The Mozambique Belt in northern Mozambique: Neoproterozoic (1100–850 Ma) crustal growth and tectogenesis, and superimposed Pan-African (800–550 Ma) tectonism
The Mozambique Belt in northern Mozambique: Neoproterozoic (1100–850 Ma) crustal growth and tectogenesis, and superimposed Pan-African (800–550 Ma) tectonism
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DOI：
10.1016/0301-9268(93)90093-h
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发表时间：
1993-04
影响因子：
3.8
通讯作者：
P. Pinna;G. Jourde;J. Calvez;J. Mroz;J. Marques
中科院分区：
文献类型：
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作者：
P. Pinna;G. Jourde;J. Calvez;J. Mroz;J. Marques
莫桑比克北部前寒武纪基底主要由1100~850 Ma莫桑比克造山过程中侵位变形的高级片麻岩、麻粒岩、混合岩和造山深成岩组成。麻粒岩推覆体(Lurio超群)被推覆于异地表壳单元(Chiure超群)之上，两个层序又被推覆至原地混合岩前陆(Nampua超群)之上。麻粒岩大多为深成成因，并提出了一种在∼1050 Ma从地幔中提取并侵位于下地壳的初始钙碱性内生物质的模式，这种内生母体被认为是在1050~850 Ma之间同动侵位的后续富碱熔融源。表壳单元包括海相变质沉积岩、与超镁铁镁铁质层序和同运动花岗岩伴生的钙碱性和拉斑玄武岩。原地前陆以深成混合岩为主，具低的锶初始比值，起源于1100~950 Ma的地幔英云闪长岩，伴生高锶初始比值的地壳熔融花岗岩，形成时间晚至850 Ma，主要表现为大的变质剪切和蛇绿岩化作用，以及向东和东南的区域逆冲作用。早期构造保存在麻粒岩杂岩和混合岩前缘，低品位的变质沉积岩(千枚岩、砂岩、砾岩和大理岩)可能与冰川有亲缘关系，不舒服地覆盖在莫桑比克的基底上，与加丹干超群对比。这些岩石和基底在∼538 Ma被泛非逆冲、横流剪切带和陆内环境中的褶皱捕获。这些新数据使我们能够重新评估整个莫桑比克带，直到现在，它被认为是一个泛非活动带，包括可变活动的克拉通。作者认为，该带是卡拉哈里克拉通和印度-南极克拉通之间的主要扇形碰撞带。
The Precambrian basement of northern Mozambique is composed mainly of high-grade gneiss, granulite, migmatite and orogenic plutonic rocks emplaced and deformed during the Mozambican orogeny between 1100 and 850 Ma. Granulite nappes (Lurio Supergroup) were thrust over allochthonous supracrustal units (Chiure Supergroup), and both sequences were then thrust over an autochthonous migmatitic foreland (Nampula Supergroup).The granulite rocks are mostly of plutonic origin, and a model is proposed of an initial calc-alkalic enderbitic mass extracted from the mantle at ∼1050 Ma and emplaced in the lower crust; this enderbitic parent is considered as the source for successive alkali-rich melts which were emplaced synkinematically between 1050 and 850 Ma. The supracrustal units comprise marine metasedimentary rocks, and calc-alkalic and tholeiitic rocks associated with ultramafic-mafic sequences and synkinematic granite. The autochthonous foreland consists mainly of plutonic migmatite, showing low Sr initial ratios and originating from mantle-derived tonalitic rocks emplaced between 1100 and 950 Ma, associated with crustal-melt granite showing higher Sr initial ratios and dated as late as 850 Ma.Major synmetamorphic shearing and blastomylonitization, and regional thrusting to the east and southeast, are the main manifestations of the Mozambican orogeny. Early structures are preserved in the granulite complex and the migmatite foreland.Low-grade metasedimentary rocks (phyllite, sandstone, conglomerate and marble), with possible glacial affinities, uncomformably overlie the Mozambican basement and are correlated with the Katangan Supergroup. These rocks, together with the basement, were caught up at ∼538 Ma in Pan-African thrusts, transcurrent shear zones and folds in an intracontinental environment.These new data allow a reassessment of the entire Mozambique Belt, until now regarded as a Pan-African mobile belt involving variably remobilized cratons. The authors believe the belt to be a major fan-shaped collision zone between Kalahari craton and an Indo-Antarctic craton.