There are a large number of structural fractures in Yangchang Formation of Ordos Basin;the crack formation mechanism, formation dynamics, relation with hydrocarbon accumulation all have get the systematic research. Secondary minerals filled in fractures, as well as relationship between secondary minerals and fracture forming time is still unrevealed. Based on the analysis of mineralization and diagenesis, the analyzing of carbon-oxygen isotopes and fluid inclusions, combining with regional tectonic thermal event and thermal evolution history of basin, is employed to research how the secondary minerals constrain the fracture forming time. First of all, through thin section observation of secondary minerals, we know that the mineral-filled fracture is tensile fracture, and can infer the fracture propagation direction. According to the diagenesis analysis, the forming time of fracture is earlier than or consistent with forming time of secondary minerals. Secondly, according to analysis of carbon-oxygenisotopes from carbonate cements in Yanchang Formation sandstone and fractures, we get the fact that forming time of E-W and N-S trending fractures filled carbonate cements in the outcrop is earlier than or the same period with carbonate veins formed. Finally, combining with the analysis of fluid inclusions and basin thermal evolution history, we know basin range hydrothermal activity mainly occur in 140～100 Ma（i.e., the Early Cretaceous）, is also the basin diagenesis period. Based on the above analysis, the forming time of EW and NS trending fracture filled carbonate cements should be earlier than or the same period in the formation of secondary minerals, namely forming time is the Early Cretaceous or before the Early Cretaceous.
Jiang Lin Qiu Zhen Guo Yusen Wu Chaofan Wu Zhijie . The analysis of secondary minerals and fracture formation time in Yanchang Formation of Ordos Basin[J]. Chinese Journal of Geology, 2017, 52(3): 915-930.