羌塘盆地孔孔茶卡地区石炭系擦蒙组烃源岩沉积环境分析

Sedimentary Environment Characteristics of Upper Carboniferous Cameng Formation in Kongkong Chaka Area of Northern Qiangtang Basin,Tibet

对羌塘盆地孔孔茶卡地区石炭系擦蒙组（C2 c）烃源岩形成的沉积环境进行探讨和研究。擦蒙组的岩石学、沉积相、元素地球化学的综合分析结果表明：该套烃源岩地层发育的沉积相为三角洲相；水解性元素和 Fe 族元素含量较高，表明其水体环境为滨岸-浅海，且古水深较浅；古气候指数 C（C ＝∑（Fe ＋Mn ＋Cr ＋Ni ＋V ＋Co）/∑（Ca ＋Mg ＋Sr ＋Ba ＋K ＋Na））的计算结果均大于0.8，指示出湿润的气候环境；Sr/Ba 比值全部小于1，介于0.13～0.23之间，表明为盐度较低的陆相淡水沉积水体；根据 V /Cr 与 V /Sc、V /（V ＋Ni）、Th/U、Ni /Co 和 Fe2＋/Fe3＋比值的变化，综合判断为富氧水体环境。上述这些条件均有利于繁殖大量的陆地生物和水生生物，这些有机物质通过水体的搬运沉积、富集形成了研究区石炭系一套较好的烃源岩。

This paper focused on the study of the sedimentary environment about the source rock of Carbonifer-ous Cameng Formation（C2 c）in Qiangtang basin,which characteristics of petrology,sedimentary facies and geo-chemistry were analyzed.The results reveal the following aspects：the sedimentary environment of the source rock in Carboniferous Cameng Formation is the delta deposit;the hydrolysable and ferrum elements are high abundant,indicating an onshore to shallow sea environment with shallow-water depth;the values of paleoclimate indexes （C）are all greater than 0.8,showing a humid environment;the ratios of Sr/Ba are all less than 1 within range of 0.13 to 0.23,indicating a low-salinity and fresh terrestrial sedimentary environment;the rela-tionship of V /Sc,V /（V ＋Ni）,Th /U,Ni /Co,Fe2 ＋/Fe3 ＋ with V /Cr all manifest an oxygen-enriched water environment.The above conditions are all favorable to mass propagation of terrestrial organisms and aquatic organisms,and these organic matters are transported and deposit,providing the materials of the source rock in the study area.