Pegmatites of the Mount Sheridan Gabbro

The Mount Sheridan Gabbro of the Wichita Mountains Igneous Province, southwestern Oklahoma contains several varieties of pegmatite. Based on field observations, five varieties of pegmatite are recognized: segregated dikes, uniform dikes, pods, diffuse pegmatite, and stringers. Two questions were proposed: 1) What is the relation between varieties of pegmatite? 2) What is the source of the pegmatite? Additional field work demonstrated different pegmatite types transition into each other. This suggests a genetic relation between pegmatite varieties. Microscope analysis of the pegmatite types shows many similarities in texture, mineralogy and alteration. Diffuse pegmatite occurs as intercumulus material in the gabbro and formed during initial crystallization. Pods formed from pools of diffuse material which merged to form dikes. Crystal-melt fractionation in the dikes leads to formation of segregated dikes, uniform dikes and stringers. Formation and transport of pegmatite material was an important process in the crystallization of the Mount Sheridan Gabbro