229-16 Assessing the Timing and Degree of Contact Metamorphism in the Funeral Mountains

Session: Crustal Petrology (Posters)

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Abstract:

Local andalusite and kyanite in Echo Canyon surrounded by a region characterized by chlorite-grade phyllites, has revealed a hidden pluton and contact aureole in the Funeral Mountains. Phase equilibria modeling indicates minimum conditions of 0.45 GPa and 535 °C —significantly higher temperatures than previously estimated for the area, implying the presence of an additional heat source. This study integrates phase equilibria modeling, petrography, Raman spectroscopy on carbonaceous material (RSCM), and Ar/Ar geochronology to characterize these anomalous assemblages and place their formation within a revised tectonic framework.  

Three different metamorphic events have been recognized based on petrographic textural analysis, M1, M1.5, and M2. M1 is associated with prograde andalusite growth as indicated by the preservation of syn-tectonic Ms+Qz+Fe-Ti Ox foliations. The identification of M1.5 correlates with kyanite growth, supported by t[1] he reaction rims near adjacent aluminosilicates. Both are interpreted as Mid-Late Jurassic[2]  in age, preceding the Late Jurassic cooling ages of nearby Indian Pass. Echo canyon is located 8 km SW of Indian Pass and was likely exhumed syn-tectonically with Indian Pass. Consistent with Indian Pass, partial exhumation during M2 is recognized, as observations of overprinting tectonic foliations and aluminosilicates by retrograde chloritoid. However, Ar-Ar dates intended to help refine the timing of these events are pending.

Previous models for the Funeral Mountains proposed retro arc under thrusting during early Sevier orogenesis. Our study supports this interpretation  for chlorite phyllites in the field area, and suggests the presence of a local contact aureole in Echo Canyon of unknown age. Magmatism can explain the origin of a heat source required to elevates temperature to push Echo Canyon into the kyanite and andalusite stability fields. A sample southeast of Lees Camp Anticline yielded peak metamorphic temperatures of 423 °C, supporting our interpretation for elevated temperatures in the field area. Mineral isograds show the change from chloritoid to andalusite and kyanite bearing assemblages occurring over ~ 2 km, suggesting a pluton at depth below Echo Canyon producing the observed contact aureole.

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

doi: 10.1130/abs/2025AM-9396

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