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Abundant mafic-felsic intrusions distributed in the Altyn Orogen record orogenic histories related to Proto-Tethys and Paleo-Tethys evolution. Zircon U-Pb dating of the intrusive rocks in the eastern Altyn Orogen identifies at least three major tectono-magmatic episodes, yielding ages of ∼426, ∼376–373 and ∼269–254 Ma. The first two emplacement episodes correspond to the post-collisional magmatism in the Altyn Orogen. The ∼426 Ma granitoids possess adakitic characteristics coupled with enriched isotopes, suggesting that they originated from partial melting of thickened lower continental crust induced by upwelling asthenospheric mantle after slab break-off of the South Altyn Ocean Plate. Next, the ∼376–373 Ma mafic-intermediate rocks and coeval granitoids represent a large thermal event that involved mantle melting with induced new juvenile lower continental crust melting in a post-collisional extensional setting. Finally, the ∼254 Ma diabase dykes intruded into the ∼269 Ma granitoids, which were related to the widespread Late Paleozoic magmatism resulting from Paleo-Tethys Ocean subduction. Post-collisional magmatism in the Altyn Orogen significantly enhances understanding of the tectono-magmatic evolution in the northern Tibetan Plateau. The penetrative influence of Paleo-Tethys Ocean subduction was more extensive than previously thought. [ABSTRACT FROM AUTHOR]

The formation of rodingites has been a continually controversial topic, largely due to the absence of minerals that can be unambiguously dated. Here, we present a case study that utilized LA‐ICPMS garnet U–Pb dating, in conjunction with field investigations, petrology and Raman spectroscopy, to reveal the age and petrogenesis of rodingite in the northern North China Craton. The rodingites are spatially associated with mafic and alkaline rocks. Our findings indicate that rodingitization occurred at ca. 388 Ma, making it about 5–10 Myr younger than its mafic protoliths, but contemporaneous with the adjoining alkaline plutons. These observations suggest that the rodingitization may be attributed to hydrothermal fluids from the alkaline magmas. Our study emphasizes the importance of utilizing garnet U–Pb dating to determine the timing of rodingitization and introduces a novel perspective on the relationship between rodingitization and alkaline magmas in extensional continental settings. [ABSTRACT FROM AUTHOR]

The Fang'an gold deposit in the Wuhe area, Anhui Province, is located in the area adjacent to the Bengbu Uplift and Wuhe Platform Depression in the southeastern part of North China. This study aimed to determine the deposit's mineralization age and the source of its metallogenic materials and mineralization processes through investigations into its geological characteristics, Rb–Sr isotopes, and S–Pb isotopes. The orebodies of the Fang'an gold deposit in the Neoarchean Xigudui Formation primarily exhibit a vein-type structure. The ore-forming process can be divided into four stages: (i) the quartz stage (Py1); (ii) the quartz–pyrite stage (Py2); (iii) the polymetallic sulfide stage (Py3); and (iv) the carbonate stage. Of these, the main mineralization stage is also the main period in which gold mineralization occurs. In situ sulfur isotope results of pyrite (Py1 to Py3) in the first three mineralization stages, suggesting a contribution of sulfur from crust–mantle magmatic fluids. The δ34S values for Py2 (average 5.51‰) are higher than Py1 (average 4.45‰) and showed that the magmatic fluids mixed with meteoric waters. The δ34S values for Py3 (average 5.18‰) are lower than Py2 (average 5.51‰), revealing that it related fluid immiscibility. The lead isotopic compositions of sulfides within the ores possessed 206Pb/204Pb ratios ranging from 16.759 to 16.93, 207Pb/204Pb ratios ranging from 15.311 to 15.402, and 208Pb/204Pb ratios ranging from 37.158 to 37.548. These lead data were plotted close to the Xigudui Formation, relatively distant from the Mesozoic granites, indicating that the Xigudui Formation was the source of lead for the Late Mesozoic ores of the deposit. Taken together, due to the degassing of mantle-derived magma in the shallow parts of the crust, it can be determined that the sources of ore-forming sulfur and lead were crust–mantle magmatic activities in the Wuhe area. Rb–Sr dating of pyrite from Fang'an gold deposit reveals that the mineralization occurred at 126.89 ± 0.58 Ma. Considering the previous research into the dating of magmatic rocks in the Wuhe area, we propose that the genesis of the Fang'an gold deposit is closely associated with magmatic activities in the area at around 130 Ma. [ABSTRACT FROM AUTHOR]

Direct dating of vertebrate fossils is difficult due to complex postburial diagenetic processes and the often low and heterogeneous concentration of radioisotopes (e.g., U) in fossilized bone material. Here, we demonstrate a novel approach to dating vertebrate fossils via laser ablation–inductively coupled plasma–mass spectrometry U-Pb dating of early diagenetic calcite cements precipitated within bone cavities of a Jurassic sauropod from the Sichuan Basin, South China. Early diagenetic calcite yielded a U-Pb age of 165.3 ± 3.6/5.6 Ma, in agreement with a maximum depositional age of 165.8 ± 1.0 Ma from detrital zircon ages of the surrounding rocks, suggesting that diagenesis occurred shortly after the death of the sauropod. This new age demonstrates that the best-known Jurassic large sauropod faunas in South China are much older than those in North America and Africa, suggesting the geographical isolation of South China. Authigenic apatite U-Pb dating on the fibrolamellar bones from the same sauropod gave a distinctly younger age, indicating more complex U-Pb system behavior, possibly due to U uptake by residual organic matter and recrystallization of apatite after early diagenesis. Our findings demonstrate that U-Pb dating of calcite cements within bone cavities has significant potential for constraining the burial age of vertebrate fossils, which could aid in constructing a more robust temporal framework for the radiation and evolution of vertebrates. [ABSTRACT FROM AUTHOR]

The Longshou Shan, located in western China, plays a crucial role in connecting the Tarim Continent with the North China Craton. It provides valuable insights into the Cenozoic intracontinental deformation, the complex dynamics of Eurasian tectonics, and the relationship between the pre-Cenozoic Tethys and Central Asian orogenic systems. Consequently, comprehending the evolution of the Phanerozoic era in this region holds immense significance. Zircon (U-Th)/He (ZHe) dating was conducted on three granite samples (n = 18) collected from the Longshou Shan. The ZHe dates of these granite rocks range from 7.2 to 517.7 Ma, showing a negative correlation with eU values. Furthermore, a limestone sample from the Longshou Shan yielded ZHe (n = 4) ages of 172.0–277.1 Ma and AHe (n = 4) ages of 17–111.9 Ma. The area has undergone complex tectonic processes involving multiple phases of uplift and burial. Using both forward and inverse modeling methods, we aim to establish plausible thermal histories. Our models reveal: (1) Late Paleozoic unroofing; (2) Early Mesozoic cooling and Late Mesozoic regional stabilization; and (3) Cenozoic reheating and subsequent cooling. By investigating the intricate thermal history of the Longshou Shan through multi-method modeling, we compare different approaches and assess the capabilities of single ZHe dating for understanding a thermal history. This research contributes to unraveling the region's geological complexities and aids in evaluating various modeling methods. [ABSTRACT FROM AUTHOR]

There has been no consensus yet regarding the precise initial timing and duration of the late Mesozoic extensional tectonics in the South‐eastern China Block. This work focusses on the growth strata of the Early Cretaceous red beds in the South‐eastern China Block to determine the late Mesozoic tectonics and the precise timing of the initiation and duration of extensional tectonics in this area. Field observation of several terrigenous basins shows that the dip angles of the Cretaceous red beds have varied from moderate to gentle from basin edges to interiors (or centres). The visible and estimated thickness within a single bed increases slightly downwards from the upper to the lower part. These characteristics indicate that the sedimentary area of these beds has undergone an extensional process with expansion and deepening of the sedimentary basins. Rotation of the border surfaces (limbs) and downward warping of the hanging walls or retreat of the footwalls of listric normal faults causes three types of extensional growth (or syntectonic) strata in the deposits of different basins. Dating of the volcanic rocks related to the growth beds reveals that the sedimentary basins were enlarged and deepened when the Early Cretaceous strata were deposited in the South‐eastern China Block from ca 140 to 137 Ma. Regionally, under the influence of Palaeo‐Pacific plate rollback since ca 140 Ma, the South‐eastern China Block stress field has led to lithospheric uplift and pull‐apart structures near the surface, causing the half‐graben basins to receive sedimentation. Although the extensional event was interrupted by a short compressional event during 120 to 105 Ma, with the oceanward retreat of the trench, the area of extension gradually enlarged and rejuvenated south‐eastwards until the end of the Cretaceous. This Cretaceous extension event of the South‐eastern China Block must belong to a worldwide geological event with global significance. [ABSTRACT FROM AUTHOR]

The Qinling Mountain Range (QMR), where more than 500 hominin fossils and Paleolithic sites have been preserved, was a major center of hominin evolution and settlement and an important link for the hominin migration and dispersal between the north and the south during the Pleistocene in China. The rich culture remains and the related data make it possible and meaningful to study the characteristics and mechanisms of hominin occupation and dispersal in the region. This paper has summarized and analyzed the geographical distributions and chronologies of 55 dated hominin fossils and Paleolithic sites in the QMR to date. By combining them with the evidence from the loess–paleosol sequence, a relatively continuous and chronological sequence of hominin occupation and dispersal has been established, in which we have identified five stages, viz. ~before 1.2 Ma, the sporadic occurrence stage of early hominin occupation; ~1.2–0.7 Ma, the initial expansion stage; ~0.7–0.3 Ma, the stability and maintenance stage; ~0.3–0.05 Ma, the large-scale expansion stage; ~0.05–0.01 Ma, the sharp decline stage of the record of hominin occupation. We conclude that the environmental and ecosystem changes associated with the MPT drove early hominins to disperse southwards across the QMR. In addition, the evidence suggests that the hominin occupation and dispersal here was broadly continuous during both glacial and interglacial scales from early to late Pleistocene, and that the southern QMR provided a glacial refuge. [ABSTRACT FROM AUTHOR]

The process of slab tearing profoundly affects interchanges of material and energy between the lithosphere and asthenosphere and has been invoked as a trigger of magmatism in modern and ancient subduction‐collision systems. Horizontal slab tears may occur after continental collision and subsequent slab break‐off, whereas vertical slab tears may occur in response to along‐strike variations in rollback velocity, thereby ripping the subducting lithosphere. Previous studies have documented tearing of subducting slabs in modern convergent settings using geophysical methods, but in ancient collisional belts, where these methods cannot be applied, detection of slab tearing is more difficult, particularly if the oceanic plate was fully subducted and the geological evidence for subduction is limited. Here, we employ multiproxy element‐isotope imaging, as well as zircon petrochronology and whole‐rock geochemistry, to assess evidence of vertical tearing of the Mianlue slab in the Triassic Qinling Orogen in central China. Our results show evidence of anomalous, inferred tear‐related magmatism east of 107°E, at 225–210 Ma. Vertical tearing of the northward subducting Mianlue slab is recorded by geochemically anomalous igneous rocks, and the recognition of N–S to NE–SW trending boundaries defined by Sr‐Nd‐Hf isotopes, elemental ratios (Nb/Ta, and Ca/Al), Mg#, and reduced crustal thickness between 107° and 108°E. The inferred vertical tear may have been driven by slab rollback of the Mianlue slab at 225–210 Ma. The results show that multiproxy element‐isotope imaging (e.g., of εNd(t), εHf(t), (87Sr/86Sr)i, Nb/Ta, Mg#, and Ca/Al) can be used to reconstruct the evolution of fossil subduction systems. Plain Language Summary: Subduction zones are natural factories for the circulation of material in the Earth as they allow tectonic plates to descend into the mantle. Pieces of subducting plates, normally referred to as slabs, can be torn and segmented, but reconstructing the geometry of such tears in ancient convergent plate boundary settings is difficult. Based on the observation that slab tearing can trigger anomalous magmatism in convergent plate margins, we present a multiproxy geochemical and isotopic imaging method that enables us to understand the process of slab tearing in the Qinling Orogen (China) during the Triassic. We found that igneous rocks from the Qinling Orogen, east of 107°E, are geochemically anomalous (relative to typical arc rocks). These rocks are dated 225–210 Ma. By imaging various geochemical characteristics, our results demonstrate that the subducting Mianlue slab was likely torn at longitude 107°–108°E, thereby producing geochemically and isotopically anomalous mafic and felsic magmatism. Key Points: The geometry of slab tearing in an ancient orogen is constrained by a multiproxy geochemical approachAnomalous arc magmatism dated at 225–210 Ma is identified in the Qinling Orogen east of 107°EThe Mianlue slab underwent southward vertical slab tearing at 107°−108°E in the Late Triassic [ABSTRACT FROM AUTHOR]

Granitoids, an important part of the continental crust, are the direct and indelible evidence of the accretion and reworking process of the continental crust in different tectonic settings. Therefore, these early geodynamic mechanisms can be roughly reconstructed by analysing the geochemical characteristics of granitoids. In this study, the Permian–Triassic Granitoids widely distributed in the East Kunlun Orogenic Belt (EKOB) are studied to determine their chronology and petrogenesis to restrict their source regions and establish the significance of their geodynamic and crustal growth. Zircon inductively coupled plasma mass spectrometry (ICP–MS) dating results show that the crystallization ages of these granitoids are between 252–240 Ma, during the early and middle Triassic. These granitoids have high SiO2 and medium Na2O + K2O contents, plotting into the granite region, and calc-alkaline to high-K calc-alkaline series on the SiO2–Na2O + K2O and SiO2–K2O diagrams, respectively. All the samples have aluminium saturation index (A/CNK) values from 1.00 to 1.25 showing peraluminous characteristics. In terms of trace and rare earth elements, the samples are depleted in high field strength elements (HFSEs) such as Nb, Ta, P, and Ti and are enriched in large ion lithophile elements (LILEs) such as Rb, K, Ba, and U. Moreover, all granitoids show right-inclined rare earth element (REE) distribution patterns with weak to moderate Eu anomalies (δEu = 0.50–0.93). In addition, the samples have low P2O5 contents, 10,000*Ga/Al ratios (1.65–2.39), and Zr + Nb + Ce + Y (212–262 ppm) displaying affinities to I-type granite. Combined with their εHf (t) values of −2.31 to 4.44, with 1.0–1.4 Ga two stage model ages (TDM2), they are considered to be the products of the reworking of the Mesoproterozoic lower crust; therefore, they are not related to the continental net growth in the EKOB. On the tectonic discrimination diagrams of granitoids, all the samples fall into the area of volcanic arc granite (VAG) and continental margin arc; this suggests that the Paleo-Tethys Ocean slab was still in the subduction stage during 252–240 Ma, and the continental collision had not yet started. Based on the plenty of magmatic rock dating results published previously, it appears there are two magmatic peak periods (260–240 Ma and 230–210 Ma) and one magmatic intermittence period (240–230 Ma) during the late Permian to Triassic of the EKOB, corresponding to three geodynamic evolution stages of subduction, post-collision extension, and syn-collision, respectively. [ABSTRACT FROM AUTHOR]

Metamorphic rocks from the Diancang Shan (DCS) complex along the Ailao Shan-Red River belt between the South China plate and Simao-Indochina block are studied in this contribution to constrain the Proto- to Palaeo-Tethys tectonic evolution of the eastern Tethys domain. LA-ICP-MS zircon U-Pb geochronological dating is conducted in this study on the metasedimentary rocks (garnet-biotite-plagioclase gneisses, biotite-quartz schists and phyllonites) from different stratigraphical horizons (Proterozoic and Triassic) of the DCS complex. The analyses yielded three major age peaks at ca. 248 Ma, ca. 441 Ma, ca. 1000–900 Ma and one subordinate age peak at ca. 828 Ma. The youngest ages for the samples help to constrain the maximum ages of deposition of the complex at Early Carboniferous and Late Triassic, respectively. The existence of the diagnostic age peak at ca. 440 Ma and the euhedral-subhedral morphology of the detrital zircons in the Palaeozoic and Mesozoic strata may indicate that there were early Palaeozoic magmatic activities along the eastern margin of the Simao-Indochina block. At the meantime, the age peak at ca. 440 Ma was never reported in the early Palaeozoic strata from the western margin of the South China plate, which supports the existence of an early Palaeozoic rift zone, i.e., the Proto-Tethys Jinsha Jiang-Ailao Shan-Song Ma rift zone, being consistent with geochemical discriminations. Furthermore, we conclude, from the significant difference between detrital zircon age data of Silurian to Devonian sedimentary rocks from the Simao-Indochina block and South China plate, the opening of the Palaeo-Tethys ocean since Early Carboniferous, the absence of evidence for the Palaeozoic orogeny, and the successive sedimentation from the Cambrian to Triassic along the western margin of the South China plate, that the Proto-Tethys rifting and subsequent Palaeo-Tethys ocean evolution along the Jinsha Jiang-Ailao Shan-Song Ma zone formed actually a complete 'Wilson Cycle' from early Palaeozoic to the Late Triassic. [ABSTRACT FROM AUTHOR]

Cave hyenas (genus Crocuta) are extinct bone-cracking carnivores from the family Hyaenidae and are generally split into two taxa that correspond to a European/Eurasian and an (East) Asian lineage. They are close relatives of the extant African spotted hyenas, the only extant member of the genus Crocuta. Cave hyenas inhabited a wide range across Eurasia during the Pleistocene, but became extinct at the end of the Late Pleistocene. Using genetic and genomic datasets, previous studies have proposed different scenarios about the evolutionary history of Crocuta. However, causes of the extinction of cave hyenas are widely speculative and samples from China are severely understudied. In this study, we assembled near-complete mitochondrial genomes from two cave hyenas from northeastern China dating to 20 240 and 20 253 calBP, representing the youngest directly dated fossils of Crocuta in Asia. Phylogenetic analyses suggest a monophyletic clade of these two samples within a deeply diverging mitochondrial haplogroup of Crocuta. Bayesian analyses suggest that the split of this Asian cave hyena mitochondrial lineage from their European and African relatives occurred approximately 1.85 Ma (95% CI 1.62–2.09 Ma), which is broadly concordant with the earliest Eurasian Crocuta fossil dating to approximately 2 Ma. Comparisons of mean genetic distance indicate that cave hyenas harboured higher genetic diversity than extant spotted hyenas, brown hyenas and aardwolves, but this is probably at least partially due to the fact that their mitochondrial lineages do not represent a monophyletic group, although this is also true for extant spotted hyenas. Moreover, the joint female effective population size of Crocuta (both cave hyenas and extant spotted hyenas) has sustained two declines during the Late Pleistocene. Combining this mitochondrial phylogeny, previous nuclear findings and fossil records, we discuss the possible relationship of fossil Crocuta in China and the extinction of cave hyenas. [ABSTRACT FROM AUTHOR]

The Lushan Massif has been considered an extensional dome which represents a typical extensional structure in South China. However, the composition and structure of the Lushan Massif are still unclear. In this study, we identified the eastern detachment fault (EDF) for the first time. In addition, many sinistral strike-slip structures have also been recognized in the Lushan area, such as the Xingzi shear zone (XZSZ) and Lianhua shear zone (LHSZ). Detailed field observation and structural analysis revealed that the former sinistral faults are tectonic boundaries of the later Lushan extensional dome (LSED). The tectonic evolution sequence was established after the structural analysis combined with zircon U-Pb dating and mica 40Ar-39Ar dating of metamorphic rocks, veins, and intrusive rocks from the strike-slip fault and detachment fault. The Lushan Massif has undergone sinistral ductile shearing within 162–150 Ma. The LSED was then formed in an extensional tectonic setting from 140 to 114 Ma. Together with the regional geological setting, we believe that the sinistral strike-slip structures, represented by the XZSZ and LHSZ, are coeval with the Tanlu fault system and could be controlled by a transpressional stress field resulting from the subduction of the Pacific Plate. The LSED was formed in a back-arc extension setting resulting from the rollback of a subducted slab. The tectonic transition from compression to extension in the South China Block took place at 150–140 Ma. [ABSTRACT FROM AUTHOR]

The Guide Basin, located in the West Qinling orogen of central China, is a typical geothermal field. However, the granodiorites occurring in the Zhacanggou area have been poorly restricted. Herein, we report new isotopic compositions of whole‐rock major‐trace elements, zircon U–Pb, and Lu–Hf, on the host granodiorites and their microgranular enclaves (MEs) in the Zhacanggou area. Zircon U–Pb dating for the host rocks (porphyritic granodiorite and granodiorite) revealed ages of 230.5 ± 1.4 Ma and 229.0 ± 1.6 Ma, similar to those (230.5 ± 1.5 Ma and 231.4 ± 1.4 Ma) of the MEs. Zircon Hf isotope analyses for the granodiorite and MEs yielded εHf(t) values from −11.0 to −1.5 and from −7.8 to −0.7, with corresponding TDM2 ages of 1,355–1,959 and 1,304–1,755, respectively. The MEs possess plagioclase phenocrysts, acicular apatites, and chilled borders. They were characterized by relatively low SiO2 (58.39–65.24 wt%) and high Cr, Ni, and MgO contents, leading to relatively high Mg# values (44–59) and low Sr/Y (14.23–19.84) ratios. The host granodioritic rocks show similar adakitic geochemical characteristics with SiO2 = 64.23–68.57 wt%, MgO = 1.29–2.22 wt%, Mg# = 48–53, Sr = 340–596 ppm, Y = 11.3–13.7 ppm, Sr/Y = 28.39–47.89, and no obvious Eu anomalies. These geochemical and isotopic data, combined with the mineralogical features, indicate that the granodiorites in the Zhacanggou area were produced by the mixing of high‐Mg# melts originating from an enriched lithospheric mantle source, and felsic magmas deriving by the partial melting of the normal lower continental crust with the tectonic regime transition from a syn‐collision to a post‐collision setting. [ABSTRACT FROM AUTHOR]

Rock art is found in many different regions of the world, with ages dated from late Palaeolithic period to the present. However, determining the precise ages for such artworks with direct chronological methods is challenging. U-series dating of secondary carbonates can constrain the age of rock art if these carbonates stratigraphically connected to the art. Hitherto, U-series isotope-dilution analyses with multi-collector inductively-coupled plasma mass spectrometry (ID-MC-ICPMS) has been increasingly used for rock art dating. This approach can achieve U–Th isotope-ratio quantification at the per-mille or submille level, but requires chemical pretreatment using isotope spikes and results in a relatively low sampling resolution. While in situ U-series dating using laser ablation-MC-ICPMS (LA-MC-ICPMS) is significantly less precise than ID-MC-ICPMS analysis, it allows to collect spatially resolved data sequences on very thin samples (<1 mm). This is important for identification of open systems and the chronological integrity of the analyses. Therefore, we developed a new method for high spatial resolution U-series in situ analysis. A piece of homogeneous stalagmite was selected as an in-house standard (RM-C1) for U-series in situ dating analysis. RM-C1 contains high U (17.3 ± 1.0 μg/g) and low Th concentrations (<5 ng/g). The 234U/238U and 230Th/238U activity ratios of 1.0116 ± 0.0006 and 0.9525 ± 0.0013, respectively, corresponding to a U-series age of 303.5 ± 1.5 ka, were determined by the ID-MC-ICPMS analyses (n = 10). Using the RM-C1 standard, we were able to date the Dansgaard–Oeschger (D/O) 19 event (with an expected age of 68.9 to 70.3 ka) in a stalagmite to a range from 68.0 ± 2.0 to 71.2 ± 2.5 ka, with an average age of 69.6 ± 1.5 ka (n = 15). This demonstrates the accuracy and reproducibility of our dating protocol. Subsequently, we conducted U-series in situ dating of secondary carbonates associated with rock paintings with two samples from the Cangyuan shelter (CY2-4 and CY2-7) and two samples from the Wanrendong Cave (SL3-A and SL5-A) in Yunnan Province, southwestern China. These samples had high U-concentration (>4 μg/g) and negligible environmental Th. The carbonate layers immediately overlying the pigments of CY2-4 and CY2-7 were dated to 3.7 ± 0.3 and 3.2 ± 0.2 ka, respectively, suggesting that the Canyuan rock paintings belongs to a late Neolithic culture of this area. The pigment layer sandwiched in the sample SL3-A was bracketed to between 8.7 ± 0.3 and 10.1 ± 0.3 ka and in SL5-A to between 10.4 ± 0.3 and 10.8 ± 0.4 ka, implying that the Wanrendong rock paintings probably were created by a hunting-gathering population during the early Holocene. [ABSTRACT FROM AUTHOR]

Summary: Lycopodiaceae are one of three surviving families of lycopsids, a lineage of vascular plants with a fossil history dating to at least the Early Devonian or perhaps the Late Silurian (c. 415 Ma). Many fossils have been linked to crown Lycopodiaceae, but the lack of well‐preserved material has hindered definitive recognition of this group in the paleobotanical record.New, exceptionally well‐preserved permineralized lycopsid fossils from the Early Cretaceous (125.6 ± 1.0 Ma) of Inner Mongolia, China, were examined in detail using acetate peel and micro‐computed tomography techniques. The anatomy of extant Lycopodiaceae was analyzed for comparison using fluorescence microscopy. Phylogenetic relationships of the new fossil to extant Lycopodiaceae were evaluated using parsimony and maximum likelihood analyses.Lycopodicaulis oellgaardii gen. et sp. nov. provides the earliest unequivocal and best‐documented evidence of crown Lycopodiaceae and Lycopodioideae, based on anatomically‐preserved fossil material.Recognition of Lycopodicaulis in Asia during the Early Cretaceous indicates the presence of crown Lycopodiaceae at this time, and striking similarities of stem anatomy with extant species provide a framework for the understanding of the interaction of branching and vascular anatomy in crown‐group lycopsids. [ABSTRACT FROM AUTHOR]

The Tianshui-Sunjiaxia area is located in the connection zone of West Qinling Orogen and North Qilian Orogen, which could provide great insights into the amalgamation processes between the northern and southern blocks of China. Three subduction- and rift-related rocks gneissic granite from North Qilian arc-interarc belt (NQAI) granite and metabasalt from North Qinling back-arc basin (NQBA) are distinguished across the connection zone. The gneissic granite was generated by melts from older crustal materials of Longshan Group with the addition of a relatively juvenile basaltic source from the lower crust during the collision process. The Liwanxincun metabasalt reflects the mixing of the partial melting of the shallow asthenospheric mantle and the metasomatized mantle in a back-arc extension setting. The LA-ICP-MS zircon U-Pb dating of gneissic granite (068, 069) yields crystallization ages of 457.0 ± 1.6 Ma and 445.9 ± 2.1 Ma. The study area is divided into six tectonic units in Early Paleozoic time involving NQAI (Yanjiadian-Xinjie) continental arc, interarc rift basin (Maojiamo-Xiwali), continental arc (Chenjiahe-Wangjiacha); NQBA back-arc rift basin (Huluhe-Hongtubao), island arc and ophiolitic melange belt (North Qinling-Shangdan). A tectonic model is proposed in which the NQAI continental arc (Yanjiadian-Xinjie) might represent the early period of subduction of North Qilian Ocean (NQO) and the interarc rift is the product of the extension triggered by southward subduction of NQO. The ongoing subduction of NQO then leads to the formation of Chenjiahe-Wangjiacha continental arc, as well as the Hongtubao back-arc spreading ridge in NQBA back-arc basin (Huluhe). The tectonic evolution of the connection zone is closely associated with the closure of the North Qilian Ocean and North Qinling-Shangdan Ocean in the context of the convergence process of micro-continental blocks, including North China block, Longshan group and North Qinling Terrane. [ABSTRACT FROM AUTHOR]

The northern Alxa orogenic belt, located in the middle segment of the Central Asian Orogenic Belt, is a junction between the North China Craton, Tarim Craton and Mongolian microcontinents. However, its Permo-Carboniferous tectono-palaeogeographic evolution has not been well established. In this study, new zircon U–Pb–Hf isotopic data for the Permo-Carboniferous clastic rocks were used to address the above issue. Based on our dating work and fossil assemblages, we confirmed that the Amushan, Maihanhada, Aqide and Haersuhai formations were formed in the late Carboniferous to early Permian, early to middle Permian, middle Permian and late Permian periods, respectively. The Amushan Formation sandstone in the Zhusileng area contains abundant Palaeozoic zircons (with age peaks at 440 Ma, 475 Ma and 539 Ma) and some Precambrian zircons. These zircon ages and the southeast transgressive direction suggest the provenance to be the local Zhusileng–Hangwula block and the nearby Yagan continental margin. The zircon age pattern with a high proportion of detrital zircons much older than the depositional time and no detrital zircons close to the depositional time suggest an extensional basin depositional setting. The clastic rocks of the Maihanhada, Aqide and Haersuhai formations inherited the source for the Amushan Formation, with a greatly increased input of Permo-Carboniferous volcanic rocks with post-collision or intraplate chemical affinity. Accordingly, a Permo-Carboniferous extensional stage was suggested. Finally, a tectono-palaeogeographic model was reconstructed for the northern Alxa orogenic belt, evolving from a late Carboniferous transgression with crustal extension to early to middle Permian rapid basin filling and a late Permian marine regression. [ABSTRACT FROM AUTHOR]

Cave hyenas (genus Crocuta) are extinct bone-cracking carnivores from the family Hyaenidae and are generally split into two taxa that correspond to a European/Eurasian and an (East) Asian lineage. They are close relatives of the extant African spotted hyenas, the only extant member of the genus Crocuta. Cave hyenas inhabited a wide range across Eurasia during the Pleistocene, but became extinct at the end of the Late Pleistocene. Using genetic and genomic datasets, previous studies have proposed different scenarios about the evolutionary history of Crocuta. However, causes of the extinction of cave hyenas are widely speculative and samples from China are severely understudied. In this study, we assembled near-complete mitochondrial genomes from two cave hyenas from northeastern China dating to 20 240 and 20 253 calBP, representing the youngest directly dated fossils of Crocuta in Asia. Phylogenetic analyses suggest a monophyletic clade of these two samples within a deeply diverging mitochondrial haplogroup of Crocuta. Bayesian analyses suggest that the split of this Asian cave hyena mitochondrial lineage from their European and African relatives occurred approximately 1.85 Ma (95% CI 1.62–2.09 Ma), which is broadly concordant with the earliest Eurasian Crocuta fossil dating to approximately 2 Ma. Comparisons of mean genetic distance indicate that cave hyenas harboured higher genetic diversity than extant spotted hyenas, brown hyenas and aardwolves, but this is probably at least partially due to the fact that their mitochondrial lineages do not represent a monophyletic group, although this is also true for extant spotted hyenas. Moreover, the joint female effective population size of Crocuta (both cave hyenas and extant spotted hyenas) has sustained two declines during the Late Pleistocene. Combining this mitochondrial phylogeny, previous nuclear findings and fossil records, we discuss the possible relationship of fossil Crocuta in China and the extinction of cave hyenas. [ABSTRACT FROM AUTHOR]

In contrast to the widespread occurrence of mafic arc magmatism during oceanic subduction, there is a general lack of such magmatism during continental subduction. This paradigm is challenged by the discovery of Early-Middle Triassic mafic igneous rocks from the southeastern margin of the North China Block (NCB), which was subducted by the South China Block (SCB) during the Triassic. Zircon U-Pb dating for these mafic rocks yields 247 ± 2–244 ± 5 Ma for their emplacement, coeval with the initial collision between the two continental blocks. These Triassic mafic rocks generally exhibit ocean island basalt (OIB)-like trace element distribution patterns, intermediate (87Sr/86Sr)i ratios of 0.7057–0.7091, weakly negative Nd(t) values of –1.2 to –3.8, and Hf(t) values of –1.3 to –3.2. Such geochemical features indicate origination from a metasomatic mantle source with involvement of felsic melts derived from dehydration melting of the previously subducting Paleo-Tethyan oceanic crust. The syn-magmatic zircons of Triassic age show variable Hf-O isotopic compositions, indicating that the crustal component was composed of both altered basaltic oceanic crust and terrigenous sediment. High Fe/ Mn and Zn/Fe ratios suggest that the mantle source would mainly consist of ultramafic pyroxenites. The melt-mobile incompatible trace elements were further fractionated relative to melt-immobile trace elements during partial melting of these pyroxenites, giving rise to basaltic melts with OIB-like geochemical signatures. The mafic magmatism may be caused by tectonic extension due to rollback of the subducting Paleo-Tethyan oceanic slab in response to the initial collision of the NCB and SCB in the Early Triassic. Therefore, the syn-subduction mafic magmatism provides new geochemical evidence for tectonic transition from oceanic subduction to continental collision in east-central China. [ABSTRACT FROM AUTHOR]

Sponges have great significance for understanding the origin and evolution of metazoans. Biomarker fossil and molecular clock studies suggest a Precambrian origin of sponges, but no unambiguous fossil of sponge spicules have been recovered from units older than the early Cambrian to date. Here, we report abundant siliceous spicules from Ediacaran-Cambrian transition strata, representing a deep-slope setting on the southeastern margin of the Yangtze Block in South China. The first appearance of monaxon spicules in the Sifangjing section is in the lower Liuchapo Formation (uppermost Ediacaran), from below the Basal Cambrian Carbon isotope Excursion (BACE), which is consistent with the timing of their initial appearance in shallow-platform settings (e.g., the Three Gorges area). These spicules are monaxons that are isolated or aggregated as spiculate bundles, the latter having a structural arrangement consistent with construction by demosponges. Polyaxial spicules first appear in phosphatic nodules of the basal Jiumenchong Formation (early Cambrian Stage 2). Relative to shallow-water settings, the appearance of polyaxial spicules in deep-water slope settings was delayed (∼10 Ma). Oxygenation of anoxic deep watermasses and increasing concentrations of dissolved Si in seawater during Cambrian Stage 2 may have facilitated the expansion of the Hexactinellida into deep-water settings. The triaene spicules from the basal Jiumenchong Formation are the oldest (∼522 to 525 Ma) Tetractinellida spicule fossils identified to date. • Sponge spicules were recovered from the Liuchapo Formation at Sifangjing section. • The first appearance of monaxons is near the Ediacaran-Cambrian boundary. • Polyaxial spicules appear in Cambrian Stage 2, marking evolution of Tetractinellida. • Siliceous sponges had an evolutionary tendency from monaxon to triaxon spicules. [ABSTRACT FROM AUTHOR]

In the Precambrian dolomites in the central Sichuan Basin, a substantial paleo-oil system previously existed, which has since evolved into a dry gas system that is currently in place. The genesis of this paleo-oil system remained poorly understood, leaving uncertainties regarding the timing of oil charging and associated source rocks. Integration of Re–Os geochronometry with basin modeling allows temporal-spatial constraints on the ancient petroleum system to be established. Two texturally distinct generations of reservoir bitumen were identified. Late-generation bitumen yielded a geologically meaningful Re–Os age of 189 ± 20 Ma (MSWD = 10.4, 2σ), distinct from the previously documented Re–Os ages such as the 414 ± 44 Ma reported by Shi et al. (2020). This new age, along with the ∼414 Ma, aligns within uncertainties with the two relative timings derived from our independent basin model (ca. 450–390 Ma and 260–180 Ma), revealing two temporally distinct oil generation-migration events. The date of ∼189 Ma also lends support to the previous oil charge timing inferred from fluid inclusions. We evaluated the imprecisions of these two Re–Os ages and considered them to result from a narrow spread in 187Re/188Os, and variations in initial Os isotopic compositions (Os i) due to the giant size of the petroleum system and a long duration of oil generation from source kitchen over a large geographical area in this play. Effects of asphaltene precipitation, due to uplift-induced decompression of the migrating oils, may also have contributed to the scatter. Separating the samples based on Os i produced a higher precision age (184.1 ± 5.7 Ma, Model 1) with an MSWD of 0.97. The first oil charge is relatively weak as shown by the basin model and observed bitumen volumes, and it had not been well preserved due to significant reservoir exhumation by Caledonian tectonism. Consequently, the younger oil charge is considered to be the principal precursor to the current dry gas accumulations. Os isotope histories for four potential source units were constructed using publicly available Re–Os data. Comparisons between bitumen and rock Os compositions tend to support the lower Cambrian Qiongzhusi Formation as the predominant source unit for the two major paleo-oil charges. However, contributions from the Duoshantuo, Dengying, and Maidiping source rocks can not be precluded. Overall, these new observations allow temporal-spatial constraints to be placed on the complex evolution, from paleo-oil generation to destruction and dry gas generation. • Two paleo oil charges sourced from the lower Cambrian Qiongzhusi shales. • Agreement between two bitumen Re–Os ages and modeled oil generation stages. • Assessing the precision limitations of hydrocarbon Re–Os ages. [ABSTRACT FROM AUTHOR]

In this work, we report the geochemical, whole-rock Sr-, Nd-, and Hf-isotopes, and zircon U–Pb age and Hf–O isotopic compositions for six granitic intrusions in northeastern Fujian, coastal region of southeastern China, to elucidate the petrogenesis of aluminous and peralkaline A-type granites in this region. Zircon U–Pb dating of these rocks (including porphyritic syenites, porphyritic granites, alkali-feldspar granites, and arfvedsonite granites) yielded Late Cretaceous ages of 94–98 Ma. Mineral assemblage and geochemical features suggested that the arfvedsonite granites were peralkaline A-type but the porphyritic syenites, porphyritic granites, and alkali-feldspar granites were aluminous A-type. Geochemical data, whole-rock Nd–Hf isotopes (ε Nd (t) = −5.5 to −4.0, ε Hf (t) = −3.6 to 0), and the zircon Hf–O isotopes (ε Hf (t) = −3.0 to +1.4, δ18O = 5.4‰–6.0‰) indicated that the porphyritic syenites were produced by partial melting of crustal rocks in the lower crust. The porphyritic granites and alkali-feldspar granites had similar geochemical features and zircon Hf–O isotopic composition with the porphyritic syenites, suggesting that they were formed by feldspar-dominant crystal fractionation of deep crust derived syenitic magma under shallow crustal level. Compared with the aluminous A-type granites, the peralkaline A-type granites had lower abundance of Al 2 O 3 , MgO, CaO, Ba, and Sr, higher abundance of SiO 2 and HFSE, as well as higher ratio of total FeO/MgO, Ga/Al, and Rb/Sr. However, the whole-rock Nd-, Hf- and zircon Hf–O isotopic compositions of the peralkaline and aluminous A-type granites were similar. It could be inferred that the peralkaline A-type granites were formed by crystal fractionation of aluminous A-type granitic magmas. Since the studied A-type granitic intrusions were coeval with the bimodal volcanic rocks and the extensional basins in the coastal region of southeastern China, they were likely produced in an extensional setting, possibly during lithospheric thinning that resulted from the subduction of the paleo-Pacific plate beneath southeastern China. • Aluminous and peralkaline A-type granites were crystallized at 94–98 Ma. • Aluminous and peralkaline A-type granites were derived from a common source. • Aluminous A-type granite was produced by partial melting of lower crustal rocks. • Peralkaline A-type granite was formed via crystal fractionation. [ABSTRACT FROM AUTHOR]

The Hegenshan–Heihe Suture (HHS) is an important suture zone between the Xing'an and Songliao–Xilinhot blocks in the eastern Central Asian Orogenic Belt (CAOB). Many studies have examined the northern and southern parts of this suture zone, but the middle segment remains under-researched and controversial. This paper presents new research into Permian felsic rocks along the middle segment of the HHS, including alkaline granites, rhyolites, and granodiorites. Zircon U–Pb dating of these rocks yielded precise Permian ages of 300.4 ± 2.5, 292.8 ± 2.7, and 293.1 ± 2.2 Ma. The alkaline granites and the rhyolites are A-type rocks that were derived from lower crustal protoliths, with the melting of these protoliths caused by asthenospheric upwelling associated with lithospheric delamination. In comparison, the granodiorites are I-type granites were generated from a mantle-derived magmatic source. The petrogenesis of these granites also involved the assimilation of sedimentary rocks and fractional crystallization. This Permian magmatism occurred during post-collisional extension following the amalgamation of the Xing'an and Songliao–Xilinhot blocks. [ABSTRACT FROM AUTHOR]

Precise time constraints of the main extrusive phase of the Emeishan large igneous province (ELIP) remain unresolved because basalts commonly do not contain suitable minerals for U-Pb dating, whereas previous 40Ar/39Ar studies on basalts yielded tectonothermal overprint ages. The timing for the ELIP was deduced from indirect dating of minor intrusions of ultramafic/mafic and felsic compositions by geochronological methods and geological correlations. The extrusive part of the ELIP consists of an older low-Ti and younger high-Ti basalt phases. We have found fresh samples of plagioclase-phyric rocks at the lower Qiaojia extrusive section (the Yunnan province of China), which belong to the ELIP unit of the high-Ti basalt series. 40Ar/39Ar dating on plagioclase from two samples conducted at two different laboratories using different age standards yielded statistically indistinguishable results with the weighted mean age of 260.1 ± 1.2 Ma for five individual measurements. This provides the direct constraints on the onset of the ELIP high-Ti basalt extrusive phase. The obtained age is within the error or slightly older than the age of the Guadalupian-Lopingian boundary and felsic ignimbrite capping the ELIP lava succession (both dated at 259.1 ± 0.5 Ma). Our new data are strengthening the short duration of the, at least, high-Ti phase of the ELIP volcanism and its temporal link with the end-Guadalupian mass extinction. Estimation of the total duration of the ELIP volcanism awaits finding of suitable for dating low-Ti basalts. [ABSTRACT FROM AUTHOR]

Excavations in Hualongdong (HLD), East China, have yielded abundant hominin fossils dated to 300 ka. There is a nearly complete mandible that fits well with a partial cranium, and together they compose the skull labeled as HLD 6. Thus far, detailed morphological description and comparisons of the mandible have not been conducted. Here we present a comprehensive morphological, metric, and geometric morphometric assessment of this mandible and compare it with both adult and immature specimens of Pleistocene hominins and recent modern humans. Results indicate that the HLD 6 mandible exhibits a mosaic morphological pattern characterized by a robust corpus and relatively gracile symphysis and ramus. The moderately developed mental trigone and a clear anterior mandibular incurvation of the HLD 6 mandible are reminiscent of Late Pleistocene hominin and recent modern human morphology. However, the weak expression of all these features indicates that this mandible does not possess a true chin. Moreover, a suite of archaic features that resemble those of Middle Pleistocene hominins includes pronounced alveolar planum, superior transverse torus, thick corpus, a pronounced endocondyloid crest, and a well-developed medial pterygoid tubercle. The geometric morphometric analysis further confirms the mosaic pattern of the HLD 6 mandible. The combination of both archaic and modern human features identified in the HLD 6 mandible is unexpected, given its late Middle Pleistocene age and differs from approximately contemporaneous Homo members such as Xujiayao, Penghu, and Xiahe. This mosaic pattern has never been recorded in late Middle Pleistocene hominin fossil assemblages in East Asia. The HLD 6 mandible provides further support for the high morphological diversity during late Middle Pleistocene hominin evolution. With these findings, it is possible that modern human morphologies are present as early as 300 ka and earlier than the emergence of modern humans in East Asia. [ABSTRACT FROM AUTHOR]

This study provides new zircon U Pb geochronological and geochemical data for Late Jurassic to Early Cretaceous granitoids in the northern Great Xing'an Range (GXR), NE China, and uses these data to constrain the late Mesozoic tectonic evolution of the GXR. The zircons from these granitoids are magmatic, as indicated by their appearances during cathodoluminescence imaging and high Th/U ratios (0.21–2.35). Zircon U Pb dating indicates that the granitoids formed during the Late Jurassic (~161 Ma) and Early Cretaceous (~132 Ma). The Late Jurassic granitoids (LJG) are dominantly monzogranites with high SiO 2 and Na 2 O + K 2 O contents, and low MgO and FeO T contents. They are metaluminous, enriched in the light rare-earth elements (LREE) and the large-ion lithophile elements (LILE), depleted in the heavy REE (HREE) and high-field-strength elements (HFSE; e.g., Nb, Ta, Ti, and P), and have an adakitic affinity. The zircons from these monzogranites yield ε Hf (t) values of +5.7 to +8.2 and two-stage model ages (T DM2 ) of 749–618 Ma. These results indicate that the primary magma for the Late Jurassic granites was originated from partial melting of a thickened lower-crustal source. The Early Cretaceous granitoids are dominantly metaluminous to peraluminous porphyritic granites with higher HREE contents than the Late Jurassic monzogranites. They display negative Eu anomalies and have ε Hf (t) values of +3.1 to +9.0 with corresponding T DM2 ages of 877–553 Ma, suggesting they formed from magmas generated by partial melting of juvenile lower-crustal material. Combining these data with the geochemistry of coeval volcanic rocks within the GXR, we infer that the northern GXR records a late Mesozoic transition from compression to extension. The compression was most likely related to the Middle Jurassic closure of the Mongol–Okhotsk Ocean, whereas the extension was related to delamination of a thickened region of the lithosphere and/or subduction of the Paleo-Pacific Plate beneath Eurasia. [ABSTRACT FROM AUTHOR]

Highly evolved Sn-polymetallic mineralization-related granites are intensively developed in the Nanling Range of South China. In this study, two types of granitic rocks (albite granite and greisenized granite) from the Laiziling pluton in the Xianghualing area were studied to elucidate magma evolution and the genesis of mineralization. The A-type Xianghualing granitic rocks are characterized by high SiO 2 (69.16–85.04%), Rb (759–2110 ppm), Ta (17.2–50.8 ppm), Nd (2.8–82.4 ppm) and 87 Sr/ 86 Sr (0.907275–4.181262) and low MgO (0.01–0.98%), TiO 2 (0.01–0.03%), Sr (1.4–70.2 ppm), Ba (1.4–132.5 ppm), Eu (0.03–0.21 ppm) and 143 Nd/ 144 Nd (0.512283–0.512326). The whole-rock εNd(t) values range from −6.3 to −6.0, with T 2DM ages of 1426–1454 Ma. The zircon εHf(t) values mostly range from −10 to −5, with dominant T DM C values of 1400–1800 Ma. This suggests that the Xianghualing granitic rocks were derived from partial melting of Mesoproterozoic basement rocks in the Cathaysian Block, in a lithospheric extension setting. Zircon U–Pb dating yielded five age clusters: Proterozoic (>900 Ma, n  = 9), Silurian (~430 Ma, n  = 4), Triassic (~220 Ma, n  = 16), Jurassic (~150 Ma, n  = 62) and Cretaceous (~80 Ma, n  = 28). Zircon internal textures, trace element contents and Hf isotopic compositions indicate that they formed from a range of sources including residual zircons from the magma source region, detrital zircons from local sediments, zircons captured from pre-existing magmatic rocks with obvious mantle signatures, magmatic and fluid-altered zircons, and late stage hydrothermal zircons. This suggests significant fractional crystallization, weak wall-rock assimilation/contamination and intense fluid differentiation/metasomatism during the genesis of the Xianghualing granitic rocks. M-type REE tetrad effects are seen not only in bulk rock compositions, but also in individual zircon grains, indicating that highly fractionated and reduced F-rich fluids played an important role in the formation of Sn-polymetallic mineralization. Guided by the major Mesozoic W–Sn ore-forming events occurring in the Cathaysian Block of South China, a multi-stage genetic model is proposed for the Xianghualing granitic-minerogenic system: initial enrichment of W–Sn in the Triassic (~220 Ma), dominant Sn-polymetallic metal precipitation in the Jurassic (~150 Ma), and superimposed mineralization in the Cretaceous (~80 Ma). [ABSTRACT FROM AUTHOR]

Abstract: The Chinese Western Tianshan terrane is a well‐known ultrahigh‐pressure (UHP) metamorphic belt that mainly consists of subducted oceanic crustal materials. While two uplift stages have been recognized, the early exhumation history has not been fully constrained. We conducted U–Th–Pb and trace element microanalysis of titanite as well as zircon from UHP eclogites. Apart from several inclusions in garnet, three types of retrograde titanite have been identified based on their petrographic occurrences: (a) in matrix enclosing relict rutile; (b) as coarse‐grained coronas around garnet; and (c) in veins coexisting with epidote and/or apatite. The three types of titanite are homogeneous in chemical composition, low in Al, enriched in middle rare earth elements (REEs), and depleted in light REEs and heavy REEs, suggesting their growth during retrograde decompression. Sensitive high‐resolution ion microprobe (SHRIMP) and LA‐ICP‐MS U–Pb dating of titanite from four samples, regardless of their textural occurrences, gave consistent ages of c. 306 Ma. Phase equilibria modelling and Zr‐in‐titanite thermometry indicate that titanite replaced rutile at ~14 kbar and ~570°C, following a nearly isothermal decompression from the UHP peak conditions of 30 kbar and 550–570°C. SHRIMP zircon U–Pb dating yields two age groups: c. 320 Ma and c. 305 Ma. The former is generally interpreted to be the age of UHP stage. The latter, overlapping the titanite ages, represents the timing of titanite growth during exhumation. Thus, we estimate that the near‐isothermal exhumation from the UHP peak conditions to the epidote–amphibolite facies retrogression (14 kbar) lasted c. 15 Ma, corresponding to an average exhumation rate of 3.4 ± 2.5 mm/yr (2σ). This exhumation rate lies within the range of oceanic LT‐HP belts in the absence of continental subduction, suggesting a similar slab exhumation mechanism that operates in the UHP regime. The consistent retrograde metamorphic ages recorded by titanite from different localities, and the general agreement among P–T paths in the adjacent area, suggest that the UHP unit of Western Tianshan metamorphic belt was likely exhumed as a coherent unit. [ABSTRACT FROM AUTHOR]

We present our new investigation into the depositional environment and provenance of the Yingshuiquan Formation in the central Qiangtang region of northern Tibet, in order to further our understanding of the environment of the Longmu Co-Shuanghu Palaeo-Tethys during the Early Triassic. The Yingshuiquan Formation is composed of oolitic limestone, calcareous sandstone, calcarenite, thin-bedded ribbon limestone, bioclastic limestone, and coarse oolite limestone that were deposited in a shallow-marine basin and contain abundant Lower Triassic conodont fossils (e.g. Hadrodontina anceps, Pachycladina sp., gen. et sp, Pachyclaina oblique, Hibbardelloides sp). We selected detrital zircons from four calcareous sandstone samples for U-Pb dating, yielding minimum age peaks of 263, 269, 275, and 280 Ma, respectively, and a minimum age of 249 Ma, based on several zircons around the same age. Analysis of the conodont biofacies and zircon LA-ICP-MS dating of calcareous sandstone indicates that the data is consistent with deposition in the Early Triassic. The Yingshuiquan Formation records Early Triassic shallow-water sediment in the Longmu Co-Shuanghu Palaeo-Tethys, and has a Southern Qiangtang and Northern Qiangtang terranes provenance. During the Early Triassic, the carbonate sediments of the Yingshuiquan Formation were deposited in an active environment around the Longmu Co-Shuanghu Palaeo-Tethys, which has became a residual sea basin. [ABSTRACT FROM AUTHOR]

Chroniosuchians are basal tetrapods owing to Anthracosauromorpha and the oldest species of chroniosuchians have been recorded in the Late Permian of Russia so far. In this study, we present evidence for their existence in the Middle Permian of China, based on well preserved diagnostic vertebrae with associated osteoderms from the Dashankou fanua in northwestern China. The finds clearly show interosteoderm articulation pattern between the adjacent scutes in bystrowianids. The features observed in Yumenerpeton yangi may warrant the close proximity or phyletic succession of the chroniosuchid and bystrowianid types of the osteoderm design. [ABSTRACT FROM AUTHOR]

Gigantopithecus was a giant ape once lived in Southeast Asia and China during the Pleistocene period. Longgupo and Jianshi Longgudong sites in West-Hubei and Three Gorges region in South China are the northernmost evidences of Gigantopithecus presence in the world up to date. To obtain the detailed chronology of these two sites, paleomagnetic and radiometric dating methods were attempted, including cosmogenic burial dating of the sediment. However, the efforts failed because of the scarce of quartz minerals in the sediment. Combined electron spin resonance and uranium series (ESR/U-series) method which could date the fossil teeth directly with the age range from Early to Late Pleistocene was also applied and the results obtained at Longgupo site already published. Here, we report the first radiometric dating results for teeth carried out from Jianshi Longgudong Western Branch cave which is renowned for the discovery of both Gigantopithecus fossils and undoubted stone artifacts. The main challenge of dating Jianshi Longgudong site is the reconstruction of external dose rate of the fossil samples where their provenance sections were not preserved. The mean radioelement concentrations in the sediments measured in the laboratory with different water content estimation were initially used to calculate the ESR/U-series ages. Our ESR/U-series dating of two mammalian fossil teeth from the lower layer 8 gives a weight mean age of 1512 ± 94 ka, while a mean age of 1044 ± 53 ka was obtained for two teeth from the upper layer 4. These ages support one of the previous paleomagnetic dating interpretation which propose that the hominin fossil layer in Jianshi site was not older than 1.78 Ma, i.e. that the upper boundary of the Olduvai subchron, and are in agreement with the faunal evidence which suggest that Jianshi site is younger than the adjacent Longgupo site dated also by combined ESR/U-series and paleomagnetic methods to 2.0-2.5 Ma. Further study of the site including the radiometric dating study of the fossil layers preserved in the Eastern Branch cave may help to achieve a definitive conclusion of the chronology of Gigantopithecus settlement in Jianshi Longgudong site. [ABSTRACT FROM AUTHOR]

Combined ESR and U-series methods have been increasingly applied to the paleolithic and paleoanthropological sites from Early to Middle Pleistocene period. However, this dating method is seldom used for the Late Pleistocene or even younger sites comparing with other radiometric methods, such as 14C charcoal dating, U-series carbonate dating and OSL sediment dating. The important advantage of ESR dating is that it allows direct analysis of fossil tooth from animal and human remains. Here, we report a combined ESR and U-series dating study of Naminan paleolithic site, a Paleolithic-Neolithic transition site located on the border between China and Myanmar. The stone artifacts with typical "Hoabinhian Industrial" characteristics indicate the human migration and interactions between Southeast Asia and South China. Apart from an obvious older age of 31 ka, our ESR analysis of ten tooth enamel samples gives the age estimation of 12-21 ka on fossils from the paleolithic cultural layer of Naminan site. The obtained ESR ages of fossil teeth are in agreement with the 14C and U-Th chronology for Naminan site in general. When dating the young fossil samples from the site like Naminan, we noticed that due to the relative low uranium concentration in the enamel tissues (0.01-0.3 ppm), the internal dose rate plays a much less important role than the external beta and gamma dose rate to the total dose rate in the fossil samples. Therefore, the dose rate evaluation of the surrounding sediment is the main source of uncertainty that may affect the reliability of the ESR dating results. In this study, we also attempt to use a standard growth curve (SGC) of enamel to determine the DE and compared with the values obtained by additive dose (AD) method (12-34 Gy). Although the current precision of DE results estimated by SGC are lower than AD, it shows the potential to quick decide a more reasonable Dmax for irradiation and identify the possible intrusion fossil samples. [ABSTRACT FROM AUTHOR]

The Pongo fossil record of China extends from the Early Pleistocene to the Late Pleistocene, but to date, no late Middle Pleistocene samples of Pongo with precise absolute dating have been identified in southern China. Here, we report the recovery of 106 fossil teeth of Pongo from Ganxian Cave in the Bubing Basin, Guangxi, southern China. We dated the speleothems using Uranium-series and dated the two rhinoceros teeth using coupled electron spin resonance/Uranium-series dating methods to between 168.9 ± 2.4 ka and 362 ± 78 ka, respectively. These dates are consistent with the biostratigraphic and magnetostratigraphic age estimates. We further describe the fossil teeth from Ganxian Cave and compare them metrically to samples of fossil Pongo (i.e., Pongo weidenreichi , Pongo duboisi , Pongo palaeosumatrensis , Pongo javensis , and Pongo sp.) from the Early, Middle, and Late Pleistocene and to extant Pongo (i.e., Pongo pygmaeus and Pongo abelii) from Southeast Asia. Based on overall dental size, a high frequency of lingual cingulum remnants on the upper molars, and a low frequency of moderate to heavy wrinkling on the molars, we attribute the Ganxian fossils to P. weidenreichi. Compared with Pongo fossils from other mainland Southeast Asia sites, those from Ganxian confirm that dental size reduction of Pongo occurred principally during the Early and Middle Pleistocene. From the Middle to Late Pleistocene, all teeth except the P3 show little change in occlusal area, indicating that the size of these teeth remained relatively stable over time. The evolutionary trajectory of the Pongo dentition through time may be more complex than previously thought. More orangutan fossils with precise dating constraints are the keys to solving this issue. [ABSTRACT FROM AUTHOR]

The Jinshandian ore field represents one of the largest concentrations of Fe skarn deposits in the Edong district of Eastern China. Orebodies of these deposits occur in skarn along the contacts between quartz diorite or quartz monzonite and Triassic sedimentary country rocks. In this paper, we present new U–Pb geochronological data for magmatic zircon and hydrothermal titanite, as well as 40 Ar/ 39 Ar ages on hydrothermal phlogopite, to determine whether multiple magmatic-hydrothermal events associated with formation of the Fe skarn deposits in the Jinshandian ore field. The robust U–Pb zircon ages demonstrate that the quartz monzonite and quartz diorite were emplaced at 130 Ma and 127 Ma, receptively. The U–Pb and 40 Ar/ 39 Ar ages of hydrothermal titanite and phlogopite form the skarn indicate that Fe mineralization also formed at ca. 131–128 Ma, but with an additional 118 Ma hydrothermal event recorded by phlogopite. This geochronology confirms a causative linkage between granitic intrusion and skarn mineralization. The data also indicate that at least two hydrothermal events took place in the Jinshandian ore field, one at 131–128 Ma and the other at ∼118 Ma. Integrating these ages from the ore field with previous geochronological data from the broader Edong district, two regional magmatic-hydrothermal events are recognized in the Edong district after 135 Ma, with the older one at 131–127 Ma in excellent agreement with the ∼131 Ma formation age of magnetite-apatite deposits in the eastern part of Middle–Lower Yangtze River region, and the younger one at 122–118 Ma post-dating emplacement of the ca. 126 Ma A-type granite and syenite in the eastern part of Middle–Lower Yangtze River region. A detailed comparison between the Fe skarn deposits and magnetite-apatite deposits in the Middle–Lower Yangtze River region suggests that these two deposit types not only share similar alteration assemblages and association with the evaporites within the ore-forming systems, but also may have formed during the same Early Cretaceous magmatic-hydrothermal event. [ABSTRACT FROM AUTHOR]

The Tiegelongnan Cu (Au) deposit is the largest copper deposit newly discovered in the Bangong-Nujiang metallogenic belt. The deposit has a clear alteration zoning consisting of, from core to margin, potassic to propylitic, superimposed by phyllic and advanced argillic alteration. The shallow part of the deposit consists of a high sulphidation-state overprint, mainly comprising disseminated pyrite and Cu-S minerals such as bornite, covellite, digenite, and enargite. At depth porphyry-type mineralization mainly comprises disseminated chalcopyrite, bornite, pyrite, and a minor vein molybdenite. Mineralization is disseminated and associated with veins contained within the porphyry intrusions and their surrounding rocks. The zircon U-Pb ages of the mineralized diorite porphyry and granodiorite porphyry are 123.1 ± 1.7 Ma (2σ) and 121.5 ± 1.5 Ma (2σ), respectively. The molybdenite Re-Os age is 121.2 ± 1.2 Ma, suggesting that mineralization was closely associated with magmatism. Andesite lava (zircon U-Pb age of 111.7 ± 1.6 Ma, 2σ) overlies the ore-bodies and is the product of post-mineralization volcanic activity that played a critical role in preserving the ore-bodies. Values of −4.6 ‰ to + 0.8 ‰ δ34S for the metal sulfides (mean − 1.55 ‰) suggest that S mainly has a deep magmatic source. The H and O isotopic composition is (δD = −87 ‰ to −64 ‰; δ18OH2O = 5.5 ‰ to 9.0 ‰), indicating that the ore-forming fluids are mostly magmatic-hydrothermal, possibly mixed with a small amount of meteoric water. The zircon εHf(t) of the diorite porphyry is 3.7 to 8.3, and the granodiorite porphyry is 1.8 to 7.5. Molybdenite has a high Re from 382.2 × 10−6 to 1600 × 10−6. Re and Hf isotope composition show that Tiegelongnan has some mantle source, maybe the juvenile lower crust from crust-mantle mixed source. Metallogenesis of the Tiegelongnan giant porphyry system was associated with intermediate to acidic magma in the Early Cretaceous (~120 Ma). The magma provenance of the Tiegelongnan deposit has some mantle-derived composition, possibly mixed with the crust-derived materials. [ABSTRACT FROM AUTHOR]

The Paleo-Tethyan arc belt is host to a small number of porphyry Cu deposits the key controls on which remains poorly understood. It has been hypothesized that the Paleo-Tethyan arc magmas were reduced and therefore less fertile for porphyry Cu formation but few studies have been conducted to directly assess the magmatic oxygen fugacity. We investigate the magma fertility of eastern Paleo-Tethyan arc igneous rocks in the Sanjiang region, SW China, represented by the Maoding (268.3 ± 2.3 Ma), Suwalong (275.6 ± 1.4 Ma to 264.7 ± 1.4 Ma) and Baimaxueshan (255.7 ± 1.5 Ma to 249.3 ± 1.1 Ma) granitoids. They have geochemical features consistent with typical continental arc rocks, formed from partial melting of the mantle wedge, with increasing contamination of crust-derived melts over time. The presence of amphibole, high Sr/Y ratios (35 ± 20, n = 17), and lack of negative Eu anomalies (Eu N /Eu N ⁎ = 1.04 ± 0.3, n = 17) are consistent with derivation from hydrous magmas. Zircons from the intrusive rocks have relatively low Eu N /Eu N ⁎ (mostly <0.4) ratios and calculated ΔFMQ values (−2.1 ± 1.2, n = 86). Combined with apatite microphenocrysts with extremely low sulfur contents (< 0.12 wt% SO 3), it suggests that the intrusions originated from water-rich but reduced arc magmas, that were less fertile for porphyry Cu formation. Our study highlights that magmatic f O 2 is probably a critical control on the prospectivity of arc systems and confirms that zircon and apatite compositions can be used to evaluate porphyry Cu fertility. • The Paleo-Tethyan arc igneous rocks were dated from ~275 to 249 Ma. • They were derived from partial melting of mantle wedge during MASH processes. • These arc magmas were reduced and less fertile for porphyry Cu formation. • Zircon and apatite compositions can be used to evaluate porphyry Cu fertility. [ABSTRACT FROM AUTHOR]

Yumidong (Corn Cave) is a newly discovered Paleolithic site in the Three Gorges region of central China. Numerous Paleolithic artifacts have been excavated from the sedimentary deposits of the cave in association with faunal remains attributed to the Middle-Late Pleistocene Ailuropoda - Stegodon fauna of southern China. To establish the chronology of the sedimentary sequence (>5 m thick), 14C dating was applied to bone and charcoal samples (n = 6); the U-series method was used to date in situ precipitated speleothems (n = 12), transported speleothem samples (n = 6) and 18 subsamples of a fossil tooth; and the coupled ESR/U-series method was used to date fossil teeth (n = 6). The derived dates were combined using a hierarchical Bayesian approach to generate a unified chronostratigraphy for the Yumidong sequence. In our Bayesian analyses, the 14C and coupled ESR/U-series dates were considered to provide direct age estimates for the target layers, while the U-series dates of the in situ precipitated speleothems and fossil tooth were used as minimum age constraints and those of the transported speleothem fragments as maximum age constraints. The Bayesian analyses provided robust time intervals for the archeological layers: L2-Upper (14–23 ka), L2-Lower (27–63 ka), L3 (106–171 ka), L4 (140–192 ka), L10 (157–229 ka), L11 (181–256 ka), and L12 (214–274 ka) with a probability of 95%, allowing the establishment of a ∼300 ka long geological and archeological history for the Yumidong site and placing it as a reference site for Paleolithic cultural evolution in the Three Gorges region from the late Middle Pleistocene to Late Pleistocene. [ABSTRACT FROM AUTHOR]

The Three Gorges and Western Hubei area in the geographic central part of China was a potential migration corridor for early hominin and mammals linking South and North China during the Pleistocene period. Some key early hominin sites are known in this region where limestone cave and fissure sites are numerous but difficult to date as beyond the dating range of OSL and mass spectrometry U-series method. Here, we report radiometric dating study for such a hominin site, Meipu (Hubei Province), by coupled ESR and U-series dating of nine fossil teeth and cosmogenic 26Al/10Be burial dating of one quartz sediment. The burial age calculated by simple burial model (573 ± 266 ka) gives a minimum age constraint of the sediment. The fossil dating provided two main age groups at 541 ± 48 ka and 849 ± 39 ka, the older age group is in agreement with the U-series age (>630 ka) of the flowstone overlying the fossil layer and the paleomagnetic data which placed the Brunhes-Matuyama boundary in the fossil layer. The reason of this age difference is probably caused by the U-content discrepancy in the enamel of the dated fossil samples. This study exhibits the limitation of ESR/U-series fossil dating and the importance of using multiple dating approach when it is possible in order to identify the problematic ages. • A key hominin site in Three Gorges area at the corridor between South and North China was dated by radiometric methods. • Two radiometric dating methods were applied directly to the fossil layer of the Meipu hominin site. • The results of multiple dating approach were compared to constrain the age of an Early-Middle Pleistocene hominin site. [ABSTRACT FROM AUTHOR]

Abstract: The tectonic–thermal history of the Huarong granitoids is used to clarify the tectonic evolution of the middle Yangtze Craton and eastern China. The Huarong granitoids include the Xiaomoshan and Taohuashan plutons and form a northeast-trending belt in the middle Yangtze Craton, eastern China. Multi-method geochronology reveals the thermal history of the Huarong granitoids from their emplacement to near-surface conditions. LA-ICP-MS U–Pb zircon dating suggests granitoid emplacement at ca. 117Ma; a cluster of zircons at ca. 127Ma is likely inherited from an earlier intrusion phase. The granitoids formed in an extensional setting, which was almost certainly associated with Pacific Plate subduction in the late Early Cretaceous. Biotite 40Ar/39Ar ages at ca. 96Ma record regional post-magmatic cooling. Apatite fission-track (AFT) and apatite (U–Th–Sm)/He (AHe) thermochronology and thermal-history modeling indicate cooling in three stages: enhanced cooling at 96–60Ma is interpreted to reflect cooling from the late Early Cretaceous regional magmatism. Tertiary (ca. 60–20Ma) very slow cooling, stagnation, or even re-heating suggests insignificant exhumation and peneplanation; this interval correlates with Late Cretaceous–Eocene red-bed deposition and rifting throughout eastern China. Causes for speculative accelerated cooling after ca. 20Ma may be a far-field effect of the India–Asia collision or Pacific Plate subduction. This study demonstrates that the middle Yangtze Craton was involved in the Cretaceous extension widely occurring in the eastern China continent and suggests that the formation of the Jianghan Basin, a major depocenter in the middle Yangtze Craton, may have initiated at ca. 120Ma. [Copyright &y& Elsevier]

Abstract: The Nihewan Basin sedimentary sequences in northern China are rich in mammalian fossil and Paleolithic sites, thus providing insights into our understanding of Quaternary land mammal biochronology and early human settlements in East Asia. Here we present high-resolution magnetostratigraphic results that place stringent age controls on the Xiashagou (XSG) Fauna (that is, the well-known Nihewan Fauna sensu stricto) in the Nihewan Basin, northern China. Results show that the XSG sequence recorded the Brunhes normal chron, the Matuyama reverse chron and the late Gauss normal chron. The XSG Fauna resides in the Matuyama reverse chron (between the pre-Reunion Matuyama chron and the post-Olduvai Matuyama chron), yielding an estimated age of ca. 2.2–1.7Ma. The Pliocene–Pleistocene boundary (Gauss/Matuyama boundary) is located in the lower part of the XSG section. The combination of our study and previously published magnetostratigraphic data suggest that the mammalian fossil sites in the eastern Nihewan Basin can be placed between the Gauss–Matuyama geomagnetic reversal and the Matuyama–Brunhes geomagnetic reversal (2.58–0.78Ma), leading to a time range of ca. 2.6–0.8Ma for the Nihewan mammalian faunas. [Copyright &y& Elsevier]

The article discusses research into the chronology and possible causes of the mass extinction event at the end-Permian of the Phanerozoic era. Biodiversity data from sediments in South China was studied, including the mass spectrometric geochronological, isotopic, and biostratigraphic information from several sites. The results indicate that the mass extinction occurred in marine and terrestrial ecosystems 252.28 ± 0.08 million years ago over the course of 20,000 years or more, and point toward thermogenic carbon dioxide or methane emissions as possible causes of the extinction event.

Abstract: The Taoxikeng tungsten deposit is located in the Jiangxi Province in the southern part of China, and is one of the largest wolframite quartz-vein type tungsten deposits in the country. The deposit is situated in Sinian (Neoproterozoic) to Permian strata at the contact with the buried Taoxikeng Granite. Sensitive High Mass Resolution Ion Microprobe (SHRIMP) zircon U–Pb analysis of the granite has yielded dates of 158.7±3.9 and 157.6±3.5Ma, which are interpreted as the emplacement age of the granite. Molybdenite separated from ore-bearing quartz-veins yields a Re–Os isochron age of 154.4±3.8Ma, and muscovite separated from greisen between the granite and country rocks yields 40Ar/39Ar plateau ages of 153.4±1.3 and 152.7±1.5Ma. These dates obtained from three independent geochronological techniques constrain the ore-forming age of the Taoxikeng deposit and link the ore genesis to that of the underlying granite. The Taoxikeng deposit is an example of a Jurassic regional-scale tungsten–tin ore-forming event between 160 and 150Ma in the Nanling region of the South China Block. The deposit''s strikingly low rhenium contents (4.9 to 13.0×10−3 μg/g) in molybdenite suggests that the ore was derived from a crustal source. This conclusion is consistent with previously published constraints from S, D and O stable isotopes, Sr–Nd systematics, and petrogenetic interpretations of spatially related granites. [Copyright &y& Elsevier]

Abstract: Kimberlite, a deep-sourced ultramafic potassic rock, carries not only diamond, but also invaluable mantle xenoliths and/or xenocrysts, which are important for tracking the evolution of subcontinental lithospheric mantle (SCLM). However, it is challenging to accurately determine the emplacement age of kimberlite and its compositions of primary magma because of modifications by crustal and/or mantle contamination and post-emplacement alteration. This paper reports emplacement ages of diamondiferous kimberlites in Mengyin and Fuxian of the North China Craton (NCC) using three different dating methods. For Mengyin kimberlite, single-grain phlogopite Rb–Sr dating yields an isochron age of 485±4Ma, U–Th–Pb analyses on perovskite give a 238U–206Pb age of 480.6±2.9Ma and a 232Th–208Pb age of 478.9±3.9Ma, and baddeleyite yields a 207Pb–206Pb age of 480.4±3.9Ma. For Fuxian kimberlite, baddeleyite gives a 207Pb–206Pb age of 479.6±3.9Ma, indicating that the Paleozoic kimberlites in the NCC were emplaced at ~480Ma. Numerous lines of evidence indicate that the studied baddeleyites are xenocrysts from the SCLM, and can be used to constrain Hf isotope compositions (ε Hf(t)~−6) of the SCLM when kimberlite erupted. Combined with data from Mesozoic–Cenozoic mantle-derived rocks and xenoliths, the Hf isotope evolution trend of the SCLM beneath NCC before craton destruction was tentatively constructed, which suggested that the Archean SLCM was enriched by metasomatism at ~1.3Ga. Further Hf isotope investigations on additional SCLM-derived materials could be used to compare with the constructed Hf isotope evolution trend before craton destruction to determine when lithospheric thinning occurred. [Copyright &y& Elsevier]

Abstract: In-situ SIMS zircon U–Pb dating and O isotope analysis as well as LA-(MC)-ICPMS zircon U–Pb dating and Lu–Hf isotope analysis were carried out for postcollisional mafic–ultramafic rocks in the Dabie orogen, China. The zircon U–Pb dating gave consistent ages of 126±1 to 131±1Ma for magma crystallization. Survival of residual zircon cores is identified by CL imaging and U–Pb dating, yielding ages of 697±10 and 770±11Ma that agree with protolith U–Pb ages of UHP metaigneous rocks in the Dabie orogen. The zircon Hf–O isotope compositions show systematic variations that can be categorized into three groups. Group I has the lowest δ18O values of 2.0 to 2.9‰ but the highest εHf(t) values of −3.5 to −1.0 with the youngest Hf model ages of 1.2 to 1.4Ga. Group II displays intermediate δ18O values of 4.0 to 5.1‰ and εHf(t) values of −22.5 to −13.2 with Hf model ages of 2.0 to 2.6Ga. Group III exhibits the highest δ18O values of 5.2 to 7.3‰ but the lowest εHf(t) values of −29.1 to −18.6 with the oldest Hf model ages of 2.4 to 3.0Ga. The three groups of Hf–O isotope compositions correspond to a three-layer Hf–O isotope structure in the subducted continental crust, suggesting their involvement in the mantle source. Along with existing data for whole-rock Sr–Nd isotopes and trace elements, it appears that the mantle source for the postcollisional mafic–ultramafic rocks is characterized by fertile lithochemistry, the arc-like signature of trace elements, the heterogeneous enrichment of radiogenic isotopes, the differential incorporation of supracrustal materials, and the variable concentrations of water. Clearly, such a source is neither the asthenospheric mantle nor the refractory subcontinental lithospheric mantle (SCLM). It is a kind of the orogenic SCLM that would be generated by reaction of the overlying SCLM-wedge peridotite with hydrous silicate melts derived from different layers of the subducted continental crust. Therefore, the postcollisional mafic–ultramafic rocks provide a petrological record of crust–mantle interaction during the continental deep subduction. [Copyright &y& Elsevier]

Abstract: This study uses a new application of the apatite and zircon (U–Th)/He thermochronometry technique to investigate the thermal history and tectonic uplift of sedimentary basins. Based on measured apatite and zircon (U–Th)/He ages, apatite fission track data and equivalent vitrinite reflectance measurements of borehole core samples, the thermal history of the Bachu Uplift of the Tarim Basin was modeled. Our analysis indicates a complicated thermal history in the Bachu Uplift region during the Paleozoic. The thermal gradient initially increased from 28–30°C/km in the Cambrian period to 30–33°C/km in the Ordovician period and increased up to 33–34°C/km in the Silurian period. The thermal gradient began to decrease during the Devonian period and was estimated to be approximately 30°C/km during the Late Devonian and the Early Carboniferous periods. The low thermal gradient phase was followed by an additional high gradient phase from the Late Carboniferous to the Early Permian when the gradient was approximately 32°C/km. Thermal gradients in the Paleozoic were substantially different than the present-day gradient (21°C/km). Tectonothermal modeling results also revealed uplift events in the Bachu Uplift region that shifted from south to north (e.g., ∼150Ma to ∼100Ma) and from west to east (e.g., ∼250Ma to ∼150Ma). This thermal evolution of the Bachu Uplift is consistent with its tectonic progression. The thermal spike in the Late Carboniferous and Early Permian periods could be related to magmatic activities in the Early Permian period. The Paleozoic thermal history of the Bachu Uplift region of the Tarim Basin could not be reconstructed properly due to a lack of reliable thermal indicators in the Lower Paleozoic successions, and a poor understanding of the thermal evolution of Lower Paleozoic source rocks during the Paleozoic has hindered petroleum exploration in this area. This study provides a new Paleozoic thermal history and shows that the Paleozoic thermal history plays an important role in the maturation process of the Lower Paleozoic source rocks. [Copyright &y& Elsevier]

Based on studies of the geochemical elements of core sediments collected from the subaqueous Yangtze River delta front, combined with 210Pb and 137Cs nuclide dating, element recording profiles were set up and anthropogenic impacts on the sedimentary records were considered. The results suggest that (1) The core formed since 1945, of homogeneous clay and silt sediments. (2) The content of most elements underwent little change, but the content of S and Nb increased gradually. In particular concentrations of these elements and heavy metals increased rapidly and were maintained at high levels in the surface and sub-surface layers (i.e. since the 1990s). The elements S, As and Nb and principal factor 4 (F4), which were sensitive to anthropogenic impacts, could be used as indicators of human activities. (3) The value of each indicator has increased gradually since 1945, with a sharp increase over the last 20 years. When divided according to changing values of the indicators at 185 cm (1955), 97 cm (1978), 47 cm (1992), and 7 cm (2003), five periods of the geochemical elements records were obtained. These corresponded to the ages of from the Chinese Civil War to the early stages of planned economy, the implementation of planned economy, the reform and opening-up period, the market economy establishment phase and the environment control and protection stage after 2003, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The studied ultrahigh-pressure (UHP) eclogites, located in the southwestern part of the North Dabie complex zone (NDZ) in central China, represent deeply subducted mafic lower continental crust of the South China Block and display a multiple metamorphic evolution. However, the exact timing of the UHP metamorphism in the NDZ is poorly constrained, and thus impedes our understanding of the tectonic evolution of this area. In order to constrain the ages of peak UHP metamorphism and subsequent retrogression during continental subduction and exhumation, zircon from the eclogites in the NDZ has been investigated by a combined petrological, trace element and U–Pb isotopic study. In combination with petrological data, the present zircon SHRIMP and LA-ICPMS U–Pb dating provides precise constraints on the timing of multistage metamorphic events on the eclogites in the region. The U–Pb isotope in zircon from the eclogites records the times of multiple discrete events in the history of the rock such as Neoproterozoic, 238±2Ma, 222±4–227±2Ma, 210±4–215±2Ma, 199±2Ma and 176±2–188±2Ma. Neoproterozoic ages defined by relic igneous cores represent their protolith time and the other age-groups reflect their metamorphic records by CL images, low Th/U ratios and mineral inclusions. By U–Pb age, trace element and mineral inclusion of zircon, at least two episodes of eclogite-facies metamorphism have been identified from the eclogites, best estimated at 226±3 and 214±3Ma, respectively. The younger ages of 199±2 and 176–188Ma most likely record the granulite-facies overprinting and amphibolite-facies retrogression occurring during exhumation whereas the age of 238±2Ma probably reflects the prograde metamorphic timing prior to the UHP metamorphism. Thus, Neoproterozoic mafic lower continental crust was subducted to depths greater than 120km (corresponding to the lowest pressure for diamond formation) and suffered from UHP metamorphism at 226±3Ma. Then these UHP metamorphic rocks were exhumed to about 60km depth at 214±3Ma and experienced high-pressure quartz eclogite-facies retrograde metamorphism, and subsequently to lower- and upper-crustal levels and overprinted by granulite- and amphibolite-facies metamorphism, respectively. [Copyright &y& Elsevier]

Abstract: The geological evolution in the southwestern Chinese Tianshan orogen in NW China is poorly understood because of controversial geochronological results of the low-temperature eclogites. It is likely due to Sm–Nd and Rb–Sr isotopic disequilibrium in different mineral fractions, excess 40Ar in the high-pressure K-bearing minerals, and multi-stage growths of zircon in U–Pb system. Rutile, as a typical eclogite-facies mineral with high U/Pb ratio, is a feasible candidate to constrain the eclogite-facies metamorphic event. In this study, we measured U–Pb rutile age data using SIMS (Cameca IMS 1280) for low-temperature eclogites from southwestern Chinese Tianshan orogen, NW China. We demonstrate that SIMS is a powerful technique for in-situ U–Pb dating of rutile with U content as low as 1ppm. SIMS U–Pb rutile dating yielded an age of 318±7Ma, which may record the time when the rocks cooled down to the closure temperature of Pb in rutile (ca. 500°C), but should be very close to the time of eclogite-facies metamorphism in terms of common fast exhumation of coesite-bearing eclogite. This new proof strongly suggests a late Carboniferous collision between Kazakhstan–Yili block and Central Tianshan microcontinent. [ABSTRACT FROM AUTHOR]

Abstract: Sediments of Chinese tamarisk (Tamarix chinensis Lour.) nebkhas in China''s arid Ala Shan Plateau document both the formation processes of these vegetated dunes and the environmental changes and geomorphological evolution in this region. Dating of the nebkhas showed that after surface water disappeared, the wadis and playas evolved into gobi deserts (desert pavements) within two centuries. The δ13C trends in the litter deposited within the nebkhas revealed three stages of fluctuating moisture conditions during the past five centuries: before the 1580s, between the 1580s and the late 1990s, and from the early 2000s to the present. However, changes in the coarse fraction of the nebkha sediments show that this region experienced at least five phases of aeolian sediment transport during the same period. The early stages of nebkha formation coincided with the initial stage, when the wadis and playas evolved into gobi deserts and nebkha sizes increased rapidly due to the abundant sediment supply provided by the playas. However, after the playa surfaces stabilized, the nebkha sediments documented environmental changes in adjacent regions. Our results also show that the formation of the Tamarix nebkhas in this region was not controlled by the groundwater table, because in most periods, the water table depth remained above the depth that limits Tamarix survival. In the Ala Shan Plateau, nebkha formation was mainly controlled by aeolian processes, and revealed the integrated effects of environmental changes, thereby providing possibilities for climate and environment reconstructions with a relatively high resolution in extremely arid areas. [Copyright &y& Elsevier]