河南汝州-鲁山一带震旦系东坡组碳酸盐沉积的碳同位素负偏及其地质意义  

Negative Anomaly of Carbon Isotope from Carbonates of Sinian Dongpo Formation in Ruzhou and Lushan,Henan Province and Its Geological Significance

作　　者：张良[1] 杜远生[1] 左景勋[2] 周琦[1] 

机构地区：[1]中国地质大学地球科学学院,湖北武汉430074 [2]河南省地质调查院,河南郑州450001

出　　处：《地球科学（中国地质大学学报）》2008年第4期523-530,共8页Earth Science-Journal of China University of Geosciences

基　　金：中石化海相油气勘探前瞻性项目(No.G0800-06-ZS-319);国家自然科学基金项目(No.40621002);教育部创新团队发展计划项目(IRT00546)

摘　　要：河南汝州、鲁山一带罗圈组冰积层之上的东坡组以页岩、粉砂质页岩及粉砂岩为主.笔者发现了东坡组夹有白云岩透镜体及白云质粉砂岩、砂岩.白云质粉砂岩具有与东坡组页岩不协调的软沉积变形.白云岩透镜体和白云质粉砂岩具有明显的δ13C负偏.白云岩透镜体的δ13C为-4.19‰～-6.18‰.白云质粉砂岩的δ13C大部分为-2‰～-4‰之间.因此认为,东坡组的白云岩透镜体及白云质粉砂岩、砂岩与华南震旦纪盖帽白云岩及南华纪Sturtian冰期冰积层之上的碳酸盐丘和菱锰矿类似,为冰积层中的天然气水合物泄漏释放的CO2和海水中的Mg2+发生快速反应快速沉淀而成的,即东坡组的白云岩、白云质粉砂岩、砂岩为冷泉成因.Sinian Dongpo Formation overlying tillite of Luoquan Formation consists mainly of shales, silty shales and siltstones. Lenticular dolomites, dolomitic siltstones and sandstones are unexpectedly found in Dongpo Formation. Soft-sediment reformation occurs in dolomitic siltstones which are inconsistent with the shales of Dongpo Formation. Negative anomaly of δ^13C is found in lenticular dolomites and dolomitic siltstones. δ^13Cof lenticular dolomites is -4. 19‰ to -6.18‰ and δ^13C of dolomitic siltstones mostly between -2‰ to -4‰. So it is considered that lenticular dolomites, dolomitic siltstones and sandstones in Dongpo Formation, similar to cap dolomite of Sinian and seep carbonates overlying tillite of Sturtian iceage in South China, have been formed by interaction between CO2 seeped from gas hydrate and Mg^2＋ in sea water, that is, lenticular dolomites, dolomitic siltstones and sandstones in Dongpo Formation are the cause of formation of cold spring.

关 键 词：冷泉碳酸盐岩 碳同位素 震旦纪 河南省 

分 类 号：P588.2[天文地球—岩石学]