T95 Recent Advances in Supercontinents: Paleogeography, Geodynamics, and Paleoclimate Evolution II

Tuesday, 27 October 2020
5:30 PM - 8:00 PM
Meeting Rooms

NEW PALEOMAGNETIC AND GEOCHRONOLOGICAL RESULTS FROM PROTEROZOIC MAFIC DYKE SWARMS, ANTI-ATLAS BELT, MOROCCO

Paper number: T95-4
Program: Technical Sessions
Time: 6:05 PM – 6:20 PM

Authors

Abstract

West African Craton (WAC) has essentially no pre-Ediacaran paleomagnetic constraints, yielding large uncertainties in its position in Proterozoic supercontinents, Rodinia and Nuna. Recent geochronological results distinguish at least five mafic dyke swarms in the Anti-Atlas Belts, Morocco, namely 2.04 Ga, 1.75 Ga, 1.65 Ga, 1.41–1.38 Ga, and 0.88–0.85 Ga. These mafic dykes provide an opportunity for yielding reliable paleomagnetic poles for WAC. Here, we present new results of the reconnaissance study of Moroccan mafic dykes. Specifically, in the Tagragra d’Akka inlier, a group of ca. 1.36 Ga NE-trending dykes show consistent paleomagnetic directions of north and moderate down. A positive inverse baked-contact test supports a primary origin. Constrained by this ca. 1.36 Ga direction, we find that the position of WAC contradicts many previous reconstruction models of Nuna. Therefore, we argue that the configuration of Nuna should be reconsidered. In the Agadir Melloul inlier, a steep direction was obtained, which passes a reversal test with a classification of C. This steep direction is presumably ca. 885 Ma, which indicates that WAC was at high latitudes in Rodinia. However, steep directions are also observed in ca. 570 Ma Ouarzazate volcanics from WAC, and it is possible that the dykes in the Agadir Melloul inlier are of Ediacaran in age. Successfully determining the reliable poles from the Moroccan mafic dykes requires a close integration of paleomagnetic and U-Pb geochronological study in the future.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-359333

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