9 D7. Geochemistry, Mineralogy, Petrology, and Volcanology (Posters)

Friday, 17 March 2023
8:00 AM - 12:00 PM
Grand Ballroom A–D

THERE AND BACK AGAIN: AN ECLOGITE TALE FROM THE ASHE METAMORPHIC SUITE

Paper number: 9-17
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

The Ashe Metamorphic Suite (AMS), in the North Carolina Appalachians, is a predominantly meta-greywacke and amphibolite complex that contains pods of variably retrogressed eclogites and dunites. Previous studies have interpreted these rocks to have formed in an accretionary mélange that formed during Taconic subduction, however robust constraints on the relative timing of peak metamorphism between the host meta-greywackes and boudinaged eclogites remain enigmatic. Various methods will be used in this study to get a better understanding of the protolith, peak, and correlation of these rocks. To obtain a better relationship between the pods, and host rocks, garnet Lu/Hf ages will be determined for the mafic amphibolites, the meta-greywackes, and the eclogite pods found within this unit to determine when peak metamorphism occurred between samples. Previous geochronology on the eclogites gave a U-Pb zircon age of 420 ± 15 Ma (Miller et al., 2000). A garnet-chlorite-magnetite lithology from the Greer Hollow locality, presumed to be related to a “blackwall” reaction, gives a bulk Lu-Hf garnet age of 455 ± 1.6 Ma. This age is interpreted to reflect the timing of fluid-rock interaction near peak metamorphic conditions. Additionally, we will present major and trace element bulk rock geochemistry from the various lithologies from the AMS and make comparisons to other like terranes within the Appalachian orogen. These data will be used to constrain the protolith of the rocks and with phase equilibria modeling, the pressure-temperature paths, to help better understand whether the AMS is a fossilized accretionary mélange provides any evidence of oceanic origins.

Geological Society of America Abstracts with Programs. Vol. 55, No. 2

doi: 10.1130/abs/2023SE-386086

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