黔西南及邻区两类赋金层序与沉积环境

TWO GOLD-BEARING SEQUENCES AND THEIR SEDIMENTARY ENVIRONMENTS IN SOUTHWESTERN GUIZHOU AND ITS ADJACENT AREAS

摘要: 贵州省西南部及其毗邻的广西西北部和云南东南部,广泛分布着晚古生代和三叠纪地层,它们系受海平面升降控制形成的复杂成因单元。该区的上二叠统至下三叠统(下部)和中三叠统(中下部)是黔桂滇“金三角”微细粒浸染型金矿两个最重要的赋矿层位,对其研究不仅具有重要的地层学意义,而且对普查找矿也有实用价值。本文将简要论述该区的区域地质背景,阐述两个赋金层序的基本特征,并进行沉积环境分析。

Abstract: The strata in which the micrograined-disseminated gold deposits are hosted in southwestern Guizhou, northwestern Guangxi and southeastern Yunnan can be divided into two sequences: the Longtoushan and Laizishan sequences on the basis of the regional geologic settings. The main goldbearing horizons of the Longtoushan sequence are confined dominantly to the Upper Permian strata and the lower part of the Lower Triassic strata, whereas those of the Laizishan sequence mainly to the lower and middle parts of the Middle Triassic strata. The host rocks consist chiefly of terrigenous lutite and siliceous rocks. The sedimentary environments of the above-mentioned sequences include tidal flat-lagoon and lower slope. Taking the emergence, development and disappearance of the palaeo-Tethys as the background, the formation of the sequences is interpreted to be closely related to divergent tectonic settings.