LACCOLITH-LIKE EMPLACEMENT MODEL FOR THE PAPOOSE FLAT PLUTON BASED ONPORPHYROBLAST-MATRIX ANALYSIS

Detailed porphyroblast-matrix analysis within the concordant metasedim entary aureole rocks surrounding the Papoose Flat pluton of eastern Ca lifornia 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 com bination with measurement of stratigraphic sections and whole-rock geo chemical analyses, we hare determined the kinematics of rotation, the change in thickness and volume, and the amount of translation of the m etasedimentary formations within the aureole. These data are consisten t Kith initial emplacement of the magma as an inclined sill and subseq uent inflation into a pluton or laccolith, The combination of structur al and porphyroblast-matrix analysis leads to a three-dimensional kine matic history of the wall rocks wherein vertical upward translation re presents a significant part of the pluton emplacement-related strain h istory.