内蒙古二连盆地白音查干凹陷热水沉积白云岩的发现及其地质与矿产意义  

Discovery of hydrothermal dolostones in Baiyinchagan sag of Erlian Basin,Inner Mongolia,and its geologic and mineral significance

作　　者：钟大康[1] 姜振昌[1] 郭强[2] 孙海涛[1] 杨喆[1] 

机构地区：[1]中国石油大学油气资源与探测国家重点实验室,北京102249 [2]核工业部北京地质研究院,北京100029

出　　处：《石油与天然气地质》2015年第4期587-595,共9页Oil & Gas Geology

基　　金：国家自然科学基金项目(41472094)

摘　　要：根据钻测井及各种分析测试数据阐明内蒙古二连盆地白音查干凹陷下白垩统腾格尔组深－半深湖相白云岩的成因。根据岩心观察和薄片鉴定，结合电子探针与能谱、微量元素及X－衍射分析白云岩的矿物成分与岩石结构及构造，在此基础上确定白云岩成因。结果表明：研究区白云岩为一套单层厚0．2～1．5 m的沸石质白云岩和沸石岩，白云岩层系由铁白云石（含Fe0．5％～5％）、钠沸石、方沸石、水镁铁石、重晶石、黄铁矿组成。白云石晶体10～200μm，波状消光，鞍状特征，具裂纹。岩石具泥粉晶结构和内碎屑结构，内碎屑为白云岩和沸石岩。发育纹层构造、同生变形构造、网脉状构造、角砾构造。自然伽马700～1100 API，为正常泥岩的2～4倍，铀和钍含量分别高达（40～60）×10－6和（60～100）×10－6。 Cu，Ni，Co，Fe，Mn等微量元素组成和分布与现代红海海底热水沉积一致。平面上沿基底断裂分布。多种资料表明这是一套“白烟型”热水沉积成因的白云岩。目前国内外对这类沉积报道较少，研究程度低，同时也缺乏相应成熟的沉积模式，通过此研究，有助于丰富和完善现有的沉积学理论，寻找更多与热水沉积有关的矿床。Based on drilling,logging and various test data,this paper studied the origin of deep-semi deep lacustrine dolo-stones of the Lower Cretaceous Tenggeer Formation in Baiyinchagan sag of Erlian Basin,Inner Mongolia.Core observation and thin section analysis data in combination with electron probe, energy spectrum, trace element and X-ray diffraction were used to analyze mineral composition and texture,structure of the rock.On this basis,we identified the origin of the dolostones.The results show that the dolostones（ zeolitic dolostones and zeolite with single layer thickness of 0.2-1.5 m） in the study area are composed of ankerite（ proportion of Fe is 0.5%-5%） ,natrolite,analcite,sjogrenite,barite and pyrite.The dolomite crystals feature in size of 10-200 μm,wavy extinction,saddle morphology and development of fis-sures.These dolostones have muddy-micritic or intraclast（ mainly from dolomites and zeolites） structures.Laminated,con-temporaneous deformation, net-veined, and brecciated structures are common.GR is 700 -1 100 API, which is 2 -4 times as large as that of normal mudstones.U and Th content is up to 40-60 ppm and 60-100 ppm respectively.Trace elements,including Cu, Ni, Co, Fe and Mn, have a similar composition and distribution with the modern hydrothermal sediments on the Red Sea floor.The dolostones are distributed along the basement faults laterally.It is concluded that this is a set of ‘white smoke chimney’ hydrothermal dolostones.However,these sediments are rarely reported.The study of the chemical and thermodynamics process is deficient,and the deposition mechanism is not very clear.This research will be helpful for enriching the theory of sedimentology and discovering more mineral resources associated with hydrothermal sediments.

关 键 词：白烟型 热水沉积 热水沉积白云岩 二连盆地 

分 类 号：TE121.3[石油与天然气工程—油气勘探]