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首页> 外文期刊>South African Journal of Geology: Being the Transaction of the Geological Society of South African: Syndie die Verhandelinge van die Geologiese Vereniging van Suid-Afrika >Review of mesoproterozoic magmatism, sedimentation and terrane amalgamation in southwestern Africa
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Review of mesoproterozoic magmatism, sedimentation and terrane amalgamation in southwestern Africa

机译：西南非洲中元古代岩浆作用，沉积和地层合并研究综述

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摘要

Mesoproterozoic crustal evolution of southwestern Africa involved a complex interplay over 600 million years of subduction, platemargin or intraplate sedimentation, volcanism and plutonism followed by terrane amalgamation, tectonism, collision, magmatism, metamorphism and final, late-stage isostatic rebound of high-grade terranes. Most terranes are underlain by ～2.0 Ga continental crust but the Areachap and Garies Terranes were juvenile Mesoproterozoic features with respective model ages of ～1.5 to ～1.3 Ga and ～1.25 Ga. Pre- and syntectonic metasediments in northwestern Namibia and in the Namaquan terranes are mid to late Mesoproterozoic in age. Volcanism or plutonism accompanied sedimentation in places. A southward younging of terrane accretion is apparent from about ～1.37 Ga in northwestern Namibia, to -1.24 Ga(?) in the region of the central Damara Orogen, <1.33 Ga in the Konkiep Subprovince, the latter on the west-dipping Namaqua Front, ～1.2 Ga (O'okiepian episode) in the Kaaien Terrane, to between ～1.11 and ～1.07 Ga in the Bushmanland and Garies Terranes. Widespread intrusion of granite into the base of the crust accompanied collision in northwestern Namibia. Syntectonic granite magmatism was extensive and voluminous during O'okiepian collision in the Gordonia Subprovince. Thereafter, local intermittent magmatism and sedimentation continued in the Rehoboth and Konkiep Subprovinces and the Kaaien, Bushmanland and Garies Terranes. In most regions from the Rehoboth Subprovince to the Garies Terrane there was an -1.1 Ga period of magmatism and/or metamorphism which Hanson et al. (2004, 2006) relate to plume activity. Redbed successions post-date the youngest magmatic rocks in the Rehoboth and Konkiep Subprovinces. The Bushmanland and Garies Terranes appear to have been subjected to intense deformation, recumbent folding and thrusting between ～1.11 and ～1.07 Ga. Open, upright folding thereafter in these two terranes was accompanied by intrusions of the Spektakel and Koperberg Suites and granulite-facies metamorphism between ～1.06 and ～1.02 Ga. Pegmatites mark the final magmatic event at about 1000 Ma. The high-grade rocks of the Gordonia Subprovince were juxtaposed against low-grade terranes to the north and south during isostatic rebound on major, late-stage, dextral shear zones at or near the margins of the subprovince. Cooling to 300 to 350°C had taken place by 850 to 800 Ma.
机译：西南非洲中元古代地壳演化涉及6亿多年的俯冲，板缘或板内沉积，火山作用和岩性作用，复杂的相互作用，随后是地层合并，构造运动，碰撞，岩浆作用，变质作用和高级地层的最终后期等静回弹。大部分的地层都被〜2.0 Ga的陆壳覆盖，但是Areachap和Garies地层是幼中元古代特征，模型年龄分别为〜1.5至〜1.3 Ga和〜1.25 Ga。纳米比亚西北部和纳马泉地层的前，构造共沉积为年龄为中元古代。火山活动或岩性活动伴随着局部沉积。从纳米比亚西北部的约1.37 Ga到达玛拉造山带中部地区的-1.24 Ga（？），Konkiep省的<1.33 Ga，后者在西倾的Namaqua Front上，明显地层向南年轻化。 ，在Kaaien Terrane中为〜1.2 Ga（O'okiepian事件），在Bushmanland和Garies Terranes中为〜1.11〜〜1.07 Ga。在纳米比亚西北部发生碰撞时，花岗岩广泛侵入地壳底部。在戈多尼亚省的奥基皮山碰撞期间，构造岩浆岩浆作用广泛而大量。此后，里霍博斯和康基普次省以及凯恩，布什曼兰和加里斯·泰拉尼斯继续发生局部间歇性岩浆作用和沉积作用。从里霍博斯省到加里斯地带的大多数地区，都有一个-1.1 Ga的岩浆作用和/或变质期，Hanson等人在此期间。 （2004年，2006年）涉及羽流活动。红床演替使里霍博斯和康基普次省最年轻的岩浆岩约会。布什曼兰和加里斯地貌似乎在〜1.11和〜1.07 Ga之间经历了强烈的变形，倾斜折叠和逆冲。此后，这两个地块中的开阔，直立折叠伴随着斯派克克和科珀伯格套房的侵入以及花岗石相变质作用。岩浆岩标志着约1000 Ma的最后岩浆事件。戈登尼亚地区的高等级岩石在该地区边缘或附近边缘的主要，后期，右旋剪切带上的等静回弹期间，与南北低等级地层并列。已经在850至800Ma下冷却至300至350℃。

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