Abstract
The identification of structural diagenesis and the reconstruction of diagenetic paragenesis in fault damage zones is important for understanding fault mechanisms and fluid flow in the subsurface. Based on the examination of core and sample thin section data, we deciphered the diagenetic parasequence and their fault controls for Ordovician carbonates in the northern Tarim intracratonic basin in NW China (Halahatang area). In contrast to the uniform nature of diagenesis observed in country rocks, there is a relatively complicated style of compaction and pressure solution, multiple fracturing, and cementation and dissolution history along the carbonate fault damage zones. The relative paragenetic sequence of the structure related diagenesis suggests three cycles of fracture activities, following varied fracture enlargement and dissolution, and progressively weaker calcite cementation. These processes of structure related diagenesis are constrained to the fault damage zones, and their variation is affected by the fault activities. The results of this study suggest that the carbonate reservoir and productivity could be impacted by the structure related diagenesis locally along the fault damage zones.
Highlights
Brittle deformation in the upper crust is a common phenomenon that can strongly influence any subsequent geological processes and the hydraulic properties of the rocks affected by this type of deformation [1,2,3]
The carbonate diagenesis within fault damage zones is difficult to predict in the subsurface, we propose the following model, based upon an integrated analysis of the carbonate fault damage zones in the Tarim Basin (Halahatang area)
Multiple phases of carbonate diagenesis in the fault damage zones may be identified from the subsurface based upon stylolite type and fracture cross-cutting relationships, fracture orientations and cementation generations in the sedimentary basin strata
Summary
Brittle deformation (e.g., faulting) in the upper crust is a common phenomenon that can strongly influence any subsequent geological processes and the hydraulic properties of the rocks affected by this type of deformation [1,2,3]. While the structure and microstructure of fault zones have been widely studied to better understand the process of faulting, by contrast, the diagenesis of and its integration with fault processes have been mostly neglected [1,2,9]. Whereas fault architecture and process can constrain the diagenesis along a fault zone, diagenetic processes can significantly influence the fault architecture, rock properties and mechanisms of brittle deformation leading to fracture or faulting [9,10,11,12,13,14,15]. We examine fracture cross-cutting and abutting relationships and orientations to understand the parasequence of the structural diagenesis. Addition, weIndiscuss the influences of veins to understand the parasequence of the structural addition, we discussofthe fault activitiesofon the activities carbonateon diagenesis in thediagenesis deep subsurface.
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