Drilling Earth's early surface environments: Moodies Group, Barberton Greenstone Belt, South Africa

通过在绿岩带的火山和沉积单元进行科学钻探连续取芯，由于可以获得新的岩性和结构，有可能获得对地球最早期地表环境的新认识。这一提案已提交给ESF资助机构（Arndt等人）。并已于2008年1月提交给国际地质对比计划。目前的建议旨在通过确定潜在的钻探地点和为巴伯顿绿岩带（约1000米）的穆迪群准备预测性地层剖面来促进这一目标。3.22-73.20 Ga），是世界上最古老的保存完好的石英质和浅水沉积序列。虽然穆迪岩群的总体变质程度较低，但其沉积、深埋、白垩纪剥露和风化后的多个区域蚀变事件影响了其深部和近地表的成分和结构。因此，只有没有表面效应的样品才有助于区分原生、成岩和风化效应。拟进行的钻探将澄清的科学问题包括确定可确定年代的落灰凝灰岩、对风化敏感的岩性的岩相学和地球化学特征以及通过核实穆迪集团顶部附近的渐进不整合面来澄清穆迪集团的构造背景。这些数据将承担重建太古代（和预测外星）的表面条件和过程，如化学风化的强度，细菌垫的作用，和早期成岩作用。

Continuous coring by scientific drilling in volcanic and sedimentary units of greenstone belts has the potential to obtain new insights in Earth's earliest surface environments due to access to fresh lithologies and textures. Such a proposal has been submitted to ESF funding agencies (Arndt et al.) and has been submitted to IGCP in January, 2008. The current proposal aims to contribute to that objective by identifying potential drill sites and prepare predictive stratigraphic profiles for the Moodies Group of the Barberton Greenstone Belt (ca. 3.22-73.20 Ga), the world's oldest well-preserved quartzose and shallow-water sedimentary sequence. Although the overall degree of metamorphism in the Moodies Group is low, multiple regional alteration events following its deposition, deep burial, Cretaceous exhumation and weathering have affected its deep and near-surface composition and texture. Thus, only samples free from surface effects will help to distinguish between primary, diagenetic and weathering effects. Scientific issues to be clarified by the proposed drilling include the identification of datable ash-fall tuffs, the petrographic and geochemical characterization of weathering-sensitive lithologies and the clarification of the tectonic setting of the Moodies Group by verifying a progressive unconformity near its top. These data will bear on the reconstruction of Archean (and prediction of extraterrestrial) surface conditions and processes such as the intensity of chemical weathering, the role of bacterial mats, and early diagenesis.