Gravity and 3D modelling combined with geochemical analysis examine the subsurface within and below the poorly exposed Palaeoproterozoic Yerrida Basin in central Western Australia. Understanding the structure of a region is important as key features indicating past geodynamic processes and tectonic activity can be revealed. However, in stable, post-depositional tectonic settings only the younger sedimentary units tend to be widely exposed, rendering direct observation of basement and intrusive rocks impossible. Geophysical imaging and modelling can reveal the structure of a region undercover. High-magnitude density anomalies around the basin cannot be reconciled with current geological knowledge in the case presented here. The gravity anomalies infer an abundance of buried and high-density material not indicated by the surface geology. A hypothetical causative source for the high-magnitude gravity anomalies is mafic rocks that were intruded and extruded during basin rifting. The simplest and plausible stratigraphic attribution of these interpreted mafic rocks is to the Killara Formation within the Mooloogool Group. However, geochemistry reveals that the Killara Formation is not the only host to mafic rocks within the region. The mafic rocks present in the Juderina Formation are largely ignored in descriptions of Yerrida Basin magmatism, and results indicate that they may be far more substantial than once thought. Sulfur isotopic data indicate no Archean signature to these mafic rocks, a somewhat surprising result given the basement to the basin is the Archean Yilgarn Craton. We propose the source of mafic rocks is vents located to the north along the Goodin Fault or under the Bryah sub-basin and Padbury Basin. The conclusion is that the formation of the Yerrida Basin involves a geodynamic history more complex than previously thought. This result highlights the value in geophysics and geochemistry in revealing the complexity of the earlier geodynamic evolution of the basin that may be indiscernible from surface geology but may have high importance for the tectonic development of the region and its mineral resources.

中文翻译：

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卧底测绘：元古代盆地的综合地球科学解释和3D建模

重力和3D建模与地球化学分析相结合，检查了西澳大利亚中部贫瘠暴露的古元古生代耶里达盆地内部和下方的地下。了解区域的结构非常重要，因为可以揭示表明过去的地球动力学过程和构造活动的关键特征。但是，在稳定的沉积后构造环境中，只有较年轻的沉积单元才容易被广泛暴露，从而无法直接观察基底和侵入性岩石。地球物理成像和建模可以揭示地下区域的结构。在这里介绍的情况下，盆地周围的高密度异常不能与当前的地质知识相吻合。重力异常可以推断出大量的埋藏的高密度材料，这是地表地质无法指示的。镁铁质岩石是盆地大裂谷期间侵入和挤出的，是造成高强度重力异常的一种可能原因。这些解释性的镁铁质岩石最简单，最合理的地层学归因于穆鲁格古群内的基拉拉组。但是，地球化学表明，基拉拉组并不是该地区镁铁质岩石的唯一寄主。在约里达盆地岩浆作用的描述中，Juderina组中存在的镁铁质岩石在很大程度上被忽略了，结果表明它们可能比以前想象的要坚固得多。硫同位素数据表明这些镁铁质岩石没有太古宙特征，考虑到该盆地的地下室是太古宙伊尔加恩·克拉顿，结果有些令人惊讶。我们认为，镁铁质岩石的来源是沿着古丁断裂带位于北面或布赖亚次盆地和帕德伯里盆地下方的喷口。结论是，耶里达盆地的形成涉及地球动力学历史，其历史比以前认为的要复杂。该结果突出了地球物理和地球化学的价值，它揭示了盆地早期地球动力学演化的复杂性，这可能从地表地质学中无法区分，但对于该地区的构造发展及其矿产资源可能具有高度重要性。