塔里木盆地东部地区寒武系白云岩成因类型  

Genetic types of dolostones in the Cambrian,eastern Tarim Basin

作　　者：金振奎[1] 杨有星[1] 余宽宏[1] 王哲[1] 董晨晨 

机构地区：[1]中国石油大学(北京)地球科学学院,北京102249 [2]辽宁盘锦长城钻探工程有限公司工程技术研究院,辽宁盘锦124010

出　　处：《古地理学报》2012年第6期747-756,共10页Journal of Palaeogeography：Chinese Edition

基　　金：国家重点基础研究发展规划(973)项目(编号:2006CB202300)资助

摘　　要：塔里木盆地东部地区(简称塔东地区)寒武系白云岩主要有泥—粉晶白云岩、细晶白云岩和中—粗晶白云岩。通过岩石学特征、有序度、碳氧同位素、锶同位素比值、阴极发光和微量元素等分析,认为该地区有4种成因的白云岩,即深水回流准同生白云岩、潮坪蒸发泵准同生白云岩、回流渗透白云岩以及深埋藏白云岩。不同类型的白云岩,其岩性及地球化学特征不同。深水回流准同生白云岩为泥—粉晶白云岩,分布在塔东盆地中,是附近的碳酸盐岩台地上蒸发浓缩形成的咸化海水在重力作用下沿海底回流到深水盆地中并使刚沉积不久的灰泥发生白云化而形成的。潮坪蒸发泵准同生白云岩亦为泥—粉晶白云岩,形成于台地潮坪环境。回流渗透白云岩为细晶白云岩,发育于潮坪准同生白云岩和蒸发岩之下。深埋藏白云岩为中—粗晶白云岩,是石灰岩在地下深处由循环流动的富含Mg2+、Ca2+的地层水白云化形成的,Mg2+、Ca2+主要来自于已经存在的白云岩的溶蚀,而非来自页岩压实排替出来的地层水。The types of dolostones in the Cambrian in eastern Tarim Basin include mud-sized to silt- sized crystalline dolostone, fine crystalline dolostone and medium-coarse crystalline dolostone. Based on sedimentary characteristics, order degree analysis, carbon and oxygen isotope analysis, strontium isotope analysis, cathodoluminescence and trace elements analysis, four dolomitization mechanisms were pro- posed for these dolostones, that is, deep water reflux penecontemporaneous dolomitization, evaporative pumping penecontemporaneous dolomitization, reflux seepage dolomitization, and burial dolomitization. Dolostones by different dolomitization mechanisms show different lithological and geochemical characteris- tics. Deep water reflux penecontemporaneous dolostone is mud-sized to silt-sized crystalline dolostone and occurs in eastern Tarim Basin. It results from penecontemporaneous dolomitization of lime mud by hypers-aline sea water, which forms on the adjacent evaporative Tarim Carbonate Platform and flows into the deep eastern Tarim Basin along sea floor. Evaporative pumping dolostone is mud-sized to silt-sized crystalline dolostone and occurs on the carbonate rock platform. It forms in the tidal-fiat environments. Reflux seep- age dolostone is fine crystalline dolostone and commonly occurs beneath evaporative pumping dolostone and evaporites on the carbonate rock platform. Burial dolostone is medium-coarse crystalline dolostone. It re- sults from dolomitization of limestone in deep burial environments by cyclic formation water rich in Mg2＋ and Ca2＋. Mg2＋ and Ca2＋ come from the dissolution of previous dolostones, rather than from compaction of shales.

关 键 词：塔里木盆地东部地区 寒武系 深水回流准同生白云岩 蒸发泵准同生白云岩 回流渗透白云岩 深埋藏白云岩 

分 类 号：P588.245[天文地球—岩石学]