T124 Sigma Gamma Epsilon Student Research Exhibition (Posters)

Monday, 10 October 2022
2:00 PM - 6:00 PM
Exhibit Hall F

LITHOLOGIC INFLUENCE ON PSEUDOTACHYLYTE-BEARING FAULT ZONES IN THE IKERTÔQ SHEAR ZONE, GREENLAND: AN NSF REU STUDY

Paper number: T124-5
Program: Technical Sessions
Time: 2:00 PM – 6:00 PM

Authors

Abstract

High-resolution mapping of an extensive pseudotachylyte system in the Ikertôq shear zone of southwestern Greenland shows that the occurrence and style of interconnected pseudotachylyte-bearing faults are influenced by the lithology of the host rocks. The Ikertôq shear zone is a frontal structure of the Paleoproterozoic Nagssugtoquidian Orogen of which includes a 50 kilometer long pseudotachylyte system. Pseudotachylytes are vein-like rock melts that formed as a result of friction in shear zones, and are considered a proxy for paleo-earthquakes. These structures give insight into seismic behavior in the mid-upper crust. As part of an NSF REU, field observations were collected and laboratory analysis will be performed using electron microprobe, optical petrology, and scanning electron microscope (SEM) instrumentation. Our mapping of the lithologic units and boundaries along a transect of Sarfannguit Island identified lithologies varying from mafic intrusions, gabbroic pods, tonalite, felsic and intermediate gneisses, and metasedimentary rocks. Field observations such as rock unit descriptions, lithologic logs and maps show that the degree of foliation in a gniess has significant influence on the development of pseudotachylyte and fault geometry. Areas with well-foliated gneiss are characterized by a complex geometry of throughgoing pseudotachylyte-bearing faults, damage zones, imbricate wedges, and relay faults. In areas with less-foliated, thicker-banded gneiss, pseudotachylytes are less abundant and exhibit a less complex Riedel geometry. Our ongoing work will focus on gaining a better understanding of the petrology and tectonic setting of the transect.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-380427

© Copyright 2022 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.