LATE CRETACEOUS DUCTILE DEFORMATION, METAMORPHISM AND PLUTONISM IN THE PIUTE MOUNTAINS, EASTERN MOJAVE DESERT

Late Cretaceous deformation in the Piute Mountains involved ductile thrusting on a network of anastomosing northeast and southwest directed shear zones. The shear zones often separate Proterozoic lithologies with strong competency contrasts, suggesting that Proterozoic crustal anisotropies were important in controlling the geometry of the shear zone network. Shear zones now divide the crust into wedge- and lozenge-shaped blocks. The Piute Mountains can be separated into two kinematic domains, each characterized by a dominant sense of shear. Peak metamorphic grade increases from upper greenschist facies in the north to upper amphibolite facies as the Lazy Daisy pluton is approached. All penetrative deformation ended before 72-71 Ma, by which time the area had cooled to below 300°C. -from Authors