EMPLACEMENT CONSTRAINTS ON SHALLOW(?) PLUTONS: PRESSURE ESTIMATES FROM OLIVINE AND AMPHIBOLE IN THE WICHITA MOUNTAINS IGNEOUS PROVINCE, OKLAHOMA

The Wichita Igneous Province (WIP) has long been interpreted as a failed continental rift. Several lines of evidence (geophysical, geochemical, geometric) suggest this may not be the case; additional tectonic settings, such as a magmatically-active transform system, could produce similar results. Critically missing are constraints on the magmatic emplacement depths of the various intrusive units. Currently, depth estimates are limited to only a few units, and other interpretations are based completely on poorly exposed contact relationships. Prior analyses from aluminum-in-hornblende geobarometry performed on samples of the Mount Scott Granite have yielded pressure estimates of approximately 210 MPa, interpreted to record a depth of 7-8 km at the time of amphibole crystallization before final ascent of the magma. Rapakivi textures present in the Mount Scott Granite were used to estimate an ultimate final emplacement depth of approximately 1.5-1 km. Both estimates require an overburden of Cambrian Carlton Rhyolite of sufficient thickness and temperature (i.e., strength) to trap the magma and prevent further immediate exhumation. Such a process (ponding at depth followed by shallow emplacement) is not limited to a failed rift scenario, and therefore more data are needed to better constrain the magmatic evolution of the WIP. This study will report results from an updated aluminum-in-hornblende geobarometer for alkaline granitic rocks to update previous estimates from the Mount Scott Granite and provide an estimated emplacement depth for the Quanah Granite. Additionally, we present preliminary results from a multiple-reaction geobarometer for olivine-bearing mafic rocks, including the Sandy Creek Gabbro and the Glen Mountains Layered Complex. This new data provides critical constraints which, when combined with recent high-precision radiometric dates, may suggest an alternate interpretation for the igneous succession in the WIP.