Megashears and hydrothermalism at the Martian crustal dichotomy in Valles Marineris

Observations of ancient deep deformation systems on Mars are important for constraining planetary dynamics, as well as to identify potential mineral resources. However, such systems were thought to be unexposed and inaccessible to analysis. Here, we apply structural and hyperspectral analyses, and correlate results with magnetic anomaly patterns, to investigate two large right-lateral brittle-ductile shear zones and fault megabreccia exposed in the deepest parts of Valles Marineris. The shear zones follow the trace of the edge of the Borealis impact basin, thought to represent the planetary dichotomy boundary. We identify hydrothermally altered mafic igneous rocks in the sheared basement. We suggest that the shear system was initiated as basin ring fault system in the pre-Noachian, with further reactivation up until the Hesperian, and may still be a potential source of marsquakes. Hydrothermal circulation through the shear zones may have initiated primary mineralizations which are promising for base and rare metal exploration.