白云岩成岩相与地球化学特征——以鄂尔多斯盆地中东部马家沟组马五_5—马五_1亚段为例  

Diagenetic Facies and Its Geochemical Characteristics of Dolomite: A case study of Ma5_5-Ma5_1 Sub-Members of Majiagou Formation in central-eastern Ordos Basin

作　　者：李百强 王起琮 张小莉 魏巍 LI BaiQiang;WANG QiCong;ZHANG XiaoLi;WEI Wei(Department of Geology / National ＆ Local Joint Engineering Research Center of Carbon Capture and Storage Technology,Northwest Universi-ty,Xi’an 710069,China;School of Earth Sciences and Engineering,Xi’an Shiyou University,Xi’an 710065,China)

机构地区：[1]西北大学地质学系/二氧化碳捕集与封存技术国家地方联合工程研究中心,西安710069 [2]西安石油大学地球科学与工程学院,西安710065

出　　处：《沉积学报》2018年第3期608-616,共9页Acta Sedimentologica Sinica

基　　金：国家科技重大专项(2017ZX05005-002-004)~~

摘　　要：白云岩成岩相研究对恢复其成岩环境具有重要意义。以鄂尔多斯盆地中东部马家沟组马五_5—马五_1亚段为例,利用岩芯及岩石薄片研究了白云岩的成岩相类型及岩相特征,并根据氧、碳稳定同位素、锶同位素以及主、微量元素等分析了各类成岩相的地球化学特征。结果显示,鄂尔多斯盆地中东部马五_5—马五_1亚段白云岩成岩相主要包括近地表环境下的膏盐溶蚀角砾相、活跃回流渗透云化相和隐伏回流渗透云化相,以及表生淡水环境下的风化岩溶角砾相等四类,其中受淡水或混合水影响的近地表环境下的膏盐溶蚀角砾相、活跃回流渗透云化相及隐伏回流渗透云化相白云岩样品具有相对奥陶纪海水"负偏"的δ^(18)O和δ^(13)C值,相对高Mn或低Fe含量,中等—强阴极发光,高于同期海水的^(87)/^(86)Sr值以及相对较低的Al和Ti含量;而表生淡水环境下的风化岩溶角砾相白云岩样品因受表生期淡水以及大量陆源碎屑物的影响,呈现出低于同期海水的δ^(18)O和δ^(13)C值,相对高Mn和过高Fe含量,弱或无阴极发光,明显高于同期海水的^(87)/^(86)Sr值以及明显较高Al和Ti含量。研究结果表明,氧、碳稳定同位素、锶同位素及主、微量元素等地化数据是识别白云岩成岩相的有效指标。It is important to study on the diagenetic facies of dolomite for the restoration of its diagenetic environment.The cores and thin sections as well as the whole rock major and trace element geochemistry, O, C and Sr isotopiccompositions were analyzed to study the diagenetic facies types and lithofacies of the dolomite as well as the geochem-istry of different diagenetic facies of Ma55 -Ma51 sub-members of Majiagou Formation in the central-eastern Ordos Ba-sin, respectively. The results show that the diagenetic facies of dolomite of Ma55 -Ma51 sub-members in central-easternOrdos Basin mainly include the gypsum and salt dissolution, active reflow seepage dolomitization and implicit refluxseepage dolomitization diagenetic facies in a near-surface diagenetic tract, and weathering karstific breccia diageneticfacies in an epidiagenetic tract. The former dolomite samples display lower δ18O and δ13C values than those of the Or-dovician seawater, higher Mn and lower Fe contents, medium-strong cathodoluminescence, higher87Sr /86Sr ratiosthan the coeval seawater as well as their high Al and Ti contents may be caused by the effects of fresh water or mixedwater, while the latter dolomite samples may be affected by the epigenetic coeval seawater shows relatively high Mnand significant high Fe contents, weak or non-cathodoluminescence, obvious higher87Sr /86Sr values than those of thecoeval seawater, significant high Al and Ti contents. The results implicate that the δ18O , δ13C, 87Sr /86Sr, major andtrace elements are the effective indicators for identifying the diagenetic facies of dolomite.

关 键 词：鄂尔多斯盆地中东部 马五5-马五1亚段 白云岩 成岩相 地球化学特征 

分 类 号：P588.2[天文地球—岩石学]