Papoose Flat pluton: Forceful expansion or postemplacement deformation?

Abstract

Intense solid-state deformation in the margin of the Papoose Flat pluton, White Mountians, California, and severe attenuation of nearby wall rocks encouraged earlier workers to suggest that this pluton was emplaced by blistering or in situ radial expansion. Reexamination of the pluton and wall rocks indicates that many features present in and around the pluton are not compatible with this model. These features include the following: (1) lack of compositional zoning or magmatic foliations in the pluton; (2) lack of high-temperature solid-state deformation or a transition from magmatic to high-temperature solid-state flow; (3) the presence of widespread moderate-to low-temperature deformation in the pluton; (4) a northwest-southeast-trending stretching lineation and associated kinematic indicators of sinistral shear everywhere within and adjacent to the western half of the pluton; (5) significant cleavage transposition after the growth of porphyroblasts in the contact-metamorphic aureole; and (6) upright to inclined folds with a steeply dipping axial-planar cleavage in wall rocks that postdate aureole cleavages and porphyroblasts. Many other plutons in the White and Inyo mountains also have deformed western or northwestern margins and weakly deformed eastern margins. Instead of interpreting all of these plutons as post-tectonic and inferring that they all expanded in a western direction,more » the authors suggest that significant Cretaceous regional deformation occurred during and after emplacement of these plutons.« less