200 D8. Recent Advances in Geochronology (Posters)

Tuesday, 11 October 2022
2:00 PM - 6:00 PM
Exhibit Hall F

A NEWLY RECOGNIZED 1.98 GA LARGE IGNEOUS PROVINCE (LIP) IN THE AMAZONIAN CRATON AND ITS RELATIONSHIP WITH THE COEVAL OROCAIMA SILICIC LIP

Paper number: 200-11
Program: Technical Sessions
Time: 2:00 PM – 6:00 PM

Authors

Abstract

The Orocaima silicic large igneous province (SLIP) of the Amazonian Craton constitutes one of the largest SLIPs recognized on Earth and possibly the most voluminous Paleoproterozoic magmatic event in Amazonia. Nevertheless, the triggering mechanisms behind this episode of large-volume felsic magmatism and its relationships with regional tectonic and/or mantle processes remain debated. Here, we present new high-precision geochronologic as well as geochemical results from multiple mafic dike swarms in the Guyana Shield of the Amazonian Craton, namely the Guaniamo, Aro, and Manteco-Supamo swarms, and show that these are geochemically unrelated but temporally and geographically associated with the Orocaima SLIP. The radial arrangement of these swarms, their clear tholeiitic geochemical affinity, and their emplacement in regions far from known arc-related magmatic centers in the Amazonian Craton at 1.98 Ga, suggest a plume-related origin for these mafic magmas. Discovery of this previously unrecognized LIP and its close association with the Orocaima suggests that heat transfer from an impacting plume triggered large-scale melting of the Amazonian lithosphere resulting in SLIP development, thus arguing against accretionary models for the origin of this voluminous silicic magmatic belt. Re-interpretation of paleomagnetic poles of the Aro swarm using our new geochronologic results, in addition to inter-cratonic correlations with other coeval LIPs globally, enables a better paleogeographic reconstruction of Amazonia in the Paleoproterozoic and a more accurate understanding of the role of this major craton in the global Precambrian supercontinent cycle.

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

doi: 10.1130/abs/2022AM-383860

© 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.