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Late Paleozoic pillow basalts are well preserved in the Youjiang Basin of SW China. In this study, we conducted geochemical and Sr−Nd isotopic study on the Late Devonian and Late Carboniferous basalts in Napo area, Youjiang Basin. The analyzed samples comprise moderate SiO2, TiO2, Mg#, and REE contents, with slightly positive or negative Eu anomalies, similar to the chemical nature of OIB (Oceanic island basalt). All basalts show low (143Nd/144Nd)i and (87Sr/86Sr)i values, close to EMI-type (I-type Enriched Mantle) magma source. Late Carboniferous basalts display higher (87Sr/86Sr)i, Nb/Th, and lower εNd(t), Zr/Nb values than those of the Late Devonian basalts, implying progressively decreased enrichment components in the magma source processes. Such evolution trend reflects a continuous lithospheric thinning event, supporting a progressive rifting setting of the Youjiang Basin along the southwestern margin of the Yangtze Block in Late Paleozoic. Combined with regional geological background, the Youjiang Basin is viewed as a continental rift basin related to the opening of the Paleo-Tethys Ocean in Late Devonian and became a passive continental margin basin in Carboniferous. The Paleo-Tethys branch ocean probably extended further to the southern Youjiang Basin, likely corresponding to the Song Ma suture zone. [ABSTRACT FROM AUTHOR]

The late Ediacaran period encompasses widespread glacial deposits and early animal radiation. The temporal and spatial context of these events is not well established. The possible links between the glacial deposits and late Ediacaran fossils are critical for understanding the co-evolution of early animals and marine environments. This study presents a detailed geochemical reconstruction from the Tuerkeng Formation on the western margin and the Dongpo Formation on the southern margin along the North China Craton (NCC). The two fossiliferous late Ediacaran formations cover a critical interval between the end of the Zhengmuguan-Luoquan glaciation and the occurrence of late Ediacaran tubular fossils (e.g., Shaanxilithes). The two formations' similar and intermediate CIA values indicate moderate weathering under a warm and humid climate. Stratigraphic covariation of water-insoluble elements in samples from Tuerkeng and Dongpo formations suggest a rapid input of terrestrial materials at the beginning of deglaciation, and these terrestrial materials continued to be input into the shallow marine environment along the western and southern margins of NCC during the deposition of the two formations. Accompanied by the continental weathering and erosion of fresh rocks during the postglacial period of late Ediacaran, abundant nutrients as well as the terrigenous materials would be continuously transported into the continental margin seawater, which may ultimately lead to the rise of the Ediacaran biota. Our results provide new insights into paleoenvironment conditions along the continental margin of NCC and highlight the critical role of the postglacial terrigenous input in the evolution of early animals. • The two studied formations' CIA values indicate moderate weathering under a warm and humid climate. • Our data show an increasing terrigenous input into the NCC's continental margin seawater during the late Ediacaran. • Our results highlight the critical role of the postglacial terrigenous input in the evolution of early animals. [ABSTRACT FROM AUTHOR]

The Late Triassic witnessed significant collisional orogenic events in the Qinling orogenic belt, accompanied by magma underplating and tectonic deformation. These processes potentially resulted in substantial crustal thickening and uplift of the Qinling orogen. However, due to the absence of igneous rock records from this period in the eastern section of the Qinling orogen, the changes in crustal thickness during this orogenic process have not been thoroughly investigated. A series of foreland basins emerged during the Early Mesozoic to the south of the East Qinling orogenic belt. These basins have preserved clastic sedimentary rocks derived from the uplift and erosion of the orogenic belt. These sedimentary records serve as crucial records to reconstruct the evolutionary history of the Qinling orogen. To further clarify the collisional orogenic process of the Qinling orogenic belt, this study conducted in situ volcanic lithic fragment geochemistry, detrital zircon U-Pb chronology and trace element composition analysis on the sandstones of the Lower Jurassic Tongzhuyuan Formation in the Zigui Basin. The results suggest that the sandstones, which exhibit a significant abundance of volcanic lithic fragments, has a characteristic detrital zircon age group of 250–200 Ma, indicating a major provenance from the Triassic volcanic rocks. Combined with regional correlation and paleocurrent analysis, the detrital zircon U-Pb age data show that the source area of volcanic rocks should be in the Qinling orogenic belt to the north of the basin. This interpretation is further supported by the Triassic granitic rocks exposed in the western part of the orogenic belt, representing the magmatism during the Triassic collisional orogenesis in the Qinling orogen. Based on the co-varying relationships between present-day crust thickness with the chemical compositions of granite rocks and zircons, the La/Yb ratio of volcanic lithic fragments in the Tongzhuyuan Formation and the Eu/Eu ratio of detrital zircons with Triassic ages indicate that the Qinling orogen experienced crustal thickening during the Late Triassic, reaching its maximum thickness of 60–70 km at ca. 220–210 Ma. This crustal thickening in the eastern Qinling orogen is temporally consistent with that in the western orogen as recorded by the Triassic granitic rocks and may be related to large-scale crustal shortening and magmatism during the collisional orogeny. [ABSTRACT FROM AUTHOR]

The Kungurian (late Cisuralian) is associated with elevated atmospheric p CO 2 levels and numerous substantial changes in the ocean and terrestrial systems, but carbon cycle perturbations through this time interval are poorly understood. Here, three well-dated organic carbon isotope (δ 13 C org ) curves from South China, paired with their respective carbonate carbon isotope (δ 13 C carb ) data published before, are presented for the first time. Their comparison demonstrates that a prominent, rapid, and synchronous negative excursion in δ 13 C org and δ 13 C carb occurred in the early Kungurian (the herein proposed KCIE event dated to ca. 277.9–277.4 Ma). A comparable shift is observed in other deeper-water marine sections in South China and two terrestrial sections in North China and eastern Australia. Based on carbon mass-balance calculations and a review of concurrent geological records, we propose that the KCIE event was driven by an intensive volcanism of a large igneous province in northern Gondwana, dissociation of voluminous methane hydrates induced by this volcanism, and the ensuing worldwide conflagrations. Predicted elevated production of greenhouse gases involved would have warmed the Earth and further resulted in ocean stagnation, anoxia, and acidification, all of which are in conformity with the documented sedimentological, geochemical, and palaeontological data. This major anomaly in the carbon cycle in the late Cisuralian is considered here to play a key role to promote the transition of the Earth to a greenhouse mode. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic has been traditionally viewed as a period of prolonged stability in terms of environmental and biological evolution, yet growing body of evidence suggests subtle, yet dynamic changes in marine biogeochemical cycles. In this study, we present a high-resolution analysis of carbonate-associated sulfate (CAS) from the Mesoproterozoic Jixian Group (1.6–1.4 Ga), North China. Combined with previously reported carbon isotopes from the same sections, sulfur isotope data provide insight into both oceanic chemistry and biospheric evolution during this period. The sulfur isotopic composition of CAS in the Jixian Group displays high-amplitude variations with a total range from +3.7‰ to +51.9‰. Stratigraphic variation in δ 34 S CAS is most noted in the Wumishan Formation and records shifts of >10‰ over stratigraphic thickness of 100–200 m, indicating a short residence time resulting from a limited oceanic sulfate reservoir. Differences in the pattern of isotopic variability between the Gaoyuzhuang and Wumishan formations suggest complex behavior of the marine sulfur cycle based on proximity of depositional environments to a local or regional chemocline, and the degree of mixing between adjacent environments. Deposition under predominantly oxic conditions favored a stable sulfate reservoir whose isotopic composition was controlled primarily by pyrite burial. By contrast, depositional environments proximal to euxinic waters were subject to rapid changes in both sulfate reservoir size and isotopic composition, resulting from growth and subsequent oxidation of a reactive hydrogen sulfide reservoir. Together, these units demonstrate the difficulty of interpreting marine sulfur cycling in a low oxygen, low sulfate world subject to a range of environmental controls. Data also reveal a long-term positive trend in average δ 34 S CAS and δ 13 C carb from approximately +10‰ to ∼+20‰, and ∼−0.5‰ to +0.5‰, respectively, which is interpreted as reflecting prolonged organic carbon and pyrite burial. Burial of reduced carbon and sulfur may have resulted in a slow, but steady release of oxygen to the biosphere, ultimately driving a gradual increase in oceanic sulfate levels. Our study, combined with previous contributions from the late Mesoproterozoic, supports hypotheses of protracted biospheric oxygenation marked by a modest increase in oceanic sulfate concentrations through the Mesoproterozoic. [ABSTRACT FROM AUTHOR]

The early Mesozoic greenhouse period was characterized by variable climate conditions. The driving mechanisms of this long-term variability are unclear due to a lack of full-period climate reconstructions. In particular, reconstructions of the terrestrial environment are rare, especially reconstructions representing South China during the early Mesozoic period. We focused on the major, trace and rare earth element compositions and clay mineralogy of 173 mudstones from the northern margin of the South China Plate. These data were used as proxies to evaluate the weathering intensity and reconstruct the climate variability from the Middle Triassic to the Late Jurassic after considering the potential effects of provenance, diagenesis and sedimentary sorting and recycling. From the latest part of the Triassic to the early Middle Jurassic, five well-correlated chemical weathering indices, the chemical index of alteration (CIA), chemical index of weathering (CIW), plagioclase index of alteration (PIA), sodium depletion index (τNa) and weathering index of Parker (WIP), imply an advanced degree of chemical weathering (e.g., CIA corr , the corrected CIA, ranging from 71.1 to 88.0) and a clay mineral assemblage zone with abundant kaolinite. Together, these findings indicate a dominant humid climate. In the pre-Late Triassic and post-Middle Jurassic, the dominant seasonally arid climate was characterized by low and widely variable chemical weathering index values (e.g., CIA corr values of 59.4–85.4) and clay mineral assemblage zones containing chlorite, smectite and mixed-layer illite–smectite but less kaolinite. We suggest that P CO 2 variations, the megamonsoon effect, plate motion and regional topography all contributed to the observed climate changes during the early Mesozoic. • Early Mesozoic terrestrial climate change on the South China Plate was revealed. • A seasonally arid climate prevailed pre-Late Triassic and post- Middle Jurassic. • The humid climate of the Late Triassic–Early Jurassic interrupted this arid climate. • P CO 2 , a megamonsoon, plate motion and topography jointly controlled climate change. [ABSTRACT FROM AUTHOR]

Abstract: Unconformity bound Permo-Triassic successions in the Qinfang Basin, South China Craton, reflect tectonic processes associated with tectonothermal activity along the margins of the craton. The provenance record of these successions, based on modal analysis, geochemical composition, detrital zircon U–Pb ages, and paleocurrent data indicate derivation from the adjoining Precambrian Yunkai massif and surrounding Paleozoic sedimentary units. The quartz dominated nature of the siliciclastic units, along with their high Th/Sc and Zr/Sc ratios indicate a recycled orogen source. Detrital zircons from Late Permian to Early Triassic samples display major age groups at 1100–800Ma, 650–500Ma, 480–420Ma, with subordinate age groups at 2800–2400Ma, 1900–1600Ma and 1400–1200Ma. Late Triassic sandstones show a similar detrital zircon age pattern as well as a 300–250Ma age group. Integration of this provenance data with regional geological information suggests that the unconformity at the base of the Permian succession is related to subduction of the Paleo-Tethys ocean to the south of the craton, whereas the major driver for Triassic tectonic activity corresponds with terrane accretion and the termination of Paleo-Tethys Ocean subduction along the southwest margin of the craton. [Copyright &y& Elsevier]

Continual deep-water sediments from the late Early Devonian to the Late Permian extended in wide areas of western Guangxi. We analyzed the major, trace, and rare earth elements of the Upper Paleozoic cherts in Badu, western Guangxi. High non-terrigenous SiO contents (Si/Si(%)> 80%) and pure chert components (> 70%) indicate a large extent of silicification in the Upper Paleozoic cherts, except for the Upper Devonian-Lower Carboniferous Luzhai Formation cherts, which have lower non-terrigenous SiO contents (avg. 71.8%) and pure chert components (40%-70%). The Al/(Al+Fe+Mn) ratios and Feter/Fe(%) values of samples from the lowest horizon of the Pingen Formation are 0.05-0.26, 13.1%-14.5%, respectively, indicating hydrothermal origins. All other samples show high Al/(Al+Fe+Mn) ratios (0.39-0.81) and high Feter/Febulk(%) values (23.1%-186.8%), indicating non-hydrothermal origins. The Pingen Formation and Liujiang Formation cherts show slightly-moderately negative Ce anomalies (0.71±0.07, 0.81±0.08, respectively) and higher Y/Ho ratios (33.49±1.27, 36.10±2.05, respectively) than PAAS. This suggests that these cherts were deposited in the open marine basin, rather than in the intracontinental rift basin as previously assumed. The Luzhai Formation cherts may be deposited near the seamount or seafloor plateaus with no negative Ce anomalies (1.09±0.07) and no significant Y-Ho fractionation (Y/Ho=28.60±1.25). The Nandan Formation and Sidazhai Formation cherts were deposited in the open-ocean basin with moderately negative Ce anomalies (0.67±0.08, 0.73±0.11, respectively) and high Y/Ho ratios (36.01±1.00, 32.00±2.25, respectively). On the basis of our studies about cherts, we conclude that the Youjiang Basin originated as part of the Paleo-Tethys that controlled the depositional environments of cherts during late Paleozoic. The rift of the Youjiang Basin had occurred at least since the Early-Middle Devonian. The basin had a trend of evolving into an open-ocean basin during the Early-Middle Permian. [ABSTRACT FROM AUTHOR]

In the northern South China Sea, the accumulation of enormous quantities of terrigenous sediment during Cenozoic rendered well-developed polymetallic nodules very rare. In this study, we analyzed a polymetallic nodule from the northwestern continental margin of the South China Sea using microscopic mineralogical observation, electron probes, X-ray diffraction (XRD), ICP-MS, and Be isotope dating. We found the nodule's shell layers rich in different types of microstructures, including columnar, laminar, stack-like, petal-like, and porphyritic structures. The major mineral components of the nodule are MnO. Unlike nodules from the eastern Pacific basin, this nodule has high contents in Fe, Si, Al, and REEs but low contents in Mn, Cu, Co, and Ni. The Mn/Fe ratio is also low and the average REEs content is 1370.4 ppm. There is a strong positive anomaly of Ce; and the Be (beryllium) isotope dating shows the initial time of growth of the nodule to be about 3.29 Ma. The inner compact layer formed from 3.29 Ma to about 1.83 Ma. The laminar and stack-like structures and the low contents of the terrigenous elements such as Fe, Si, REE, and Al indicate the paleoceanographical environment with weak undersea currents and favorable oxidizing conditions. From 1.83 Ma to 0.73 Ma, the growth rate of the nodule increased by about 3%; the microstructures formed during this period are stack-like and columnar. The contents of Si and Al are increased by nearly 10%, indicating an increase of terrigenous sediment input in the northern South China Sea. The content of Ce is decreased by about 16%, indicating a significant weakening of the oxidizing conditions at the seabed. From 0.73 Ma to 0.69 Ma, the growth rate of the nodule rapidly rose up to 8.27 times that of the nodule's average growth rate, and the contents of Fe, Al, and REEs in the layer also increased, forming a loose layer characterized by oolitic, granular, porphyritic, and petal-like structures, indicating the paleoceanographical environment with a high sedimemtation rate and abundant supply of terrigenous sediment in the northern South China Sea. From 0.69 Ma to 0.22 Ma, the growth rate of the nodule suddenly slowed and the outer compact layer formed. Contents of Fe, Si, REE, Al, Mn, Cu, Co, and Ni in this layer were significantly lower than in other layers. The main structures of the layer are laminar and fissure filling structures. These reflect the paleoceanographical environment with stable undersea currents, poor oxidizing conditions, and other conditions not conducive to nodule growth. The growth process of nodule S04-1DG-1 was found to respond sensitively to the changes of the paleoceanographical environment of the northern South China Sea during the late Cenozoic. [ABSTRACT FROM AUTHOR]

Abstract: Analyses of marine carbon isotope profiles have provided much of our current understanding of the evolution of Earth surface environments, particularly in the latter portion of the Proterozoic Eon. Earlier Mesoproterozoic successions, however, have received comparatively little attention due to the relatively subdued nature of carbon isotope variation. In this study, we present high-resolution isotopic profiles from three sections in the Yanshan Basin, North China craton that, combined, comprise the entirety of the early Mesoproterozoic (1600–1400Ma, Calymmian period) Jixian Group. High-resolution profiles of both carbonate and organic carbon provide critical data for global comparison and permit us to better constrain both the pattern and origin of isotopic variation in the Mesoproterozoic. Marine carbonate rocks of the Jixian Group show generally muted isotopic variation with average values near 0‰, consistent with previous observations from the early Mesoproterozoic. Data furthermore record an increase in isotopic variation through the succession that is interpreted to reflect a long-term decrease in pCO2 and, consequently, in the isotopic buffering capacity of marine dissolved inorganic carbon (DIC). By contrast, the isotopic composition of marine organic matter suggests facies-dependent differences in carbon cycling. Organic carbon compositions suggest a dominance of autotrophic carbon fixation and aerobic decomposition in shallow-water environments, and increased remineralization by anaerobic heterotrophs in deeper-water environments. Correlation between organic carbon composition and depositional environment are interpreted to reflect differences in carbon cycling within benthic microbial mats under low oxygen conditions and dynamically maintained stratification of marine waters. [Copyright &y& Elsevier]

One hadean zircon from the Cambrian sandstone in the southern part of South China has a U-Pb age of 4107±29 Ma with ɛ( t) value similar to that of the homochronous depleted mantle and Hf model age of 4102±21 Ma. This demonstrates the existence of hadean crustal remnant in South China. A close match between the U-Pb age and Hf model age with the highly position ɛ( t) value indicates the growth and immediate reworking of juvenile crust from the depleted mantle at ca 4.1 Ga. The prominent 'Pan-African' and Grenville zircons derived from the exotic sources were also found in the sample, which indicates a linking between South China and Gondwana in the Cambrian period. The southern part of South China has complex histories of crustal growth and tectonic evolution. [ABSTRACT FROM AUTHOR]

Abstract: Upper Ordovician to Silurian strata along the northeastern margin of the Yangtze Block, South China Craton, were deposited in a syn-orogenic basin related to the Early Paleozoic Kwangsian Orogeny in the adjoining Cathaysia Block. U–Pb age data for 450 detrital zircons from six sandstones samples range in age from Archean to the early Paleozoic. All samples have a dominant age peak between 0.8 and 0.9Ga and subordinate peaks around 2.5Ga and 1.8Ga, with the youngest samples also containing zircons between 0.47 and 0.43Ga. The detrital zircon age spectrum is indicative of derivation from the southeast with Precambrian grains derived from the basement of Cathaysia Block and the Early Neoproterozoic Jiang-Shao suture, and Early Paleozoic zircons derived from igneous activity associated with the Kwangsian Orogeny. The restriction of Paleozoic detritus to the latter phases of the Kwangsian Orogeny (which started by 460Ma) suggests progressive exhumation of the Cathaysia Block, perhaps due to thrusting over the Yangtze Block, with the latter remaining a site of active sedimentation during orogenesis. [Copyright &y& Elsevier]

The southwest basin is a key to study the origin and development of the South China Sea (SCS). We do not know much about its boundaries, geological history, and the formation of its sea floor because it has a complex and highly regional structural background, notable sediment activity, and yet few floor rocks. Here a granodiorite sample was collected from the southern margin of the southwest basin of the South China Sea. The results indicated that the Ar-Ar ages of biotites in the sample are 110.3±0.5 Ma, suggesting that they were products of magmatic intrusion during the Early Cretaceous period. The sample's geochemistry showed it had high SiO, KO, and AlO but low TiO levels. Tectonic discriminant diagrams suggested that the sample might represent extrusion-related magmatism, either in an arc or forearc setting in the SCS area and that the sample mainly belonged to the syncollision type, whose formation was related to orogenies. The sample may be part of the main rock that made up the boundaries of rift system. The process of tension cracking was similar to the development of the Red Sea, in which the rifting and sagging occurred in the continental crust. The southwest basin may not be an original ocean, but a rift developed through finite extension on continental crust basement. The oceanic crust came into being when the width and depth of the rift valley reached a certain scale. The granodiorite sample we collected provides a means of determining the boundary of the southwest basin and the clues that may help researchers expand relevant models. It constitutes an important datum regarding the analysis of the formation and development of the SCS. [ABSTRACT FROM AUTHOR]

This paper reports LA-ICP-MS zircon U-Pb ages and REE compositions on detrital zircons (Type 1) and hydrothermal zircons (Type 2) from low-metasedimentary rocks in the Mesoproterozoic Gaoyuzhuang Formation, Pingquan area, Hebei Province that provide important constraints on the tectonic evolution along the northern margin of the North China Block. The detrital zircons are characterized by an oscillatory magmatic core, surrounded by a narrow structureless rim in CL images. They yield Pb/Pb ages ranging from 1703 to 2543 Ma with two age peaks at 2473 and 1794 Ma, which is consistent with the Neoarchean and Paleoproterozoic tectono-thermal events recorded in the NCB basement, indicating that the source of the detritus was locally derived. By contrast, the hydrothermal ones are euhedral, sector zoning or internally structureless. They have relatively higher U and Th contents and Th/U ratios (U=139-2918 ppm, Th=35-1327 ppm, Th/U (average) =0.78 vs. U=15-1044 ppm, Th=8-341 ppm, Th/U (average) =0.57 for detrital zircons). Moreover, they are also enriched in REEs relative to detrital zircons and show a lower positive Ce anomaly (ΣREE = 659-2418 ppm vs. 231-611 ppm for detrital zircon; Ce/Ce*=2-13 vs. 33-174 for detrital zircons), similar to known hydrothermal zircons derived from many locations. These characteristics, combined with our field petrographic observations, indicate that the hydrothermal zircons possibly formed from a low temperature aqueous fluid. Twelve concordant or near-concordant analyses on hydrothermal zircons yield weighted mean Pb/U ages of 325-327 Ma, which provide unambiguous evidence that the northern NCB underwent late Paleozoic low temperature hydrothermal modification. This timing of this hydrothermal event is compatible with that of the late Paleozoic magmatic and metamorphic-deformational events occurred on the northern margin of the NCB, it appears likely that the hydrothermal activity resulted from southward subduction of the Paleo-Asian Oceanic plate underneath the NCB during late Paleozoic. [ABSTRACT FROM AUTHOR]

Abstract: Devonian strata in the North Qilian Belt of the Qilian Orogen accumulated in a foreland basin formed through collision between the North China Craton and the Central Qilian Belt. U–Pb age data for 393 detrital zircons from four sandstone samples from the Lower to Middle Devonian Laojunshan Formation and Upper Devonian Shaliushui Formation range in age from 3.6Ga to 0.4Ga and indicate input from a multi-component source. Detrital zircons older than the early Mesoproterozoic (1.4Ga) were likely derived from the North China Craton, whereas late Mesoproterozoic to Neoproterozoic zircons were derived from the Central Qilian Belt. Early Paleozoic zircons were derived from the North Qilian continental arc and associated ophiolites. The occurrence of Neoproterozoic zircons indicates that their source, the Central Qilian Belt, was likely once part of the Yangtze Block of the South China Craton prior to its separation from the craton in the late Neoproterozoic. [ABSTRACT FROM AUTHOR]

• Genesis of Mn-ores of post-Sturtian Datangpo Formation in Nanhua Basin, South China. • B/Ga salinity proxy integrated with redox and other environmental geochemical data. • Episodic hydrothermal events delivered Mn(II) to deep basin for Mn-ore formation. • Benthic microbial activity catalyzed deep-basin Mn-carbonate precipitation. • First salinity-based model for Datangpo Formation Mn-ore deposits developed. The genesis of manganese (Mn)-carbonate deposits in the Cryogenian Datangpo Formation (∼662.9–654.5 Ma), Nanhua Basin, South China remains controversial. Here, we combine new proxy data (B/Ga) for watermass salinity with existing data (major- and trace-element concentrations, bulk-rock Sr and Nd isotopes, pyrite sulfur isotopes, and organic and inorganic carbon isotopes) for redox and other environmental parameters to gain new insights into the conditions under which these deposits formed. Our analysis focuses on the Mn-carbonates of the 1st Member of the Datangpo Formation, which were deposited at the termination of the Sturtian Ice Age, with an emphasis on understanding their environment of formation, Mn sources, and microbial processes. Close relationships between Mn content and salinity (B/Ga), redox (C org /P, Cu EF), and carbon-cycle (δ13C carb , δ13C org) proxies reveal a dominant role of salinity in the development of these Mn-rich deposits. These relationships document Mn accumulation in a watermass that fluctuated between brackish, euxinic conditions (Mn-shale beds) and saline, ferruginous conditions (Mn-carbonate beds). Significant correlations between Mn content and hydrothermal proxies (Eu/Eu*, 87Sr/86Sr and εNd(i)), as well as covariation of (87Sr/86Sr) i vs εNd(i) and Fe/Ti vs Al/(Al + Fe + Mn), suggest that Mn was sourced mainly from hydrothermal vents in the deep Nanhua Basin. Episodic hydrothermal activity also provided nutrients that boosted primary productivity and organic matter accumulation rates in the form of mineralized biomats. Partial oxidation of the organic carbon coupled to dissimilatory Mn(IV) reduction promoted Mn(II)-carbonate formation in conjunction with high levels of glacially generated alkalinity. A similar confluence of factors (i.e., high background alkalinity, hydrothermal inputs of Mn and nutrients, and microbial activity) may have played a role in the formation of large-scale Mn-ore deposits during other geologic epochs. [ABSTRACT FROM AUTHOR]

The article focuses on a study which examined the paleoclimate inference from the evolution of Palaeophycus and Beaconites and trace fossil assemblages in Triassic in Jiyuan, Central China. Information on formations in the Triassic succession is given. According to the study, sharp scratch marks on the wall of the Palaeophycus indicate a firm substrate while Beaconites suggests a dry environment during the Early Triassic. It notes the dominance of vertical assemblages in Late Triassic.

The glacial-interglacial transitions of ice ages are associated with large, rapid changes in climate, which potentially can be reconstructed from stratigraphic profiles of the chemical index of alteration (CIA). Here, we present a case study based on high-resolution CIA profiles of Neoproterozoic glacial deposits from South China (paleolatitude ~30° N) as a record of the climate transition at the termination of the Sturtian Glaciation (~663 Ma). Drillcore ZK2115 (Gaodi Deposit) exhibits a progressive upsection increase in mean CIA over a ~50-m interval, from 58 (range 52–65; note: all ranges are given as 16th–84th percentiles) in the synglacial upper Tiesi'ao Formation to 67 (range 64–69) in the deglacial basal Datangpo Formation cap carbonates, and to 68 (range 66–70) in the postglacial Datangpo Formation black shales. A coeval section from the Lijiawan Deposit also exhibits an increasing CIA trend upsection within shallow-water Mn-carbonate facies. These CIA patterns show no relationship to lithology and are interpreted to reflect climatic warming and intensified chemical weathering during the Sturtian deglaciation. Similar large increases in postglacial CIA values are seen in Paleoproterozoic and Late Paleozoic successions, and at least moderate increases in CIA values are recorded during warm stages of the late Quaternary (e.g., the Bølling-Allerød and Holocene) relative to the cold stages (e.g., the Last Glacial Maximum and Younger Dryas). The rapidity of CIA changes in Quaternary systems (~1 to 10 kyr) suggests that weathering intensity may have changed at similarly rapid rates in more poorly dated deep-time glacial successions, with potential implications for Snowball versus Slushball models of Cryogenian glaciations. These examples show that CIA can be a robust proxy for climate changes (i.e., enhanced chemical weathering intensity) during glacial-interglacial transitions of both ancient and recent ice ages. • Large increases in chemical index of alteration (CIA) during major deglaciations. • Case study of CIA changes in end-Sturtian deposits of Nanhua Basin (South China). • CIA increase from 59 ± 6 in synglacial Tiesi'ao Fm. to 66 ± 3 in postglacial Datangpo Fm. • CIA increase concentrated within terminal glacial deposits of uppermost Tiesi'ao Fm. • Similar CIA increases for glacial-interglacial transitions from Paleoproterozoic to Recent. [ABSTRACT FROM AUTHOR]

Late Permian ultramafic–mafic igneous rocks in the Pingxiang area, Guangxi, South China include wehrlite, gabbro, diabase, and amygdaloidal basalt. Geochemical characteristics document interaction between the Emeishan Large Igneous Province (ELIP) and the mantle wedge related to subduction of the Paleo–Tethys. Gabbro and basalt show chondrite–normalized rare earth elements (REEs) and primitive mantle–normalized trace element patterns that parallel ocean island basalts (OIB) and mafic intrusions from the ELIP. Melts in equilibrium with clinopyroxenes, in both wehrlite and gabbro, have REEs and trace element compositions similar to OIB and high–Ti mafic rock of the ELIP. The clinopyroxenes also show a rift–related compositional trend and cover those from the ELIP rocks. These compositional features, along with their moderate initial 87Sr/86Sr and ε Nd (t) values (−0.8 to +3), are consistent with derivation from an enriched mantle plume source. This is the first time that ultramafic–mafic rocks are reported beyond the established extent of the ELIP and could represent an offshoot from the main mantle plume or indicate that the ELIP plume was considerably bigger than current proposals but has been significantly denuded by subsequent erosion. In addition, the Pingxiang rock units display slightly enriched ε Nd (t) values and slight negative Nb, Ta, and Zr relative to OIB rocks, indicating an enriched component in the mantle source. Formation of the ELIP spatially and temporally overlapped with subduction of the Paleo–Tethys ocean and interaction between the plume and mantle wedge accounts for the compositional diversity of the ELIP. Such interaction is probably common along the southwestern–southern margin of the Yangtze Block. • Permian ultramafic-mafic units in Pingxiang, south China were derived from mantle plume modified by Paleo-Tethys subduction • The subducted Paleo-Tethys Ailaoshan zone extends to the southeastern margin of the Greater Youjiang Basin • The original areal extent of the Emeishan Large Igneous Province is likely much greater than presently mapped [ABSTRACT FROM AUTHOR]

The article focuses on findings of a study on Zircon U-Pb Age of the Babu Ophiolites in Southeast Yunnan, China and Constrains of Plate Subduction Time. It states that mafic and ultramafic rocks have been inferred to be part of the Emeishan large igneous province (LIP) by some researchers, and mentions that Zircon grains from sample TGZl as euhedral or prismatic. It notes that mafic and ultramafic rocks in Malipo do not belong to part of the Emeishan LIP.

The Lower Carboniferous Jiujialu Formation bauxite deposits of northern Guizhou Province, China, are a Kazakhstan subtype of karst bauxite deposits. The provenance of the Jiujialu Formation has long been debated, with uncertainty about the formation of the bauxite deposits. Here we report new geochemical data that indicate the affinity between the Lower-Middle Ordovician clastic rocks and argillaceous dolostones and the overlying Carboniferous bauxite deposits, all of which are characterized by high Al2O3, K2O, and ΣREE contents, flat post-Archean Australian shale (PAAS)-normalized REE patterns, and uniform immobile element ratios (TiO2/Al2O3, Nb/TiO2, and Zr/TiO2). Their similar detrital zircon age distributions further indicate the link between the bauxite deposits and the clastic rocks and argillaceous dolostones. Zircon age spectra of clastic rocks of the Lower Silurian Hanchiatien Formation in northern Guizhou match those of the bauxite deposits, with a maximum age peak at ∼980 Ma and other secondary age peaks, suggesting these clastic rocks may represent the provenance of the bauxite deposits. The youngest detrital zircons (∼445 Ma) occur only in the bauxite deposits and are probably sourced from K-bentonite beds of the Ordovician-Silurian transition. Our analyses indicate that the source materials of the bauxite deposits in the Jiujialu Formation are of mixed provenance: Lower-Middle Ordovician aluminosilicate rocks and argillaceous dolostones of the underlying strata, and Lower Silurian clastic rocks and K-bentonite from adjacent areas. A comparison of Early Carboniferous bauxitic provenances in northern and central Guizhou indicates that paleotopography was the major factor controlling the provenance of these bauxite deposits. [ABSTRACT FROM AUTHOR]

Hydroclimate is an important factor controlling landscape evolution. But establishing the impact of hydroclimate is complicated by the influences of other processes and is especially hard to prove for those in deep time from geological record. During the late Permian, voluminous basaltic sediments were derived from the erosion of the Emeishan large igneous province in western South China. They provide a unique record critical in understanding the responses of tropical basaltic erosion to hydroclimate change without impacts of orogenic uplift, lithologic variation, vegetational difference and glacial‐interglacial change. Sampled successions define a negative carbon isotope excursion capable of making regional and global stratigraphic correlations in the middle Wuchiapingian interval corresponding to the final phase of the late Paleozoic ice age. This interval is associated with a petrofacies shift and a decreasing source weathering intensity, a downward shift of erosion loci, and a reduced coastal water paleosalinity. Applying present‐day temperature dependence pattern of basaltic weathering and using land surface temperatures approximated from nearby paleo‐seawaters, denudation rates were calculated for the Emeishan basaltic province and shows an increase from ∼71 to ∼107 m/Ma. This erosional acceleration is temporally correlated with a decrease in paleosalinity and likely linked to enhanced freshwater discharge in the middle Wuchiapingian. Scaling and landscape erosion modeling suggest ∼80%–130% increase in catchment precipitation could have driven this acceleration in denudation. Our work provides a positive test for the hydroclimate forcing on landscape erosion in deep time and underlines the mechanistic linkage of sediments with erosion and climate change. Plain Language Summary: Sedimentary records provide a unique way to track source weathering and erosion in the deep geological past. During the late Permian to early Triassic voluminous basaltic sediments were eroded from the Emeishan large igneous province, which was emplaced at ca. 260 Ma in southwestern China, into the adjacent basins. These late Permian sedimentary records are studied to understand the denudation of this tropical basalt province in the final period of the late Paleozoic ice age (LPIA). Our data reveal a negative organic carbon isotope excursion, decreasing weathering intensity and deepening erosional loci in the Emeishan basaltic province, and a reduced salinity due to greater rainfall in the middle Wuchiapingian interval. Denudation rate was estimated for the Emeishan province and a correlation of high denudation rates with lowered paleosalinity was documented in the Wuchiapingian. The accelerated denudation in the Emeishan basaltic province was ascribed to ∼80%–130% increase in catchment precipitation during the final phase of the late Paleozoic ice age. This work highlights the importance of sedimentary records to understand the deep time landscape evolution. Key Points: A negative carbon isotope excursion enables middle Wuchiapingian stratigraphic correlations from South China to GondwanaA decrease in weathering intensity and a deepening of erosional exhumation are indicated for the Emeishan basaltic provinceDenudation was accelerated due to ∼80%–130% increase in precipitation during the late Permian in SW China [ABSTRACT FROM AUTHOR]

Phosphorite of the Ediacaran Doushantuo Formation accumulated in the central Guizhou province during the Neoproterozoic-Cambrian Phosphogenic Event, producing the first true phosphorite giant in Earth history. Deposition is interpreted to have occurred on a wave-dominated epeiric platform along the northern margin of the Qianzhong Uplift. Lithofacies stacking patterns and two paleokarst surfaces record phosphogenesis through at least two sea-level cycles. As in younger Phanerozoic epeiric sea phosphorites, the delivery of upwelled phosphorus is interpreted to have stimulated phosphogenesis in a range of shallow-water environments. Ten phosphatic and associated lithofacies are recognized in the Doushantuo Formation. Wavy and horizontal laminated pristine facies were the locus of phosphogenesis and reflect the authigenic precipitation of francolite in accumulating fine sediment. Granular, cross-stratified phosphorite is interpreted to have been produced through storm-wave winnowing of pristine facies and the subsequent transport, redeposition, and concentration of phosphatic peloids into economic beds. Beds with the highest concentration of phosphorus formed in shallow, wave-agitated environments around paleo-topographic highs. Paragenetic analysis suggests that secondary meteoric processes further enriched the phosphorus content (>35 wt%) of these granular beds during sea-level lowstands. Such aerially extensive, upwelling-related phosphorite contrasts Paleoproterozoic and Neoproterozoic phosphatic deposits. Throughout much the Proterozoic francolite precipitation was restricted to shallow-water, photosynthetic oxygen oases where redox sensitive phosphogenic processes were focused in the sediment. The Doushantuo Formation is interpreted to record the oxygenation of the water column and concomitant expansion of phosphogenic environments during the Neoproterozoic Oxygenation Event. This progressive ventilation of the deep ocean forever changed the biogeochemical cycling of phosphorus in the marine realm and set the stage for the deposition of phosphorite giants that punctuate the Phanerozoic stratigraphic record. [ABSTRACT FROM AUTHOR]

The last glaciation during the late Paleozoic ice age commenced at around the Guadalupian–Lopingian (G–L) boundary and is synchronous with the emplacement of the Emeishan large igneous province. Using CA-TIMS zircon U–Pb dating, we obtained an age of 259.51 ± 0.21 Ma for the uppermost tuff from the Puan volcanic sequence in the eastern Emeishan large igneous province, constraining the timing of Emeishan volcanism and providing another candidate age for the G–L boundary. In addition, we determined an age of 259.69 ± 0.72 Ma for a basal claystone in the immediately overlying Longtan Formation from a drill core section in southwest South China. These ages, along with source weathering trends of mudstones from the lower Longtan Formation, and compiled paleotemperature records, indicate an earliest Wuchiapingian cooling coinciding with the onset of the last Permian glaciation. This global cooling is associated with positive shifts in both organic and carbonate carbon isotopic records and likely a decrease in atmospheric p CO 2 . A hypothesised causal linkage is proposed in which the rapid post-eruptive basaltic weathering of the Emeishan province in an equatorial humid belt may accelerate the atmospheric CO 2 consumption and lead to climate cooling. Our work supports the long-term climate cooling effects of large igneous provinces. [ABSTRACT FROM AUTHOR]

Provenance analyses of Lower to Middle Triassic strata from the Greater Youjiang Basin along with the Permian strata of Hainan Island, provide a record of the collisional assembly of the South China Craton and Indochina Block and their incorporation into Asia. Detrital zircons from Lower and Middle Triassic samples show similar overall age spectra ranging from Archean to Triassic with major age groups at 300–250 Ma, 480–420 Ma, and 1200–900 Ma, as well as at 400–300 Ma in one Triassic sample. Permian siltstones from Hainan Island, to the southeast of the Greater Youjiang Basin, record different age spectra with major age groups at 400–300 Ma and 530–420 Ma and subordinate components at 1200–900 Ma and 1900–1700 Ma. These age data in combination with available paleocurrent data and regional geological relations suggest that Precambrian detrital zircons were derived from the Precambrian basement or recycled from the overlying early Paleozoic sedimentary rocks that contain Precambrian detritus. Early Paleozoic detrital zircons were derived from igneous rocks in the South China Craton. Devonian-Triassic detrital zircons in the Triassic strata were likely sourced from coeval magmatic activity related to closure of Paleo-Tethys branch ocean that lay to the southwest, whereas 400–300 Ma detrital zircons in the Permian siltstones of Hainan Island were likely derived from a Paleozoic magmatic arc source that extended along the eastern-southeastern margin of China from Hainan Island to Japan in response to subduction of the Paleo-Pacific oceanic crust. Detrital zircon, trace element, and sandstone modal data for Permo-Triassic strata from the Greater Youjiang Basin indicate that the basin evolved from a trailing-edge passive margin setting to a peripheral foreland basin during closure of the Paleo-Tethys Ocean and collision between Indochina and South China. The initiation time of the foreland basin decreases from southeast to southwest across the basin, probably reflecting oblique collision. In contrast, the Permian strata on Hainan Island record a provenance history distinct from the Greater Youjiang Basin, which is related to late Paleozoic to Mesozoic subduction of the Paleo-Pacific Plate beneath South China. [ABSTRACT FROM AUTHOR]

The Qin-Fang Trough, South China, trends northeast-southwest, orthogonal to the adjoining southern margin of the craton. The Devonian strata within the trough are unconformable on late Neoproterozoic units of the Yunkai Massif, indicating that strata within the trough are autochthonous. U-Pb ages and Hf isotope compositions of detrital zircons from the Silurian to Devonian succession are consistent with derivation from the massif. In comparisons of our data with those fromequivalent units in the Ailaoshan Belt andHainan Island, detrital zircons fromthe Silurian strata show similar age distributions andHf isotope compositions, indicating that the three areas shared a common source andwere adjacent to each other during the Silurian. In contrast, the age distributions of detrital zircons preserved in Devonian strata in the Qin-Fang area are different from those of equivalent units in the Ailaoshan Belt. This, along with the absence of Devonian strata on Hainan Island, suggests that the Qin-Fang area had separated fromthe Ailaoshan Belt by the Devonian. This change is linked to opening of the Ailaoshan Ocean, which was synchronous with expansion of the Qin-Fang Trough and the adjoining Youjiang Basin into epicontinental basins during the Devonian and Carboniferous. Combining these findings with temporal and spatial correlations, we conclude that the Qin-Fang Trough originated as an aulacogen: a "failed" rift of a three-armed rift system, with the other two rift arms evolving into the AilaoshanOcean during the opening of Paleo-Tethys. The Ailaoshan Ocean was an Atlantic-type oceanic basin with rifting commencing in the Early Silurian. [ABSTRACT FROM AUTHOR]

• We reported trace elements and δ34S CAS data from the Gaoyuzhuang Formation. • Heterogeneous δ34S was caused by low sulfate concentrations and redox stratification. • δ34S CAS and Ce anomalies indicate pulses of oxygenation in the early Mesoproterozoic. • Pulses of oxygenation likely promoted eukaryotic evolution. The early Mesoproterozoic (1.6–1.4 Ga) is a critical stage for oxygenation of Earth's surface and early eukaryote evolution. However, the relationship between both remains uncertain. Here, we provide new carbonate associated sulfate (CAS) sulfur isotopic compositions (δ34S CAS) and trace elements from the 1.6 to 1.55 billion-year-old Gaoyuzhuang Formation in multiple sections within the Yanshan Basin, North China, to investigate the temporal and spatial variation of ocean redox conditions. New and collected δ34S CAS data from five sections (Pingquan, Kuancheng, Qianxi, Jixian and Gan'gou sections) reveal similar sulfur isotopic excursions, but the differences in absolute values indicate spatial heterogeneity of sulfur isotopic compositions, which may reflect marine low-sulfate concentrations and oceanic redox stratification. The most elevated δ34S CAS values appeared at the top of the Second Member of the Gaoyuzhuang Formation, followed by distinct negative excursions at the bottom of the Third Member, suggesting a dynamic sulfur cycle and seawater redox status during this period. Combined with previous reported carbon and sulfur isotopes and some redox proxies (e.g., Ce anomalies, manganese-rich deposit, I/(Mg + Ca) and Fe speciation), we suggest that at least two possible oxygenation events may have occurred in the Gaoyuzhuang Formation: (1) the bottom of the Second Member and (2) the bottom or middle part of the Third Member. Different sections show asynchronous timing of these events, indicating that the redox status was spatial heterogenous within the Yanshan Basin. The spatial heterogeneity may be controlled by facies and paleogeographic locations. Considering that decimeter‐scale multicellular eukaryotes are preserved in the middle part of the Third Member, we argue that oxic bottom water condition may be a critical factor for early eukaryote evolution. [ABSTRACT FROM AUTHOR]

Little attention has been focused on the stratigraphical imprints of the Late Paleozoic Ice Age on the equatorial eastern Paleo-Tethys. An integrated study of biostratigraphy, microfacies, and stable carbon isotope stratigraphy was carried out on Pennsylvanian–middle Guadalupian carbonates of the Gongchuan section in the Bama Platform, South China. It records seven cooling and two warming pulses in the pre-Kungurian interval, comparing with ice-proximal stratigraphical records and far-field indirect proxies in lower latitudes. A Kungurian negative δ 13 C excursion (from + 4.4‰ at the base of the Kungurian to + 1.6‰) recorded only in the subequatorial belt is documented here. It is followed by a global positive δ 13 C trend reaching + 5.3‰ near the Cisuralian–Guadalupian boundary. Seven third-order shallowing–upward cycles are reported for the first time from the Kungurian succession. The duration of each cycle is estimated to ca. 1 myr. These cycles are interpreted as being of glacioeustatic origin and mainly driven by long-period modulations of obliquity (~ 1.2 myr) under major p CO 2 decreasing condition. This interpretation is supported by recent climate–ice sheet modeling and Cenozoic glaciation studies, which argue that astronomical forcing will be amplified by large-magnitude perturbations in the carbon cycle, when only localized ice-centers persist. Our results emphasize the need for integration of sedimentological and paleoclimatological proxies in elucidating the dynamics of the deglacial phases of the Late Paleozoic Ice Age. [ABSTRACT FROM AUTHOR]

Sturtian cap carbonate deposits, previously unknown in South China, are documented in this study from the base of the Datangpo Formation in the Nanhua Basin (Guizhou Province). The age of these deposits is constrained by an LA-ICP-MS U-Pb zircon age of 662.7 ± 6.2 Ma from the overlying Mn-shale layer, which is approximately coeval with the termination of the Sturtian glaciation globally. The newly discovered cap carbonates are composed of massive, laminated, pisolitic, and sandy dolomites, and formed subtidally on the summits of horsts within the Nanhua Basin. Two δ 13 C carb profiles (from the JJS-1 and ZK01 sections) show positive shifts of 4–5‰ from the base to the top of the cap carbonates with a ∼2‰ offset between the profiles. These features suggest both a large global perturbation as well as local influences on carbonate carbon isotopes during the Sturtian deglaciation, which is consistent with aspects of both the Snowball Earth and gas hydrate destabilization hypotheses for the origin of cap carbonates. The newly discovered cap carbonates are inferred to be correlative with rhodochrosite (Mn-carbonate)-bearing deposits of the basal Datangpo Formation in adjacent grabens of the Nanhua Basin. This correlation is based on (1) the equivalent stratigraphic positions of the cap carbonates and Mn-deposits, both of which are found at the base of the Datangpo Formation, and (2) consistent U-Pb dates of 667–663 Ma for tuff layers interbedded with these deposits at two locales. The Mn-deposits show significantly higher TOC content (1–3% vs <0.7%) and more negative δ 13 C carb values (−10.5 to −5.5‰ vs −4.0 to +2.5‰) than the cap carbonates. The upsection trend toward higher δ 13 C carb in the cap carbonates may reflect increases in marine productivity and the burial rate of organic carbon following the Sturtian glaciation. Despite coeval formation, the dolomitic cap carbonates deposited on horsts and the Mn-carbonate sediments deposited in grabens are heterogeneous facies with different formation mechanisms. [ABSTRACT FROM AUTHOR]

The Neoproterozoic Datangpo Formation of the Nanhua Basin in South China records interglacial sedimentation between the ~ 720–660-Ma Sturtian and ~ 654–635-Ma Marinoan glaciations. The lower part (1st Member) of this formation contains manganese-rich deposits that represent a mixture of two main components, Mn-carbonates and Mn-bearing aluminosilicates (clay minerals). The Mn-carbonate component is characterized by high La/Sc ratios, high initial 87 Sr/ 86 Sr ratios, and low initial εNd(t) values, and the siliciclastic component by low La/Sc ratios, low initial 87 Sr/ 86 Sr ratios, and high initial εNd(t) values. The likely source of the non-radiogenic siliciclastic material is weathering of Neoproterozoic continental flood basalts on the Yangtze Block. Discriminant plots show that the Mn-ore samples have compositions consistent with at least partial derivation from hydrothermal sources. Mn-carbonate deposition was the result of reactions between aqueous Mn and sedimentary organic matter during early diagenesis that led to elevated Mn 2 + concentrations and alkalinity in sediment porewaters. Based on these observations, we propose a new metallogenic model for the Datangpo Formation manganese deposits. During the Sturtian glaciation, the anoxic Nanhua Basin accumulated abundant dissolved Mn, a substantial fraction of which was derived from hydrothermal sources. When glaciation ended and a redox-stratified water column developed in the basin with an oxic surface layer and an anoxic deep layer, the accumulated dissolved Mn precipitated as Mn-oxides on the basin floor during episodic ventilation events. After co-burial with organic-rich sediments, these Mn-oxides were reduced during organic matter oxidation, which led to the formation of secondary Mn-carbonates (rhodochrosite) through increases in sediment porewater Mn 2 + and in alkalinity via microbial sulfate reduction and microbially mediated Mn reduction. [ABSTRACT FROM AUTHOR]

Bauxite deposits at the base of the Upper Permian Heshan Formation in the Youjiang Basin, South China, contain zircons with dominant age peaks at 263–262 Ma. During the Middle to Late Permian, the Youjiang Basin consisted of a number of isolated and attached carbonate platforms separated by inter-platform troughs. The bauxite deposits are limited to the isolated carbonate platform facies and are not present on attached carbonate platforms and inter-platform troughs. Discriminant plots based on the trace element composition of the zircons indicate a combination of within-plate/anorogenic and arc-related/orogenic sources. Geochemical and isotopic data suggest that the metallogenic materials of the bauxite deposit came from felsic volcanic rocks of the Emeishan Large Igneous Provence (ELIP) in South China and from the Truong Son volcanic arc located between the South China and Indochina cratons. The northwestern and southeastern parts of the Youjiang Basin received larger amounts of ELIP detritus and volcanic arc detritus, respectively. Coarser siliciclastic material in proximal attached carbonate platform and inter-platform trough settings was delivered by rivers, but finer siliciclastics that accumulated on distally located carbonate platforms in isolated deep-water areas was probably transported by wind. [ABSTRACT FROM AUTHOR]

Silicic eruptive units can constitute a substantive component in flood-basalts-dominated large igneous provinces, but usually constitute only a small proportion of the preserved volume due to poor preservation. Thus, their environmental impact can be underestimated or ignored. Establishing the original volume and potential climate-sensitive gas emissions of silicic eruptions is generally lacking for most large igneous provinces. We present a case study for the ∼260 Ma Emeishan province, where silicic volcanic rocks are a very minor component of the preserved rock archive due to extensive erosion during the Late Permian. Modal and geochemical data from Late Permian sandstones derived from the province suggest that silicic volcanic rocks constituted some ∼30% by volume of the total eroded Emeishan volcanic source rocks. This volume corresponds to > 3 × 10 4 km 3 on the basis of two independent estimate methods. Detrital zircon trace element and Hf isotopic data require the silicic source rocks to be formed mainly by fractional crystallization from associated basaltic magmas. Based on experimental and theoretical calculations, these basalt-derived ∼10 4 km 3 silicic eruptions released ∼10 17 g sulfur gases into the higher atmosphere and contribute to the contemporaneous climate cooling at the Capitanian–Wuchiapingian transition (∼260 Ma). This study highlights the potentially important impact on climate of silicic eruptions associated with large igneous province volcanism. [ABSTRACT FROM AUTHOR]

Changes in Mississippian global paleogeography derived from the reconfiguration of the continents have been suggested to result in a change in oceanic circulation, carbon cycling, as well as in global cooling. Here, integrated δ 13 C carb chemostratigraphy and foraminiferal biostratigraphy across the Mississippian (late Tournaisian, Visean, early Serpukhovian; MFZ6–MFZ16 foraminiferal biozones) of the Gongchuan section located in the isolated Bama Platform in the Youjiang Basin, South China, are presented. The δ 13 C carb trend shows an abrupt decline during late Visean (Asbian-early Brigantian; MFZ13–14). This decline is also observed in subequatorial western Euramerica, whereas coeval sections in subequatorial eastern Euramerica show consistently elevated δ 13 C values across the entire Visean. The δ 13 C decline in western Euramerica and the South China Block (eastern Paleo-Tethys) coincides with a global regression with a suggested glacioeustatic origin, the onset of high-frequency climate and sea-level oscillations, and the closure of the Rheic seaway between Euramerica and Gondwana. We propose a model explaining the divergence of δ 13 C records resulting from the closure of the Rheic seaway and development of upwelling zones in the western margin of Euramerica and the eastern Paleo-Tethys realm. Quantitative microfacies analysis across the Mississippian succession in the Gongchuan section shows facies-independent disappearance of corals and increased proportion of cortoids and filter-feeding organisms at the onset of the Asbian δ 13 C decline, which may support an increase in nutrient level that can be expected as a result of upwelling. [ABSTRACT FROM AUTHOR]

Deglaciation following the Sturtian Ice Age led to widespread manganese carbonate precipitates within marine mudrocks, reflecting unique climatic and oceanographic changes. The Mn carbonates hold economic importance in the Datangpo Formation, Yangtze Block, South China. Although their genesis in the Nanhua Rift Basin is well understood, little is known regarding their formation mechanism in the North Margin Rift Basin (NMRB). With growing interest in Mn ore exploration in this region, this study examines the weathering trend, climate patterns and watermass conditions using a variety of geochemical proxies. The results reveal two phases of climate variation during the deglaciation. Climate during the early phase (Phase I) was unstable, characterized by fluctuating values of Chemical Index of Alteration (CIA = 65 ± 4) and elevated Li isotope (8.8 ± 3.0‰) patterns. The degree of chemical weathering during the later stage (Phase II) was relatively stable (CIA = 65 ± 1, δ7Li = 5.4 ± 2.7‰), but the weathering intensity increased due to the reduced denudation rate, possibly related to a shift in the basin development. Fe speciation data indicate euxinia prevailing much of the section. However, Mo and U enrichment (> 1) and fluctuating ratios of Mo versus total organic content (0–40) suggest that pulses of freshwater influx associated with climate variation during Phase I caused the fluctuation of the chemocline along the continental shelf, facilitating the formation of Mn carbonates through the particulate Fe-Mn-hydroxide shuttle. With the establishment of stabilized climate, basin tectonics, and watermass circulation during Phase II, the accumulation of Mn carbonates in the sediments became less significant. The accumulation of Mn carbonates in the NMRB conforms to the "bathtub ring model", distinct from the metallogenic model in the NRB, providing valuable guidance for Mn ore prospecting within this area and elsewhere with similar settings. • Detailed geochemical analyses of mudrocks in the less studied Datangpo Fm. • Patterns of climatic variation and weathering trend are identified. • Persistent watermass anoxia existed during the accumulation of the Datangpo Fm. • Mn carbonate formation is strongly linked to fluctuating chemocline. • An alternative model is proposed for Mn ore accumulation in the Datangpo Fm. [ABSTRACT FROM AUTHOR]

Known as the Guadalupian-Lopingian boundary (GLB), the unconformity between the Guadalupian (Middle Permian) and Lopingian (Late Permian) is widespread in the South China Block. This boundary presents an important period with actives of the Emeishan Large Igneous Provenance (ELIP), the regression and the mass extinction. In Zunyi and Liupanshui areas of Guizhou Province, southwestern China, marine deposits of the Middle Permian Maokou Formation were covered by the terrigenous deposits of the Upper Permian Longtan Formation, the bauxitic claystone at the bottom of the Longtan Formation indicates the exposure during the Middle - Late Permian transition. The provenance of this bauxitic claystone in the South China is complicated, previous studies argue that the flood basalt and submarine volcanic rocks in the ELIP and the aeolian tuff in the Indochina Block are potential sources. In this study, new mineralogical, geochronological and geochemical data are got from the NW Guizhou, our new data constrain the age of bauxitic claystone in Zunyi and Liupanshui are 262.1 ± 1.5 Ma and 267.0 ± 2.7 Ma, respectively. Combined with trace element geochemical analysis, the source materials of bauxitic claystone in Zunyi is mainly derived from the intermediate-acid extrusive rocks in the ELIP, while the provenance of bauxitic claystone in Liupanshui is derived from the submarine volcanic activities during the initial stage of the ELIP. From the central area of ELIP to the outer area, the provenance of early Late Permian sediments transforms from the volcanic rocks of ELIP to Paleo-Tethys magmatic arc. Mass balance calculation and geochemical multivariate statistical methods show that the bauxitic claystone in Zunyi experienced two groundwater level variations in the land surface leaching stage, and Fe 2 O 3 、P 2 O 5 、HREE show similar geochemical behaviors. HREE is adsorbed by iron phase minerals and phosphate minerals, resulting in simultaneous migration. Our study also finds that paleogeographic location is an important factor for Late Permian bauxitization in South China. The different paleogeographic location determines the supply mode of provenance, provenance lithology, exposure time, leaching degree and other factors. [Display omitted] • New geochronological and geochemical data for Late Permian bauxitic claystone • Provenance of bauxitic claystone was from Emeishan Large Igneous Province. • Two-period changes of groundwater level and element migration are identified. • Paleogeographic location is an important factor for Late Permian bauxitization. [ABSTRACT FROM AUTHOR]

The Biyang Depression, lying in the eastern Nanxiang Basin, has a dustpan-shape with faults developed to the southwest and southeast. The Paleogene Hetaoyuan Formation in this depression hosts one of the oldest soda-deposits, the Anpeng deposit. These sodium carbonate-bearing strata consist of lutites, muddy dolomites, and bedded soda-deposits, which are dominated by nahcolite with little trona, mirabilite, and halite. In the top Unit 3 and lower Unit 2 of Hetaoyuan Formation where the sodium carbonates are concentrated, dolomitic shale, muddy carbonate, and sodium carbonate can be separated based on their distinct AlO, TiO, NaO, MgO+CaO, and LOI (loss on ignition) contents. By using NaO/(MgO+CaO) ratio as an indicator for the relative concentration of Na carbonates to Mg-Ca carbonates, the muddy dolomites can be classified into two groups. One group with NaO/(MgO+CaO)<0.6 exhibits a positive correlation between this ratio and AlO+TiO content, an proxy for terrigenous clastic input and the other group with NaO/(MgO+CaO)>0.6 presents a negative correlation. As the clastic proportion decreases, the former indicates that it tends to form pure Mg-Ca carbonates reflecting evaporation less than or equal to replenishment for the lake water in a relative humid climate, and the latter reveals a trend to form sodium carbonates with lake water's evaporation more than replenishment in a relatively dry climate. From muddy dolomite to sodium carbonate samples, with NaO/(MgO+CaO) ratio increasing, the Al normalized Zr, Ti, La, K, Rb, and Ba tend to be enriched and the post-Archean Average Shale (PAAS) normalized positive Eu anomaly becomes more obvious. Integrated with the high B contents and the report of searlesite in the bedded sodium carbonates and the regional extensional tectonic regime, the above geochemical characteristics were interpreted to signify hydrothermal contribution to forming these soda-deposits through the deep fault systems of basin margins. [ABSTRACT FROM AUTHOR]

The Cambrian–Ordovician boundary unconformity in the southern part of the South China Craton is spatially and temporally related to coeval orogenic activity along the Indian margin of east Gondwana. Detrital zircon age spectra from strata above and below the unconformity range in age from 3580–450 Ma, with peaks in the late Mesoproterozoic and Neoproterozoic. The patterns are similar to time equivalent sequences elsewhere in South China and together with regional facies relationships and paleocurrent data indicate derivation from a Gondwana source. The disconformity at the base of the Ordovician succession forms part of a regional break that has also been documented in the Himalaya, Qiangtang, Lhasa, Sibumasu, and Western Australia. All these successions have similar detrital zircon age spectra suggesting derivation from common source(s). In South China the effects of this tectonic event are relatively mild and are represented by a local disconformity at the base of the Ordovician succession, but elsewhere in north Gondwana this event is marked by an angular unconformity with metamorphism of older units and relatively widespread magmatic activity. South China was likely located in a distal location to the northeast of the pulse of tectonic activity, which was focused in the Himalaya region, and was close to the continent–ocean boundary between northern Gondwana and the proto-Tethys. [ABSTRACT FROM AUTHOR]

The conodont faunas of Tournaisian shallow-water carbonates from central Guangxi are described mainly for biostratigraphic purposes. A complete series of samples was collected from the Long’an and Du’an formations in the Long’an section. These formations are characterized by lime-mudstone, skeletal and peloidal wackestone, packstone and grainstone with typical shallow-water biota. Overall, these samples produced 809 identifiable Pl elements, belonging to 50 species in 11 genera, of which one species and one subspecies are new. The fauna enables the establishment of seven biozones (in ascending order): Polygnathus spicatus , Siphonodella homosimplex , S. sinensis , S. dasaibaensis , Polygnathus communis carina Acme, Gnathodus cuneiformis , and P. communis porcatus zones. Based on these new collections from central Guangxi and on data from the literature, a conflated Tournaisian conodont zonation is proposed for shallow-water successions in South China. Most of the conodont zones correlate well with their counterparts recognized in Western Europe, which may be of greater significance in stratigraphic correlation than previously thought. [ABSTRACT FROM AUTHOR]

Abstract: The rare earth element (REE) behavior and the related Ce anomalies of two profiles in bauxite of the Xinmo Syncline from Wuchuan–Zheng'an–Daozhen (WZD) area (Northern Guizhou, China) have been studied. The bauxite has diaspore as its main ore mineral, with lesser amounts of boehmite. Clay minerals, including kaolinite, chlorite, illite and smectite, are a minor mineral constituent. Furthermore, a significant Ce-bearing mineral parisite (Ce2Ca(CO3)3F2) is found near the bottom of the profiles. The bauxites have flat HREE (Er–Lu) shape relative to NASC, with variable weak depletion to weak enrichment patterns of LREE (La–Nd) and MREE (Sm–Ho) across the profiles. Strong positive Ce-anomalies (normalized to NASC) are also noticeable in the uppermost part of the profiles. Mass balance calculations suggest that an obvious fractionation exists among different REE and LREE are more mobile than HREE during the leaching process. In addition, the samples collected along a vertical profile show that a downward increase for the REE concentration and a remarkable enrichment of REE are found at the basement of the bauxite deposits. A similar downward increase trend is also observed in the values of LaN/YbN and GdN/YbN. The above characteristics show that the REE losses caused by leaching decreased gradually from the top to the bottom of the profile. The higher mobility of LREE in the profile might be due to differences in the stabilities of the original REE-bearing minerals during leaching process. The REE enrichment at the basement of bauxite deposits is attributed to the increase of pH around the parent rock as well as the presence of mineral ligands during bauxitization. The value of [Ce/Ce*]NASC decreased downwards, and increased again near the bottom of the profile. The positive Ce-anomaly in the uppermost part of the profile has been attributed to the redox change of Ce3+ to Ce4+ and the consequent precipitation of cerianite (CeO2). A decrease in the oxidation state downwards causes the decrease of the value of [Ce/Ce*]NASC. The formation of parisite near the bottom of the profile leads up to the increase in the value of [Ce/Ce*]NASC again. The precipitation of parisite may occur via reactions between the fluoride complexes (CeF2+ or CeCO3F0) and Ca2+ and HCO3 −. [Copyright &y& Elsevier]

Abstract: Sandstone petrology, geochemistry, and detrital zircon U–Pb ages and trace elements are integrated to investigate the provenance of Middle Triassic strata from the Youjiang Basin, SW China. Variations in abundance of volcanic lithic fragments and ratios of Th/U, Zr/Sc and Th/Sc suggest that sandstones from the southwestern portion of the basin display less sedimentary recycling and have a lower felsic average source composition than time-equivalent strata from the central, eastern and northern portions of the basin. All sandstones exhibit an overall similar detrital zircon U–Pb age distribution pattern with major age groups at 1200–900Ma, 480–420Ma and 300–240Ma together with some Devonian–Carboniferous and Neoproterozoic grains. Combined with the compiled paleocurrents, the detrital zircon ages suggest multiple-sourced components. Pre-Devonian detrital zircons were likely derived from the recycled late Neoproterozoic–early Paleozoic clastic rocks and from magmatic and metamorphic rocks related to the early Paleozoic orogeny in the southeastern segment of the South China Craton. Late Paleozoic–Triassic detrital zircons together with the presence of well preserved volcanic lithic fragments were considered to indicate first-cycled detrital input from a subduction–collisional mountain belt to the southwest of the craton. These provenance data argue for an Indosinian mountain building event following the closure of a Paleo-Tethys branch ocean rather than for a thermotectonic reactivation event as recently proposed for the Indosinian orogeny in the southwestern China. In association with this orogeny the Youjiang Basin evolved into a foreland basin. [Copyright &y& Elsevier]

Abstract: Whole-rock geochemistry and zircon trace element and U-Pb age data for Late Permian–early Middle Triassic volcanogenic sedimentary rocks in SW China show a change from Large Igneous Province to subduction-related sources immediately before the Permian–Triassic boundary. Zircons from Late Permian samples give identical within-error ages to the adjoining Emeishan Large Igneous Province (LIP). The bulk-rock geochemistry of these Late Permian units shows no depletion in high field strength elements and is similar to the high-titanium basalts of the Emeishan. Six samples of latest Permian–earliest Triassic tuff and two earliest Middle Triassic tuffs samples yield U-Pb zircon ages at of ~252Ma and ~247Ma, respectively. These tuffs and interstratified volcanogenic sedimentary rocks show significant depletion in high field strength elements, akin to magmatic arc-related rocks. Zircons from the tuffs have Nb/Hf, Th/Nb and Hf/Th ratios similar to those from arc/orogenic-related settings and distinct from the zircons from the Late Permian samples which display within-plate/anorogenic characteristics. Our data demonstrate that there is a compositional change of the volcanogenic sediments across the Permian–Triassic boundary in South China. [Copyright &y& Elsevier]

Studies on carbon isotopes of bulk carbonates from Longan and Baping sections of Lower Carboniferous in Guangxi of China show that the stable carbon isotope compositions in carbonate rocks of the isolated platform and deep slope facies were resistant to the influence of early meteoric diagenesis and late burial diagenesis. Three major positive carbon isotope excursions have been recognized in Lower Carboniferous in South China. The first major positive δC shift of 4.19‰ occurred in the middle part of Siphonodella isosticha-upper Siphonodella crenulata zone (Tournaisian); the second with an amplitude of 4.65‰ occurred near the Tournaisian/Visean boundary; and the third of 2.23‰ in the lower part of Gnathodus bollandensis zone. The three positive shifts of δC can be correlated with global carbon isotope excursions and are consistent with the fall in global sea level, indicating that abundant organic carbon burial, lowering of atmospheric CO, and glaciation may have occurred during these time intervals. [ABSTRACT FROM AUTHOR]

The closure of Mianlue Ocean lead to the collisional assembly between the North China Block (NCB) and the South China Block (SCB). But the timing of initial continental collision remains unclear, with the proposed ages ranging from the Late Permian to the Late Triassic. This study presents stratigraphic, sedimentological, tectonic subsidence, and provenance data from the Triassic strata in the Zigui and Dangyang basins lying along the eastern Qinling Orogenic Belt. These data document a tectonic transition in the central northern-SCB, and locally provide constraints on the timing of initial SCB–NCB collision. The Lower Triassic Daye Formation was deposited in a marginal basin to slope environment, and consists of mudrocks containing detrital zircons with major age peaks at ca. 1900 and 850 Ma. The overlying Lower Triassic Jialingjiang Formation comprises a shallowing carbonate sequence, with intercalated evaporites at the top of the formation. It contains mudrocks that are rich in detrital zircons with of ca. 270‐–245 Ma. The mixed carbonate and siliciclastic sequences of the Middle–Upper Triassic Badong Formation records tectonic uplift at its base, and contains detrital zircons with U Pb age peaks at ca. 2500, 1850, 920–800, 450 and 350–220 Ma. Combined with petrographical observations and tectonic subsidence calculation, these detrital zircon U Pb ages record a significant provenance change from recycled material derived from the SCB to newly generated detrital material from the NCB. This provenance change records the initial SCB–NCB collision in the eastern Qinling Orogenic Belt during the Early Triassic. • An Early Triassic provenance change was recognized from the Zigui and Dangyang basins. • These basins started to receive sediments from Qinling Orogen during the late Early Triassic. • Tectonic subsidence analysis denotes a basement uplift in the Middle Triassic • Initial collision between South China and North China in eastern Qinling occurred during the Early Triassic. [ABSTRACT FROM AUTHOR]

• We present paired Mo and U isotopes from the Cryogenian Datangpo Formation. • The Cryogenian interglacial seawater δ98Mo was ~+1.5‰ • The Cryogenian interglacial seawater δ238U was between −1.20‰ to −0.73‰ • Paired δ238U-δ98Mo data document widespread anoxia in Cryogenian interglacial ocean. The delayed diversification of early animals until the middle Ediacaran Period, despite their likely origin in the Cryogenian Period or earlier, has been attributed to low levels of dissolved O 2 in global seawater. To provide more robust constraints on the extent of global-ocean oxygenation during the mid-Cryogenian Period, we analyzed paired U (δ238U) and Mo (δ98Mo) isotope compositions of organic-rich shale in the basal Datangpo Formation from two separate drillcores in South China. This unit yielded an average δ238U of −0.39 ± 0.23‰ (2SD; relative to standard CRM145), which is significantly lower than the average δ238U (+0.02 ± 0.12‰) of euxinic sediments of the modern restricted Black Sea and well below a modeled δ238U of +0.2‰ for modern unrestricted euxinic facies (e.g., Saanich Inlet). The U/Al ratios of our samples indicate that ~ 40% of U was derived from detrital materials (δ238U detrital = ~−0.3‰), suggesting that the δ238U of authigenic U is even lower than the measured bulk-sample values. Taking into consideration the 0.4–0.8‰ enrichment of 238U in euxinic sediments relative to seawater, the δ238U values of the Datangpo shales correspond to contemporaneous seawater δ238U of −1.20‰ to −0.73‰. Owing to mass balance considerations, these low seawater δ238U values are indicative of widespread development of anoxia in the Cryogenian interglacial ocean (~658–654 Ma). These shales yield mostly low δ98Mo values (+0.56 ± 0.46‰), although the youngest samples have values as high as +1.21 ± 0.23‰ (relative to NIST SRM 3134 = +0.25‰), all of which are significantly lower than modern seawater δ98Mo (+2.34 ± 0.10‰). The Datangpo shales either directly record the global seawater δ98Mo signature or provide a minimum estimate thereof (in the event of local influences). The consistently low δ98Mo values of the Datangpo shales thus confirm widespread anoxia in the Cryogenian interglacial ocean. These findings based on paired δ238U-δ98Mo analyses thus provide key information regarding global-ocean redox conditions during the interval immediately preceding the rise of macroscopic and morphologically complex animals [ABSTRACT FROM AUTHOR]

[Display omitted] • Early Carboniferous bauxite deposits in the SW South China Craton were formed in karstic depressions. • Formation processes of Early Carboniferous bauxite deposit were reconstructed. • Paleosalinity proxies indicate that bauxite deposits formed in the alternant freshwater and seawater environments. The Carboniferous karstic bauxite-bearing rock series within the Jiujialu Formation were widely distributed in central Guizhou, South China, with a prominent enrichment of ferrous clay materials at the lower part and fluctuations of Al contents at the upper part of those deposits. Yet, the evolution, distribution and formation mechanism of those bauxite ore-bearing rock series require further investigation. We used thickness data from ∼ 800 drillcores in central Guizhou to generate a high-precision paleo-geomorphological reconstruction of the study area, which reveals a series of karstic depressions from Southwest to the Northeast on a coastal karstic plain. Based on a typical drillcore of ZK47-12 located at a karstic depression, a relatively complete depositional records of bauxite deposits in the Jiujialu Formation have been yielded. The study bauxite deposit contains the lower Fe-rich layer and upper Al-rich layer. Within Al-rich deposits, bauxite ore comprises Al-bearing minerals including diaspore, boehmtie, with slight amounts of Fe-bearing and clay minerals, while bauxitic claystone yields higher contents of clay minerals. And Fe-rich layers comprise Fe-bearing minerals (mainly for chamosite). Geochemistry of the drillcore samples and mass changes reveal strong losses of most mobile elements, relative enrichment of Al within the bauxite ores and enrichment of some trace elements and REEs within claystones, caused by leaching process. Mineralogical and geochemical cycles within the upper Al-rich layer directly link with variations of the groundwater table (GWT) during the bauxitization in central Guizhou. The B content and B/Ga ratios indicate that the Jiujialu Formation in central Guizhou contains variations of paleosalinity, this evidence further supports that the fluctuations of GWT may cause by the Early Carboniferous sea-level changes. Our new data indicate that multiple factors control the formation of the Carboniferous bauxite deposits in central Guizhou. Paleo-geomorphological features of a series of karstic depressions upon the underlying carbonate rocks providing deposition space, tropical climate near the paleo-equator contributing to the weathering process, frequent fluctuation of groundwater table enhancing or releasing the intensity of leaching process, glacio-eustatic cycles promoting karstification and driving the fluctuations of GWT, and input of seawater influencing the intensity of leaching process during bauxitization. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Doushantuo phosphorites are petrographically subdivided into pristine and reworked type. • Major element results suggest a concentration of P from pristine to reworked phosphorites. • Mass change calculation reveals the enrichment and loss of different elements. • A three-stage model of chemical/biochemical enrichment, hydrodynamic reworking, and chemical leaching is proposed. • Such multi-stage metallogenic processes contribute to enrichment of P and loss of impurities. Economic phosphorite from Ediacaran Doushantuo Formation is the first true phosphorite giant and represents the onset of the Precambrian-Cambrian global phosphogenic event. The Doushantuo phosphorite may have deposited during the early-middle Ediacaran (ca. 632–574 Ma) according to the latest radiochronological data. Petrographically, in central Guizhou, it can be subdivided into two types of lithofacies: pristine phosphorite (micritic phosphorite, phosphatic shale, banded phosphorites) and reworked phosphorite (intraclastic phosphorite, vuggy intraclastic phosphorite, unconsolidated phosphorite). Geochemical data show that chemical/biochemical enrichment is the most effective process to condense the phosphatic sediments and obviously improve the grade of P 2 O 5 (can reach 38.8 wt%). Hydrodynamic reworking may not play an important role in the further enrichment of P 2 O 5 content but effectively got rid of SiO 2 and Al 2 O 3 components in phosphorite by the removal of lighter terrigenous particles and clays. Mass change calculation shows that Ca and Mg are heavily depleted in the chemical leaching process, implying it is a key process to upgrading the quality of phosphorite by separating the carbonate constituents from phosphorite. Therefore, a multi-stage metallogenic model of chemical/biochemical enrichment, hydrodynamic reworking, and chemical leaching is proposed, quantified the composition changes and elucidated the constrained factors in the formation of high-graded phosphorite. Such a metallogenic process effectively produced high-quality phosphorite deposits and bring great benefits to metallurgy. [ABSTRACT FROM AUTHOR]

• An earliest Jurassic provenance change has been recognized in the Zigui Basin in central China. • Late Triassic sediments in the Zigui basin were mainly derived from the South China block. • Early Jurassic sandstones in the Zigui basin denote a volcanic source in the Qingling orogen. • Provenance change was ascribed to the collisional orogensis in the Qinling orogen. The Qinling mountains are situated in central China and mark the collisional assembly between the North and South China blocks. To understand the early Mesozoic evolution of the Qinling orogenic belt, we present new paleocurrent data, sandstone petrology and detrital zircon U-Pb ages for Upper Triassic-Lower Jurassic sedimentary successions in the Zigui Basin in the northern margin of the South China block. The deltaic sandstones in the Upper Triassic Jiuligang Formation have high concentrations of quartz grains and the basal alluvial conglomerates of the Lower Jurassic Tongzhuyuan Formation contain abundant chert gravels with sandy matrixs rich in quartz grains. Both the Upper Triassic sandstones and Lower Jurassic conglomerate have two major detrital zircon U-Pb age groups of 2100–1700 Ma and 950–700 Ma with very few Phanerozoic ages. The overlying fluvial sandstones of the Tongzhuyuan Formation display relative enrichment in volcanic and metamorphic rock fragments. They are characterized by primary zircon U-Pb age groups of 250–200 Ma and 950–700 Ma. Consistent with the northwestward paleocurrents, zircon grains of 2100–1700 Ma and 900–700 Ma were likely derived directly or recycled from the Paleoproterozoic and Neoproterozoic basement of the South China Block, with the latter also possibly sourced from the Qinling orogen. The 250–200 Ma age group is understood to be associated with volcanic rock fragments and, considering the southward paleocurrents, indicates a volcanic source within the Qinling orogen. Along with the increased low-grade metamorphic rock fragments in sandstones, this significant provenance change in the Early Jurassic indicates the initial massive erosion and rapid southward propagation of the south Qinling orogen. [ABSTRACT FROM AUTHOR]

Geomorphology is an important control on the formation of bauxite. However, geomorphological research on bauxite deposit formation is usually hampered by the lack of systematic detailed data collection. This study focuses on the Wuchuan–Zheng'an–Daozheng (Wu–Zheng–Dao) area of northern Guizhou Province, South China, an area containing bauxite deposits of the Dazhuyuan Formation. These deposits formed during the early Permian in a period associated with the peak timing of the late Paleozoic Ice Age (LPIA). This study used data from 329 drillcores within the Dazhuyuan mining district (DMD) to generate high-precision geomorphological reconstructions for the period of bauxite formation. This includes a series of contour maps showing the total thickness of the bauxite deposit, ore grades, the thickness of Lower (bauxitic claystone) and Upper (bauxite ore) members of the bauxite formation, and the distribution of different types of bauxite ore. These maps indicate that thicker deposits of bauxite are concentrated in deep depressions, whereas no bauxite is found in highly elevated erosional regions. High-grade bauxite ores, including clastic, oolitic, and porous types of mineralization, are located within depressions or in gently sloping areas, whereas low-grade bauxite deposits, including massive bauxite and bauxitic claystone mineralization, are located at the bottom of depressions or are present as thin units within uplifted areas. The geochemistry of the drillcore samples from the study area indicates that leaching is the main control on bauxite ore quality in the study area. Finally, a low groundwater table and water-permeable underlying units provide good drainage, which also contributes to the generation of high-grade bauxite ores. • Geomorphological reconstruction in the Dazhuyuan Mining District, South China • Leaching process rebuilding based on geochemical profiles • Formation model for the early Permian bauxite deposit of the Dazhuyuan Formation [ABSTRACT FROM AUTHOR]

The 87Sr/86Sr minimum of the Capitanian seawater is one of the most significant features in the Phanerozoic seawater 87Sr/86Sr history. In order to assess possible contribution of the Emeishan large igneous provinces (LIPs) to strontium isotope evolution of the Capitanian seawater, 87Sr/86Sr ratios were measured from the Capitanian limestones which are locally interlayered with the Emeishan basalts. The limestones underlying the Emeishan basalts have high 87Sr/86Sr ratios (0.7070–0.7074). However, extremely low 87Sr/86Sr ratios (0.7068–0.7070) were identified in the late Capitanian Jinogondolella prexuanhanensis–J. xuanhanensis zones, which correspond to the eruption time of the Emeishan LIP. The temporal coincidence of these two phenomena supports the idea of a potential linkage between Capitanian 87Sr/86Sr minimum and eruption of this igneous province. The strong submarine hydrothermal activity and erosion of the Emeishan LIP could have released large amounts of non-radiogenic Sr to the oceans and play an important role in strontium isotope evolution of the seawater. [ABSTRACT FROM AUTHOR]