珠峰地区晚石炭世冰海相杂砾岩石英颗粒表面结构

石英颗粒表面结构类型以及它们和形成环境间的对应关系,国外已有初步总结^1,2,3]。对石英颗粒表面结构应用于历史环境分析,有着不同的意见^4-6]。多数研究者认为,对于松散的或未固结的沉积物(主要为第四纪的)中的石英颗粒表面结构,具有显著的环境分析意义,而对于地质年代久远、早已半固结或固结成岩的则看法不一,有的则予以否定。因为,地质年代愈老,成岩作用(包括浅变质作用)影响也就愈大。但也有些情况表明^7,8],虽已固结成岩,其物源区的搬运、沉积过程中产生的机械结构,仍然部分或大部分被保存下来,仍可以指示其环境。

SCANNING ELECTRON MICROSCOPIC STUDY OF SURFACE TEXTURE OF QUARTZ GRAINS FROM LATE CARBONIFEROUS GLACIO-MARINE DIAMICTITE IN MT.QOMOLANGMA REGION,SOUTHERN XIZANG,CHINA

In the Mt.Qomolangma region,diamictites related to the Upper Palaeozoic glacia-tion in Gondwana land are called the Zhadari diamictite on northern slope of the Mt.Qomolangma and the Kewoxiga diamictite in east of Kangmar county,respectively,97 quartz grains from the Kewoxiga diamictite are observed by SEM,showing their proper mechanical surface texture in the quartz grains formed in glacial environment.The SEM microphotographs of 84 quartz grains from the Zhadari diamictite are characteristic merely of chemical surface texture due to diagenesis and absent from mechanical surface texture.It is preliminarily concluded that the sources of these quartz grains with different mechanical surface textures from the two kinds of diamictites mentioned above may be related to tills and fluvioglacial deposits,so that making a better understanding about the glacio-marine deposits of Late Carboniferous age in Mt.Qomolangma region.