浙江丽水地区磨石山群火山岩时代归属  

Age assignment of the Moshishan Group volcanic rocks in the Lishui area,Zhejiang Province

作　　者：王加恩 刘远栋 汪建国 王振 陶丽 

机构地区：[1]浙江省地质调查院,杭州311203

出　　处：《华东地质》2016年第3期157-165,共9页East China Geology

基　　金：中国地质调查局地质调查项目"浙江省1:50000双溪等四幅区调项目";"浙江省1:50000杜泽等五幅区调项目"(项目编号:1212010011601;12120113065000);"浙江省1:250000衢州幅区调修测项目"(项目编号:1212011220549)资助

摘　　要：为查明浙江丽水地区中生代磨石山群火山岩的时代,在区域地质调查、火山机构划分的基础上,选择该群代表性火山岩进行锆石年龄测定。结果表明,大爽组底部流纹质晶屑熔结凝灰岩的SHRIMP锆石U-Pb年龄为154.9±5.5 Ma、LA-ICP-MS锆石U-Pb加权平均年龄为152.0±7.0 Ma,属晚侏罗世基默里奇阶;高坞组流纹质晶屑熔结凝灰岩SHRIMP锆石U-Pb年龄为131.6±2.7 Ma,两个火山机构的西山头组流纹质晶屑凝灰岩LAICP-MS锆石U-Pb加权平均年龄分别为128.6±1.7 Ma和139.5±2.5 Ma。认为浙南磨石山群火山岩时代:大爽组为晚侏罗世,高坞组、西山头组、茶湾组和九里坪组为早白垩世。On the basis of regional geological survey and volcanic structure divisions, this study carried out U-Pb dating for zircons from some typical volcanic rocks of Moshishan Group to precisely determine the stratigraphic age of the Mesozoic Moshishan Group volcanic rocks in the Lishui area, Zhejiang Province. The result shows that the SHRIMP zircon U-Pb age and LA-ICP-MS zircon U-Pb weighted average age of rhyolitic crystal welded tuffs on the bottom of Dashuang Formation are 154. 9 ± 5. 5Ma and 152. 0± 7. 0Ma, respectively, indicating that the Dashuang Formation belongs to the Kimmeridgian Stage of late Jurassic. SHRIMP zircon U_Pb dating yields an age of 131. 6 ± 2. 7Ma for rhyolitic crystal welded tuffs of the Gaowu Formation and two weighted ages of 128. 6±1. 7Ma and 139. 5±2. 5Ma for the rhyolitic crystal welded tuffs of the Xishantou Formation from two volcanic apparatus. It can be inferred based on the study above that the Dashuang Formation should belong to Late Jurassic while Gaowu, Xishantou, Chawan and Jiuliping Formations to Early Cretaceous.

关 键 词：浙南 中生代 火山岩 磨石山群 时代归属 

分 类 号：P539.2[天文地球—古生物学与地层学]