Chronology and Tectonic Evolution of the Southern Anti-Atlas Orogen, Morocco

Syracuse University, Syracuse NY

Investigators

Abstract

0106853 Samson Substantial advances have been made in recent years in the understanding of the geological evolution of several major North American and European 'pan-African' Neoproterozoic (750-550 million year old) terranes, but there is still a fundamental gap in the knowledge of 'pan-African' orogenic belt evolution in Africa itself. Much of the uncertainty about the accretionary history of the African Neoproterozoic orogens stems from the limited database of reliable radiometric ages of structurally important units, combined with a lack of detailed modern kinematic analysis in these deformed regions. These critical data are being collected by performing combined structural, uranium-lead geochronological, and neodymium-lead-hafnium isotopic analyses of one of the pivotal Neoproterozoic African orogens, the Anti-Atlas orogen of Morocco. Through a detailed structural analysis of the deformed rocks in the region, combined with high precision uranium-lead zircon age determinations, many significant questions about the accretionary history of the southern Anti-Atlas belt are being answered. Such questions include the age and timing of obduction of ocean-floor crust (ophiolites), the relationship of these ophiolites to one another, the connections between arc-terranes to the north with ophiolites and an associated blueschist belt to the south, the age and nature of the basement of these terranes, the degree of interaction of basement with Neoproterozoic magmas, and the timing of accretion of these terranes to the West African Craton. Through modern, multi-disciplinary studies the geological 'family-tree' of the circum-Atlantic terranes with the orogens surrounding the West African Craton is being established.