柴西地区新生界湖相碳酸盐颗粒结构多样性及成因  

Structural diversity and genesis of Cenozoic lacustrine carbonate particles in western Qaidam Basin

作　　者：王建功[1,2] 张永庶 孙秀建 李翔[1] 高妍芳[1] 龙国徽[3] 白亚东 吴颜雄 WANG Jiangong;ZHANG Yongshu;SUN Xiujian;LI Xiang;GAO Yanfang;LONG guohui;BAI Yadong;WU Yanxiong(Northwest Banch of Rsearch Institute of Petroleum Exploration and Development,CNPC,Lanzhou,Gansu 730020,China;Key Lab of Reservoir Description of CNPC,Lanzhou,Gansu 730020,China;PetroChina Qinghai Oilfield Company,Dunhuang,Gansu 736200,China)

机构地区：[1]中国石油勘探开发研究院西北分院,甘肃兰州730020 [2]中国石油集团油藏描述重点实验室,甘肃兰州730020 [3]中国石油青海油田分公司,甘肃敦煌736200

出　　处：《中国矿业大学学报》2021年第6期1134-1152,共19页Journal of China University of Mining & Technology

基　　金：中国石油天然气股份有限公司重大科技专项(2016E-01)。

摘　　要：为明确湖相碳酸盐颗粒多样性及成因机理,利用大量露头、岩芯、薄片及分析化验资料,开展柴西地区新生界碳酸盐颗粒的沉积特征研究,根据外部形态与内部结构划分颗粒类型,分析颗粒多样性成因机制及差异分布.通过研究下干柴组上段(E^(2)_(3))—下油砂山组(N^(1)_(2))的沉积环境,分析认为咸化湖泊边缘与浅水区有利于碳酸盐岩颗粒的形成,其成因主要与蓝细菌等微生物的活动密切相关.研究结果表明:碳酸盐颗粒广泛发育,镶嵌于泥晶灰岩中,可以形成颗粒碳酸盐岩(颗粒体积分数为25%~50%),以及泥粒灰岩(颗粒体积分数为10%~25%)与粒泥灰岩(颗粒体积分数小于10%);也可以在微生物席中发育,构成微生物岩的结构组分.根据外部形态及内部结构,识别出卵球粒、聚合粒、胞鞘粒、鲕粒、核形石、皮质醇等6种颗粒类型.颗粒碳酸盐岩通常与微生物岩互层分布、形成特定岩相组合,不同沉积环境及不同层系差异分布.下干柴沟组上段(E^(2)_(3))分布局限,单层厚度较大、主要分布50~300 cm,最大10 m.上干柴沟组(N_(1))零星分布,规模最小,单层厚度以20~30 cm为主.油砂山组(N^(1)_(2)—N^(2)_(2))微生物岩与颗粒碳酸盐岩广泛分布,纵向叠加连片,单层厚度分布30~200 cm,最大5 m.碳酸盐岩颗粒与微生物活动密切相关,但结构与形态多样性受多种因素综合影响,主要包括微生物类型与生态习性、沉积环境与水动能、以及生物化学与及物理作用的影响.球形蓝细菌主导控制卵球粒与聚合粒的形成,丝状蓝细菌主导控制胞鞘粒的形成,鲕粒与核形石的形成与丝状蓝细菌增生密切相关,其内核质点的形成与球形蓝细菌相关.皮质醇由小型微生物群落控制形成,内核由球形蓝细菌、藻球及微生物群落演化形成,而外壳则由丝状蓝细菌控制形成.In order to clarify the particle structure diversity and genesis mechanism of lacustrine carbonate, a large number of outcrops, cores, thin-sections and analytical and laboratory data were used to study the sedimentary characteristics of Cenozoic carbonate particles in western Qaidam Basin. According to the external morphology and internal structure, the genetic mechanism and differential distribution of particle diversity were analyzed. The evolution of saline lake sedimentary environment of the upper section of the lower Ganchaigou formation(E^(2)_(3))-the lower Youshashan formation(N^(1)_(2)) was explored in this study. It is considered that the margin of saline lake and shallow water area are favorable for the formation of carbonate particles, and their genesis is closely related to the action of microbials e.g. cyanobacteria. The results show that carbonate particles are widely developed and embedded in micrite, which can form the granular carbonate rocks(the particles volume fraction is 25%—50%), the packstone(the particles volume fraction is 10%—25%), and the wackstone(the particles volume fraction is less than 10%). The carbonate particles can also be developed in microbial mats, which constitute the structural components of microbialites. According to the characteristics of external morphology and internal structure, six types of carbonate particles were identified, including oocyte particles, aggregate particles, sheath particles, oolite, oncolite, and cortoid particles. Granular carbonate rocks are usually interbedded with microbialites, forming specific lithofacies association, and distributed differently in different sedimentary environments and strata. The upper section(E^(2)_(3)) of the lower Ganchaigou formation is limited in distribution but thick in thickness. The thickness of single layer is mainly 50—300 cm, with a maximum of 10 m. The upper Ganchaigou formation(N_(1)) is scattered with the smallest scale and the thickness of single layer is mainly 20—30 cm. The microbial and granular

关 键 词：湖相碳酸盐岩 微生物岩 颗粒碳酸盐岩 卵球粒 鲕粒 核形石 柴达木盆地 

分 类 号：P618[天文地球—矿床学]