广西东攀剖面粘土岩的火山岩特征及LA-ICP-MS锆石U-Pb年龄  

Volcanics characteristics and LA-ICP-MS zircon U-Pb ages of clay rocks along Dongpan section of Guangxi

作　　者：赵天宇[1] 冯庆来[1,2] 刘嵘[1] 周秋娥[1] 位荀[1] 

机构地区：[1]中国地质大学(武汉)地球科学学院,湖北武汉430074 [2]中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉430074

出　　处：《地质通报》2013年第9期1402-1409,共8页Geological Bulletin of China

基　　金：教育部高等学校博士学科点专项科研基金项目(编号:20110145130001);地质过程与矿产资源国家重点实验室和国家理科基地资金项目

摘　　要：广西扶绥县柳桥镇东攀地区出露1套上二叠统大隆组和下三叠统罗楼组,大隆组含Ophiceras sp.,罗楼组含Ophiceras tingi Tien生物化石,二者为整合的连续沉积地层。生物特征显示,在第12-3层和第13-1A层之间为二叠系—三叠系的界线,界面附近存在较厚的粘土岩层。从结构上看,粘土岩具有较明显的火山岩碎屑结构和沉凝灰构造,岩石地球化学研究也显示其具有钙碱性中酸性火山岩的特征,沉积环境为大陆边缘环境。在粘土岩中选取自形程度较高的火山成因锆石进行激光剥蚀法U-Th-Pb同位素测年研究,岩石中锆石的结晶年龄为254.7Ma±3.7Ma,表明本区二叠纪—三叠纪之交存在着火山活动。There exist Penman Dalong Fomaation and Lower Triassic Luolou Formation along Dongpan section crossing PTB. Da- long Formation contains Ophiceras sp., and Luolou Formation contains Ophieeras tingi Tien, suggesting that they are continuous. The evidence from paleontology indicates the PTB lies between 12-3 and 13-1A. There exists several claystone layers near the Penman Triassic boundary, and the layers have obvious volcanic debris and tuffite structure. Geochemical data also show that clay- stones have volcanogenic features. U-Th-Pb zircon isotope data show a weighted mean ^206Pb/^238U age of 254.7Ma±3.7Ma, which represents the crystallization age of the protolith of the clays, roughly identical with the zircon U-Pb age 253.4Ma±0.2Ma of the bottom boundary of the Changhsingian period. It is also shown that strong volcanic eruptions occurred in this area.

关 键 词：二叠纪一三叠纪 粘土岩 岩石学 地球化学 锆石 

分 类 号：P588.14[天文地球—岩石学] P597.3[天文地球—地质学]