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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 >AMPHIBOLITES OF THE CENTRAL ZONE: NEW SHRIMP U-PB AGES AND IMPLICATIONS FOR THE EVOLUTION OF THE DAMARA OROGEN, NAMIBIA
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AMPHIBOLITES OF THE CENTRAL ZONE: NEW SHRIMP U-PB AGES AND IMPLICATIONS FOR THE EVOLUTION OF THE DAMARA OROGEN, NAMIBIA

机译：中央地带的两栖类：新的U-PB年龄及其对纳米比亚达马拉造山带演化的影响

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摘要

New SHRIMP U-Pb zircon and titanite data are presented for two amphibolites from the Central Zone of the Damara Orogen, Namibia. These data (the first ages for amphibolites in the Central Zone) show that amphibolites are derived from both Palaeoproterozoic (2026.9 +/- 2.3 Ma sample ACAM-1) and Pan-African (557.2 +/- 7.4 Ma - sample LKR021) precursors emplaced into the Palaeoproterozoic Abbabis Complex basement in the Central Zone. The younger amphibolites are interpreted as part of a mafic to dioritic phase of magmatism in the Central Zone (the Goas Suite), and major- and trace-element geochemistry from a suite of amphibolites from the southwestern Central Zone confirms this relationship. This phase of mafic to dioritic magmatism is contemporaneous with the onset of collision between the Congo and Kalahari Cratons. It is suggested that delamination of dense mafic lower crust and underplating of mantle-derived magmas following crustal thickening may have led to partial melting of pre-Pan-African mafic lower crust, generating this mafic to dioritic suite of rocks. Metamorphic zircon overgrowths in sample LKR021 give an age of 520 +/- 6.9 Ma, consistent with recent estimates for the age of peak metamorphism in the southwestern Central Zone. Titanites from LKR021 give an age of 493.4 +/- 6.4 Ma, and this is interpreted as a cooling age for the Central Zone.
机译：给出了纳米比亚达马拉造山带中部地区的两种闪石的新的SHRIMP U-Pb锆石和钛矿数据。这些数据（中部地区闪石的第一个年龄）表明，闪石既来自古元古代（2026.9 +/- 2.3 Ma样品ACAM-1）又来自泛非（557.2 +/- 7.4 Ma-LKR021样品）前体进入中部地区的古元古代Abbabis复杂地下室。较年轻的角闪石被解释为中心带（戈阿斯组）岩浆作用的镁铁质至闪长岩期的一部分，西南中部带的一组闪石的主要元素和微量元素地球化学证实了这一关系。从镁铁质到闪长岩浆岩的这个阶段与刚果和卡拉哈里克拉通之间的碰撞开始同时发生。有人认为，地壳增厚后致密的镁铁质下部地壳分层和地幔衍生岩浆的下盘作用可能导致了泛非前的镁铁质下部地壳的部分熔融，从而形成了这种镁铁质至闪长岩的组合。样品LKR021中的变质锆石过度生长的年龄为520 +/- 6.9 Ma，这与最近对西南中部地区最高变质年龄的估计一致。 LKR021的钛矿的年龄为493.4 +/- 6.4 Ma，这被解释为中部地区的冷却年龄。

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