T82 Unravelling Timescales of Magmatism, Metamorphism, and Crustal Evolution I

Monday, 16 October 2023
8:00 AM - 12:00 PM
327

MULTI-STAGE THERMAL EVOLUTION OF THE HYLAND RIVER METAMORPHIC COMPLEX IN SOUTHEAST YUKON, CANADA

Paper number: T82-7
Program: Technical Sessions
Time: 9:35 AM – 9:50 AM

Authors

Abstract

The upper Hyland River area, located in southeast Yukon, Canada, is characterized by Neoproterozoic – Cambrian metasedimentary rocks of the Selwyn Basin. Rocks in this area underwent low-grade regional metamorphism during the Jurassic-Cretaceous and are overprinted by a later medium- to high-grade stage. In the field, the metamorphic complex has been mapped as a series of semi-concentric metamorphic zones. These zones are cut by a series of mid-Cretaceous granitic intrusions, including the Hyland River suite (ca. 105-100 Ma) and the Tay River and Tungsten suites (ca. 99-95 Ma).

This study focusses on constraining the tectono-metamorphic history of the Hyland metamorphic complex using P-T pseudosection modelling linked with LA-ICPMS garnet mapping to better understand the thermal evolution of these rocks, and its association with emplacement of the Cretaceous plutons.

Results from structural analysis and phase-equilibria modelling indicate the phyllites that host the intrusive rocks are overprinted by two metamorphic stages. The first metamorphic event occurred at medium pressure (~0.5-0.6 GPa) and temperatures ranging from 400°C to 850°C with the highest temperatures associated with abundant partial melting being recorded in the core of the metamorphic complex. This metamorphic stage records a complex history of growth and resorption garnet which occur both under sub- and supra-solidus conditions. The second metamorphic stage is characterized by growth of andalusite and its replacement by sillimanite at <0.3 GPa. These two metamorphic events can either be interpreted as a single metamorphic cycle associated with exhumation or two distinct tectono-metamorphic events.

Constraints on the timing of metamorphism are being undertaken to better understand the P-T-t evolution of these rocks and the relationship to Cretaceous plutonism and emplacement of Au-bearing quartz-calcite veins in the region.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-393796

© Copyright 2023 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.