Structural Analysis of the Victoria Quadrangle Fault Systems on Mercury: Timing, Geometries, Kinematics, and Relationship with the High-Mg Region

Three nonparallel fault systems occur in the Victoria quadrangle of Mercury. The most prominent system (Victoria system) includes the NNW-SSE trending Victoria Rupes-Endeavour Rupes-Antoniadi Dorsum (VEA) array, one of the major fault alignments on the planet, and shorter parallel fault arrays. West and northwest of the Victoria system, two additional fault systems with NE-SW (Larrocha system) and NW-SE (Carnegie system) trends, are found. The timing analysis reveals that the three systems are coeval and were active until ~3.7 Ga. Measures of rim offset within faulted craters on the VEA array and on Carnegie Rupes segment of the Carnegie system were used to derive the kinematics of faults and to perform a finite stress inversion, which provides an ENE-WSW trending regional shortening axis. Results of the stress inversion and age relationships, together with geometrical and morpho-structural observations, suggest that the NE-SW and NW-SE systems acted as right-transcurrent and left-transpressional, respectively, at the time when the computed strain field was active. The distribution of the three systems spatially coincides with the boundaries of the high-Mg region and of other regional geochemical terranes. Lateral geomechanical variation of the crust combined with tidal despinning and global contraction processes drove the localization and slip pattern of faults in a kinematically consistent displacement field. Moreover, crustal heterogeneities controlled the lateral changes in density and spacing of fault segments along the VEA. Following the demise of faulting, the established lateral variation of geometry along the VEA favored the growth of volcanic vents at high-permeability segment boundaries.