四川盆地西南缘下三叠统铜街子组-雷口坡组地球化学特征及其古环境意义  

Geochemical Characteristics and Its Paleoenvironmetal Significance of the Lower Triassic Tongjiezi and Leikoupo Formations on the Southwestern Margin of the Sichuan Basin

作　　者：白宪洲[1] 文龙[1] 王玉婷[1] 马继跃 巴金[1] 鄢圣武[1] BAI Xian-zhou;WEN Long;WANG Yu-ting;MA Ji-yue;BA Jin;YAN Sheng-wu(Sichuan Institute of Geological Survey,Chengdu610081)

机构地区：[1]四川省地质调查院

出　　处：《四川地质学报》2019年第3期387-393,共7页Acta Geologica Sichuan

基　　金：中国地质调查局东特提斯成矿带大型资源基地调查工程乌蒙山区地质矿产综合调查项目四川乌蒙山区1∶5万洪溪幅(H48E021005)、觉洛幅(H48E022005)、中普幅(H48E022003)、申果庄幅(H48E022004)区域地质调查子项目(委托业务工作编码:DD20160019-07)

摘　　要：沉积岩的微量元素及稀土元素蕴含了大量的地质信息,是研究沉积物沉积时的古气候、古环境的有效手段。作者选取了四川盆地西南缘下三叠统铜街子组-雷口坡组的9件样品进行了主量元素、微量元素及稀土元素的测定。基于能够敏感反应沉积环境的微量元素指标及特征微量元素、稀土元素比值,对四川盆地西南缘早三叠世铜街子组-雷口坡组沉积时期的古环境、古气候进行了研究。结果表明:四川盆地西南缘下三叠统铜街子组-雷口坡组的岩石具有富TiO2、MgO、CaO、K2O等,贫SiO2、Na2O的特点。相对于地壳,稀土元素总量较高,具中等的负铕异常,w(LREE)/w(HREE)比值较高。四川盆地西南缘下三叠统铜街子组-雷口坡组的沉积环境演化分为9个时期:自下而上,干热(氧化,水体分层弱)→温湿(氧化,水体分层弱)→冷湿(缺氧、水体分层性极弱)→干热(氧化,水体分层弱)→温湿(缺氧,水体分层强)→干热(氧化,水体分层弱)→温湿(氧化,水体分层弱)→温湿(氧化,水体分层性强)→干热(氧化、水体分层性中等-强)。为该区早三叠世环境演化研究提供基础资料。This paper has a discussion on paleoenvironment and paleoclimate of the Sichuan basin in the Early Triassic based on analyses of major elements,trace elements and REE for 9 samples from the Lower Triassic Tongjiezi and Leikoupo Formations.The analyses indicate that the samples are rich in TiO2,MgO,CaO and K2O,and poor in SiO2 and Na2O with higherΣREE,moderate negative Eu anomaly and high LREE/HREE ratio.Study results show that sedimentary environment evolution on the southwestern margin of the Sichuan basin during the Lower Triassic(from Tongjiezi period to Leikoupo period)may be divided into 9 stages:dry heat(oxidation,weak water layer),warm and humid(oxidation,weak water layer)-cold and humid(anoxia,very weak water layer)-dry heat(oxidation,weak water layer)-warm and humid(anoxia,strong water layer)-dry heat(oxidation,weak water layer)-warm and humid(oxidation,weak water layer)-warm and humid(oxidation,strong water layer)-dry heat(oxidation,medium-strong water layer).

关 键 词：四川盆地 下三叠统 铜街子组 雷口坡组 地球化学特征 古环境 

分 类 号：P596[天文地球—地球化学]