珠江三角洲南部晚第四纪环境变化的稀土元素记录

珠江三角洲南部平原PRD05孔稀土元素(REE)的分布特征与晚第四纪沉积环境变化密切相关。随着不同时期沉积环境的波动,稀土元素分布也发生相应的变化。约31000calaBP以前,研究区发育河流环境,受矿物组成和沉积物粒度的影响,ΣREE含量偏低,且重稀土元素(HREE)相对富集。31000—16600calaBP期间,ΣREE含量明显高于前一阶段,并显示轻稀土元素(LREE)富集;稀土元素分布模式表现为河口半咸水环境特征;其上部沉积物经历了末次冰盛期的风化作用,稀土元素分布模式与下部近平行,但LREE的富集程度略高。16600—10300calaBP为冰后期海平面上升初期,研究区发育沼泽环境,由于有机质含量高而导致稀土元素含量普遍较高。10300—5600calaBP为全新世海侵期,研究区持续发育河口湾—浅海环境,其ΣREE含量总体较高,并显示LREE富集;随着水体深度和盐度条件发生多次波动,稀土元素分布特征也表现出小幅度变化。5600calaBP以来,河流作用逐渐增强,并受到潮汐作用间歇性影响,其ΣREE含量显著下降,但波动频繁。

Geochemical Signatures of Early Paleogene Source Rocks in the Sanshui Basin, South China

The Honggang member of the early Paleogene Buxin Formation is the main source rock in the Sanshui Basin, characterized by organic-rich black shales with the cyclic recurrence of organic- poor sediments. The geochemical characteristics of the Honggang member have been documented to determine the organic matter types and depositional environments in this paper. The organic matter of the black shales mainly consists of a mixture of land plant-derived and phytoplankton-derived organic matter. Total organic carbon content （TOC）-sulfur-iron （Fe） relationships suggest that the organicrich black shales were deposited under dysoxic-to-euxinic water conditions. The time that iron minerals remained in contact with H2S in anoxic waters possibly influenced the formation of syngenetic pyrite, and organic carbon controlled the formation of diagenetic pyrite. Organic-poor intervals usually show pyrite sulfur enrichment and higher degree of pyritization values relative to low organic carbon contents. This resulted from HS- diffusing downward from overlying organic-rich sediments and formed Fe sulfides through reactions with sufficient Fe. Trace elements generally exhibit low concentrations and little TOC dependence, suggesting some degree of depletion in these elements in the early Paleogene sediments of the Sanshui Basin. This probably resulted from cyclic recurrences of oxic benthic conditions, which promoted the remobilization of trace elements and caused the low concentration of trace elements.

Biostratigraphic and Chemostratigraphic Correlation for the Base of the Middle Ordovician between Yichang and Western Zhejiang Areas,South China

The base of the Middle Ordovician （i.e. Dapingian Stage） has been defined at the first appearance datum （FAD） of conodont Baltoniodus？ triangularis at Huanghuachang, Yichang, China,but the precise correlation of the boundary to regions of other facies remain to be resolved. Herein we review the biostratigraphy and chemostratigraphy of the Huanghuachang Global Standard Stratotype-Section and Point （GSSP） section, and present our latest stratigraphic work on the nearby Chenjiahe s ection in Yichang, and the Hengtang Quarry section, Jiangshan, Zhejiang, which is regarded as representative of slope facies. The conodont and graptolite biostratigraphy as well as chemostratigraphy of the Chenjiahe section indicate that the base of the Middle Ordovician also falls within the graptolite Azygograptus suecicus Zone, and coincides with a high or maximum δ13C value within a minor positive carbon isotope excursion, suggesting that the base boundary can be readily recognized across the entire Yangtze Gorges area. The integrated graptolite and conodont biostratigraphy and chemostratigraphy of the Hengtang section, Jiangshan, indicates that the basal boundary probably falls within the graptolite lsograptus caduceus imitatus Zone that overlies the Azygograptus suecicus Zone, and coincides with a remarkable drop of δ13C. This difference indicates that a multi-disciplinary approach is critical to identify the base boundary in those regions where the Baltoniodus ？ triangularis is absent.

Using LIDAR and ground truth for landslide recognition and characterization of geotechnical and morphological parameters in sedimentary rocks,a case study in Northern Bavaria (Germany)

The use of LIDAR-derived shaded relief maps led to the identification of all potential landslide areas in a hilly region in Northern Bavaria(1590 km^2), Germany. Every possible structure was investigated by field investigation which resulted in a detailed database of 1002 landslides within the study area. The analysis of geological, lithological, topographical and morphological properties(spatial ratio, lithological and geological setting, length/width distribution, material properties and slope angle) revealed characteristic appearances of the landslides and possible relationships between different aspects. Strong relations between the lithological setting, spatial ratio of the mapped landslides and distribution of slope angle could be observed. This study shows the value of high-resolution shaded relief maps for detecting and mapping landslides in a large area with comparatively little work and time in comparison to the traditional approach to mapping. It reveals that many landslides were not known before. Landslides are much more common in Northern Bavaria and have a higher influence on the denudation rate of the Franconian Alb than expected before.

Preliminary Estimation of Paleoproductivity via TOC and Habitat Types:Which Method Is More Reliable?—A Case Study on the Ordovician-Silurian Transitional Black Shales of the Upper Yangtze Platform, South China

New total organic carbon （TOC） data from the two Ordovician-Silurian transitional graptolite-bearing black shale intervals, the Wufeng （五峰） Formation and the Longmaxi （龙马溪） Formation in Central Guizhou （贵州） and West Hubei （湖北）, respectively, as well as previously reported TOC data from the same intervals in other places on the Yangtze platform of South China, have been used to produce an initial estimate of the primary paleoproductivity via a conventional inverse method （i.e., Rpp.inverse）. The values of the Rpp.inverse are estimated to be 32 （43-21） gC/（m^2·a）（Wufeng Formation） and 21 （27-16） gC/（m^2·a） （Longmaxi Formation）. Also, simultaneously, the habitat types （i.e., HT; cf., BA： benthic assemblage） and their temporal and spatial changes have been documented from the same succession, and an initial estimate of the primary paleoproductivity has been produced using a forward method （i.e., Rpp-forward） Beingbounded mainly by the peritidal to inner-shelf environment shelly-facies or mixed-facies successions with BA1 to BA3 faunas both at the top and the base, which indicates the habitat types from HT Ⅱ to HT Ⅲ2, the biohabitat type of the two graptolite-bearing black shale intervals can be limited to HT III to HT IV, corresponding to the inner shelf to the outer shelf, with depths from roughly 60 m to 200-300 m. Based on the current data from the South China Sea and the southern part of the East China Sea, values of Rpp-forward should be about 100 to 400 gC/（m^2·a）. The difference in the results via the two methods suggests that paleoproductivity estimates from the geological strata need to be made cautiously, with particular attention paid to the paleogeographic setting, oxic-anoxic conditions, as also the preservation factor of organic carbon.

Large Scale Mass Movements Triggered by the Kashmir Earthquake 2005,Pakistan

The SPOT image analysis in Muzaffarabad Azad Kashmir,northwest Himalayas,Pakistan reveals that the Kashmir earthquake 2005 triggered a number of coseismic mass movements along the hanging wall block of the Muzaffarabad Fault.The Neelidandi and Langarpura rock falls have been identified as two major reactivated mass movements with an estimated volume of 3.1 × 106m3and 5.76 × 106m3,respectively.The Neelidandi and Langarpura mass movements were initiated during earthquake in the direction of northwest-southeast extension and northeastsouthwest directed thrusting,respectively.The Neelidandi rock fall occurred in sheared cherty dolomites and limestones of the Cambrian Muzaffarabad Formation,whereas the Langarpura rock fall occurred in alternating clays,shales,claystones,siltstones and sandstones of the Miocene Murree Formation.These rock units along the fault are highly fractured and jointed.The geotechnical maps and geological longitudinal profiles show the relationship between the geometrical characteristics and mechanism of these mass movements.Their characteristics were analyzed according to the role of topographic,seismic,geological and tectonic factors.The steep topography,sheared rocks,lithology,coseismic uplift and strong ground shaking of the hanging wall block along Muzaffarabad Fault facilitated the gravity collapse of these mass movements.

A reconstruction of Turkey’s potential natural vegetation using climate indicators

Turkey,containing three of the world’s biodiversity hotspots,is a hub for genetic biodiversity.However,the vegetation cover has drastically changed in recent decades as a result of substantial transformations in landuse practices.A map of the potential natural vegetation can be used to represent the biodiversity of a country,and therefore a reference to effectively develop conservation strategies.The multinomial logistic regression is used to simulate the probability of different biomes occurring in the country using elevation,climatological data and natural vegetation data.A correlation test was applied to the climatological data to determine which predictors influence vegetation the most.These were temperature,precipitation,relative humidity and cloudiness.The Ordinary Kriging method was employed to transform the data into the format for the multinomial logistic regression model.The model showed that temperature was the most influencing factor with respect to Turkey’s vegetation and distribution follows a similar distribution as the various macroclimates.Broadleaf forests are mostly found in the Black Sea region,which is also the wettest region of the country.The Marmara region is the only other region where there are broadleaf forests.Mixed forests and shrublands are mostly located in Central Anatolia due to the region’s low humidity which favours herbaceous flora.Coniferous forests were dominant in the Aegean and Mediterranean regions,attributed to high temperatures.

西藏喜马拉雅地区三叠系-侏罗系界线动物群扩散事件及古环境

西藏喜马拉雅格米格地区的三叠系-侏罗系界线地层的菊石类和双壳类曾生活在热带浅海环境.建立在菊石带基础上的高分辨率地层可用于确定一些动物群的发生.双壳类Aguilerella和Ctenostreon展现了泛热带迁移的模式,它们首先出现在喜马拉雅,然后向东迁移到东南太平洋;这一模式同样为菊石类Choristoceras,Discamphiceras,Pleuroacanthites和Psiloceras calliphyllum的地理分布所支持.一些在其他地方晚三叠世业已绝灭的属种,如菊石类有Choristoceras和Eopsiloceras,双壳类有Newaagia,Terquemia,Persia,Ryderia guangdongensis和Cultriopsis angusta,在西藏喜马拉雅地区却延续到早侏罗世早期.这一现象表明西藏喜马拉雅地区可能在晚三叠世的生物大绝灭过程中起到了避难所的作用.

西南地区晚三叠世卡尼期牙形石研究进展

我国西南地区海相中-上三叠统沉积记录良好,但晚三叠世卡尼期牙形石生物地层划分和对比研究较为薄弱.通过对云南省罗平县和贵州省贞丰县、关岭县等地4条剖面的杨柳井组、竹杆坡组以及瓦窑组进行高精度的牙形石采样,以及牙形石生物地层学和系统分类学研究,共描述牙形石3属23种.结合前人研究材料,由下至上共建立了8个牙形石带,分别为:Paragondolella foliata带,Quadralella polygnathiformis带,Quadralella tadpole带,Quadralella praelindae带,Quadralella aff.auriformis带,Quadralella robusta带,Quadralella noah带和Quadralella ex gr.carpathica带.以此为基础,对西南地区卡尼期地层进行区域内和跨大区的对比和划分研究以及对牙形石分子演化规律进行探讨.

Late Quaternary palaeoenvironmental changes documented by microfaunas and shell stable isotopes in the southern Pearl River Delta plain,South China

Ahigh resolution study of sediments,microfaunas(ostracods and foraminifers),and stable isotopes of ostracod shells from core PRD05,sampled from the Da’ao plain of the Pearl River Delta,provides new data about palaeoenvironmental changes during the Late Quaternary.The basal fluvial gravelly sediments of the core,representing the lowest deposits of the Quaternary at the core site,were possibly formed prior to the transgression associated with the last interglacial stage.This fluvial setting changed into a marginal marine setting during the last interglacial stage,any record of calcareous fossils were destroyed by subsequent dissolution during the last glacial phase,when the upper part of the deltaic sediments experienced subaerial oxidation,indicated by a mottled clay layer in the core.The postglacial sealevel rise in the South China Sea began at16,700 cal yr B.P.During the first phase of sea-level rise(from ~16,700 to 10,100 cal yr B.P.),a swamp environment developed at the core site.At ~10,100 cal yr B.P.,marine waters intruded onto the Da’ao plain and reached the core site through the Modaomen channel.This timing was earlier than in other parts of the Pearl River Delta.Since then,a semi-enclosed estuarine environment developed and was maintained until ~5560 cal yr B.P.During this transgressive interval,short-term environmental fluctuations can be recognized based on microfauna and shell geochemical data.From ~10,100 to 8630 cal yr B.P.,the sea-level rose,which was followed by a fall from ~8630 to 8520 cal yr B.P.An expanded transgression occurred between ~8520 and 7900 cal yr B.P.The time intervals from ~8520 to 8200 cal yr B.P.and from ~8080 to 7900 cal yr B.P.were marked by peak transgression.From ~7900 to 5560 cal yr B.P.,the core site generally showed a reduced marine influence and enhanced freshwater input.A fluvial environment developed from ~5560 to 3100 cal yr B.P.,and was succeeded by an alluvial plain setting.

Interbasinal marker intervals——A case study from the Jurassic basins of Kachchh and Jaisalmer, western India

The Kachchh Basin and the Jaisalmer Basin are two neighboring Mesozoic sedimentary basins at the western margin of the Indian craton. The Jurassic succession of the Kachchh Basin is more complete and more fossiliferous than that of the Jaisalmer Basin. Consequently, intrabasinal correlation of the sedimentary units has been possible in the Kachchh Basin, but not in the Jaisalmer Basin. However, some marker beds existing in the Kachchh Basin can be recognized also in the Jaisalmer Basin. Ammonite evidence shows that they are time-equivalent. The following four units form marker intervals in both basins: (1) the pebbly rudstone unit with Isastrea bernardiana and Leptosphinctes of the Kaladongar Formation (Kachchh Basin) and the Isastrea bernardiana-bearing rudstone of the Jaisalmer Formation (Jaisalmer Basin) both represent transgressive systems tract deposits dated as Late Bajocian; (2) bioturbated micrites with anomalodesmatan bivalves within the Goradongar Yellow Flagstone Member (Kachchh Basin) and bioturbated units in the Fort Member (Jaisalmer Basin) represent maximum flooding zone deposits of the Middle to Late Bathonian; (3) trough-crossbedded, sandy packto grainstones of the Raimalro Limestone Member (Kachchh Basin) and the basal limestone-sandstone unit of the Kuldhar section of the Jaisalmer Formation (Jaisalmer Basin) correspond to Late Bathonain transgressive systems tract deposits; and (4) ferruginous ooid-bearing carbonates with hardgrounds of the Dhosa Oolite member (Kachchh Basin) and the middle part of the Jajiya Member (Jaisalmer Basin) are Oxfordian transgressive systems tract deposits. The fact that in both basins similar biofacies prevailed during certain time intervals demonstrates a common control of their depositional history. As the two basins represent different tectonic settings, the most likely controlling factors were the relative sea-level changes produced by eustatic processes, a common subsidence history of the northwestern margin of the Indian craton, and the paleoclimate.

Facies analysis and palaeoecology of the Jurassic Spiti Shale Formation in the Spiti area,Northern India

The Spiti Shale Formation is a widely distributed stratigraphic unit of the passive northern margin of the Indian craton,deposited between the Callovian and earliest Cretaceous.The siliciclastic strata are dominated by dark-grey to black argillaceous silt.As the formation has undergone intense tectonic stress involving folding and faulting,it is very difficult to document a complete section.In the type area,the Spiti Valley,six sections have been measured that document parts of the three informal members of the formation,the Lower,Middle,and Upper members.Despite its uniform appearance,eight facies/biofacies types could be distinguished,ranging from the anoxic shale facies,with ammonites and belemnites as the only faunal elements,to the dysoxic Malayomaorica and Bositra biofacies,and the oxic to anoxic offshore shelf facies,which are characterized by low-diversity macrobenthos associations.Other facies are the condensed glauconiticphosphoritic mudrock facies and the Fe-oolitic siltstone facies(both characterized by sediment starvation),the aerated argillaceous silt-sandstone facies,and the tide-influenced nearshore shelf facies.The benthic macrofauna represents four bivalve-dominated associations all characterized by a very low to low species diversity.They are the Bositra buchii,the Australobuchia spitiensis,the Palaeonucula cuneiformis-Pruvostiella hermanni-Indogrammatodon egertonianus,and the Malayomaorica sp.-Australobuchia spitiensis-Retroceramus haasti association.Sediments and macrobenthic associations indicate that the Spiti Shale Formation represents outer to inner shelf environments,which for much of the time were subjected to upwelling and anoxic to dysoxic conditions.Distinct shallowing at the top characterizes the transition to the overlying Lower Cretaceous Giumal Formation.

Dispersal events of Triassic-Jurassic boundary faunas, and paleoenvironment of Tibetan Himalaya

End-Triassic ammonoid and bivalve faunas of the Germig area, Tibetan Himalaya, lived in a tropical, shallow-water environment during the Triassic-Jurassic boundary interval. High stratigraphic resolution based on ammonite-biochrons allows to tracing the place of origin of several faunal elements. The bivalves Aguilerella and Ctenostreon occurred first in the Tibetan Himalaya and migrated from there to the eastern South Pacific, exhibiting a pantropic dispersal pattern. This dispersal route is supported by the distribution pattern of the ammonites Choristoceras, Discamphiceras, Pleuroacanthites, and Psiloceras calliphyllum. A few taxa, which went extinct everywhere else by the end of the Triassic, survived in the Tibetan Himalaya into early Early Jurassic times. They include the ammonites Choristoceras and Eopsiloceras, and the bivalves Newaagia, Terquemia, Persia, Ryderia guangdongensis, and Cultriopsis angusta. This suggests that the Tibetan Himalaya may have played a refugia role in the course of the end-Triassic mass extinction.

Osteogenic lithium-doped brushite cements for bone regeneration

This study investigated the osteogenic performance of new brushite cements obtained from Li+-dopedβ-tricalcium phosphate as a promising strategy for bone regeneration.Lithium(Li+)is a promising trace element to encourage the migration and proliferation of adipose-derived stem cells(hASCs)and the osteogenic differentiation-related gene expression,essential for osteogenesis.In-situ X-ray diffraction(XRD)and in-situ 1H nuclear magnetic resonance(1H NMR)measurements proved the precipitation of brushite,as main phase,and monetite,indicating that Li+favored the formation of monetite under certain conditions.Li+was detected in the remaining pore solution in significant amounts after the completion of hydration.Isothermal calorimetry results showed an accelerating effect of Li+,especially for low concentration of the setting retarder(phytic acid).A decrease of initial and final setting times with increasing amount of Li+was detected and setting times could be well adjusted by varying the setting retarder concentration.The cements presented compressive mechanical strength within the ranges reported for cancellous bone.In vitro assays using hASCs showed normal metabolic and proliferative levels.The immunodetection and gene expression profile of osteogenic-related markers highlight the incorporation of Li+for increasing the in vivo bone density.The osteogenic potential of Li-doped brushite cements may be recommended for further research on bone defect repair strategies.

Roadian-Wordian(Middle Permian)Conodont Biostratigraphy,Sedimentary Facies and Paleotemperature Evolution at the Shuixiakou Section,Xikou Area,Southeastern Qinling Region,China

Focusing on the Shuixiakou Section(Xikou area,Zhen’an County,Shaanxi Province,southeastern Qinling region,China),the Roadian-Wordian conodonts are investigated.More than 2000 conodont elements including 6 genera and 14 species have been obtained.Based on these materials,the Guadalupian Jinogondolella nankingensis and J.aserrata zones have been recognized.The Roadian-Wordian boundary is tentatively defined by the first occurrence of J.aserrata in the lower part of UnitⅢin the Shuixiakou Formation.The sedimentary succession of Xikou area records similar sea-level changes to those observed in Laibin area(South China).The 40 m-thick bioclastic limestone of UnitⅣin this section can be correlated with the reefs of Bed 114 in Laibin area.A temperature drop indicated byδ18Oapatite values suggests this Wordian interval coincides with a period of glaciation and global regression.

Lithological and Structural Control of Hattian Bala Rock Avalanche Triggered by the Kashmir Earthquake 2005, Sub-Himalayas, Northern Pakistan

The Kashmir earthquake 2005 （magnitude MW 7.6） triggered thousands of mass move-ments in northern Pakistan. These mass movements were mainly rock falls, debris falls, rockslides and rock avalanches. The mass movements vary in size from a few hundred cubic meters up to about 100 million cubic meters estimated for the Hattian Bala rock avalanche, the biggest one associated with this earthquake. This mass movement, which moved in southeastern direction, created two natural dams on the valley bottom and blocked the water ways of the Karli and Tung tributaries of the Jhelum River. Topographic, lithologic and structural information were used to investigate the Hattian Bala rock ava-lanche. Geotechnical and structural maps were prepared to understand relationship between geology and structure of Hattian Bala rock avalanche. The geometry and failure mode of this rock avalanche are controlled by southeast plunging synclinal structures, lithology, a bedding parallel slip surface and a pre-existing old rockslide. The structural map shows that the mass movement failure was due to Danna and Dandbeh synclinal structures plunging southeast on the hanging wall block of the reacti-vated Muzaffarabad fault. The slip surface of the mass movement followed the bedding planes along mudstone, claystone and sandstone surfaces. The mass movement perfectly followed the pre-existing synclinal morphology of the Danna and Dandbeh synclines.

Sequence architecture of a Jurassic ramp succession from Gebel Maghara(North Sinai,Egypt):Implications for eustasy

The Jurassic succession at Gebet Maghara, North Sinai, Egypt, represents a mixed carbonate-siticictastic sequence. Combining information from both fossits and rocks attowed a ptausibte reconstruction of the depositionat environments and of the basin evotution. The Ju- rassic succession of Gebel Maghara was deposited on a ramp, and the architecture of the ramp facies was strongty controtted not onty by sea-revel changes but atso by extensionat tectonics in connection with rifting of the Tethys, North Gondwana. Seven tectonicalty modified thirdorder sequences （DS 1-DS 7） have been recognized. The first three sequences （DS 1-DS 3）, ranging from the Toarcian to the Bajocian, record sea invasion （intertidat to shattow subtida[lconditions） across an intracratonic area as a resutt of eustatic sea-fever changes during a quiescent rift stage. The remaining sequences （DS 4-DS 7） reflect open marine mid to outer ramp settings. Non-marine conditions around the Bajocian-Bathonian boundary, documented by catiche, represent the maximum regression of the sea. During an active extensionat stage, horsts, which formerty acted as barriers separating the Maghara sub-basin from the main ocean, subsided. Subsequent rejuvenation and reactivation of fautts shifted the homoctinat physiography of the ramp to a distatty steepened ramp during the earty Bathonian, creating a 200-m-thick dettaic wedge. SimiLar processes during the earty Kimmeridgian created a catcirudite-catcarenite succession of stope origin. The diversity and the epifaunat/infaunat percentage of the macrofauna disptay a cyctic pattern which coincides more or tess with the sequence stratigraphic architecture.

Thermal Efficiency Optimization of a Ground Source Heat Pump System by Assistant Preheating/Precooling: A Case Study on a Heating-Load Dominated Building

Operation strategies of Ground Source Heat Pump System(GSHPS) such as continuous or intermittent approaches have been extensively studied. In this work, a novel strategy was proposed to maximize the energy efficiency of GSHPS. In this approach, the buildings was first air-conditioned by the preheating/precooling mode and the rest thermal load was covered by the heat pump(HP) mode. The system performance can then be optimized by considering the combination of these two operating modes. A case study was made to examine the thermal performance of a GSHPS installed in Nuremberg, Germany. Thermal performance of the HP and the preheating/precooling operating modes was examined. The system was optimized by deploying the assistant preheating/precooling approach and over one-year period monitoring showed that the seasonal Coefficient of Performance(COP) of the GSHPS was 4.12 in winter and 5.01 in summer. These COP values are higher than that of the conventional GSHPS. Thus, this proposed strategy could be an efficient way to improve the thermal performance of GSHPS.

Crustal Contamination of the Mantle-Derived Liuyuan Basalts:Implications for the Permian Evolution of the Southern Central Asian Orogenic Belt

The Permian basalts in the Central Asian Orogenic Belt(CAOB)are crucial for constraining the closure of the Paleo-Asian Ocean.However,the origin of these basalts is still under discussion.Here,we present comprehensive bulk-rock geochemical,Sr-Nd-Pb-Hf isotopic,and zircon U-Pb-Lu-Hf isotopic data of the Liuyuan basalts and coexisting gabbros,which are located in the Beishan Orogen in the southern CAOB,to constrain their emplacement setting and tectonic implications.Our new gabbro ages of ca.288–294 Ma are interpreted to represent the formation time of the Liuyuan basaltic belt.The Liuyuan basalts show MORB-like rare earth element(REE)patterns and bulk-rockε_(Hf)(t)andε_(Nd)(t)values of 11.0–15.4 and 4.6–9.2,respectively,suggesting an origination mainly from a depleted mantle source.However,positive Pb anomalies,Nb-Ta depletions,and high Th/Yb ratios as well as evolved Sr-Nd-Pb-Hf isotopic compositions of some samples indicate variable continental crustal contribution.According to the covariation of Pb anomalies(Pb^(*)=2×Pb_(N)/(Ce_(N)+Pr_(N)))with Sr-Nd-Pb-Hf isotopic compositions,we speculate that parent magma of the Liuyuan basalt was contaminated by continental crustal materials during the eruption rather than having been generated from an enriched mantle source.As revealed by mixing modelling,the Liuyuan basaltic magmas would require a minor(<10%)upper continental crustal assimilation to explain the enriched trace elemental and radiogenic Sr-Nd-Pb-Hf isotopic signatures.Consequently,the Liuyuan basaltic belt is believed to have been generated in a continental extensional environment instead of an oceanic setting and does not constitute a Permian ophiolitic suture zone as previously suggested,since the Paleo-Asian Ocean was already closed in the southern Beishan Orogen in the Early Permian.