鄂尔多斯盆地奥陶系白云岩成岩相地球化学特征

发布时间：2018-07-06 14:59

本文选题：白云岩 + 成岩相　；参考：《古地理学报》2017年05期

【摘要】：白云岩是鄂尔多斯盆地奥陶系海相碳酸盐岩层系最主要的岩石类型和天然气藏的主要储集层。文中探讨了鄂尔多斯盆地奥陶系马家沟组白云岩成岩相的岩相与地球化学特征及其识别方法。根据岩心及露头观察、薄片鉴定、全岩X衍射、元素分析和碳、氧、锶同位素测试数据,识别出8种白云岩成岩相类型(准同生云化相、膏盐溶角砾相、活跃回流云化相、隐伏回流云化相、海水云化相、表生岩溶角砾相、埋藏溶蚀相和埋藏重结晶相),其分别形成于蒸发海水、中等盐度海水、正常海水、早期淡水、表生淡水及地层水成岩环境,隶属于近地表、风化壳及中—深埋藏3个成岩系统。建立了Fe-Mn、Cs-Sc、(K×Tl)/Na-(Sc×Ni)/Sr、δ~(13)C-87Sr/86Sr成岩相判别模版。弱活动性元素Sc、Ni和稳定重同位素13C、18O富集于蒸发海水类成岩相,较活动性元素Cs富集于中等盐度及正常海水类成岩相;K、Tl富集于还原环境成岩相,Fe、Mn富集于氧化环境成岩相;表生类成岩相以富含大量吸附态分散元素和87Sr为特征。研究结果表明,近地表及风化壳成岩系统决定了研究区马家沟组白云岩的成岩相及其地球化学特征,且岩相学研究及地球化学实验是开展白云岩成岩机理研究的有效手段。
[Abstract]:Dolomite is the main rock type of Ordovician marine carbonate formation and the main reservoir of natural gas reservoir in Ordos Basin. The lithofacies and geochemical characteristics of dolomite diagenetic facies of the Majiagou formation of Ordovician in Ordos Basin and their identification methods are discussed in this paper. According to core and outcrop observation, thin slice identification, whole rock X-ray diffraction, elemental analysis and carbon, oxygen and strontium isotopic data, eight types of dolomite diagenetic facies (quasi-syngeneic cloud facies, gypsum salt-soluble breccia facies, active return cloud facies) were identified. The underlying convective cloud facies, seawater cloud facies, epigenetic karst breccia facies, buried dissolution facies and buried recrystallization facies) are formed in the diagenetic environments of evaporative seawater, moderate salinity seawater, normal seawater, early fresh water, epigenetic fresh water and formation water, respectively. It belongs to three diagenetic systems: near surface, weathering crust and mid-deep burial. Fe-MnCs-Sc, (K 脳 TL) / Na- (SC 脳 Ni) -Sr, 未 ~ (13) C-87Sr-86Sr diagenetic facies discriminant templates have been established. The weak active element SCN Ni and the stable heavy isotope 13C ~ (18) O are enriched in the evaporative seawater diagenetic facies, while the active elements Cs are enriched in the medium salinity and normal seawater diagenetic facies (K _ (K) T _ (l) in the diagenetic facies in the reduction environment and in the oxidized diagenetic facies in the diagenetic facies. The epigenetic diagenetic facies are characterized by abundant adsorptive dispersed elements and 87 Sr. The results show that the diagenetic facies and geochemical characteristics of the dolomite in Majiagou formation are determined by the near-surface and weathered crust diagenesis system, and the lithofacies and geochemical experiments are effective means to study the diagenetic mechanism of dolomite.
【作者单位】：西安石油大学地球科学与工程学院;
【基金】：国家科技重大专项(编号:2017ZX05005-002-004)资助~~
【分类号】：P588.245;P618.13

【相似文献】