关键词: 碳酸盐岩, 成岩作用, 成岩相, 奥陶系马家沟组, 鄂尔多斯盆地

Abstract:

During the deposition of the 8th oil-bearing member of Yanchang Formation, Upper Triassic, deltaic depositional systems were developed and muti-provenances were provided around Jiyuan area, which was located in the middle-western part ofOrdos Basin. Based on the analysis of thin sections，detrital framework grains and heavyminerals and their associations, and with the combination of sedimentary structures, paleontology and the tripartite trend surface analysis of sandbody distributions, the provenance of the 8th member in Yanchang Formation was studied, and the following results were concluded: ①The sources during the deposition of the 8th oil-bearing member of Yanchang Formation were fromnortheast, northwest and south.②There were certain differences in the nature of source rocks. The northwest source area was dominated by volcanic rocks and light tomiddle metamorphic rocks association, the northeast by volcanic rocks-lower metamorphic rocks association, and the southwest by metamorphic rocks-sedimentary rocks association.③The distribution directions of sand bodies were same to that of the lithologic reservoirs. The above results would provide important geological basis for the prediction of sand bodies and lithologic reservoirs in the 8th oil-bearing member ofYanchang Formation.

Key words: carbonate rocks, diagenesis, diagenetic facies, Ordovician Majiagou Formation, Ordos Basin