鄂尔多斯盆地三叠系延长组砂岩中的白云石胶结物及形成机制

白云石是鄂尔多斯盆地三叠系延长组砂岩中最为重要的自生矿物之一,多数已属于铁白云石的范畴.白云石的分布方式,以及相应的矿物学、岩石学和地球化学特征,尤其是碳、氧同位素特征,表明这些白云石是在较早成岩阶段形成的,印支期不整合面及暴露时间间隔中大气淡水作用对白云石的分布具有明显的控制作用,白云石的物质来源与同期或非同期海相碳酸盐物质的溶解有关.白云石形成机制的研究为对砂岩储集的演化研究提供了重要线索.

Dolomite cement and its formation mechanism in the Triassic Yanchang sandstone, Ordos Basin, China

Dolomite is one of the most abundant cements in the Triassic Yanchang sandstones of Ordos Basin,and most of it is ankerite.The distribution pattern,mineralogical and petrological evidences,geochemical characteristics(especially oxygen and carbon isotope data) of dolomite show that the precipitation of the dolomite occurred at earlier diagenesis.The unconformity during Jurassic and Triassic and the leaching by meteoric water during the time of subaerial exposure play an important role in the dolomite formation.The material sources of the dolomite cement should be from the coetaneous or non-coetaneous marine carbonate dissolution.The study of mechanism for dolomite formation provides an important clue for the porosity evolution of sandstone.