滇西北羊拉铜矿区地层划分

Stratigraphic Subdivision of the Yangla Copper Ore Districtu,Northwestern Yunnan

通过滇西北羊拉矿区7.5km实测地层剖面的岩石地层划分,矿区原定二叠纪嘎金雪山群巨厚洋盆沉积实际由泥盆纪至二叠纪构造岩块高度混杂而成。因矿区经历了金沙江洋盆的初始裂开、扩张、俯冲消减、碰撞造山的洋—陆转换过程,岩石普遍发生绿片岩相变质作用,缺少古生物化石,原岩层序难以恢复。基于前人成果和本次工作发现的牙形石,结合矿区沉积特征和金沙江洋演化历史,将地层修订为下泥盆统江边组岩块、中泥盆统—石炭系岩块、二叠系岩块,并讨论了其构造演化。

The actual measurement and lithostratigraphic subdivision for a 7.5 km geological profile across the Yangla mining area shows that the thick ocean-basin sediments in the mining area, which used to be defined as the Permian Gajinxuanshan Group, consists of highly mixed Devonian and Permian structural rocks. A series of oceanic-terrestrial transition in the Jishajiang oceanic basin, such as initial splitting, oceanic expanding, subduction and collision orogeny, resulted in widespread greenschist facies metamorphism. Lack of paleontological fossils makes it difficult to restore original sequence order. Therefore, this study, based on the previous work and discovery of conodonts,reclassified the strata into Lower Devonian massif of Tongjiangbian Group, Middle Devonian and Carboniferous massif, Permian massif, and finally discussed tectonic evolution.