滇西双江县勐库地区榴闪岩的发现与厘定

Firstly Discovered Garnet-Amphibolite from Mengku Area, Shuangjiang County, Western Yunnan Province, China

本文报道了云南省境内发现的榴闪岩。在双江县勐库一带进行的1∶5万区域地质调查初步将前人厘定的湾河蛇绿混杂岩带向北延伸了20 km,并在其中发现了多个榴闪岩形成的构造透镜体。榴闪岩坚硬致密,石榴石呈中细粒状散布在角闪石中,部分呈细粒条带状产出,显示了原始的火成堆积结构。从现有的多期退变质矿物组合大致可以推断出变质峰期的矿物组合可能为:绿辉石+石榴石+金红石+石英。该榴闪岩在产出的区域构造位置、岩石类型上都可与藏东八宿地区的退变质榴辉岩进行对比。这一发现为滇西地区特提斯构造演化提供了更多的约束条件。

This paper reports garnet-amphibolite firstly discovered in Western Yunnan Province, the southwest of China. Garnet-amphibolite tectonic lenses were found in Wanhe ophiolite mélange zone, which is extending 20 km northward, by regional geologic survey in Mengku area, Shuangjiang County, Western Yunnan Province in the scale of 1∶50000. Garnet-amphibolite is very hard and dens and the medium-fine grained garnet is mainly distributed in amphibole with parts of garnet show multi-layered band, implicating primary igneous accumulated bedding. According to the existing multi-stage retrometamophic mineral assemblage, we think that the deduced mineral assemblage of metamorphic peak is Omp＋Gt＋Ru＋Q. Regional tectonic site and rock types of the new found garnet-amphibolite can be contrast with those from Basu area, Eastern Tibet, China. The discovery provides more constrained conditions for the evolution of Tethys tectonics.