川北江油—广元一带二叠系—三叠系界线粘土岩稀土元素地球化学特征及其地质意义  

REE geochemistry of claystone at the Permian-Triassic boundary in the Jiangyou-Guangyuan area, northern Sichuan, China and its geological implications.

作　　者：甘媛[1] 于林松[1] 何明友[1] 张玥[1] 刘峰[1] 王玉婷[1] 阙微[1] 

机构地区：[1]成都理工大学核技术与自动化工程学院和材料与化学化工学院,四川成都610059

出　　处：《地质通报》2008年第3期380-387,共8页Geological Bulletin of China

基　　金：四川省教育厅自然科学基金重点项目<古生代中生代环境突变的元素地球化学研究>(编号:2005A154)资助

摘　　要：选择川北江油滚柴坡和广元上寺、杨家湾二叠系—三叠系界线剖面为研究对象,利用中子活化法分析了粘土岩样品中稀土元素的组成。通过对稀土元素丰度、标准配分模式和特征参数的比较研究,探讨了稀土元素地球化学与自然环境突变的关系。结果表明,各剖面的δEu、δCe、ΣLREE/ΣHREE-ΣREE、Eu/ΣREE-ΣLREE/ΣHREE、球粒陨石标准化曲线图解和La-Th-Sc三元图解一致反映了界线事件的存在及界线时期稀土元素的地球化学特征与环境突变的关系。同时,通过对3条剖面稀土元素地球化学特征与标准剖面的对比研究,认为P/T(二叠系/三叠系)界线事件时期环境不仅受中酸性火山作用的影响,还可能受(碱性)基性—超基性或地外溅射物的影响。研究结果为从元素地球化学的角度探讨这一重要地质时期的灾变事件提供了新的资料。In this paper, the Permian-Triassic boundary （PTB） sections of Jiangyou, Gunchaipo, Guangyuan Yangjawan and Shangsi in northern Sichuan are selected for the INAA （instrumental neutron activation analysis） analysis of the REE geochemistry of claystone samples. Through a comparative study of the REE abundances, chondrite-normalized distribution pattern and characteristic parameters of claystone samples from three PTB sections, the paper explores the relationship between REE geochemistry and sudden environmental change at the PTB. The results demonstrate that the δEu,δCe, ∑LREE/∑HREE-∑REE, Eu/∑REE-∑L/∑H and chondritenormalized REE distribution patterns and La - Th - Sc ternary discrimination diagrams for claystone at the three sections all reflect the occurrence of the boundary event and the relationship between the REE geochemistry and sudden environmental change. In addition, through a comparative study of the REE geochemistry of the three PTB sections and standard section, the authors think that the envi- ronment during the period of the PTB event was affected not only by intermediate-acid volcanism but also possibly by （alkaline） basic-ultrabasic rocks or ejectas of volcanoes or an extraterrestrial planet. The research results provide new evidence for the study of the catastrophic event of this important geological period in the element geochemical context.

关 键 词：二叠系/三叠系界线 粘土岩 稀土元素地球化学:川北 

分 类 号：P534.46[天文地球—古生物学与地层学] P534.51[天文地球—地质学]