Petrogenetic Evolution of the Neoproterozoic Igneous Rocks of Egypt
Petrogenetic Evolution of the Neoproterozoic Igneous Rocks of Egypt
复制标题
埃及新元古代火成岩的岩石成因演化
DOI：
10.1007/978-3-030-49771-2_13
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
P. Asimow
中科院分区：
文献类型：
--
作者：
M. Azer;P. Asimow
埃及西奈半岛和东部沙漠新元古代晚期的基底出露代表了努比亚盾的北部，在红海开放之前，努比亚盾与阿拉伯盾毗邻。这两个盾牌一起形成了阿拉伯-努比亚盾牌(ANS)。ANS形成于东西冈瓦那碰撞的新元古代泛非造山运动期间，是地球上保存最完好的新元古代大陆年轻地壳。努比亚地盾的演化经历了(1)超大陆裂谷漂移(1000~900 Ma)、(2)洋盆俯冲消减(870~750 Ma)、大陆碰撞造山(750~630 Ma)、造山后伸展与坍塌(620~580 Ma，后期活动持续至540 Ma)等一系列阶段。然而，新元古代(870-580 Ma)年轻大陆地壳的发展，特别是ANS的埃及努比亚地盾段，最合乎逻辑的讨论分为三个主要阶段：碰撞前、碰撞和碰撞后。碰撞前阶段(~870~700 Ma)形成了与大洋内岛弧共存的完整的海洋蛇绿岩组合。所有埃及东部沙漠蛇绿岩都强烈变形、变质，并受到多种类型的蚀变作用的影响。它们以解体、构造体和枕状变质玄武岩、辉长岩和可变蚀变超镁铁质岩石的混合岩的形式出现。沿剪切带，蛇绿岩超镁质岩高度蚀变为滑石碳酸盐、菱镁矿和硅铅矿。碰撞阶段(670-630 Ma)包括俯冲阶段，产生火山-沉积岛弧序列和钙碱性辉长闪长岩杂岩，随后发育科迪勒拉式钙碱性辉长岩和花岗闪长岩及其喷发等价物，以西冈瓦那和东冈瓦那合并结束。碰撞阶段的所有单元均为弱变形，仅经历了低级变质作用。碰撞后阶段(~620-580 Ma)以壳内熔融为特征，首先产生钙碱性花岗岩类，然后逐渐转变到末期，产生相对少量的碱性岩浆，既以深成单元保存，又以火山单元保存。在时间上，碰撞后钙碱性岩浆作用与碱性岩浆作用在时间上是重叠的。本章从火成岩岩石学的角度讨论努比亚的演化，包括深成岩(花岗岩类和镁铁质-超镁铁质)和火山记录。在努比亚地盾演化的每个阶段，埃及都侵位了花岗岩类：碰撞前的花岗岩类包括高度变形的奥长花岗岩、英云闪长岩和花岗闪长岩；同碰撞的花岗岩类是弱变形的花岗闪长岩和较少见的花岗岩；碰撞后的花岗岩类包括未变形的钙碱性和碱性二长花岗岩、正长花岗岩、碱性长花岗岩和碱性/过碱性花岗岩。埃及努比亚地盾中的新元古代镁铁质-超镁铁质杂岩包括更老的和更年轻的杂岩。较老的镁铁质-超镁铁质杂岩要么形成遮挡蛇绿岩序列的组成部分，要么构成与俯冲有关的钙碱性辉长闪长岩杂岩的成员。年轻的镁铁质-超镁铁质杂岩大多是新鲜的、未变形的、未变质的，并侵位于造山后环境。在埃及新元古代地壳中发现了四个主要的火山幕，包括蛇绿质变火山岩、岛弧变火山岩、多汗火山岩系列和后…
The Late Neoproterozoic basement exposures in the Sinai Peninsula and Eastern Desert of Egypt represent the northern part of the Nubian Shield, which was contiguous with the Arabian shield before the opening of the Red Sea. These two Shields together form the Arabian-Nubian Shield (ANS). The ANS, formed during the Neoproterozoic Pan-African orogeny due to collision between East and West Gondwana, is the best-preserved juvenile continental crust of Neoproterozoic age on Earth. The Nubian shield evolved through a series of stages that can be characterized as (1) supercontinent rift and drift (1000–900 Ma), (2) subduction and consumption of intervening ocean basins (870–750 Ma), (3) continental collision and orogeny (750–630 Ma), and (4) post-orogenic extension and collapse (620–580 Ma plus minor later activity extending to 540 Ma). The Neoproterozoic (870–580 Ma) development of the juvenile continental crust specifically of the Egyptian Nubian Shield segment of the ANS, however, is most logically discussed in three main stages: pre-collisional, collisional, and post-collisional. The pre-collisional phase (~870–700 Ma) produced complete oceanic ophiolite assemblages coexisting with intra-oceanic island arcs. All the Egyptian Eastern Desert ophiolites are strongly deformed, metamorphosed, and affected by several types of alteration. They occur as dismembered, tectonized bodies and mélanges of pillowed metabasalt, gabbro, and variably altered ultramafic rocks. Along shear zones, the ophiolitic ultramafics are highly altered into talc-carbonates, magnesite, and listvenite. The collisional stage (670–630 Ma) includes a subduction period that produced volcano-sedimentary island arc successions and calc-alkaline gabbro–diorite complexes, followed by development of Cordilleran-style calc-alkaline gabbros and granodiorites and their extrusive equivalents, ending with the merger of West and East Gondwana. All the units of the collisional stage are weakly deformed and experienced only low-grade metamorphism. The post-collisional phase (~620–580 Ma) was characterized by intracrustal melting that first generated calc-alkaline granitoids and then gradually shifted to a terminal stage that produced relatively small volumes of alkaline magma, preserved as both plutonic and volcanic units. Temporally, the later stages of post-collisional calc-alkaline magmatism and the alkaline magmatism overlapped. This chapter discusses the evolution of the Nubian from an igneous petrology perspective, including the plutonic (granitoid and mafic–ultramafic) and volcanic records. Granitoids were emplaced in Egypt during each phase of evolution of the Nubian Shield: pre-collisional granitoids include highly deformed trondhjemite, tonalite, and granodiorite; syn-collisional granitoids are weakly deformed granodiorite and less commonly granite; post-collisional granitoids include undeformed calc-alkaline and alkaline monzogranite, syenogranite, alkali feldspar granite, and alkaline/peralkaline granites. The Neoproterozoic mafic–ultramafic complexes in the Egyptian Nubian Shield include older and younger complexes. The older mafic–ultramafic complexes either form an integral part of obducted ophiolite sequences or constitute members of subduction-related, calc-alkaline gabbro–diorite complexes. The younger mafic–ultramafic complexes are mostly fresh, undeformed, and unmetamorphosed, and were emplaced in post-orogenic settings. Four major volcanic episodes have been recognized in the Neoproterozoic crust of Egypt, including ophiolitic metavolcanic rocks, island arc metavolcanic rocks, the Dokhan volcanic series, and post …
影响因子：
3.8
作者：
Breitkreuz, Christoph;Eliwa, Hassan;Murata, Mamoru
通讯作者：
Murata, Mamoru