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Crustal evolution of the Paleoproterozoic Ubendian Belt (SW Tanzania) western margin: A Central African Shield amalgamation tale
Gondwana Research ( IF 6.1 ) Pub Date : 2020-12-24 , DOI: 10.1016/j.gr.2020.12.009
Ariuntsetseg Ganbat , Tatsuki Tsujimori , Nelson Boniface , Daniel Pastor-Galán , Shogo Aoki , Kazumasa Aoki

The Ubendian Belt between the Archaean Tanzania Craton and the Bangweulu Block, represents a Paleoproterozoic orogeny of these two constituents of the Congo craton at ~1.8 Ga, forming the Central African Shield, during the Columbia Supercontinent cycle and consolidated during the Gondwana assembly. Metagranitic rocks from the Southern and Northern Ufipa Terrane (Western Ubendian Corridor) and those of the Bangweulu Block are compositionally similar and are contemporaneous. The protolith of the Ufipa Terrane is originated from the collided crustal rocks of the Bangweulu Block. New LA-ICP-MS zircon Usingle bondPb age of metagranitoids and granoporphyries confirmed magmatic events from 1.89 to 1.85 Ga. The metagranitoids of the Western Ubendian Corridor and that of the Bangweulu Block cannot be distinguished by it is trace element characteristics and age. Geochemically, they belong to high-K calc-alkaline to tholeiite series. The 1.89–1.85 Ga metagranitoids and granoporphyries are characterized by evolved nature, which are common for slab-failure derived magmas. Such geochemical features and the presence of ~2.0 Ga eclogites suggest an Orosirian oceanic subduction and subsequent slab break-off. Melt derived from the mafic upper portion of torn slab lead to the partial melting of crust which formed high-K and calc-alkaline, I- and S-type magmatism in the Bangweulu Block and the Ufipa Terrane. Zircons from two metagranites from the Northern Ufipa Terrane show Neoproterozoic (Ediacaran) overprints at ~570 Ma, suggesting the Bangweulu Block collided with the continental margin of the Tanzania Craton. However, we found non-annealed Orosirian apatite in metagranitoids from the Southern Ufipa Terrane and the Kate–Ufipa Complex, implying that areal heterogeneity of the Pan-African tectonothermal overprint in the Ufipa Terrane. All evidences suggest that the Bangweulu Block and Ubendian Belt participated in amalgamation of Central African Shield as a separated continent surrounding oceanic crusts during Paleoproterozoic Eburnean orogeny and Neoproterozoic Pan-African orogeny.



中文翻译:

古元古代乌本德地带(坦桑尼亚西南部)西缘的地壳演化:中非盾构合并故事

太古坦桑尼亚克拉通和班古鲁地块之间的乌本地带代表了刚果克拉通的这两个组成部分的古元古代造山运动,形成了中非非洲盾构,在哥伦比亚超大陆循环期间形成了中非盾构,并在冈瓦纳大会期间巩固了它的位置,形成了约1.8 Ga。南部和北部乌菲帕地带(西乌本地走廊)和班古鲁地块的后生代岩石在成分上相似且是同期的。Ufipa Terrane的原石起源于Bangweulu区块碰撞的地壳岩石。新型LA-ICP-MS锆石U单键偏岩质和古植物的铅矿年龄证实了1.89至1.85 Ga的岩浆事件。西乌本底走廊和班古鲁地块的偏岩质不能通过微量元素特征和年龄来区分。从地球化学上讲,它们属于高钾钙碱性至黄铁矿系列。1.89-1.85 Ga偏岩质和花斑岩的特征是自然演化,这对于板状断裂衍生的岩浆很普遍。这样的地球化学特征和〜2.0 Ga榴辉岩的存在表明了Orosirian大洋俯冲和随后的平板破裂。来自撕裂的板的镁铁质上部的熔体导致地壳部分融化,在班古鲁区块和乌菲帕地块形成高K和钙碱性,I型和S型岩浆作用。来自北部乌菲帕地带的两个变质岩中的锆石显示,新元古代(Ediacaran)在〜570 Ma上叠印,表明Bangweulu区块与坦桑尼亚克拉通的大陆边缘相撞。但是,我们在南部乌菲帕地带和凯特-乌菲帕复合体的偏尼古兰体中发现了未退火的奥罗西亚磷灰石,这表明乌菲帕地带泛非洲构造热套印的区域非均质性。所有证据表明,在古元古代Eburnean造山运动和新元古代泛非造山运动期间,Bangweulu区块和Ubendian带参与了中非盾构的合并,成为一个围绕大洋壳的分离大陆。我们在南部Ufipa地带和Kate-Ufipa复杂体的偏尼古龙中发现了未退火的Orosirian磷灰石,这暗示了Ufipa地带泛非洲构造热套印的区域非均质性。所有证据表明,在古元古代Eburnean造山运动和新元古代泛非造山运动期间,Bangweulu区块和Ubendian带参与了中非盾构的合并,成为一个围绕大洋壳的分离大陆。我们在南部Ufipa地带和Kate-Ufipa复杂体的偏尼古龙中发现了未退火的Orosirian磷灰石,这暗示了Ufipa地带泛非洲构造热套印的区域非均质性。所有证据表明,在古元古代Eburnean造山运动和新元古代泛非造山运动期间,Bangweulu区块和Ubendian带参与了中非盾构的合并,成为一个围绕大洋壳的分离大陆。

更新日期:2020-12-24
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