268-11 New Time and Pressure Constraints in a Short-lived(?) Magmatic System: Updated Geochronology and Geochemistry in the Wichita Igneous Province, Oklahoma

Session: Old and the New, Long and the Short: Perspectives on Integration of Timescales of Magmatic Processes: Special Session Related to MGPV Awards to Madison Myers and Anita Grunder (Posters)

Presenting Author:

Authors:

Abstract:

The Wichita Igneous Province (WIP) of southwestern Oklahoma is a Cambrian bimodal igneous province that has long been interpreted as evidence of a failed continental rift known as the Southern Oklahoma Aulacogen (SOA). Alternative hypotheses, such as magmatic activity along a transform boundary, have been proposed, but the failed rift paradigm persists. Within the WIP, there are limited geochemical and geochronological data. Several smaller intrusive units have no published dates or geochemistry beyond major element analyses and modal mineralogy. Recently published zircon U-Pb data have suggested that the magmatism in the SOA was short-lived (9 Myr), but this is not consistent with other known rift settings where magmatism lasts longer (such as the Midcontinent rift, where magmatic activity lasted ~25 Myr). In addition to temporal uncertainty, we have an incomplete understanding of emplacement depths for magmatic units. Only the Mount Scott Granite has published emplacement depth estimates; older Al-in-Hbl estimates and granite compositional analyses suggest ponding at 7-8 km, with Rapakivi textural data yielding a final emplacement depth of 1-1.5 km. Layered mafic rocks of the Glen Mountains Layered Complex are interpreted to lie lithostratigraphically beneath the granite sills, while nearly-coeval (slightly older?) rhyolites cap the intrusives. Therefore, considering only these depths and known dates, gabbro, rhyolite, and granite must have been emplaced and erupted into little to no overburden in less than 9 Myr. Here we present (1) preliminary zircon U-Pb geochronology for previously undated units and (2) updated emplacement depth estimates utilizing modern Al-in-Hbl geobarometry for alkaline granites and multi-phase geobarometry for mafic rocks and. Our preliminary data show (1) a more protracted magmatism, with dates ranging from 545-520 Ma in olivine gabbro and a late granite, respectively and (2) a wide range of emplacement depths for gabbros (10-22 km) but similar depths for granites (3-4 km) Constraints provided by these critical new data may ultimately force us to reinterpret the tectonic environment and existing crustal structure during emplacement of the WIP.

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

doi: 10.1130/abs/2025AM-9637

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