贵州西部中、上二叠统界线附近风化壳类型及成矿作用

ANCIENT WEATHERING CRUST AND ITS MINERALIZATION NEAR THE MIDDLE-UPPER PERMIAN BOUNDARY IN WESTERN GUIZHOU PROVINCE,CHINA

贵州西部中、上二叠统界线附近普遍存在不整合面,在不整合面上往往发育厚度不等的风化壳。风化壳主要可归纳为三种类型:茅口组顶部的喀斯特漏斗、洼地中堆积的红粘土风化壳,锰质(铁质)风化壳,峨眉山玄武岩喷发间断面上或玄武岩顶部与龙潭组(宣威组)之间的的高铝高岭石风化壳。喀斯特侵蚀面上的红土风化壳是红土型金矿的赋存层位,峨眉山玄武岩喷发间断面上的高铝高岭石风化壳是铜矿、铝土矿赋存层位,喀斯特侵蚀面上的锰质(铁质)风化壳是锰矿、铁矿赋存层位,而玄武岩顶部与龙潭组(宣威组)之间的高岭石粘土风化壳是稀土、硫铁矿、铝土矿赋存层位。中、上二叠统界线附近风化壳对金、铜、铝土、硫铁、锰和稀土有明显的控制作用。

Ancient weathering crust developed well near the Middle-Upper Permian boundary. According to lithology and mineralization, contract relationship between the weathering crust and overlying and underlying strata, the authors suggested that ancient weathering crust near the Middle-Upper Permian boundary may divide into three types： e.g. （ 1 ） basaltlateritic weathering crust of karst-type overlying the Maokou Formation （limestone） ; （2） manganese and iron weathering crust of karst-type overlying the Maokou Formation （limestone）; and （3） tuff-weathering crust （kaolinite） between two basalt erupting episodes, with high contents of Al and kaolinite, or tuff-weathering crust （kaolinite） between basalt and the Longtan Fonnation/Xuanwei Formation. The basalt-lateritic weathering crust contains abundant lateritic gold deposits, and tuff-weathering crust （kaolinite） between two basalt erupting episodes common contains copper deposits and bauxites, and tuff-weathering crust （kaolinite） between basalt and the Longtan Fonnation/Xuanwei Formation commonly contains rareearth deposits, pyrite deposits, bauxites and manganese deposits, Therefore, ancient weathering crusts near the Middle- Upper Permian boundary play an important role in mineralization of gold, copper, bauxites, pyrite, manganese and rareearth deposits.