塔里木盆地中寒武统泥晶白云岩红层的地球化学特征与成因探讨

塔里木盆地中寒武统泥晶白云岩红层的地球化学特征与成因探讨

陈永权1,2，周新源1，赵葵东2，杨文静1，阮洋1，董晨阳2

1. 中国石油塔里木油田分公司勘探开发研究院，库尔勒 841000；2. 南京大学地球科学及工程学院，内生金属成矿作用研究国家重点实验室，南京 210093

收稿日期:2008-12-20 修回日期:2008-12-20 出版日期:2008-12-20 发布日期:2008-12-20

Geochemical Research on Middle Cambrian Red Dolostones in Tarim Basin: Implications for Dolostone Genesis

CHEN Yong-quan1,2, ZHOU Xin-yuan1, ZHAO Kui-dong2, YANG Wen-jing1,Ruan Yang and DONG Chen-yang2

1. Tarim Oil Field Company Exploration and Development Research Institute, Korla 841000, China;2. State Key Laboatory for Mineral Deposits Research, Nanjing University, Nanjing 210093, China

Received:2008-12-20 Revised:2008-12-20 Online:2008-12-20 Published:2008-12-20

摘要/Abstract

摘要： 塔里木盆地西部克拉通台地区寒武系中寒武统发育大量泥晶白云岩红层。钻孔岩芯观察及岩石学分析表明，该白云岩以岩芯呈暗红色、显微镜下呈泥粉晶结构、并伴随有纤状石膏假晶与陆源石英碎屑为主要特征，指示了该白云岩形成于潮上带蒸发环境。地球化学分析结果表明，该白云岩具有固有属性的CaO％，MgO％含量正相关特征, 因此，塔里木盆地中寒武统泥晶白云岩红层属于典型的潮上带Sabkha型沉积的“原白云石”。泥晶白云岩红层U，Mo含量亏损，指示了该白云岩形成于氧化环境，与色泽较红相一致；稀土元素特征上，该泥晶白云岩红层稀土元素配分模式呈右倾特征，但是在陆源碎屑的影响下，常出现中稀土元素富集的“帽”型特征；碳氧同位素分析表明，泥晶白云岩红层碳同位素变化没有规律性，多数δ18OPDB值变化在-7‰~-4.4‰之间，与潮上带蒸发沉积的Sabkha特征一致；英买7井白云岩红层δ18OPDB值较低（＜-10‰），可能为成岩作用过程中热液改造的结果；由于泥质矿物的存在，潮上带白云岩87Sr/86Sr比值一般比同期海水值偏高。

Abstract: In the Middle Cambrian Awatage Formation of Tarim Basin occur thick strata of upper-tidal red dolostones.Geochemical research was performed and results show a obvious positive correlation between the CaO% contents and the MgO% contents of dolostones, which suggests a sedimentary genesis. The relatively low contents of U and Mo suggest that the red dolostones might have formed in an oxidized environment, coincident with the red color. The PAAS-normalized rare earth element characteristics show a MREE-enriched pattern, which may result from high contents of Fe2O3％. There is no general regularity in carbon isotope variation among the studied wells. The oxygen isotope analyisis of dolostones from wells Tacan 1, Fang 1, and Yaha 5 shows high δ18O values, ranging -7‰~-4.4‰, indicating an evaporated sedimentary genesis, while the oxygen isotope of dolostones from Yingmai 7 well shows a relatively lower δ18O values (-11.2‰~-10.2‰), indicating the hydrothermal alteration character during the diagenesis process.

陈永权,周新源，赵葵东，杨文静，阮洋，董晨阳. 塔里木盆地中寒武统泥晶白云岩红层的地球化学特征与成因探讨[J]. J4.

CHEN Yong-quan1,2, ZHOU Xin-yuan1, ZHAO Kui-dong2, YANG Wen-jing1,Ruan Yang and DONG Chen-yang2. Geochemical Research on Middle Cambrian Red Dolostones in Tarim Basin: Implications for Dolostone Genesis[J]. J4.