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

近年来，在对北美和欧洲几个主要的“泛非”新元古代(7.5亿-5.5亿年前)地体的地质演化的认识上取得了实质性的进展，但对“泛非”造山带演化的认识在非洲本身仍然存在着根本的空白。关于非洲新元古代造山带沉积历史的不确定性，很大程度上源于构造上重要单元的可靠辐射年龄数据库有限，加上这些变形区域缺乏详细的现代运动学分析。这些关键数据是通过对关键的新元古代非洲造山带之一--摩洛哥反阿特拉斯造山带--进行结构、铀-铅年代学和钕-铅-氦同位素分析而收集的。通过对区内变形岩石的详细构造分析，结合高精度的铀-铅锆石年龄测定，解答了有关南部反阿特拉斯带增生史的许多重大问题。这些问题包括洋壳(蛇绿岩)俯冲的时代和时间，这些蛇绿岩相互之间的关系，北部弧形地体与蛇绿岩之间的联系，以及南部伴生的蓝片岩带，这些地体的基底的年龄和性质，基底与新元古代岩浆相互作用的程度，以及这些地体向西非克拉通吸积的时间。通过现代、多学科的研究，正在建立起环大西洋地体与西非克拉通周围造山带的地质“谱系”。

0106853SamsonSubstantial 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.