192 D21. Recent Advances in Petrology, Igneous and Metamorphic (Posters)

Tuesday, 12 October 2021
2:30 PM - 6:30 PM
Exhibit Hall A

A NEW TYPE OF GRANITE: EXPLORING THE PETROGENESIS OF SUB-MOHO GRANITES FROM THE SAMAIL OPHIOLITE

Paper number: 192-1
Program: Technical Sessions
Time: 2:30 PM – 6:30 PM

Authors

Abstract

Granitoids with evolved chemical signatures, intrusive both in peridotite and mafic rocks, are well known in the Samail supra-subduction ophiolite of Oman and United Arab Emirates. In this study, we use major and trace element geochemical data to investigate their origin and better constrain relative contributions of sedimentary and mantle-derived sources. We compare granitoid composition based on intrusive loci, providing a baseline for understanding the petrogenesis of felsic intrusions in other ophiolite settings. Crust-hosted granitoids are predominantly ferroan, calcic, and metaluminous, resembling trondhjemites and ridge ‘tholeiitic’ granitoids with normal mid ocean ridge basalt (MORB)-like affinity formed by fractionation of mafic melt under fluid-present conditions from slab dehydration and partial melting of mafic rocks. Mantle-hosted granitoids are magnesian, calcic to calc-alkaline, and peraluminous, sharing similarities with cordierite- and muscovite-bearing peraluminous granitoids with enriched MORB-like affinity. Most mantle-hosted granitoids formed by mixing between amphibolite and sedimentary melts, with undetectable to minor mantle contribution. We hypothesize that the crust-hosted granitoids have a similar origin to trondhjemites in other ophiolite settings (e.g., Troodos) with a subduction-modified MORB source. The mantle-hosted felsic intrusions have divergent and unique geochemical signatures, and may represent a type of granite not accounted for in existing paradigms.

Geological Society of America Abstracts with Programs. Vol. 53, No. 6

doi: 10.1130/abs/2021AM-366863

© Copyright 2021 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.