The Proterozoic Bushveld Catastrophe, South Africa

本研究的重点是(1)Rooiberg Felsite的独特化学和淬火结构，它是巨大的Bushveld复合体中最早的成员。(2) Rooiberg Felsite下强应变石英沉积物的渐进再结晶（t1200℃）成晶针网；(3)Bushveld-Vredefort体系的结构与演化。目前的数据表明，一颗解体的小行星或彗星的多重撞击导致了布什维尔德-弗里德堡灾难；内源性替代方案是可能的，但涉及新的和未经验证的过程。弗里德堡岩石以平面特征的形式提供了冲击的证据，包括石英、破碎锥、伪铜绿石、铜绿石和辉石。在Bushveld复合体中，相等构造位置的岩石没有暴露；在其他地方，再结晶和初期熔融破坏了早期的结构和矿物。尽管如此，将继续在有利的地方寻找冲击特征，开展其他实地工作，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长期以来对世界上最大的层状基性复合体及其非常广泛的矿床起源的看法。

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.