黔西滇东地区浅海、滨海及海陆交互相二叠系—三叠系界线附近粘土岩研究

STUDY ON CLAYROCKS OF THE NERITIC,LITTORAL AND MARINE-TERRIGENOUS FACIES ACROSS THE PERMIAN-TRIASSIC BOUNDARY IN THE EASTERN YUNNAN AND WESTERN GUIZHOU,SOUTH CHINA

对黔西滇东地区的贵州普定高窝、贵州六枝中寨和云南宣威密德3条剖面二叠系—三叠系界线附近粘土岩的大山物源成因和界线地质意义进行研究发现:在界线粘土岩中,其主要粘土矿物均为伊/蒙混层矿物,见少量高岭石、伊利石或绿泥石;碎屑物质中有六方双锥石英、锆石、长石等与火山活动有关的物质。推断该地区在晚二叠世晚期—早三叠世早期至少经历一至两次强烈的火山作用,并且有多个火山喷发源。界线粘土岩中火山物质的富集与贫乏可能与剖面离火山喷发源的远近有关。粘土岩物源物质的成因均为火山喷发,火山灰伴随正常沉积物沉积而形成即凝灰沉积而形成,与华南大部分地区二叠系—三叠系界线粘土岩的物源成因是一致的。

Applying the concept of the Permian-Triassic Boundary Stratigraphic Set (PTBST) to the Permian-Triassic boundary section in Western Guizhou and Eastern Yunnan Province, South China,it is found that the clayrocks of the PTB in these sections have the same origin and exhibit similar vertical succession to most of the marine Permian-Triassic boundary in the South China. The clay minerals in the clayrocks of the PTBST are mainly composed of illite-montmorillonite interlayers, with few kaolinite and/or chlorite. Some special mineral contents, such as hexagonal dipyramid quartz, zircons and so on, are attributed to their special volcanic formation. According to these particular characteristics,it is considered that the research area was undergone one or two times of volcanic activities in the late Permian and early Triassic and have multi- volcanic eruptive centres.The concentration of volcanic materiasl and scanty of the PTBST are correlated to a distance of volcanic eruptive centres.