江西冷水坑银铅锌矿田推覆构造的形成时代:来自年代学的约束

摘要

Lengshuikeng ore field in Jiangxi Province is located in the northern margin of North Wuyi uplift.In this paper,after a brief description of the geological characteristics of the ore field,the weighted average age of the tuff of the Daguding Formation of (157.6±3.2) Ma has been obtained by zircon SHRIMP U-Pb dating;the tuff hosted the volcanic sedimentary-hydrothermally reformed type of lead-zinc-silver ore bodies.This age may represent the lower limit age of mineralization.It is shown that the activity time of the nappe structure in the ore field is consistent with the Late Jurassic volcanic activity.The development of nappe structure in the ore field suggested that the tectonic regime in the eastern China had transformed from EW Tethyan tectonic domain into NNE Pacific tectonic domain in this period.The Late Jurassic volcanism and nappe structure development were the result of subduction of the Izanagi plate under the Eurasian plate along the NW direction.%冷水坑矿田位于北武夷隆起北缘.在简要介绍该矿田地质特征基础上,通过锆石SHRIMP U-Pb法测年,获得了矿田内赋存火山沉积-热液改造型银铅锌矿体的打鼓顶组凝灰岩加权平均年龄(157.6±3.2) Ma,表明打鼓顶组火山岩形成于晚侏罗世.该年龄可以代表成矿作用的下限年龄,并说明矿田推覆构造的活动时间与晚侏罗世火山活动的时间基本一致.推覆构造的发育说明中国东部构造体制已经从近东西向的特提斯构造域转换为北北东向的滨太平洋构造域.晚侏罗世火山活动及推覆构造的发育是Izanagi板块沿北西方向向欧亚板块之下俯冲所产生的结果.