【摘要】 根据大地构造背景、岩石学特征、生物标志和盐类矿物分析,鄂尔多斯盆地古隆起周边奥陶系马家沟组沉积于局限的陆表海碳酸盐台地,其中马五段沉积于水文循环差、盐度高的含膏云坪和膏盐湖环境,马四段沉积环境相对开阔。压实作用使得碳酸盐原始沉积物的孔隙度大大降低。白云石δ18O值较高,δ13C值改变不大,Sr87/Sr86值高,Fe2+含量高,Sr2+和Na+含量低,有序度低且变化大。白云石在局限且高盐度环境下通过微生物作用沉淀,后经岩溶作用和埋藏作用改造。溶蚀作用形成了各种类型的溶蚀孔、洞、缝;岩溶作用形成了由南向北依次发育的岩溶高地、岩溶台地、侵蚀坡地和岩溶盆地等岩溶地貌。白云石化作用和岩溶作用是建设性成岩作用,压实作用、胶结作用和去白云石化作用是破坏性成岩作用。靠近膏盐湖的膏云坪沉积了大量的硬石膏结核,有利于硬石膏结核溶模孔形成。古岩溶斜坡岩溶作用强烈,易形成大量顺层分布的溶蚀孔、洞、缝。古岩溶斜坡与盆地过渡区岩溶作用弱,胶结作用和去白云石化作用较强。受沉积作用、成岩作用和古岩溶地貌三方面因素的共同控制,该区碳酸盐岩储层形成、发育过程极为复杂。更多还原

【Abstract】 Based on the analysis of tectonic setting, petrology characteristics, biologic criteria and saline minerals, The Ordovician Majiagou Formation in the surrounding area of paleo-uplift in Ordos Basin deposited in a carbonate platform of restricted epeiric seas. The fifth member of Majiagou Formation deposited in gypsodolomite flat and gypsic saline lake where water cycle was restricted and salinity was high. The sedimentary environment of the fourth member of Majiagou Formation was relatively broad. Due to the compaction, porosity of the original carbonate sediments decreased greatly. The degrees of order for dolomite display low and changeable values. The dolomites are characterized by high δ18O values, Fe2+ contents and Sr87/Sr86 ratios, low Sr2+ and Na+ contents, and stable δ13C values comparing with original sedimentary values. The dolomites precipitated through microbial activity in the restricted environments with high salinity, and reformed by the karstification latter. The dissolution created different types of pores, caverns and fractures. The karstification formed karst geomorphic unites, such as karst highlands, karst platforms, eroded slopes and karst basins. The dolomitization and karstification are constructive processes, while compaction, cementation and dedolomitization are destructive processes. Abundant anhydrite nodules deposited in the anhydrite dolomite flats near anhydrite salt lakes, which is favorable for the creation of anhydrite nodule mold pores. The karstification developed well in karst eroded slopes, where abundant horizontal strata-bound dissolved pores and vugs were easily formed. In the transitional zones of slopes and basins, karstification was weak, while dedolomitization and cementation developed well. Because of the influence of sedimentation, diagenesis and karstification, the formation and evolution of the carbonate reservoirs are complicated.更多还原