Southern Anhui Research Articles

The Tao Way Follows Nature, The Highway Stems From Culture:The Application of Green Concept in Engineering Design of Tong-Huang Highway

The Highway from Tongling to Huangshan locates in the scenic area with two mountains and one lake (those are Yellow Mountain, Jiuhua Mountain and Taiping Lake). It is not only an important passageway in Anhui Province that connects the north and the south, but also a tourism corridor in the scenic area. During the design of the Project, the unique natural landscape in southern Anhui is taken into account; a design objective of bearing Hui culture and fitting in the landscape is set; a design philosophy of ecological road, tourism road, scientific road and cultural road is executed; and the old philosophical thought and design method of "the Tao way follows nature, the highway stems from culture is applied. Eventually an environmental friendly, resource-conserving,innovative and humanistic harmonious demonstration highway project is successfully made.

Pulses of Late Mesozoic magmatism: Zircon ages and Hf-O isotopic composition of the Qingyang-Jiuhuashan granitic complex, southern Anhui province, eastern China

Late Mesozoic magmatic rocks are widely distributed in southern Anhui province, and are represented by the Qingyang-Jiuhuashan granitic complex, which consists dominantly of the Qingyang pluton of granodiorite and monzogranite, and the Jiuhuashan pluton of K-feldspar granite. These two plutons have zircon U-Pb ages of 138Ma–128Ma. Combining the new data with previously reported age data, the magmatism in southern Anhui province can be subdivided into three stages: early stage of ∼152–136Ma, middle stage of ∼136–130Ma, and latest stage of ∼130–120Ma. Granodiorite (early stage) and monzogranite (middle stage) of the Qingyang pluton have SiO2 contents of 66–68wt%, total alkali contents of 7.5–8.6wt%, K2O/Na2O ratios of 1.1–1.3, A/CNK ratios of 0.9–1.1, and low FeOT/(FeOT+MgO) values of 0.71–0.73. These rocks show depletion in Nb, Ta, and Zr and slightly negative Eu anomalies. K-feldspar granite (late stage) of the Jiuhuashan pluton is characterized by high SiO2 contents (>75wt%), K2O/Na2O ratios of 1.1–1.3, and A/CNK ratios of 0.9–1.2, and high FeOT/(FeOT+MgO) values of 0.88–0.93. They have high concentrations of Nb, Ta, and Zr, and strongly negative Eu anomalies. Initial εHf values of zircon grains from the granodiorite and monzogranite range from −8.01 to −6.71 and −11.40 to −9.43, with δ18O values varying from 7.16‰ to 8.04‰ and 7.26‰ to 8.06‰, respectively. Zircon grains from K-feldspar granites have relatively high initial εHf values of −7.62 to −4.78, but similar δ18O values of 7.03–8.84‰. Geochemical features of granodiorite and monzogranite point to an I-type signature, whereas those of K-feldspar granite show an A-type affinity. We propose that the granodiorite and monzogranite originated from mixing melts produced by partial melting of lithospheric mantle metasomatized by fluids and crustal rocks induced by underplating basaltic magmas, related to subduction of the Paleo-Pacific oceanic crust, whereas the K-feldspar granite formed from crustal anatexis in an extension setting caused by rollback of the subduction.

Geochemistry and fluid inclusions of scheelite-mineralized granodiorite porphyries from southern Anhui Province, China

We report petrological, cathodoluminescence (CL), major and trace element analyses and fluid inclusion studies on scheelite (W)-mineralized granodiorite porphyries from Dongyuan and Zhuxiling, southern Anhui Province (China). In Dongyuan, the larger part of the granodiorite porphyry body is mineralized with W concentrations up to 1140g/t (total WO3 reserves >140 000 tonnes), whereas in Zhuxiling mineralization is spatially more limited. All mineralized rocks are strongly altered, containing abundant calcite and no fresh plagioclase. W-mineralized rocks show higher K, Pb and lower Na, Sr, Ti contents compared to the non-mineralized ones. Co-variations between mobile elements (K, Na, Pb, Sr, Rb, etc.) and W, combined with petrological observations, demonstrate that fluid alteration must have controlled the mineralization. In quartz from both deposits 4 types of fluid inclusions have been recognized, i.e., aqueous-carbonic (WC-type), aqueous (W-type, subdivided into Wm-type containing minor detected CO2 and Wn containing no CO2), carbonic (pure CO2, C-type) and late secondary aqueous inclusions (LW-type). WC- and LW-type inclusions represent the original magmatic fluids and meteoric waters, respectively. The other inclusions represent evolved magmatic fluids which are closely related to alteration and mineralization. WC-, Wm- and Wn-type inclusions show higher salinity and lower homogenization temperatures, indicating fluid immiscibility with CO2 effervescence. Additionally, during plagioclase alteration and precipitation of K-feldspar and sericite the K/Na ratio is lowered and Ca released. The precipitation of scheelite must have been promoted by increasing Ca contents in the fluid and also by increasing pH due to CO2 loss. The present study demonstrates that for granitic rocks without calcareous wall rock, plagioclase breakdown must have been the key factor for scheelite mineralization. The presence of CO2-rich fluid indicates that both deposits formed in the same intracontinental extension setting as those in the Nanling region. Thus, the Yanshanian granites from southern Anhui Province may have a great potential for W mineralization, especially the blind ones in deep levels.

Petrogenetic contrastive studies on the Mesozoic early stage ore-bearing and late stage ore-barren granites from the southern Anhui Province

Yanshanian magmatisms are intensive in the southern Anhui Province and can be divided into early (152–137 Ma) and late (136–122 Ma) stages. A Yanshanian granitic zone was found to crop out along Qingshan to Changgai areas in the Tunxi district in Field investigation which has a genetic link with molybdenum multiple metal mineralization. To be a representative syenitic granite in the southern Anhui Province, the Huangshan pluton has not been found so far to have any genetic link with mineralization. Zircon LA-ICP-MS dating indicate that the four granitic bodies from the Qingshan-Changgai zone have concurrent formed ages from 140±4 to 141±2 Ma, belonging to the Yanshanian early stage magmatism. However, the Huangshan granite is dated to be 129±2 Ma, belonging to the Yanshanian late stage magmatism. The Qingshan-Changgai granites show high SiO2 and K2O contents, low P2O5 contents and middle Al2O3 contents and are high-K calc-alkaline series metaluminum I-type granite. These rocks are characterized by enrichments in the large ion lithophile elements and light rare earth elements (REE), depletions in the high field-strength elements, and middle degree negative anomalies of Eu, geochemical features of arc or continent crustal derived magma affinities. These rocks have 87Sr/86Sr( t ) ratios from 0.7120 to 0.7125, e Nd( t ) values from ‒7.24 to ‒4.38 and zircon e Hf( t ) values of ‒4.4 to 6.7, similar to that of the coeval ore-bearing granodiorites in the southern Anhui Province. Integrated geochemical studies indicate that the Yanshanian ore-bearing granodiorites were formed by partial melting of the Meso-Neoproterozoic accreted thickened low crust. Meanwhile, the Qingshan-Changgai granites were formed through a AFC process of plagioclase+amphibole+Shangxi Group of magmas that formed the ore-bearing granodiorites. The Huangshan granites are characterized by high SiO2 and K2O contents, moderate Al2O3 contents, seagull shape REE distributed pattern and distinct Eu negative abnormities. Comparing with the Qingshan-Changgai granites, the Huangshan granites show more Ba, Sr, P, and Ti negative abnormities with no Nb and Ta depletions and are high-K calc-alkaline series metaluminum A-type granite. e Hf( t ) values of the Huangshan granites are from ‒6.6 to ‒1.2, similar to that of the early stage ore-bearing granodiorites, indicating that they were also formed by anatexis of the Meso-Neoproterozoic accreted crust, but their magma sources might be residual granulitic crust which ever underwent Yanshanian early stage I-type intermediate-acid magma extraction. Comparing studies on the two stages granites indicate that the early stage granites derived from a relative thickened low crust under a lower temperature condition. Their magma sources were Meso-Neoproterozoic accreted crust which enriched in ore-forming materials and further became more enriched through processes of magma AFC evolution. However, the late stage A-type granites originated from relative shallow crust under a higher temperature condition. Their magma source was depleted in ore-forming materials due to the early stage magma extraction and thus had weak ore-forming capacity. From early to late stage, the magmatisms tectonic setting translated from post-orogenic to anorogenic and the later corresponded to a back-arc extensional setting as increase of the slab subducted angle of the Paleo-Pacific plate.

ENSO-induced drought hazards and wet spells and related agricultural losses across Anhui province, China

Using daily precipitation data from 25 meteorological stations for a period of 1961–2014, spatiotemporal features of wet spells and droughts and related impacts on agricultural production across Anhui province, China, were investigated with a linear regressive technique, the Standardized Precipitation Evapotranspiration Index (SPEI) and the modified Mann–Kendall trend test method. Results indicated that: (1) ENSO-induced wet spells and droughts accounted for 83 and 68% of the total wet spells and droughts and droughts were closely related to La Nina events of the same and subsequent years. Wet spells, however, were closely related to El Nino events; (2) a larger variability was found in the SPEI, showing larger flood and drought risks during spring and autumn than those during summer and winter seasons. Generally, wet spells in winter were relatively high and the drying tendency was identified in winter during recent years; (3) relations between SPEI and SSTA were shifting during warm and cold phases of ENSO. The warm phase of ENSO tended to have larger impacts on SPEI in southern Anhui province, and the cold phase of ENSO had a greater impact on the SPEI variation in northern Anhui province. Comparatively, SSTA had an increasing impact on wet spells and droughts with increasing lag time; and (4) the reduction of rice and maize production in southern Anhui province was found mainly during 1 year earlier to the ENSO events. The amount of reduction of maize was larger in northern Anhui province and Jianghuai region, years with maize reduction were more often in southern Anhui province. Irrigation in central Anhui province can mitigate the negative effects of wet spells and droughts.

New oospecies of dinosaur eggs from the Upper Cretaceous of South Anhui

A new oogenus and oospecies, Umbellaoolithus xiuningensis oogen. et oosp. nov., is described on the basis of specimens from the Upper Cretaceous Huizhou Formation in the Huangshan area of Anhui Province, China. The Mesozoic strata developed in South Anhui, producing a large number of dinosaur skeletons, dinosaur eggs, dinosaur footprints and so on. The Xiuning Basin is a small intermountain basin during the Mesozoic. The Triassic strata are scattered and the Jurassic and Cretaceous strata are intact in the basin. The Jurassic strata include the lower Jurassic Yuetan Formation, and Middle Jurassic Hongqin Formation. The Cretaceous strata include the lower Cretaceous Bingqiu Formation, Shiling Formation and Yantang Formation, Upper Cretaceous Huizhou Formation, Qiyunshan Formation and Xiaoyan Formation. The materials we studied were found in the Huizhou Formation of Qiyunshan, Xiuning, in 2011. There is an incomplete egg nest consisting of at least 9 dinosaur eggs. The eggs are oval, arranged along the long axis of all the eggs parallel to each other, and not at the same horizontal level within the clutch, obviously differing from the elongated eggs, paired, regular arrangement and radial orientation seen in clutches attributable to the Elongatoolithidae and Macroelongatoolithidae. The eggs of Umbellaoolithus xiuningensis also differ in typical alignment from those of the Prismatoolithidae, which are vertical or near vertical. The average diameter of the eggs is 13.86 cm, the equatorial diameter is 10.43 cm, and the shape index is 75.25. In general, the eggshell units have the shape of an umbrella, triangle or cone, and are arranged irregularly, unlike in the Spheroolithidae, Stalicoolithidae and Ovaloolithidae. The cones are hemispherical in shape. The cone layer is very thin, its average thickness of 0.12 mm representing approximately 1/6 of the total eggshell thickness. Umbrella-like eggshell units are well-developed near the inner and outer surfaces of the columnar layer. The eggshells have numerous irregular pores, unlike in several oofamilies including the Dictyoolithidae and Faveoolithidae. Consequently, we established a new oofamily: Umbellaoolithidae oofam. nov.. This new specimen unambiguously represents a distinct oospecies of dinosaur eggs in southern Anhui, and provides new paleontological evidence bearing on the classification and correlation of Upper Cretaceous strata in southern Anhui.

Predictions of the Potential Geographical Distribution and Quality of a Gynostemma pentaphyllum Base on the Fuzzy Matter Element Model in China

Specific spatial information about medicinal plants is becoming an increasingly important part of their conservation. Gynostemma pentaphyllum (Thunb.) Makino is a traditional Chinese medical plant, and gypenosides is one of the main active components of G. pentaphyllum. In our research, many samples of G. pentaphyllum and the data of gypenosides content in these samples were collected from 43 sampling sites, and based on the Fuzzy Matter Element model (FME), the relationships between gypenosides content and 19 environmental variables were established. Then, the maximum entropy model was used to determine the relative importance of each environmental variable, and thus determine the most limiting habitat criteria. Finally, the weighted average method was applied to determine the potential distribution of G. pentaphyllum in China, which was based on the content of gypenosides. The results showed that the areas of marginally suitable and suitable habitats for G. pentaphyllum in China were approximately 1.2 × 106 km2 and 0.3 × 106 km2, respectively. The suitable habitats were mainly located in southern China, including Hunan, Hubei, Chongqing, Anhui, Jiangxi, Zhejiang, Shaanxi, and other regions. In conclusion, the FME model could accurately evaluate the habitat suitability of G. pentaphyllum, quantify the area of a suitable habitat, and analyze the spatial distribution.

Zircon SHRIMP U-Pb ages and geochemistry of Late Mesozoic granitoids in Western Zhejiang and Southern Anhui: constraints on the model of lithospheric thinning of Southeast China

ABSTRACTWe report geochemical data and zircon SHRIMP U-Pb ages for Late Mesozoic granitoids from the western Zhejiang province and southern Anhui province (the WZSA region) from southeast China. In combination with published geochronological and geochemical data, the granitoids in the region can be divided into three stages: 171–141 Ma, 140–121 Ma, and 120–95 Ma. The first stage of these granitoids is mainly composed of granite porphyry and granodiorite which are similar to I-type granitoids, including having weakly negative Eu anomalies with enrichment in light rare earth elements (LREE), Rb, Th, and U. The second stage of granitoids consists of monzogranite, syenogranite, and granite with the characteristics of both A-type and I-type granitoids including strongly negative Eu anomalies; depletion of Ba, Sr, and Ti; and enrichment of K, Rb, and high field strength elements (HFSEs) (such as Th and U). The third stage of granitoids is mainly composed of granite, quartz monzonite, quartz diorite, and mafic rocks with weakly negative Eu anomalies and also enrichment in LREE, Rb, Th, U, and K. From our work, we propose a transition from compressional to extensional magmatism at ~141 Ma. Based on the geochemical characteristics of these granites and coeval mafic rocks, we propose that the formation of the A-type magmatism in the WZSA region formed as the result of lithospheric extension and asthenospheric upwelling during the Early Cretaceous.

Geochemical and zircon U–Pb geochronological study of the Yangshan A-type granite: Insights into the geological evolution in south Anhui, eastern Jiangnan Orogen

The Early Cretaceous Yangshan granite is an A-type granitic intrusion that was emplaced along the eastern Jiangnan Orogen in southern Anhui Province, South China. The Yangshan intrusion mainly consists of syenite porphyry (127.0±0.6Ma) and alkali-feldspar granite porphyry (126.0±1.0Ma). As a part of Qingyang–Jiuhuashan complex intrusion, the Yangshan A-type granites have lower MgO, CaO, Co, Sr, and higher Rb, Nb, Th and HREE contents, with enrichment in large-ion lithophile elements (LILE) and light rare earth elements (LREE), and slightly negative Eu anomalies. However, the syenite porphyry and the alkali-feldspar granite porphyry differ in terms of zircon εHf(t) values: small variations in the syenite porphyry from −5.5 to −3.7, corresponding to Hf model ages (tDMC) between 1.42Ga and 1.53Ga, and large variations in the alkali-feldspar granite porphyry from −6.4 to +4.4, yielding tDMC of 0.90–1.59Ga. While both rocks also have similar εNd(t) values ranging from −7.02 to −5.47, corresponding Nd model ages (TDMC) are 1.37–1.49Ga, falling within the Hf model ages. We take these features to indicate that the Qingyang I-type granites, which are isotopically similar, and Yangshan A-type granites were originated from partial melting of Mesoproterozoic–Neoproterozoic crust, with minor juvenile crust input for the alkali-feldspar granite porphyry, followed by fractional crystallization. In combination with previous studies, we propose that the Cretaceous A-type granitic rocks formed between 135Ma and 122Ma, implying an important Mesozoic extensional event in eastern Jiangnan Orogen, which facilitated underplating of mantle-derived magma and crustal heating. This may have occurred in a back-arc extension in response to the drift of subduction direction of the Paleo-Pacific plate, which started as early as ~135Ma ago.

Petrogenesis and W-Mo fertility indicators of the Gaojiabang “satellite” granodiorite porphyry in southern Anhui Province, South China

The Gaojiabang W-Mo mineralized granodiorite porphyry occurs as a “satellite” intrusion on the northern margin of the Qingyang-Jiuhua pluton in southern Anhui Province, South China. The geology, mineral and whole-rock geochemistry of the granodiorite porphyry is I-type and formed from a reduced melt. The Gaojiabang mineralized granodiorite porphyry was derived from the transition zone between the lower crust and upper mantle, and underwent high-degree fractional crystallization during emplacement. There is no obvious genetic relationship between the granodiorite porphyry and the granodiorite pluton of the Qingyang-Jiuhua plutonic complex. The key characteristics of the W-Mo mineralized Gaojiabang granodiorite porphyry include: 1) small volume (<0.5km3), 2) an abundance of hornblende (>5vol%), 3) low ∑REE concentrations (145.50–159.46ppm) accompanying weak negative Eu anomalies (0.85–0.94), 4) high differentiation-indices degree and water contents, and 5) low oxygen fugacity. These criteria can be used to identify potential W-Mo mineralized intrusions in southern Anhui Province, South China.

Petrogenesis and tectonic implications of late Mesozoic granitoids in southern Anhui Province, southeastern China

ABSTRACTLate Mesozoic granitoids are widely distributed in southern Anhui Province, southeastern China, which also contains significant W–Mo–Cu mineralization. This study presents new geochronological and geochemical data that reveal the petrogenesis and tectonic affinity of the granitoids in this region. These granitoids can be divided into a high-K calc-alkaline and peraluminous I-type granodiorites, and an alkaline and metaluminous A-type granites, with zircon U–Pb dating indicating that they formed at 150–138 and 133–124 Ma, respectively. The early stage I-type granodiorites are adakitic, enriched in the light rare earth elements, and depleted in Nb, Ta, P, and Ti. They have negative zircon εHf(t) values (–19.8 to –2.5) that correspond to Hf crustal model ages of 2.4–1.4 Ga. These early stage granodiorites were derived from partial melting of thickened Palaeoproterozoic–Mesoproterozoic lower crust. The late-stage A-type granites with strong depletion in Sr, P, and Ti, contain higher Zr, Y, and Yb contents, higher zircon εHf(t) values (–1.5 to +2.1), and younger zircon Hf model ages (1.1–1.3 Ga) than the early stage granodiorites. The geochemistry of these A-type granites indicates they were likely generated by the reworking of Mesoproterozoic to Neoproterozoic juvenile crustal material that experienced the fractional crystallization of plagioclase and accessory minerals. Combining these data with other geological data from the study area indicates that the early stage granodiorites formed in a continental arc setting, whereas the late-stage granites formed in an extensional setting associated with roll-back of the subducted Palaeo-Pacific slab. The results indicate that zircon Ce4+/Ce3+ value can provide useful insight into oxygen fugacity conditions during magmatism.

Changes in soil bacterial communities in an evergreen broad-leaved forest in east China following 4 years of nitrogen addition

Purpose Evergreen broad-leaved forest ecosystems are common in east China, where they are both ecologically and economically important. However, nitrogen (N) addition over many years has had a detrimental effect on these ecosystems. The objective of this research was to evaluate the effect of 4 years of N addition on microbial communities in an evergreen broad-leaved forest in southern Anhui, China.

Mammal resource status in the mountain forest ecosystems of southern Anhui Province based on camera trap data

Mammal resource status in the mountain forest ecosystems of southern Anhui Province based on camera trap data

皖南地区大型韧性剪切带的精确厘定

皖南地区发育多条北东向大型韧性剪切带，其发育在不同地质体的边界。本文利用天井山、小贺、白石坑、田子坑、韩家、大片等6条重要实测构造地质剖面，和大量室内显微构造的专题研究，从构造几何学、构造岩石学、构造运动学等方面进行了璜茅–五城–屯溪韧性剪切带的精确厘定。阐述了韧性剪切带的延伸方向、规模、剪切变形特征、变形条件及形成的变质相。 There are many large size ductile shear zones of northeastern run in southern Anhui province. And they were developed in the boundary of different geological bodies. This paper uses the Tianjingshan section, Xiaohe section, Baishikeng section, Tianzikeng section, Hanjia section and Dapian section that 6 geological sections and a large number of microstructures research to precise determination the Huangmao-Wucheng-Tunxi ductile shear zone from the structural geometry and structural petrology, structural kinematics etc. And we described the ductile shear zone about the extension direction, scale, shear deformation characteristics, deformation condition and the metamorphic facies.

Survey of organochlorine pesticides in the atmosphere and soil of two typical landforms of Southern Anhui Province, China: Sources and air-soil exchange

Organochlorine pesticides (OCPs) were detected in the atmosphere and soil of Southern Anhui, China. The average concentration of ∑OCPs in the atmosphere along the Yangtze River (YR) was 950 ± 400 pg m−3, and was higher than that in the Huangshan Mountain (HM) which was 560 ± 120 pg m−3. The average concentration of ∑OCPs in the soil along the YR was 4.4 ± 1.9 ng g−1, and was lower than that in the HM which was 8.3 ± 2.3 ng g−1. Fugacity fraction (ff) values of DDTs, endosulfan I, and γ-HCH found in Southern Anhui were <0.3, suggesting obvious net gaseous deposition. For HCB, almost all the sites in Southern Anhui had ff > 0.7, suggesting obvious volatilization. For α-HCH, sites in the HM showed obvious net volatilization, and both volatilization and deposition of α-HCH could occur along the YR. The α/γ-HCH values in the atmosphere were lower than that in the technical HCH mixtures, probably indicating the inputs of lindane. Patterns of DDT congeners indicated that atmosphere of Southern Anhui was largely influenced by external fresh input of technical DDT. In the HM, atmospheric endosulfan I, p,p′-DDT and o,p′-DDT mainly came from other source regions by the atmospheric transportation, while both local soil re-emission and external input would have influence on the atmospheric α-HCH. For atmospheric HCB in the HM, re-emission from local soil might be the primary source. Air back trajectories analysis showed high levels of OCPs found along the YR might attributed to the atmospheric transport from the lower reach of the Yangtze River basin.

Pore system characteristics of the Permian transitional shale reservoir in the Lower Yangtze Region, China

The Permian shale, a set of transitional shale reservoir, is considered to be an important shale gas exploration target in the Lower Yangtze region. Due to little research conducted on the pore system characteristic and its controlling factors of the shale gas reservoir, SEM, FE-SEM, low-pressure N2 adsorption, and mercury intrusion tests were carried out on the Permian shales from the outcrop and HC well in the southern Anhui. The results show that the Permian shales mainly consist of organic matter, quartz, illite, calcite, and pyrite, of which pyrite occurs as framboids coexisting with organic matter and the organic matter is distributed in shales in stripped, interstitial, thin film and shell shapes. The basic pore types are inorganic mineral pore (intercrystalline pore, intergranular edge pore, intergranular pore, and interlayer pore in clay minerals) and the organic pore and microfracture, of which organic pore and microfracture are the dominating pore types. In shale, organic pores are not developed at all in some organic grains but are well developed in others, which may be related to the types of and maceral compositions of kerogen. Under tectonic stress, shale rocks could develop mylonitization phenomenon exhibiting organic grains well blend with clay minerals, and produce a mass of microfractures and nanopores between organic matter grains and clay minerals. Mercury intrusion tests show that the shale is mainly composed of micropore and transition pore with high porosity, good pore connectivity and high efficiency of mercury withdraw, while the shale that mainly dominated by mesopore and macropore has a low porosity, poor pore connectivity, and low efficiency of the mercury withdraw. The volume percentage of mesopore and marcopore is increasing with the increase of quartz, and that of micropore and transition pore has a decreased tendency along with the increase of soluble organic matter (S1). Organic matter is the main contributor to the specific surface area. However, clay minerals could significantly inhibit the numbers of the microscopic pore and specific surface area due to the clay minerals being mainly dominated by illite and chlorite.

Heterogeneous volcanism across the Permian–Triassic Boundary in South China and implications for the Latest Permian Mass Extinction: New evidence from volcanic ash layers in the Lower Yangtze Region

Volcanism has been suggested to have occurred widely in South China across the Permian–Triassic boundary (PTB); this has important implications for understanding the cause of the Latest Permian Mass Extinction (LMPE). However, few volcanic deposits have been reported in the Lower Yangtze Region and the extent of volcanism is uncertain. Herein we report new discoveries of intensive volcanism in this region for the first time, as evidenced by multiple (n>20) and thick (3–5cm) claystones (volcanic ash layers, K-bentonite) found in three deep-water outcrops in Xuancheng city, southern Anhui Province. Detailed petrographic and geochemical analyses of the ash layers were conducted to understand their origin and implications for the cause of the LPME, including X-ray diffraction, scanning electronic microscopy, energy dispersive spectroscopy, and whole-rock geochemistry. The petrological and mineralogical results show that the claystones contain clastic minerals indicative of a volcanic origin, such as zircon, analcites, pentagonal dodecahedral pyrite, and micro-spherules. The whole-rock geochemical data of the claystones suggest that the source rock of the ash layers was intermediate–acidic rhyodacite. The claystones are different from previously known claystones in the Middle–Upper Yangtze regions, indicating the occurrence of chemically heterogeneous volcanism in South China at the PTB.

Trend analysis of temperature and precipitation extremes in major grain producing area of China

ABSTRACTTo identify whether the spatial and temporal distribution of temperature extremes and precipitation extremes has changed in central and eastern China including Henan, Shandong, Anhui and Jiangsu provinces, the spatial and temporal distributions of extreme temperature and precipitation indices trends during 1961–2011 were investigated and analysed. To guarantee the accuracy of trend analysis, daily maximum and minimum surface temperature and daily precipitation from 299 meteorological stations were used. Eight extreme temperature indices and seven extreme precipitation indices were chosen. Mann–Kendall method was used to check the statistical significance of trends, while Sen's nonparametric method was used to calculate the trend magnitudes. The analyses of extreme temperature indices detected significant and stable trends in the majority of the stations, especially for the most part of southern Anhui and southern Jiangsu provinces. The strongly stable downward trends in cold extremes and the strongly stable upward trends in hot extremes were recorded in most of the regions. In contrast, significant and stable positive trends were insignificantly recorded for precipitation extremes in the study area, which predominantly occurred in the southern part of the region. Furthermore, the positive trends were more frequent than the negative trends in most extreme precipitation indices. The results may provide a reference for a more particular knowledge of the climate change in this region and provide guidance for agriculture development.

U–Pb age and Hf isotope composition of detrital zircons from Neoproterozoic sedimentary units in southern Anhui Province, South China: Implications for the provenance, tectonic evolution and glacial history of the eastern Jiangnan Orogen

Neoproterozoic sedimentary units at the southeastern margin of the Yangtze Block, South China, record a complex geological history including development of the Jiangnan Orogen during assembly of the Yangtze and Cathaysia blocks and later episodes of glacial activity. The timing of these events is controversial, and we have used U–Pb–Hf compositions of detrital zircons from the Lantian type section to constrain their ages in southern Anhui Province, at the eastern end of the Jiangnan Orogen. This section comprises the Xikou Group below an angular unconformity, and the Xiuning Formation and overlying glacial Leigongwu Formation above the unconformity. Detrital zircons in all three units are dominated by 2.6–2.4Ga, 2.1–1.9Ga and 960–740Ma age populations suggesting erosion from similar source regions, and an increasing proportion of older grains up through the sequence reflects a change in depositional environment from syn-collisional to extensional. Pre-Neoproterozoic zircon grains were derived from the Yangtze Block basement, much of which is now concealed by younger rocks, while the Neoproterozoic population was eroded from local igneous rocks in the Jiangnan Orogen. Zircon Hf isotope compositions indicate that 2.6–2.4Ga source rocks were a mix of juvenile and reworked crust, while 2.1–1.9Ga source rocks were dominated by reworked crust. Neoproterozoic sources show a switch from 960–860Ma juvenile crust to 860–740Ma juvenile and reworked crust, reflecting a transition in the Jiangnan Orogen from subduction to collision and extension. The youngest detrital grains in the Xikou Group and overlying Xiuning Formation indicate deposition after ca. 810Ma and ca. 732Ma, respectively, correlating closely with comparable sequences elsewhere in the Yangtze Block. This demonstrates that the unconformity in South Anhui is part of a regional erosion surface that formed more or less synchronously throughout the orogen at 830–800Ma, consistent with it dating the end of collision between the Yangtze and Cathaysia blocks. The age of the overlying glacial Leigongwu Formation is difficult to constrain from detrital zircons because of a paucity of post-720Ma source rocks, but our data suggest the Leigongwu diamictite in the Lantian section is a single Marinoan-age glacial unit deposited after 649±13Ma. It follows that a carbonate layer in the middle of the Leigongwu diamictite in the Lantian section most likely reflects later faulting, rather than two separate glacial sequences, although we cannot rule out the presence of both Sturtian and Marinoan diamictite elsewhere in South Anhui.

Late Mesoproterozoic to early Neoproterozoic ridge subduction along southern margin of the Jiangnan Orogen: New evidence from the Northeastern Jiangxi Ophiolite (NJO), South China

The Precambrian ophiolites in South China include the Northeastern Jiangxi Ophiolite (NJO) and the Fuchuan Ophiolite in southern Anhui. These two ophiolites contain important information on the Precambrian tectonics of South China. The NJO occurs along the southern margin of the Jiangnan Orogen, considered as the suture between Yangtze and Cathaysia Blocks in South China. Here we report new results for NJO from our field observations, U–Pb ages and Hf isotopic compositions of zircons from the cumulate and diabase units, chemical compositions of the clinopyroxene from the cumulates, and whole-rock geochemistry of the dismembered ophiolite units in an attempt to evaluate the late Mesoproterozoic to early Neoproterozoic evolution of the South China. Zircon U–Pb age data indicate that NJO formed at ∼1020Ma. Whole-rock geochemistry reveals that the tholeiitic cumulate and diabase members from the NJO have elemental compositions deviating from typical MORB- to arc-signatures. Clinopyroxene from the cumulates exhibits non-alkaline rifting-related features. Whole-rock and mineral chemistry, in combination with depleted MORB mantle (DMM)-like zircon Hf isotope composition (ɛHf(t)zircon=12–16) and whole-rock Nd isotope compositions (ɛNd(t)=4.5–7.8), argues that the cumulates and diabases share a common depleted mantle source with variable contamination by continental crust during magma ascent and/or emplacement. Elemental geochemistry and Nd isotope compositions of the serpentinites also reveal their DMM signature.Based on our new geochronological and geochemical data for NJO, as well as previous studies on the slightly younger adakites (970Ma) intruded into NJO and the Nb-enriched basalts (∼930Ma) in the northeastern section of the suture zone between Yangtze and Cathysia Blocks, we propose that NJO was a ridge-subduction type ophiolite. This new model may shed new light on the late Mesoproterozoic to early Neoproterozoic tectonic evolution of the South China.