论东川地区前震旦系地层层序:来自锆石SHRIMP及LA-ICP-MS测年的证据  

Assessing Precambrian Stratigraphic Sequence of Dongchuan Area:Evidence from Zircon SHRIMP and LA-ICP-MS Dating

作　　者：朱华平[1] 范文玉[1] 周邦国[1] 王生伟[1] 罗茂金[1] 廖震文[1] 郭阳[1] 

机构地区：[1]成都地质矿产研究所,成都610081

出　　处：《高校地质学报》2011年第3期452-461,共10页Geological Journal of China Universities

基　　金：中国地质调查局地质调查项目(编号:1212010813066)资助

摘　　要：对东川地区的因民组内部辉绿岩体(TW1)、洒海沟组熔结凝灰岩(TW2)和平顶山组沉积砾岩(TW3)进行了锆石U-Pb年龄测定。结果表明,TW1获得上交点年龄为(1667±13)Ma,指示因民组内部辉绿岩体侵入时代为中元古代早期。TW2获得两组年龄,其中207Pb/206Pb加权平均年龄(2285+12/-11)Ma,指示火山岩形成时代为古元古代;上交点年龄为(2742±48)Ma,表明东川地区存在着一套更老的岩石地层。TW3获得最年轻一组碎屑锆石的207Pb/206Pb加权平均年龄为(1838±10)Ma,它代表平顶山组最大的沉积时限。基于以上定年数据,笔者认为东川地区的前震旦系地层层序由老至新分别为:洒海沟组、望厂组、菜园湾组、平顶山组、因民组、落雪组、黑山组、青龙山组、大营盘组。The authors got a series of zircon U-Pb ages for 3 samples in Dongchuan area,Yunnan province：the diabase（TW1） cutting Yinming Formation,the ignimbrite（TW2） of Sahaiguo Formation,and the sedimentary conglomerate（TW3） of Pingdingshan Formation.The SHRIMP zircon U-Pb dating for TW1 yielded an upper intersection age of（1667±13） Ma,which indicates the timing of diabase intrusion activity in Mesoproterozoic.The SHRIMP zircon U-Pb dating for TW2 showed two ages：an everage weighted age of（2285±11） Ma can be considered as the eruption timing of lava in Paleoproterozoic,and the upper intersection age of（2742±48） Ma indicates that a series of older rocks might exist in the Dongchuan area.The LA-ICP-MS dating for sample TW3 yielded an youngest concordant age of（1838±10） Ma,which constrained the oldest sedimentation age of the Pingdingshan Formation.Based on these dating results,the Precambrian stratigraphic sequence fitting the Dongchuan area from the older rocks upwards is as follows：Sahaiguo Formation,Wangchang Formation,Caiyuanwan Formation,Pingdishan Formation,Yinming Foramation,Luoxue Formation,Heisan Formation,Qinglongsan Formation and Dayingpang Formation.

关 键 词：锆石SHRIMP及LA-ICP-MS年龄 地层层序 前震旦系 东川地区 

分 类 号：P539.2[天文地球—古生物学与地层学] P597[天文地球—地质学]