd-Pb isotopes on the lamprophyres from the Nangang area in the Jiurui district, in an attempt to provide a comprehensive understanding in their petrogenesis, as well as the Mesozoic lithospheric mantle characteristics, and geodynamical control of the extensive Mesozoic magmatism in the Jiurui district. The Nangang lamprophyres belong to alkaline lamprophyre. They are characterized by low contents of SiO 2 and TiO 2 , high Mg # values and high contents of compatible elements, and are enriched in LREE and LILE but depleted in HFSE (with Nb-Ta-Ti negative anomalies). They show moderate enriched Sr-Nd isotopic compositions with initial 87 Sr/ 86 Sr values of 0.70598 to 0.70715 and ε Nd (t) values of − 2.2 to − 1.6. They also show radiogenic Pb isotopic compositions with ( 206 Pb/ 204 Pb) i values of 17.678 to 18.558, ( 207 Pb/ 204 Pb) i values of 15.544 to 15.591 and ( 208 Pb/ 204 Pb) i values of 38.349 to 38.664. Combining new data from the Nangang lamprophyres with those of previously published data for lamprophyres in the Jiurui (i.e. Wushan I and II lamprophyres) and Edong districts (i.e. Ruanjiawan lamprophyres), we suggest that the Jiurui lamprophyres were likely derived from partial melting of the enriched lithospheric mantle characterized by phlogopite-bearing lherzolite in spinel-garnet transition zone at 75–85 km depth. The feature of enriched-mantle source region was formed by metasomatism of subducted slab-derived fluids and melts, which is likely related to the Mesozoic subduction of the paleo-Pacific plate underneath the eastern China continent and the Neoproterozoic subduction of Cathaysia Block towards the Yangtze Craton. In contrast, the Ruanjiawan lamprophyres from the Edong district have the geochemical characteristics (such as the Nb-Ta positive anomalies) which are obviously different from the Jiurui lamprophyres, and we conclude that the Ruanjiawan lamprophyres, which are located more inland than the Jiurui district, were likely derived from the depleted asthenospheric mantle that show no significant influence by the subduction-related metasomatism. Furthermore, interpretation of the Sr-Nd-Pb isotope data for the Jiurui lamprophyres suggests slightly different petrogenesis for the various lamprophyre dikes, namely, the Nangang and Wushan–I lamprophyres were derived mainly from the enriched lithospheric mantle, but with addition of depleted asthenospheric mantle materials, whereas the Wushan–II lamprophyre dikes were product of the enriched lithospheric mantle without any signature for addition of depleted asthenospheric mantle materials. Given that these lamprophyres with distinct different isotopic compositions are sympatric and coeval, we consider that in the Late Jurassic to Early Cretaceous period (ca. 155–125 Ma), the lithosphere was thinned to about 75–85 km depth. The enriched lithospheric mantle was heated by the underlying convective asthenosphere and underwent partial melting to generate the Wushan–II lamprophyres. Subsequently, the enriched lithospheric mantle delaminated into depleted asthenospheric mantle, followed by partial melting coupled with an intensive interaction with the asthenospheric mantle to generate the Nangang and Wushan–I lamprophyres, respectively. Towards more inland, the Ruanjiawan lamprophyres were derived from the depleted asthenospheric mantle. [ABSTRACT FROM AUTHOR]

The widespread occurrence of late Mesozoic volcanic rocks in the Gan-Hang Belt in South China is associated with similarly widespread mineralization, but many important questions surrounding these volcanic rocks have not been clearly answered. The Tianhuashan basin located in the northern Wuyi Mountain volcanic belt is one of the most important volcanic basins in the Gan-Hang Belt, and it is primarily composed of the Daguding and Ehuling Formations and their intrusive counterparts. LA-ICP-MS zircon U–Pb dating shows that the Daguding Formation erupted in the Late Jurassic (152–160 Ma), whereas the Ehuling Formation erupted in the Early Cretaceous (131–139 Ma) in the Tianhuashan basin. Volcanic rocks are rhyolite and share similar trace and rare earth element patterns with an enrichment of LREEs and a depletion in Sr, Ba, Nb, Ta, P, Eu and Ti. They are also characterized by negative whole rock ε Nd (t) and zircon ε Hf (t) values with Paleoproterozoic t 2DM ages, suggesting that they were derived primarily from the remelting of ancient crustal materials. Daguding volcanic rocks are strongly peraluminous and show a higher Mg# than pure crustal melts, implying that they were likely derived from Paleoproterozoic metasedimentary basement materials. However, Ehuling volcanic rocks are weakly peraluminous and have a pronounced A 2 -type geochemical signature. Detailed elemental and isotopic data suggest that they were formed by the partial melting of the Paleoproterozoic metamorphic basement (including metasedimentary and metaigneous rocks) at a high temperature (~ 840 °C), followed by fractional crystallization. These results imply that during the Late Jurassic, South China on the Gan-Hang Belt was a continental arc coupled with the subduction of the Paleo-Pacific plate. Since the beginning of the Early Cretaceous, an intra-arc rift has formed along the Gan-Hang Belt as a consequence of slab rollback. These results also indicate that the extension in the Gan-Hang Belt began later than the southwestern part of the Shi-Hang Zone and lasted from 139 Ma to 122 Ma. [ABSTRACT FROM AUTHOR]

In situ zircon U–Pb ages and Hf isotope data, major and trace elements and Sr–Nd–Pb isotopic compositions are reported for coeval syenite–granodiorites–dacite association in South China. The shoshonitic syenites are characterized by high K 2 O contents (5.9–6.1 wt.%) and K 2 O/Na 2 O ratios (1.1–1.2), negative Eu anomalies (Eu/Eu* = 0.65 to 0.77), enrichments of Rb, K, Nb, Ta, Zr and Hf, but depletion of Sr, P and Ti. The adakitic granodiorite and granodiorite porphyry intrusions are characterized by high Al 2 O 3 contents (15.0–16.8 wt.%), enrichment in light rare earth elements (LREEs), strongly fractionated LREEs (light rare earth elements) to HREEs (heavy rare earth elements), high Sr (438–629 ppm), Sr/Y (29.2–53.6), and low Y (11.7–16.8 ppm) and HREE contents (e.g., Yb = 1.29–1.64 ppm). The calc-alkaline dacites are characterized by LREE enrichment, absence of negative Eu anomalies, and enrichment of LILEs such as Rb, Ba, Th, U and Pb, and depletion of HFSEs such as Nb, Ta, P and Ti. Geochemical and Sr–Nd–Hf isotopic compositions of the syenites suggest that the shoshonitic magmas were differentiated from parental shoshonitic melts by fractional crystallization of olivine, clinopyroxene and feldspar. The parent magmas may have originated from partial melting of the lithospheric mantle with small amount contribution from crustal materials. The adakitic granodiorite and granodiorite porphyry have Sr–Nd–Pb isotopic compositions that are comparable to that of the mafic lower crust. They have low Mg# and MgO, Ni and Cr contents, abundant inherited zircons, low ε Nd (t) and ε Hf (t) values as well as old whole-rock Nd and zircon Hf model ages. These granodiorites were likely generated by partial melting of Triassic underplated mafic lower crust. The Hf isotopic compositions of the dacites are relatively more depleted than the Cathaysia enriched mantle, suggesting those magmas were derived from the partial melting of subduction-modified mantle sources. The coeval shoshonitic, high-K calc-alkaline and calc-alkaline rocks in Middle to Late Jurassic appear to be associated with an Andean-type subduction. This subduction could have resulted in the upwelling of the asthenosphere beneath the Cathaysia Block, which induced partial melting of the mantle as well as the mafic lower crust, and formed an arc regime in the coastal South China during Middle to Late Jurassic. [ABSTRACT FROM AUTHOR]

Uranium-lead (U–Pb) dating was conducted on zircons in tuff layers and sandstone samples from the uppermost Liantuo Formation and in a tillite sample from the lowermost Nantuo Formation in Three Gorges area, South China, using SHRIMP and LA-ICP-MS techniques. Zircons from these samples yielded age spectrum (within 1000 Ma) of ∼890, ∼830, ∼780, ∼730, and 646 Ma. Zircons from the Liantuo tuffs have a weighted mean 206 Pb/ 238 U age of 734.1 ± 8.1 Ma (2σ, n = 7, MSWD = 0.48), which was regarded as the best estimation of the upper boundary age of the Liantuo Formation. Combining with previous geochronologic data, the Liantuo Formation was proposed to be a pre-Chang′an glaciation unit, and it is comparable to the middle-upper Banxi/Danzhou Group in South China. [ABSTRACT FROM AUTHOR]

The Early Paleozoic Orogen in South China has been a topic of hot debate; in particular with regard to the relative contributions of crustal and mantle sources to the generation of granites. To address this issue, we report geochronological and geochemical data for three related suites of granites (Tuantian, Suite 1, Nanlao, Suite 2, and Laochengpo, Suite 3) from the Laojunshan district in the southeast Yunnan Province, western South China Block (SCB). LA-ICP-MS U-Pb dating of zircons indicates magmatic crystallization ages of ~ 436Ma, ~ 430Ma and ~ 427 Ma for Suites 1, 2, and 3 granites, respectively. The ε Hf(t) values of magmatic zircons in all three suites are heterogeneous, ranging between + 3 and − 14. All three suites also contain inherited zircon cores with Proterozoic U-Pb and Hf model ages. Bulk compositions form well-defined mixing arrays, with Suites 1 and 2 being strongly peraluminous (A/CNK > 1.1), whereas Suite 3 is weakly peraluminous (A/CNK = 1.0–1.1). Suites 1 and 2 have lower TFe 2 O 3 , Al 2 O 3 , MnO, MgO, CaO, TiO 2 , Na 2 O, Mg # and Nb/Ta but higher K 2 O, Rb/Sr, Rb/Ba and ε Nd (t) than those of Suite 3. These results suggest that Suite 1 and Suite 2 were formed by partial melting of Proterozoic metasedimentary rocks with little or no input of mantle-derived materials, but Suite 3 was derived from a mixture of a crustal melt with mantle derived mafic magma. The apparent paradox that the mantle-derived component has lower ε Nd (t) values than the crustal components is consistent with the very low ε Nd (t) values found in mantle-derived basalts in the SCB. The Wuyi-Yunkai orogenic collapse may have caused lower crustal melting of the Cathaysia Block. The early Paleozoic granitoid magmatism with mafic magma input indicates an extensional environment in the western SCB, in response to post-collisional orogenic collapse. Asthenospheric upwelling and basaltic underplating probably contributed heat and melts triggering felsic magmatism in the western SCB. [ABSTRACT FROM AUTHOR]

Abstract: Mesozoic lamprophyres are widely present in gold province in the Jiaodong Peninsula. In this study, we analyzed major and trace elements and Sr–Nd–Pb isotopic compositions of lamprophyres from the Linglong and Penglai Au-ore districts in the Jiaodong Peninsula, in an attempt to better understand Mesozoic lithospheric evolution beneath the eastern North China Craton. These lamprophyre dikes are calc-alkaline in nature, and are characterized by low concentrations of SiO2, TiO2 and total Fe2O3, high concentrations of MgO, Mg# and compatible element, enriched in LREE and LILE but variably depleted in HFSE. They display initial 87Sr/86Sr ratios of 0.709134–0.710314, εNd(t) values of −13.2 to −18.3, 206Pb/204Pb of 17.364–17.645, 207Pb/204Pb of 15.513–15.571 and 208Pb/204Pb of 37.995–38.374. Interpretation of elemental and isotopic data suggests that the Linglong and Penglai lamprophyres were derived from partial melting of a phlogopite- and/or amphibole-bearing lherzolite in the spinel–garnet transition zone. The parental magma might have experienced fractionation of olivine and clinopyroxene, and minor crustal materials were incorporated during ascent of these mafic magmas. Before ~120Ma of emplacement of these calc-alkaline lamprophyres, the ancient lithospheric mantle was variably metasomatized by hydrous fluids rather than melts from subducted/foundered continental crust. It is proposed that continuous modification by slab-derived hydrous fluids from the Paleo-Pacific plate converted the old cratonic lithospheric mantle to Mesozoic enriched lithospheric mantle. Geodynamic force for generation of these lamprophyres may be related to large scale lithospheric thinning coupled with upwelling of the asthenosphere beneath the North China Craton. Continental arc-rifting related to the Paleo-Pacific plate subduction is favored as a geodynamic force for the cratonic lithosphere detachment. [Copyright &y& Elsevier]

Abstract: Direct radiometric dating of the Lower/Middle Permian epochs has not been well accomplished. Shales and bedded cherts of the geologically well-documented Middle Permian Gufeng Formation are exposed in the Chaohu area, Anhui province, South China. Through detailed field examination and mapping of the Gufeng stratigraphic section, we found at least four volcanic ash beds within the basal shale strata. This new discovery indicates the existence of prominent volcanic activity during Gufeng sedimentation and provides the opportunity to precisely date the age of the Middle Permian. Zircon grains separated from two near-basal horizon yield LA‐ICP‐MS U–Pb ages of 272.0±5.5Ma (MSWD=2.6) and 271.5±3.3Ma (MSWD=1.7). As the first precise isotopic age (272Ma) of the Middle Permian Gufeng Formation in South China, our data offer precise geochronological constraints for the division and correlation of Middle Permian not only in South China but also worldwide. [Copyright &y& Elsevier]

Abstract: The Shi-Hang zone is an important NE trending Mesozoic magmatic belt composed of granites with relative high εNd(t) values and young TDM model ages in South China. However, the petrogenesis and the tectonic environment for the Shi-Hang zone magmatic rocks remain controversial. We report here mineral chemistry, geochemical and Sr–Nd–Hf isotopic data for the Cailing and Furong granites and mafic microgranular enclaves (MMEs) from the Qitianling granite batholith in southern Hunan province, South China. The Qitianling granite batholith is a multi-staged composite pluton with three phases (Cailing, Furong, and Huangtangling) according to their ages and petrography. The Cailing (163–160Ma) and Furong (157–153Ma) phases are mainly composed of porphyritic amphibole–biotite monzogranite, and they share similar geochemical and isotopic characteristics. Both of them show similar SiO2 contents from 66.50 to 70.28%, and metaluminous A/CNK values of 0.80 to 0.98. The granites are characterized by high contents of large ion lithosphile elements (LILE) such as Rb, Th, U, Pb; high field strength elements (HFSE) such as Nb, Ta, Zr, Hf; and Zr+Nb+Ce+Y contents >350ppm, and high 10,000∗Ga/Al ratios >2.6. Chondrite-normalized REE patterns show relative enrichment of light rare earth elements (LREEs) and significant negative Eu anomalies. Mineralogical and geochemical features suggest that the Cailing and Furong granites are A-type, which can be further classified as A2 subtype. They have relatively lower (87Sr/86Sr)i ratios (0.7091–0.7132), higher εNd(t) values (−5.5 to −7.6) and younger Nd isotopic model ages (1.48–1.56Ga) than those common S-type granites in South China. Zircon εHf(t) values vary from −8.1 to −3.7. The MMEs in the Cailing phase show similar trace element and Sr–Nd isotopic characteristics with the host granites. But zircons from the MMEs show different εHf(t) values (−6.4–+2.6) with those from the host granites (−8.1 to −3.7). This indicates that the MMEs and host granites were crystallized from different sources of magmas, providing direct evidence for mafic–felsic magma mixing processes. The isotope data indicate that the Cailing and Furong granites from the Qitianling batholith were derived from a hybrid magma consisting of about 80% felsic magma derived from old crust and about 20% mantle-derived mafic magma. The strong magma mixing at about 160–155Ma caused by intra-arc rifting or back arc extension related to subduction of the Paleo-Pacific plate, is favored to explain the petrogenesis of the Cailing and Furong granites, as well as the Shi-Hang zone. [Copyright &y& Elsevier]

Abstract: The Middle–Lower Yangtze River metallogenic belt (MLYRMB), extending from Daye in Hubei Province in the west to Zhenjiang in Jiangsu Province in the east, hosts a number of large polymetallic (Cu–Au–Mo, Fe, Zn, Pb, and Ag) deposits and constitutes one of the most important metallogenic belts in China. The Cu–Au–Mo deposits in the Jiurui district are an important component of the MLYRMB. In this study we carried out precise and detailed zircon U–Pb dating for all types of magmatic rocks from the Wushan ore deposit in the Jiurui district. Three samples of Cu–Au–Mo-related porphyries from different ore belts at Wushan were analyzed and yielded zircon U–Pb ages of 148.0±1.0Ma, 145.4±0.9Ma and 147.3±0.9Ma, respectively. A series of dykes were emplaced immediately following the Cu–Au–Mo-related porphyries at Wushan. A dark-colored basic dyke which intruded into the granodiorite porphyry at Wujia gold deposit near Wushan was dated at 144.5±1.2Ma. Two lamprophyre dykes taken from the north ore belt at Wushan underground mining stops were dated at 143.6±0.9Ma and 144.3±0.9Ma, respectively. A late-stage dyke which was also taken from the Wushan north ore belt yielded an age of 142.6±1.0Ma and might represent the end of magmatism in the Wushan ore deposit. These new geochronological data demonstrate that the time range of magmatism in the Wushan ore deposit is approximately between 148Ma and 143Ma, showing that the magmatic activity at Wushan was rapid and intensive. The ages of Cu–Au–Mo-related porphyries from other areas in the Jiurui district, such as the Dongleiwan, Yangjishan and Chengmenba ore deposits, were also measured and yielded zircon U–Pb ages of 141.5±1.7Ma, 143.4±1.4Ma and 146.6±1.0Ma, respectively. Combined with those previously reported zircon U–Pb age results from the Jiurui district, the present age data set demonstrates that extensive magmatism in the Jiurui district was coeval and intensive, marked by a magmatic activity in the age range of 148 to 138Ma and peaked between 148Ma and 142Ma. According to the statistics of all those precise zircon U–Pb ages, the Cu–Au–Mo-related porphyries in the Edong and Tongling districts in the MLYRMB show similar ages, and they have a slightly younger peak age and a longer duration than that of the Jiurui district. The geographic shape of the MLYRMB in the Cretaceous shows an arcuate structure, the Jiurui district is located at the transitional point of the arcuate structure and the Edong and Tongling districts are situated on both sides of the arcuate structure. Considering that the Jiurui district has a slightly older peak age and a shorter duration of magmatic activity than that in the Edong and Tongling districts, it seems that the arcuate structure of the MLYRMB played an important role in the formation of these Cu–Au–Mo-related porphyries. Consequently, we suggest that the genesis of the Late Mesozoic magmatic rocks along the MLYRMB may have been due to a tectonic activity developed from southeast to northwest, which probably has a close relationship with the subduction of the paleo-Pacific plate beneath the Eurasian plate in Mesozoic times. [Copyright &y& Elsevier]

Abstract: Black shales occur widely in the Lower Cambrian and Neoproterozoic strata on the Yangtze Platform, South China. In this study, Lower Cambrian black shales from Xiuning section and Late Neoproterozoic black shales from Weng’an section were studied and Pb isotopic compositions were analyzed following a stepwise acid-leaching technique. The 206Pb/204Pb ratios in both sections show large variations, from 18.906 to 43.737 in the Weng’an section and from 24.811 to 38.110 in the Xiuning section. In contrast, the ranges for 207Pb/204Pb and 208Pb/204Pb values in both sections are relatively smaller from 15.649 to 17.126 and 37.744–38.199 in the Weng’an section, and from 16.034 to 16.783 and 38.602–39.391 in the Xiuning section, respectively. These data yielded two Pb isotope isochron ages of 536±39 and 572±36Ma, respectively. These ages well accord with other published data and we suggest that they represent the depositional ages for the Lower Cambrian Hetang Formation and the upper Neoproterozoic Doushantuo Formation in South China. [Copyright &y& Elsevier]