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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Field evidence of Eros-scale asteroids and impact-forcing of Precambrian geodynamic episodes, Kaapvaal (South Africa) and Pilbara (Western Australia) Cratons
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Field evidence of Eros-scale asteroids and impact-forcing of Precambrian geodynamic episodes, Kaapvaal (South Africa) and Pilbara (Western Australia) Cratons

机译：爱神规模的小行星和前寒武纪地球动力学事件，Kaapvaal（南非）和Pilbara（西澳大利亚州）克拉通的撞击证据

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The role of asteroid and comet impacts as triggers of mantle-crust processes poses one of the fundamental questions in Earth science. I present direct field evidence for close associations between impact ejecta/fallout units, major unconformities and lithostratigraphic boundaries in Archaean and early Proterozoic terrains, including abrupt changes in the composition of volcanic and sedimentary assemblages across stratigraphic impact boundaries, with implications for the nature and composition of their provenance terrains. As originally observed by D.R. Lowe and G.R. Byerly, in the Barberton Greenstone Belt, eastern Kaapvaal Craton, South Africa, 3.26-3.24 Ga asteroid mega-impact units are closely associated with the abrupt break between an underlying simatic mafic-ultramafic volcanic crust and an overlying association of turbidites, banded iron formations, felsic tuff and conglomerates of continental affinities. Contemporaneous stratigraphic relationships are identified in the Pilbara Craton, Western Australia. Evidence for enrichment of seawater in ferrous iron in the wake of major asteroid impacts reflects emergence of new source terrains, likely dominated by mafic compositions, attributed to impact-triggered oceanic volcanic activity. Relationships between impact and volcanic activity are supported by the onset of major mafic dyke systems associated with similar to 2.48 Ga and possibly the 2.56 Ga mega-impact events.
机译：小行星和彗星撞击作为地幔-地壳过程触发的作用提出了地球科学中的基本问题之一。我提供了直接的实地证据，证明了太古代和元古代时期的撞击喷射/沉降单元，主要不整合面和岩石地层边界之间的紧密联系，包括跨越地层撞击边界的火山和沉积组合物的组成突然变化，对自然和构造有影响的起源地正如D.R.劳和G.R.过去，在南非东部Kaapvaal Craton的Barberton绿岩带中，3.26-3.24 Ga的小行星巨型撞击单元与潜在的基性镁铁质-超镁铁质火山地壳与上覆的浊积体，带状铁质形成之间的突然断裂密切相关，长相凝灰岩和大陆相似性集团。在西澳大利亚州的皮尔巴拉克拉顿（Pilbara Craton）发现了同时期的地层关系。在发生小行星重大撞击之后，有色金属中的海水富集的证据反映出新的源头地形的出现，这很可能是由镁铁质成分主导的，这归因于撞击触发的海洋火山活动。冲击与火山活动之间的关系由与约2.48 Ga和可能的2.56 Ga特大冲击事件有关的主要铁质堤坝系统的出现所支持。

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