黔东钾镁煌斑岩分布控制因素及其侵位模式

Distribution-controlling factors and emplacement mode of lamproite in southeastern Guizhou Province

黔东地区发现大量的钾镁煌斑岩体,具有区域椭圆状分布和局部带状产出的基本特征,据测年资料,主要形成于晚奥陶世。结合地史演化分析,经武陵运动、雪峰运动和加里东期郁南运动及都匀运动等多期(幕)运动,在黔东钾镁煌斑岩区基底应存在类似于"江南古陆"区菱块状构造格架的地质构造条件,并因此而控制黔东钾镁煌斑岩区域椭圆状分布和局部带状产出。另据岩相古地理分析,黔东钾镁煌斑岩或应主要为基底构造控制下的"泥鳅钻豆腐"侵入模式,故而找矿勘查方向应主要和首先关注已知岩区的"攻深找盲"问题。

A large number of lamproite plutons were discovered in eastern Guizhou Provence, which are distributed either as regional elliptical pattern and/or local banding pattern. Dating information reveals that they were mainly formed in late Ordovician. Geohistory analyses suggest that geological structural conditions of the substrate of the lamproite pluton regions should resemble those of the rhombic structural framework that characterized the“Jiangnan old land”, after experiencing multiphase tectonic movements including Wuling Orogeny, Xuefeng Orogeny, and Yunan Orogeny as well as Duyun Movement in the Caledonian. The resulting geological structural condition thus accounted for the formation of the lamproite plutons, i.e., elliptical pattern in regional and banding pattern locally. In combination of dating data and lithofacies paleogeography studies, the authors hold that lamproite plutons were emplaced at the position with the mode of“loach throw bean-curd”, which was controlled by substrate structural conditions. The prospecting and exploration policy should primarily focus on“exploring to the deep and unknown places”of existing deposits.