摘要
皖南地区井潭组变质火山岩原划归新元古界历口群，层位在中元古界上溪群之上。通过重新认识本区的地质条件后，发现它是一套生成于岛弧环境的钙碱性火山岩组合，而原上溪群中部分地层则是与之有关的火山沉积，其层位应在井潭组变质火山岩之上。本次对井潭组变质火山岩ＳｍＮｄ同位素年龄的研究获得以下信息：一是井潭组的等时线年龄为９９０Ｍａ，指示其形成时代为新元古代；二是其模式年龄平均为１８０７Ｍａ，结合上溪群中已有的ＳｍＮｄ模式年龄和其他地质资料，进一步证明它是原上溪群的物源供给区；三是以井潭组变质火山岩为主体的构造岩石单位可以与浙江的双溪坞群和江西的双桥山群部分层位对比。这些信息为认识本区乃至整个“江南古陆”的构造格局和演化提供了重要的佐证。
In the past,the metamorphic volcanic rock of the Jingtan Formation in southern Anhui Province was regarded as the Neoproterozoic era and ascribed to the Likou Group which was settled on the Shangxi Group of the Mesoproterozoic era.After the geological condition of this area was investigated again, the authors consider the Jingtan Formation as a set of calc alkaline volcanic rocks of arc products,while a part of the Shangxi Group is a set of pyroclastics related to the metamorphic volcanic rock of the Jingtan Formation,and should lie on it.In this paper,the study of Sm Nd isotopic data for the metamorphic volcanic rocks of the Jingtan Formation gives some information:(1) isotopic isochrone age of 990 9Ma suggests that the time of the Jingtan Formation should be the Neoproterozoic;(2) the mean model age of the Jingtan Formation is 1807Ma,whereas the Sm Nd model ages of the Shangxi Group and other geologic information suggest that it can be the source region of the Shangxi Group;(3) tectono petrologic unit mainly composed of the Jingtan Formation is similar with part of the Shuangxiwu Group in Zhejiang Province and the Shuangqiaoshan Group in Jiangxi Province.This information gives some important evidences for the further understanding of the tectonic framework and evolution process of this area,even whole ‘Jiangnan Old Land’.
出处
《现代地质》
CAS
CSCD
北大核心
1998年第4期548-554,共7页
Geoscience
基金
国家自然科学基金
安徽省地质矿产局联合资助
关键词
火山岩
变质火山岩
锶-钕同位素
大地构造意义
Jiangnan Old Land’,tectono petrologic unit,the Jingtan Formation,Sm Nd isotope
