陕北盐盆奥陶系马家沟组沉积相特征与沉积演化  

Sedimentary Facies and Evolution of the Ordovician Majiagou Formation in Salt Basin of Northern Shaanxi

作　　者：施立志[1,2] 王卓卓[1,3] 张永生[1] 苏奎[1] 邢恩袁[1] 桂宝玲[1] 

机构地区：[1]中国地质科学院矿产资源研究所,国土资源部盐湖资源与环境重点实验室,北京100037 [2]大庆油田有限责任公司勘探开发研究院,黑龙江大庆163712 [3]北京市地质工程勘查院,北京100048

出　　处：《地质学报》2015年第11期2122-2133,共12页Acta Geologica Sinica

基　　金：国家重大基础研究计划“973”课题“鄂尔多斯奥陶纪古陆表海盆成钾条件、机理和后期演化”(编号:2011CB403001);中国地质调查局地质调查工作项目“陕北奥陶纪盐盆地钾盐资源调查评价”(编号:1212011085516)和联合资助

摘　　要：本文主要依据陕北盐盆地的镇钾1井等8口基干井,通过岩心观察、测井解释、镜下薄片鉴定,同时结合区域构造资料并参考前人研究成果,对陕北盐盆奥陶系马家沟组岩石类型、沉积相、沉积演化进行了研究。结果表明岩石类型以碳酸盐岩和蒸发岩为主,碎屑岩等其他沉积岩发育较少。主要发育碳酸盐岩台地相,可进一步划分出开阔台地和局限蒸发台地两种亚相,开阔台地可识别出灰泥丘微相;局限蒸发台地可识别出云坪、盐湖、膏湖、淡化泻湖等微相。沉积演化表明,马一期-马六期,陕北盐盆经历了三次海进-海退旋回,沉积演化为陕北盐盆及钾岩的形成创造了良好的成盐古地理环境,海进期,海水提供充足的成钾物质补给,海退期形成的继承性盐盆,四周隆起,又处在有利的低纬度干旱蒸发气候环境,十分有利于钾岩的形成。陕北盐盆奥陶系马家沟组五段六亚段沉积期,盆底总体表现为"两坳夹一隆"的构造样式,即自西向东依次为呈NNE向展布的西部盐坳、中部隆起和东部盐坳,"西部盐坳"可进一步分为3个次级盐凹,自北向南依次为"西一盐凹"、"西二盐凹"和"西三盐凹";"东部盐坳"可进一步分为2个次级盐凹,即北部的"东一盐凹"和南部的"东二盐凹",这5个盐凹的盐系地层厚度大于150m,是陕北盐盆最佳成钾盐凹,也是优先进行钾盐探井部署的有利目标区。Based on 8wells（e.g.Zhenjia 1well,etc）in the Northern Shaanxi salt basin,cores observation and well logging interpretation,identification of microscopic flakes,combined with regional tectonic data and previons research achievements,the Ordovician majiagou Formation rock types,sedimentary facies and sequence stratigraphy were studied.The rock types are mainly carbonates and evaporites,clastic rock and other sedimentary rocks less development.The main development of carbonate platform facies can be further divided into two subfacies：open platform and restricted evaporate platform.Open platform can identify limemud mound microfacie and the microfacies contain dolomitic flat,salt lake,gypsum lake.Sedimentary evolution shows that the salt basins in northern Shaanxi had experienced three timestransgressive-regressive cycles from Ma1 to Ma6period.Sedimentary evolution created good salt palaeogeographic environment for Shaanxi salt basin and sylvite forming,and the sea-water supplied enough potassium material in the transgression.Inheritance of salt basins formed in the regressive period around the uplift at favorable evaporation low latitudes drought climate environment are was very favorable for the formation of potassium rock.Shaanxi salt basin showed the tectonic pattern of＂two depressions and one lifting＂,for west salt sags,middle uplift,east salt sags which are NNE-striking from west to east.west salt sags are made of＂west 1salt sags＂,＂west 2salt sags＂and ＂west 3salt sags＂from north to south;East salt sags were made of＂east 1salt sage＂in the north and＂east 2salt sage＂in the south.The five salt sags with the thicknesses of more than 150 meters in this region are the best locations for potassium salt formation in Shaanxi salt basin,suggestion a priority targets for potash exploratory well deployment in the favorable area.

关 键 词：陕北盐盆 马家沟组 沉积 灰泥丘 

分 类 号：P619.211[天文地球—矿床学]