The Piuquencillo fault system: a long-lived, Andean-transverse fault system and its relationship with magmatic and hydrothermal activity

Abstract. Lithospheric-scale fault systems control the large-scale permeability in Earth's crust and lithospheric mantle, its proper recognition is fundamental to understand geometry distribution of mineral deposits, volcanic plutonic complexes geothermal systems. However, their manifestations at current surface can be very subtle, as many cases they are oriented oblique continental margin axis magmatic arc; partially obliterated by younger, arc-parallel faults; also covered sedimentary through which might propagate vertically. The Piuquencillo system (PFS) a proposed lithospheric-scale system, located Main Cordillera central Chile. Here, we present results first detailed field study PFS, based on structural data collected 82 stations distributed across all western Cordillera. published U–Pb zircon ages for La Obra batholith, bounded south PFS but affected younger reactivations it, were obtained. They yielded 20.79 ± 0.13 Ma (granodiorite) 20.69 0.07 (monzogranite). Statistical analysis fault-plane shows that presence reflected strong preferred NW WNW strike, with variable dip directions, evident from total population individual segments PFS. In some segments, major NE- ENE-striking faults intersect orientation planes. Preferred orientations hydrothermal veins, breccias dikes show both capable channelling fluids magma. Kinematic dynamic reveals most was reactivated sinistral reverse kinematics during Neogene, under strike-slip transpressive regime E- ENE-trending shortening direction (?1). Detailed kinematic analyses completed various different rock units it. This supports concept strongly controlled deformation flow magmas Neogene. forms part larger, margin-transverse structure, Maipo zone, continental-scale discontinuity cut entire Chilean has been active least since Jurassic.