Study on the Origin of the Dolostone Intercalcated in the Black Shales in Middle Permian Lucaogou Formation Eastern Part of Southern Margin of Junggar Basin
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摘要: 准噶尔盆地南缘东部中二叠流芒草沟组是一套温暖潮湿气侯条件下形成的半深湖至深湖相黑色页岩夹白云岩沉积。本文通过芦草沟组黑色页岩及其白云岩夹层在岩石学和地球化学等方面的对比研究认为:①黑色页岩形成环境及其有机质演化为白云岩的形成提供了十分有利的热力学、动力学条件;②白云岩是在黑色页岩形成环境及其有机质演化过程中、底层水盐度提高、CO32-浓度增大的条件下原生沉淀的。Abstract: The black shales and dolostones intercalcated with them had been researched petrologi-cally and geochemically of middle Permian Lucaogou Formation,eastern part of southern. Margin of Junggar Basin. The great similarity between them has been found. Based on the above study and the discussion of carbon and oxygen stable isotopie composition of the dolo-stone,it is concluded that: 1). Special thermodynamical and kinetic condition favorable for the formation of the environment where black shales were formed and organic evolution in then including: A): CO32-,B):Low So42-,C):High Mg2+/Ca2+ ratio and D) :organic-rich alkline and reducing environment. 2) The dolostones may had been precipitated in the evolution process of the environment where black shales were formed,and organic matter,accompaning with the increase of salinity and CO32- content of bottom water.
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