湖南慈利晚二叠世长兴期珊瑚礁白云石化及其成岩环境  

Dolomitization and Diagenetic Environments of Late Permian Changxingian Coral Reefs in Cili, Hunan, South China

作　　者：杨万容[1] 杨长庚[2] 沈建伟[1] 

机构地区：[1]中国科学院南京地质古生物研究所,210008 [2]中国石化股份有限公司无锡实验地质研究所,214151

出　　处：《地质学报》2002年第1期114-123,T004,共11页Acta Geologica Sinica

基　　金：国家自然科学基金资助项目(编号49672123)

摘　　要：笔者对近期在湖南慈利发现的长兴期珊瑚礁的白云石化作用及成岩环境进行了研究。通过对礁灰岩白云石化的分布、岩石结构构造、微量元素和碳、氧稳定同位素成分的测试研究,对白云石化的环境进行了分析。主要有:①潮上蒸发形成的高盐度交代白云石化;②深埋藏高盐度热水条件下白云石化;③区域抬升埋藏变浅,大气水渗入淡化的热水条件下发生的白云石化。据各类白云石化在礁岩成岩序列中的位置,从早到晚分别命名为Ⅰ、Ⅱ、Ⅲ3个世代,并分析了埋藏白云石化的物源,建立了Ⅱ、Ⅲ两个世代埋藏白云石化的概略模式。最后通过实例说明了研究礁岩埋藏白云石化作用对油气、铅锌矿产勘探的实用意义。A Late Permian Changxingian coral reef was recently discovered in Cili, Hunan Province, South China. It is a large well-developed massive reef limestone, of which 85% is composed of bushy Waagenophyllum. Corals are preserved in original growing attitude. The reef limestone is strongly dolominized and distributed along the northwest margin of the Jiangnan platform with a thickness of more than 60 m. The authors studied the distri-bution of dolomitization and textures and structures of the rocks, analyzed trace elements and oxygen and carbon stable isotopes in the dolomitized reef rocks andstudied the environment of dolomitization. Three main different environment types of dolomitization are recognized: (1) dolomitzation resulting from high-salinity replacement due to supratidal evaporation; (2) dolomitization under deep-buried, high-salinity, hot water conditions; (3) dolomitization under the desalinated hot water conditions resulting from percolation of meteoric water as the buried environment becomes shallower after regional uplift. The above-mentioned three environment types of dolomitization, in terms of their positions in the diagenetic sequence, include three generations, namely ,I,Ⅱ and Ⅲ from young to old. An obvious dissolution hiatus exists between generations Ⅱ and Ⅲ . The dolomitiza-tion is related with the hot water system occurring in a certain period under a certain buried environment. Ele-ments for buried dolomitization possibly came from saline water in the Permian and Lower Triassic beds. The movement of the elements with the hot water is through faults, disconformity surfaces, pressure solution sur-faces, voids, pores and cracks. In the study area the diagenetic process occurs contemporaneously with rapid re-gional subsidence and subsequent uplift of the early Indosinian movement in the Late Triassic. In the paper the authors present a summary model for generations I and I buried dolomitization. They also present several ex-amples to show the significance the buried dolomitization of ree

关 键 词：晚二叠世长兴期 珊瑚礁 白云石化作用 成岩环境 湖南 岩石构造 氧同位素 

分 类 号：P588.245[天文地球—岩石学]