贵州六盘水地区二叠纪茅口组中晚期碳酸盐岩微相特征和沉积环境分析

Microfacies Characteristics and Sedimentary Environment Analysis of Carbonate Rocks in Mid-late Maokou Formation of Permian in Liupanshui Area,Guizhou Province

贵州省六盘水地区是茅口组的命名地区,研究发现该地区的茅口组岩相分异明显、顶部可能存在缺失,基于简单岩性及生物组合的划分标志已无法支撑对其进行内部划分对比、沉积环境研究、地质找矿等需求。为解决这一问题,笔者综合运用区域地质调查、剖面测量、岩矿薄片分析、碳酸盐岩微相划分对比等手段,识别出该区茅口组存在5种碳酸盐岩微相类型,进而将该区茅口中晚期的沉积相划分为:半局限台地相、台沟相、开阔台地相、台地边缘砂质浅滩相等4种亚相。六盘水地区二叠纪茅口中晚期古地理格局由南西侧“台沟”与北东侧“台地”组成。这一认识为研究六盘水及邻区茅口中晚期茅口组划分、古地理以及锰矿找矿提供基础资料。

Liupanshui area is Maokou formation named area,in the study,it’s found that Maokou formation facies differentiation is obvious,at the top of the well can exist,based on simple lithology combination of ancient and biological classification marks have been unable to support research on its internal classification and correlation,sedimentary environment,the demand such as geological prospecting work.In order to solve this problem,it used regional geological survey,profile measurement,rock thin-section analysis,carbonate microfacies classification and correlation,identified the Maokou formation in the region:homogeneous micro-no fossils micrite,have rich spicule biological important-micrite,containing abundant foraminiferal or algae particles of limestone chip,cladding biological granular limestone,rich in limestone of spines dander 5 types of carbonate microfacies.The sedimentary facies in the Mid-Late Maokou stage can be divided into four sub-facies:semi-limited platform facies,platform trench facies,open platform facies and sandy shoal at platform edge.It is concluded that the paleogeographic environment of the Mid-Late Maokou stage in the study area is a sedimentary environment changing from the“platform trench”in the southwest to the“platform”in the east of the north.It provides new data for the lithofacies paleogeographic analysis of the Mid-Late Maokou stage and the internal division of Maokou Formation in the study area and its adjacent area,and for further manganese ore prospecting.