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Provenance and paleogeography of Archean Fig Tree siliciclastic rocks in the East-Central Barberton Greenstone Belt, South Africa
Precambrian Research ( IF 3.2 ) Pub Date : 2021-01-07 , DOI: 10.1016/j.precamres.2020.106041
Emily Stoll , Nadja Drabon , Donald R. Lowe

The 3.6–3.2 Ga Barberton Greenstone Belt, South Africa, is a complex terrain divided into multiple structural blocks. The structural deformation and poor geochronological constraints often make correlation among blocks difficult. To overcome structural complexities, provenance proxies including sandstone petrography, shale geochemistry, and detrital zircon geochronology are here used to compare source terrain signatures among multiple structural blocks in the East-Central Domain of the Barberton Greenstone Belt. This will expand our understanding of Paleoarchean paleogeography and the nature of crustal uplift in the southeastern part of the Barberton Greenstone Belt.

The Manzimnyama and Mlumati Synclines are composed of 600 m-thick sections of the Fig Tree Group, Mapepe Formation. These synclines have high sedimentary and volcanic lithic contents in sandstones, an upward transition from felsic to mafic signatures in shales, and a detrital zircon age distribution transition from a basal member with a main peak at 3.28 Ga to members with a peak at about 3.45 Ga. There are three other East-Central Domain, fault-bounded blocks made up mostly of Mapepe Formation strata. The Eastern Barite Valley lies northwest of the Manzimnyama Syncline. From older to younger strata, the Eastern Barite Valley progresses from high lithics to more quartz and feldspar in sandstones, from more mafic to felsic signatures in shales, and from a unimodal 3.45 Ga detrital zircon signature at the base to complexly mixed age distributions with a strong 3.24 Ga peak at the top. The Paulus Syncline, southeast of the Manzimnyama Syncline, has a high chert content, mafic to ultramafic geochemistry signatures, and a main detrital zircon peak at 3.28–3.30 Ga with a minor peak at 3.45 Ga. The Emlembe Syncline, southeast of the Paulus Syncline, has a high monocrystalline quartz content, mixed geochemistry signatures, and unimodal 3.28–3.30 Ga detrital zircon ages. The proximity and sedimentology of these structural blocks could suggest deposition in a single basin; however, contrasts in provenance suggests sediments were deposited in different basins, at different times, or in one basin with provenance partitioning. The blocks likely had locally different sources, implying the sequences were not part of a single large source, transport, and depositional fairway.



中文翻译:

南非东-中巴伯顿绿岩带太古代无花果树硅质碎屑岩的物源和古地理

南非的3.6–3.2 Ga巴伯顿绿石带是一个复杂的地形,分为多个结构块。结构变形和不良的地质年代学约束常常使块体之间的关联变得困难。为了克服结构上的复杂性,此处使用了包括砂岩岩相学,页岩地球化学和碎屑锆石年代学在内的物源代理来比较巴伯顿绿岩带东中部多个构造块之间的源地地形特征。这将拓宽我们对巴伯顿绿岩带东南部古古地理古地理学和地壳隆升性质的了解。

Manzimnyama和Mlumati向斜线由无花果树组Mapepe组的600 m厚的断面组成。这些向斜线在砂岩中具有高的沉积和火山岩含量,在页岩中从长英质向镁铁质特征向上过渡,并且碎屑锆石年龄分布从主峰位于3.28 Ga到峰值位于约3.45 Ga的成员过渡。 。还有其他三个中东部地区,断层界块主要由马佩普组地层组成。东重晶石谷位于Manzimnyama Syncline的西北。从较旧的地层到较年轻的地层,东部重晶石谷地从高岩性发展到砂岩中更多的石英和长石,从页岩中的更多的镁铁质到长石质特征,以及单峰3。底部为45 Ga碎屑锆石特征,复杂的混合年龄分布,顶部为3.24 Ga强峰。在Manzimnyama Syncline东南的Paulus Syncline具有高的石含量,镁铁质至超镁铁质的地球化学特征,碎屑锆石的主峰位于3.28-3.30 Ga,次要峰位于3.45 Ga。 ,具有高的单晶石英含量,混合的地球化学特征和单峰的3.28-3.30 Ga碎屑锆石年龄。这些构造块的邻近性和沉积学可能暗示在一个盆地中沉积。但是,物源方面的对比表明沉积物沉积在不同的盆地,不同的时间,或在一个具有物源分配的盆地中。这些街区可能有本地不同的来源,

更新日期:2021-01-07
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