Crustal evolution of the Paleoproterozoic Ubendian Belt (SW Tanzania) western margin: A Central African Shield amalgamation tale
Crustal evolution of the Paleoproterozoic Ubendian Belt (SW Tanzania) western margin: A Central African Shield amalgamation tale
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DOI：
10.1016/j.gr.2020.12.009
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发表时间：
2021-03
影响因子：
6.1
通讯作者：
Ariuntsetseg Ganbat;T. Tsujimori;N. Boniface;D. Pastor‐Galán;S. Aoki;K. Aoki
中科院分区：
文献类型：
--
作者：
Ariuntsetseg Ganbat;T. Tsujimori;N. Boniface;D. Pastor‐Galán;S. Aoki;K. Aoki
太古代坦桑尼亚板块和Bangweulu板块之间的Ubendian带代表了刚果板块的这两个组成部分在哥伦比亚超大陆旋回期间在~1.8 Ga组装形成中非地盾的古元古代造山带，并在冈瓦纳组装期间得到巩固。乌菲帕地体南部和北方（乌本底安走廊西部）的变花岗岩类与班韦乌卢地块的变花岗岩类在成分上相似，并且是同生的。Ufipa地体的原岩来自Bangweulu地块的碰撞地壳岩石。变质花岗岩类和花岗斑岩的LA-ICPMS锆石U-Pb年龄证实了1.89 ~ 1.85Ga的岩浆事件。西部乌本底安走廊和Bangweulu地块的变花岗岩类不能通过微量元素特征和年龄区分。地球化学上属高钾钙碱性-拉斑玄武岩系列。1.89- 1.85Ga变质花岗岩类和花岗斑岩具有演化特征，是板裂岩浆的常见特征。这种地球化学特征和~2.0 Ga榴辉岩的存在表明Orosirian洋俯冲和随后的板片断裂。来自撕裂板片上部的镁铁质熔体导致地壳部分熔融，在Bangweulu地块和Ufipa地体中形成高钾和钙碱性I型和S型岩浆活动。来自乌菲帕地体北方的两个变质花岗岩的锆石显示新元古代（埃迪卡拉纪）的叠印在~570 Ma，表明Bangweulu地块与坦桑尼亚大陆边缘碰撞。然而，我们发现非退火Orosirian磷灰石变质花岗岩从南部Ufipa地体和凯特-Ufipa复杂，这意味着泛非构造叠加在Ufipa地体的区域异质性。所有的证据表明，Bangweulu块体和Ubendian带在古元古代Eburnean和新元古代泛非造山运动期间，作为被大洋地壳包围的分离大陆参与了中非地盾的合并。
The Ubendian Belt between the Archean Tanzania Craton and the Bangweulu Block, represents a Paleoproterozoic orogeny of these two constituents of the Congo Craton assembled at ~1.8 Ga, forming the Central African Shield, during the Columbia Supercontinent cycle and consolidated during the Gondwana assembly. Metagranitoids from the Southern and Northern Ufipa Terranes (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-ICPMS zircon U–Pb 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 their trace element characteristics and ages. 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 led 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 apatites 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 the Ubendian Belt participated in the amalgamation of the Central African Shield as separated continents surrounded by oceanic crusts during the Paleoproterozoic Eburnean and the Neoproterozoic Pan-African orogenies.