青藏高原东缘若尔盖盆地表层沉积物粘土矿物组成及其环境意义探讨  

CLAY MINERAL COMPOSITION AND ITS ENVIRONMENTAL SIGNIFICANCE OF THE SURFACE SEDIMENT IN THE ZOIGêBASIN ON THE EASTERN TIBETAN PLATEAU

作　　者：张晓燕 张春霞[1,2,4] 李佩[1,5] ZHANG Xiaoyan;ZHANG Chunxia;LI Pei(Key Laboratory of Cenozoic Geology and Environment,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029;Innovation Academy for Earth Science,CAS,Beijing 100029;University of Chinese Academy of Sciences,Beijing 100049;College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao 266590,Shandong;China Earthquake Disaster Prevention Center,Beijing 100029)

机构地区：[1]中国科学院地质与地球物理研究所,中国科学院新生代地质与环境重点实验室,北京100029 [2]中国科学院地球科学研究院,北京100029 [3]中国科学院大学,北京100049 [4]山东科技大学地球科学与工程学院,山东青岛266590 [5]中国地震灾害防御中心,北京100029

出　　处：《第四纪研究》2022年第2期435-448,共14页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:42072209、41722206和41888101);中国科学院(B类)战略性先导科技专项项目(批准号:XDB26000000);国家重点研究发展计划项目(批准号:2016YFA0600503)共同资助。

摘　　要：青藏高原东缘若尔盖盆地的古气候和物源研究一直备受关注,但现有指标研究尚不足以探讨若尔盖盆地物源、降水变化及流域化学风化特征。本研究选择若尔盖盆地表层沉积物和基岩为研究对象,以X射线衍射(XRD)分析为主,结合X荧光光谱(XRF)分析,系统获取了该盆地表层沉积物和基岩的粘土矿物组合、全岩地球化学元素组成变化特征,开展了不同指标间的对比分析。研究结果显示:1)盆地表层沉积物和基岩的粘土矿物组成以伊利石为主,含绿泥石、少量高岭石和蒙脱石(含伊/蒙混层矿物),盆地表层沉积物中粘土矿物组成及含量变化受物源和风化的双重影响;2)与全岩样品地球化学指标呈现化学风化趋同特征,难以区分物源和风化影响不同,若尔盖盆地表层沉积物的粘土矿物指标,可有效区分物源、径流量变化和流域化学风化的影响,绿泥石/伊利石(Ch/I)可指示物源和化学风化程度,高岭石/伊利石(Kao/I)可指示流域内径流量变化,蒙脱石(含伊/蒙混层矿物)/伊利石(SI/I)可指示汇水区季节性变化的水位环境。本研究为利用粘土矿物指标重建若尔盖盆地的长尺度古径流变化和古气候演化提供了科学依据和基础。The paleoclimate changes of the ZoigêBasin on the eastern edge of the Tibetan Plateau have attracted much attention.However,previous researches are still not enough to reveal the affections of the provenance,paleoclimate changes on lacustrine sediments of the ZoigêBasin.In this study,clay mineral assemblages and bulk geochemical elements of the surface sediment(35 river sediment samples and 42 topsoil samples)and 14 bedrock samples of ZoigêBasin(32.33°~34.17°N,101.75°~103.42°E)were analyzed using X-ray diffraction(XRD)and X-ray Fluorescence(XRF)to determine the affections of the provenance and chemical weathering.The following results can be drawn from the present investigation of the ZoigêBasin:(1)The geochemical weathering degrees of surface sediments in the ZoigêBasin are primary to medium with the leaching of Na and Ca elements.Geochemical weathering proxies of surface sediments are affected by both the bedrock and the climate,which are not enough to distinguish the effects of above two factors;(2)The clay mineral assemblages of surface sediments and bedrock samples in the ZoigêBasin are primarily composed of illite(bedrock:56%~97%;surface sediment:70%~92%)followed by chlorite(bedrock:0~45%;surface sediment:3%~30%)and a minor amount of kaolinite(bedrock:0~18%;surface sediment:0~12%)and smectite(including irregular mixed-layers of illite,I/S)(bedrock:0;surface sediment:0~18%).Smectite(including I/S)only occurs in the surface sediment samples at the center of catchment area in the north of the ZoigêBasin and is absent in bedrock samples,which is chemical weathering product and mainly affected by the seasonality in the catchment area.Kaolinite in surface sediments mainly comes from bedrock;its content shows high values in the northeast and low values in the southwest,which is mainly controlled by the distribution of bedrock with kaolinite,topography and runoff in the ZoigêBasin.Chlorite content is high in the southeast and low in the northwest of the ZoigêBasin,which is affected by both the input of

关 键 词：青藏高原 若尔盖盆地 河流沉积物 表土 粘土矿物 古气候意义 

分 类 号：P534.632[天文地球—第四纪地质学] P595[天文地球—古生物学与地层学]