The Proterozoic Bushveld Catastrophe, South Africa

这项研究的重点是(1)巨大的布什维尔德杂岩中最早的成员Rooiberg Felite独特的化学和淬火结构。(2)Rooiberg辉石下强烈应变的石英岩沉积物的逐步重结晶(T1,200oC)，形成鳞石英针状网络；(3)Bushveld-Vredefort体系的结构和演化。目前的数据表明，瓦解的小行星或彗星的多次撞击导致了布什维尔德-弗雷德福德灾难；内生替代方案是可能的，但涉及新的和未经证实的过程。Vredefort岩石在石英、破碎锥、假玄武岩、柯石英和辉石中以平面特征的形式提供了冲击波的证据。在布什维尔德杂岩中，处于相同构造位置的岩石不会暴露；在其他地方，重结晶和早期熔融破坏了早期的结构和矿物。尽管如此，仍将继续在有利地点寻找地震特征，开展其他野外工作，并进行详细的岩石学和地球化学研究。这项研究有可能彻底改变人们长期以来对世界上最大的层状镁铁质杂岩及其非常广泛的矿藏的起源的看法。

This research is focused on (1) unique chemistry and quench textures of Rooiberg Felsite, the earliest member of the giant Bushveld Complex. (2) progressive recrystallization (T1,200oC) of intensely strained quartzose sediments below the Rooiberg Felsite into a network of tridymite needles and (3) structure and evolution of the Bushveld-Vredefort system. Present data suggest that multiple impacts of a disintegrating asteroid or comet caused the Bushveld-Vredefort catastrophe; endogenic alternatives are possible but involve novel and unverified processes. Vredefort rocks furnish evidence for shock in the form of planar features in quartz, shatter cones, pseudotachylite, coesite and stishovite. Rocks in equivalent structural positions are not exposed in the Bushveld Complex; elsewhere, recrystallization and incipient melting have destroyed earlier textures and minerals. Nevertheless, a search for shock features will continue in favorable localities, other field work will be carried out, and detailed petrologic and geochemical studies will be made. This study has the potential to completely change long standing ideas as to the origin of the world's largest layered mafic complex and its very extensive ore deposits.