195 Evolution of Orogenic Belts Through Time: Insights from Sedimentation, Deformation, Magmatism, and Metamorphism (Posters)

This session explores the evolution of orogenesis on Earth, encompassing applications of sedimentology, petrology, geochemistry, paleomagnetism, geochronology, and structural geology. We encourage studies combining field observations with laboratory and modeling techniques to unravel tectonic processes.

Tuesday, 21 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Petro-structural and geochronological constraints on Ediacaran shear tectonics in the Pan-African orogeny: A case study from the Mayo-Darle mylonite, northwest Cameroon

Paper number: 195-5
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The Precambrian geology of Cameroon is a complex mosaic of ancient and younger crustal blocks, shaped by major orogenic events during the Paleoproterozoic and Neoproterozoic. The region is divided into two main domains: the stable Congo Craton and the highly deformed Central African Fold Belt (CAFB). The CAFB, in turn, is split into the North-West Cameroon Domain, Adamawa-Yadé Domain (AYD), and the Yaoundé Group. The North-West Cameroon domain contains a mix of low- to high-grade metamorphic rocks and various granitoids, while to the south, the Adamawa-Yadé Domain is characterized by extensive Pan-African granitoid intrusions into an older Archean to Paleoproterozoic gneissic basement. This research focuses on the Mayo Darle area within the northwestern border of the Adamawa-Yadé domain along the Tcholliré-Banyo Shear Zone. The geology here consists of intrusive Pan-African granitoids and younger, highly fractionated granites, such as quartzolite (tin-rich greisen), quartz-rich granitoid, alkali feldspar granite, syenogranite, monzogranite, and mylonitic granitoids and banded amphibolite, which cut through the gneissic basement. This study provides a comprehensive investigation of the Mayo-Darle mylonitic corridor to understand the multiple deformation events that shaped the area. Using detailed field mapping, kinematic and microstructural analyses, and U-Pb zircon geochronology, the goal is to precisely date these events and connect them to the broader regional tectonics. Initial results reveal a complex polyphase deformation history involving at least four distinct events. The earliest, a ductile D₁ phase, was followed by a more pervasive D₂ sinistral ductile phase. A transitional D₃ phase then occurred, showing both brittle and ductile characteristics. The final D₄ phase was a purely brittle event, marked by faults and fractures. This progression from ductile to brittle deformation shaped the structural framework of the area. U-Pb geochronological dating of the mylonitic amphibolite yielded an Ediacaran age of 601.8 ± 2.5 Ma, which is considered as the age of metamorphic resetting during Pan-African orogeny. The presence of a sinistral shear zone suggests the area was subjected to significant regional shear stresses, likely from events like continental collision or crustal extension. These findings have important implications for understanding the tectonic evolution of the AYD and its connection with the North-West Cameroon Domain in the Pan-African orogeny.

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

doi: 10.1130/abs/2025AM-413189

© Copyright 2025 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.