MOUNT SCOTT GRANITE ENCLAVES, WICHITA GRANITE GROUP, OKLAHOMA: CHARACTERIZATION, COMPARISON, CLASSIFICATION

The Wichita Mountains in southern Oklahoma host exposures of the Cambrian Wichita Granite Group (WGG), shallowly-emplaced sheet plutons resulting from rift-induced magmatism. The Mount Scott Granite is the largest of the WGG lithodemes. Mafic enclaves are found throughout the Mount Scott, and they are one of its defining characteristics. Preliminary study characterized mafic minerals in three enclave samples through EDS on SEM. The enclaves’ mafic minerals are iron oxides, Hbl, and Bt. Although these are typical to the Mount Scott Granite, curiously, the mafic phases in the immediate granite matrix are dominated by iron oxides and Opx. Ap and Zrn, also typical of the Mount Scott, are in the adjacent matrix but not in the enclaves. The three examined specimens serve as examples of the population's microstructural variation; these populations exhibit defined to diffuse boundaries with the matrix, and distinct to indistinct crystal assemblages within the enclave.

The origin of the enclaves remains enigmatic. Given evidence for granite-basalt mixing elsewhere in the WGG, we hold as a working hypothesis that the enclaves are remnants of disarticulated basaltic dikes. Continued work will incorporate optical petrography and laser ablation and/or EPMA, chiefly to document the mineral chemistry of the enclave phases for comparison with those generally distributed in the granite. The study also aims to assess and categorize microstructure by measuring the enclaves' apparent Feret diameters and distribution on outcrop surfaces.