震旦系灯影组核形石白云岩成因机制及其意义:以柳湾剖面为例  

Genetic Mechanism and Significance of Oncoidal Dolostone in Sinian Dengying Formation:A Case Study of Liuwan Section

作　　者：田腾振 李泽奇 鲁鹏达 张航 吴娟[1,2] 孙玮[2] 刘树根[2] 何若玮 张洁伟 邓宾[1,2] Tian Tengzhen;Li Zeqi;Lu Pengda;Zhang Hang;Wu Juan;Sun Wei;Liu Shugen;He Ruowei;Zhang Jiewei;Deng Bin(School of Energy,Chengdu University of Technology,Chengdu 610059,China;State Key Laboratory of Oil and Gas Reservoir Geology and Development Engineering,Chengdu University of Technology,Chengdu 610059,China;Northeast Sichuan Gasfield of Southwest Company,CNPC,Chengdu 610059,China)

机构地区：[1]成都理工大学能源学院,四川成都610059 [2]成都理工大学油气藏地质及开发工程国家重点实验室,四川成都610059 [3]中国石油西南油气田川东北气矿,四川成都610059

出　　处：《地球科学》2023年第4期1568-1586,共19页Earth Science

基　　金：国家自然科学基金项目(No.U19B6003);四川省科技计划重点研发项目(No.2018JZ0078);四川省科技创新人才项目(No.2022JDRC0001).

摘　　要：震旦系灯影组核形石白云岩作为典型的前寒武纪微生物碳酸盐岩,是我国古老深层油气勘探的岩石类型之一.核形石成因模式的研究,对研究古水体、恢复古环境及其成储模式有重要指导意义.根据核形石结构特征和成因机制将灯影组核形石分为6类,结合岩石学、沉积学和地球化学等研究手段,开展了四川盆地北缘核形石分布特征和沉积过程的综合研究.结果显示:灯影组二段核形石发育于潮下带-潮间坪环境下,水动力和微生物条件的差异影响着微生物生长、自身钙化作用、微生物膜粘结和捕获作用、化学沉淀作用4种核形石纹层形成机理;进一步体现在水动力条件控制着核形石纹层发育厚度、形态特征和伴生岩石类型,而微生物活动习性控制影响着核形石主微量、稀土元素分异特征:贫藻纹层较富藻纹层有较高的Fe/Mn比、实体藻较非实体藻有较高Cu/Zn比,纹层稀土元素富集度一般低于核心.综上所述,灯二段核形石的形成存在4种机理,且它们被海平面变化下的微生物和水动力条件联合控制.As a typical Precambrian microbial carbonate rock,the Sinian Dengying Formation oncoidal dolostone is one of the rock types of ancient deep oil and gas exploration in China.The study on the genetic model of oncoids has important guiding significance for the restoration of paleoenvironment,the study of paleo-water and its reservoir-forming model.In this paper,the oncoid of Dengying Formation is divided into six types based on its structural characteristics and genetic mechanism.Combined with petrology,sedimentology,geochemistry and other research methods,a comprehensive study of the distribution characteristics and depositional process of oncoids in the northern margin of the Sichuan basin has been carried out.The results show that the second member of Dengying Formation sedimented in the environment of subtidal flat and intertidal flat.The differences of hydrodynamic and microbial conditions affect the four kinds of formation mechanisms of oncoidal laminations:microbial growth,microbial calcification,bonding and capturing of microbial biofilm,and chemical precipitation.On the other hand,hydrodynamic conditions control the development thickness of laminations,morphological characteristics and associated rock types of the oncoids.The microbial activity habits affects the differentiation characteristics of the main trace and rare earth elements of the oncoids.The Fe/Mn ratio of the pooralgae lamina is higher than that of the rich algae lamina;the Cu/Zn ratio of the solid algae is higher than that of the non-solid algae;and the enrichment of rare earth elements in the lamina is generally lower than that the oncoidal nuclei.In summary,there are four formation mechanisms for oncoids in the second member of Dengying Formation,and they are jointly controlled by microbial and hydrodynamic conditions under sea level change.

关 键 词：核形石 微生物 水动力 灯影组 柳湾剖面 岩石学 

分 类 号：P581[天文地球—岩石学]