127-11 The Craig Hill Dike, a Unique Expression of Wichita Igneous Province Diabase in Medicine Park, Oklahoma

Session: Mineralogy, Geochemistry, Petrology, and Volcanology Student Session

Presenting Author:

Authors:

Abstract:

The Craig Hill Dike is a largely subhorizontal expression of Cambrian diabase that occurs on the southern wall of a road cut along the eastbound lane of Oklahoma Highway 49 at Medicine Park. The dike cuts the 530.45 ± 0.14 Ma Mount Scott Granite, and is part of a series of diabases that cut all members of the Wichita Igneous Province (WIP), a region of intense magmatism related to the rifting of the Laurentian margin. The host granite expresses minor thermal alteration and a network of fractures. The dike’s largely recumbent orientation differs from the more common subvertical dikes exposed in the WIP. Hand-transit measurements coupled with high-accuracy GPS readings  document a subhorizontal orientation from its exposure at its west end for 109 m to the east. We observed its westernmost orientation as N48°W 06°S, with an average trend of N69°W. The dike gently rolls to an upward inclination for a minimum of 19 m. Measurements on this portion were N25°W 40°S and N46°W 43°S, with an average mapped trend of N58°W. Apart from its unique orientation, the Craig Hill Dike is a typical, although weathered, expression of WIP diabase. Quantitative XRF analysis reveals 44.6 wt.% SiO2, 18.8 wt.% Fe2O3, 4.9 wt.% MgO, and 7.44 wt.% CaO, which are comparable to other WIP diabase. Despite recent excavation, the dike is heavily weathered by extensive groundwater incursion. Combined XRD and microanalysis (optical microscopy and SEM-EDS) document primary minerals of intermediate plagioclase (An54), apatite, iron oxide, and ilmenite. Plagioclase laths are roughly 100 x 30 μm, exhibiting preferential alignment in three directions, a behavior within the range of plagioclase orientation distributions measured in other WIP diabase. These are surrounded by subophitic augite that has substantially altered to two modes of chlorite and an abundance of montmorillonite. Sparse quartz and alkali feldspar are present, likely xenocrysts originating from the surrounding granite.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10769

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