Abstract

Detailed porphyroblast-matrix analysis within the concordant metasedimentary aureole rocks surrounding the Papoose Flat pluton of eastern California indicates that inclusion trails within porphyroblasts can be used as strain markers to restore the aureole rocks to their prepluton emplacement position. Using porphyroblast-matrix relationships in combination with measurement of stratigraphic sections and whole-rock geochemical analyses, we have determined the kinematics of rotation, the change in thickness and volume, and the amount of translation of the metasedimentary formations within the aureole. These data are consistent with initial emplacement of the magma as an inclined sill and subsequent inflation into a pluton or laccolith. The combination of structural and porphyroblast-matrix analysis leads to a three-dimensional kinematic history of the wall rocks wherein vertical upward translation represents a significant part of the pluton emplacement-related strain history.

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