NEW INSIGHTS ON THE SOUTHERN OKLAHOMA AULACOGEN: PETROGENETIC AND GEOCHEMICAL ANALYSES OF MAFIC ROCKS FROM THE WICHITA IGNEOUS PROVINCE

The Wichita Mountains of southwestern Oklahoma have long been interpreted as a rift-generated igneous province which underwent reactivation during the late Paleozoic Marathon-Ouachita orogeny. However, several components of a typical rift zone are missing from the Southern Oklahoma Aulacogen, including pervasive mafic volcanism and large volumes of sedimentary graben fill, sometimes calling into question the viability of this hypothesis. In order to better understand the formational processes of the Wichita Igneous Province (WIP), we present new petrologic and U-Pb in situ geochronological data from mafic rocks in the WIP. Petrogenetic sequencing based on petrography and geochemical analyses suggest long-lived crystallization of plagioclase (labradorite) in the GMLC and younger gabbros, along with later alteration to mafic phases which suggest infiltration of fluids and/or weathering influences. Combined with similar analyses from plutonic and volcanic felsic rocks in the region, we consider alternate processes which may have contributed to the formation and later evolution of the WIP.