黔东南从江地区新元古代下江期花岗斑岩的特征及其地质意义

摘要

The Neoproterozoic granite porphyries in the Hunan-Guizhou zone are seldom reported. The acidic magmatic rocks in the lower part of the Xiajiang Group in the Congjiang region,southeastern Guizhou have long been interpreted as migmatites by the previous workers. In the present paper,the authors contend,according to the studies of lithology,geochemistry and geochronology and tectonic setting,that these rocks should be assigned to the in-situ partially remelted S-type granite porphyries and constitute the bimodal magmatic associations together with the basic rocks and basic volcanic rocks in the lower part of the Xiajiang Group,representing the important tectonic-magmatic thermal events at the onset of the Wuling post-orogenic rift basin. The recent results of research may provide new data for the refinement of the evolution of the Precambrian palaeocontinent and metallogenic responses in the study area.%产出于黔东南从江地区下江群下部的一套酸性岩浆岩，一直被认为是混合岩。本文通过新的实际资料，对其产出特征、岩石学、地球化学、年代学等方面进行了分析研究，并对其形成的大地构造背景进行了探讨，认为其系局部就地重熔 S 型花岗斑岩，与同产出于下江群下部的基性岩、基性火山岩构成类似双峰式的岩浆岩石建造组合，系武陵造山后拉张盆地裂陷开启初期重要的构造岩浆热事件。这一新认识对该地区前寒武纪古大陆演化及成矿响应提供了新的资料。