赣南-粤北地区晚白垩世早期长英质火山岩SHRIMP锆石U-Pb年龄及其地质意义  

SHRIMP zircon U-Pb dating of the early Late Cretaceous felsic volcanic rock in southern Jiangxi-northern Guangdong area and its geological significance

作　　者：巫建华[1] 徐勋胜 刘帅[3] 

机构地区：[1]东华理工大学核资源与环境国家重点实验室培育基地,江西南昌330013 [2]核工业270研究所,江西南昌330200 [3]东华理工大学地球科学学院,江西抚州344000

出　　处：《地质通报》2012年第8期1296-1305,共10页Geological Bulletin of China

基　　金：中国核工业总公司项目<中国中-新生代铀成矿作用研究>(编号:中核地计[2008]74号)

摘　　要：中国东南部晚白垩世早期广泛发育红色沉积岩系,沉积岩系底部常见玄武岩夹层,但赣南-粤北的长塘、仁居、寻乌盆地以长英质火山岩为主体,底部也夹有玄武岩层,构成"大量流纹岩-少量玄武岩"的双峰式组合。SHRIMP锆石U-Pb年龄表明,长塘、仁居盆地流纹岩和寻乌盆地碎斑熔岩的锆石206Pb/238U年龄分别为96.8Ma±1.4Ma、95.5Ma±1.3Ma、96.7Ma±1.1Ma,属晚白垩世早期。鉴于版石盆地火山岩系为长英质火山岩组合,且中部凝灰岩和上部流纹岩SHRIMP锆石U-Pb年龄分别为142.5Ma±1.3Ma和131.4Ma±1.3Ma,地质时代属早白垩世早期,长塘、仁居和寻乌盆地的火山岩系不能与版石盆地的火山岩系对比。赣南-粤北长塘、仁居和寻乌盆地长英质火山岩地质时代的确认,证实余姚-丽水-政和-大浦-莲花山断裂以东和以西"大量流纹岩-少量玄武岩"构成的不对称双峰式组合具有不同的地质时代,显示出东早西晚的特征,这对于研究中国东南部中生代岩浆活动和构造演化具有重要意义。The early Late Cretaceous red sedimentary rocks with basalt intercalations at the bottom are widely developed in southeastern China,and the asymmetric bimodal volcanic rocks of felsic volcanic rocks comprising mainly rhyolite and some basalt intercalations at the bottom are extensively spread in Changtang,Renju and Xunwu basin in south Jiangxi-north Guangdong area.The zircon SHRIMP U-Pb dating results of felsic volcanic rocks show that rhyolite ages in Changtang and Renju are 96.8Ma±1.4Ma and 95.5Ma±1.3Ma respectively,and the porphyroclastic lava age in Xunwu is 96.7Ma±1.1Ma.The felsic volcanic rocks belong to early Late Cretaceous.The volcanic rocks are all felsic volcanic rocks in Banshi basin,and the zircon SHRIMP U-Pb age of middle tuff and upper rhyolite are 142.5Ma±1.3Ma and 131.4Ma±1.3Ma respectively,suggesting that they were formed during early Early Cretaceous period.So the volcanic rocks in Changtang,Renju and Xunwu basin cannot be correlated with the volcanic rocks in Banshi basin.Geological age studies of the felsic volcanic rocks in Changtang,Renju and Xunwu basin have proved that asymmetric bimodal volcanic rocks composed mainly of rhyolite with some basalt on west and east sides of Yuyao-Lishui-Zhenghe-Dapu fault occurred in different geological periods,formed earlier in the east and later in the west.These results have important significance for the study of magmatic activity and tectonic evolution during Mesozoic in southeastern China.

关 键 词：长英质火山岩 SHRIMP锆石U-PB年龄 晚白垩世早期 赣南-粤北 

分 类 号：P588.34[天文地球—岩石学] P597[天文地球—地质学]