Characteristics Of Structural Deformation And Fluid Activity In Changning Area And Its' Perphery,Southern Sichuan

Based on the analyses of deformation,thermal history and paleo-fluid activity etc,it suggsets that there is a coupling relationship among the deformation patterns,deformation strength,uplift denudation and fluid activity across the Changning area and its'perphery,southern Sichuan basin.Our conclusions are as follows:?1?The Changning anticline is charaterized with a steeper dip in its norhtern limb,a gentle dip in its southern limb,as a box-shape anticline with a gentle deformation.The Weixin anticline outcrops Palaeozoic in core and Cenozoic in limbs,in particular,it domiantes with narrow and steep core of anticline,as a transitional fold-style.The Weixin anticline is thus an asymmetric anticline.Furthermore,the Yanjin anticline outcrops Lower Paleozoic in the core,and is charaterized with fracturing and faults,thus a strong deformation occurred across the anticline.?2?Based on detailed field observations,it indicates that the vein with paleo-fluid activity is concentrated in the region with strong deformation,e.g.,in the anticline core,fault of the anticline,thus the veins are dominated with calcite or dolomite.?3?Based on fractal statistics in the Changning area,it suggests that the region is generally characterized with wide viens,dispersed distribution,indicating that the paleo-fluid activity is medium intensity.The Weixin area is characterized with fine veins and dispersed distribution.In particular,the Permian is characterized with wide veins and scattered distribution,that indicates paleo-fluid activity is moderate to strong intensity.However,the Yanjin area is covered with vegetation,no enough data to understand about the paleo-fluid activity.?4?Based on the strontium,carbon and oxygen isotopes geochemistry,it shows that the fluid in the Changning anticline is mainly composed of intra layer activity,and the isotopic endogenesis characteristics are obvious.The ⁸⁷Sr/⁸⁶Sr ratio of veins in Lower Paleozoic across the Weixin and Yanjin anticlines is higher than that of host strata,indicating of a rich strontium fluid inflow,e.g.,crust source.Given the widespread fault and fracture in those anticlines,we argued that the fault cut through Lower Paleozoic,could probably destroy the preservation conditions of the Lower Paleozoic shale gas.?5?According to homogenization temperature of the inclusions,thermal history,and burial history etc.,it suggests that the capture time of inclusions is during the Late Cretaceous to Paleogene.?6?Based on the fractal and fluid geochemistry etc.,there is a coupling relationship between structural deformation strength and fluid activity,that is,the stronger of defromation,the more intense of fluid activity,which would affect signifcant influence on the preservation conditions of Lower Paleozoic shale gas.