粤北新丰雷公寨早侏罗世火山岩的厘定及其形成构造环境  

U-Pb age dating and it's tectonic significance of Early Jurassic volcanic rocks at Leigongzhai,Xinfeng,northern Guangdong province

作　　者：林小明 李宏卫 林杰春 黄建桦 黄孔文 

机构地区：[1]广东省地质调查院,广东广州510080

出　　处：《华南地质与矿产》2017年第1期34-46,共13页Geology and Mineral Resources of South China

基　　金：中国地质调查局地质矿产调查评价专项(编号:12120113063100)

摘　　要：本文对粤北新丰雷公寨地区火山岩成岩时代进行了测定,对其主量元素、稀土元素、微量元素等元素地球化学特征进行了研究。高精度LA-ICP-MS锆石U-Pb定年结果显示,研究区火山岩中流纹质凝灰岩锆石加权平均年龄为185.7±3.4Ma,英安斑岩锆石加权平均年龄为184.8±4.6 Ma,流纹斑岩锆石加权平均年龄为190.1±2.3 Ma,均属于早侏罗世。主量元素分析结果表明其为高钾钙碱性系列和钙碱性系列,稀土元素配分曲线具有轻稀土富集、Eu和Ce中等亏损、总体为右倾斜等特征,微量元素特征具有富集Rb、Th、U、Zr大离子亲石元素和La、Ce、Nd、Hf、Sm、Lu和Y等元素,亏损Ba、Sr、P、Ti、Nb等元素。显示嵩灵组火山岩形成的构造背景为板内环境,成岩作用处于陆内拉张构造环境。In this paper,the volcanic rock diagenetic age in the Leigongzhai,Xinfeng,northern Guangdong,was measured and the geochemical characteristics of elemental elements,rare earth elements and trace elements were studied.The zircon U-Pb dating results show that the zircons weighted average age of rhyolite tuff in the study area is 185.7 ± 3.4 Ma,and the weighted average age of the zirconia porphyry is 184.8±4.6 Ma,The weighted average age of zircons in the porphyry is 190.1 ± 2.3 Ma,which belongs to the Early Jurassic.The results of the main elemental analysis show that it is a highly arsenic and alkaline series and a calc-alkaline series.The rare earth elemental distribution curves are characterized by light rare earth enrichment,Eu and Ce medium loss,the general right tilt and so on.The trace elements have rich in Rb,Th,U,Zr,La,Ce,Nd,Hf,Sm,Lu and Y,depleted in Ba,Sr,P,Ti,Nb and so on.It is shown that the tectonic setting of the volcanic rocks in the Songling Formation is the intraplate environment,and the intrusion is in the tectonic environment of the inland section.

关 键 词：元素地球化学特征 LA-ICP-MS锆石U-PB定年 早侏罗世 火山岩 粤北 

分 类 号：P581[天文地球—岩石学] P597.3[天文地球—地质学]