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New geochronological constraints on the middle Archean Shurugwi greenstone belt toward an understanding of the crustal evolution of the Zimbabwe craton
Journal of African Earth Sciences ( IF 2.2 ) Pub Date : 2021-01-01 , DOI: 10.1016/j.jafrearsci.2020.104021
Hikaru Sawada , Yusuke Sawaki , Shuhei Sakata , Akira Ishikawa , Brian Muteta , Yukio Isozaki , Shigenori Maruyama

Abstract The Shurugwi greenstone belt (SGB) in the central Zimbabwe Craton is one of the major volcano-sedimentary belts in the craton, but its formation age and tectonic history have not been well constrained. For revealing the evolution of SGB, this study performed in-situ U–Pb dating of zircons from meta-sedimentary rocks of the Wanderer and Mont d’Or formations in SGB, granitoids/orthogneisses around SGB, and also whole-rock Re–Os isotopic analysis of chromitite in an ultramafic unit in SGB. Igneous zircons from granitoids which intruded into SGB were dated ca. 2.91 Ga, whereas those from the orthogneiss were dated ca. 3.01 Ga. The Re–Os isotopic analysis provided an intrusive age of ca. 3.0 Ga for the ultramafic unit that is unconformably covered by the Wanderer Formation. These ages indicate that the Wanderer Formation was deposited between 3.0 and 2.91 Ga and the SGB was tectonically emplaced over the basement with 3.01 Ga orthogneiss. By ca. 2.91 Ga. The depositional age of the Mont d’Or Formation is constrained between ca. 3.59 Ga and 3.0 Ga nonetheless the age range is still large. The age spectrum of the detrital zircons from the Mont d’Or Formation resembles that of the Wanderer Formation, sharing a dominant age cluster at ca. 3.59 Ga. For the Wanderer Formation, a significant time gap of nearly 600 million years between the depositional age and the 3.59 Ga major cluster in detrital zircon age spectra suggests that the SGB had a remarkable provenance which prevented large-scale supply of young detrital grains from tectono-magmatically active region.

中文翻译:

对理解津巴布韦克拉通地壳演化的中太古代 Shurugwi 绿岩带的新地质年代学约束

摘要 津巴布韦克拉通中部舒鲁格维绿岩带(SGB)是克拉通内主要的火山-沉积带之一,但其形成时代和构造历史并未受到很好的制约。为了揭示 SGB 的演化,本研究对 SGB 中 Wanderer 和 Mont d'Or 地层变质沉积岩、SGB 周围的花岗岩/正片麻岩以及全岩 Re-Os 的锆石进行了原位 U-Pb 定年SGB 超镁铁质单元中铬铁矿的同位素分析。侵入 SGB 的花岗岩中的火成岩锆石的年代大约在 2000 年。2.91 Ga,而那些来自正麻岩的年代大约为 2.91 Ga。3.01 Ga。Re-Os 同位素分析提供了大约 3.01 Ga 的侵入年龄。3.0 Ga 对于被 Wanderer 地层不整合覆盖的超基性单元。这些年代表明,Wanderer 组沉积在 3.0 至 2.91 Ga 之间,SGB 在基底上以 3.01 Ga 正方麻岩构造侵位。通过约。2.91 Ga。Mont d'Or 地层的沉积年龄限制在大约 2.91 Ga。尽管如此,3.59 Ga 和 3.0 Ga 的年龄范围仍然很大。来自 Mont d'Or 地层的碎屑锆石的年龄谱类似于 Wanderer 地层的碎屑锆石,在大约 3.59 Ga。对于Wanderer组,碎屑锆石年龄谱中沉积年龄与3.59 Ga主簇之间的近6亿年的显着时间差距表明SGB具有显着的物源,阻止了年轻碎屑颗粒的大规模供应来自构造岩浆活动区。91 Ga 和 SGB 以 3.01 Ga 正方麻岩在基底上构造。通过约。2.91 Ga。Mont d'Or 地层的沉积年龄限制在大约 2.91 Ga。尽管如此,3.59 Ga 和 3.0 Ga 的年龄范围仍然很大。来自 Mont d'Or 地层的碎屑锆石的年龄谱类似于 Wanderer 地层的碎屑锆石,在大约 3.59 Ga。对于Wanderer组,碎屑锆石年龄谱中沉积年龄与3.59 Ga主簇之间的近6亿年的显着时间差距表明SGB具有显着的物源,阻止了年轻碎屑颗粒的大规模供应来自构造岩浆活动区。91 Ga 和 SGB 以 3.01 Ga 正方麻岩在基底上构造。通过约。2.91 Ga。Mont d'Or 地层的沉积年龄限制在大约 2.91 Ga。尽管如此,3.59 Ga 和 3.0 Ga 的年龄范围仍然很大。来自 Mont d'Or 地层的碎屑锆石的年龄谱类似于 Wanderer 地层的碎屑锆石,在大约 3.59 Ga。对于Wanderer组,碎屑锆石年龄谱中沉积年龄与3.59 Ga主簇之间的近6亿年的显着时间差距表明SGB具有显着的物源,阻止了年轻碎屑颗粒的大规模供应来自构造岩浆活动区。0 Ga 尽管如此,年龄范围仍然很大。来自 Mont d'Or 地层的碎屑锆石的年龄谱类似于 Wanderer 地层的碎屑锆石,在大约 3.59 Ga。对于Wanderer组,碎屑锆石年龄谱中沉积年龄与3.59 Ga主簇之间的近6亿年的显着时间差距表明SGB具有显着的物源,阻止了年轻碎屑颗粒的大规模供应来自构造岩浆活动区。0 Ga 尽管如此,年龄范围仍然很大。来自 Mont d'Or 地层的碎屑锆石的年龄谱类似于 Wanderer 地层的碎屑锆石,在大约 3.59 Ga。对于Wanderer组,碎屑锆石年龄谱中沉积年龄与3.59 Ga主簇之间的近6亿年的显着时间差距表明SGB具有显着的物源,阻止了年轻碎屑颗粒的大规模供应来自构造岩浆活动区。
更新日期:2021-01-01
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