相山“流纹英安岩”单颗粒锆石U-Pb年龄及地质意义  

Single-zircon U-Pb age of rhyodacite from Xiangshan area and its geological implications

作　　者：张万良[1,2] 李子颖[1] 

机构地区：[1]核工业北京地质研究院 [2]核工业270研究所,江西南昌330200

出　　处：《岩石矿物学杂志》2007年第1期21-26,共6页Acta Petrologica et Mineralogica

基　　金：国防基础研究项目(A0120060596)

摘　　要：相山火山-侵入杂岩主要由晚中生代打鼓顶组、鹅湖岭组火山岩和浅成-超浅成侵入岩所组成,主要岩石类型有酸性火山碎屑岩、碎斑熔岩、花岗斑岩和“流纹英安岩”等,“流纹英安岩”长期作溢流相火山岩处理。应用单颗粒锆石U-Pb法,对相山“流纹英安岩”进行了测年,获得其年龄为129.54±7.93Ma,该年龄小于相山火山-侵入杂岩的主体岩石——碎斑熔岩的年龄,结合其产状形态特征,认为“流纹英安岩”属火山期后浅成-超浅成侵入的流纹英安斑岩。结合前人测年资料,参照上侏罗统与下白垩统的145.5Ma界线年龄,提出相山火山-侵入杂岩的形成时代为早白垩世的新认识。The Xiangshan volcanic-intrusive complex consists of Late Mesozoic acid pyroclastic rocks interbedded with sedimentary rocks, acidic lava, intermediate-acidic shallow-ultrashallow intrusive rocks, composed mainly of clastoporphritic lava, granitic porphyry and rhyodacite. The magmatic activity started with the eruption, experienced mainly volcanic effusion and ended at shallow-ultrashallow magmatic intrusion. The rhyodacite, once as the overfall facies, belongs to 2^nd member of Upper Jurassic Daguding Formation. The single-zircon U- Pb dating of the rhyodacite shows that the age of the rhydacite is 129.54 ± 7.93 Ma, younger than the age of clastoporphritic lava which is the principal part of Xiangshan volcanic-intrusive complex. Combined with the modes of occurrence and shape characteristics of the rhyodacite, this paper holds that rhyodacite is a post- volcanic shallow or ultrashallow intrusive body, i.e., rhyodacitic porphyry. According to the age data available and the borderline age of 145.5 Ma between Jurassic and Cretaceous, the authors consider that the formation age of the complex is Early Cretaceous.

关 键 词：“流纹英安岩” 单颗粒锆石定年 流纹英安斑岩 早白垩世 相山地区 

分 类 号：P588.13[天文地球—岩石学] P597.3[天文地球—地质学]