Geochronology of the Gold and Sulfide Mineralization of the Archean Witwatersrand Basin

威特沃特斯兰太古代盆地一直是地球系统争论的中心，争论的范围从太古代大气的氧含量到地幔中的金流量。这些争论的核心问题是硫化物、金和铀矿物是作为沉积成因的碎屑颗粒还是作为热液流体的沉淀物进入盆地的。我们最近的Re-Os测年研究产生了令人信服的等时线，表明约。3.01很老了。这个年龄需要碎屑的起源，因为颗粒比盆地更古老，并且可能在太古代期间支持非常减少-氧气贫乏-的大气。然而，由于研究的样本数量有限，这项工作被认为是有争议的。该奖项将扩大分析范围，以更全面地描述金和硫化物矿化，并回答诸如金提取与卡普瓦尔克拉通固结和地幔金通量之间的关系等问题。更广泛的影响包括研究生教育和与私营部门的国际合作。Placer Dome和Anglogold公司将提供访问，后勤和一些科学支持。

EAR-0308656RuizThe Witwatersrand Archean basin has been at the center of Earth-system debates ranging from the oxygen content of the Archean atmosphere to the flux of gold from the mantle. At the heart of these debates is the question of whether sulfide, gold and uranium minerals were introduced into the basin as detrital grains of sedimentary origin or precipitates from hydrothermal fluids. Our recent Re-Os dating study produced convincing isochrons indicating a ca. 3.01 Ga old age. This age requires a detrital origin since the grains are older than the basin, and may support a very reduced--oxygen poor--atmosphere during the Archean. The work, however, is considered controversial due to the limited number of samples studied. This award will expand the set of analyses to more completely characterize gold and sulfide mineralization and answer questions such as the relationship of gold extraction to consolidation of the Kaapvaal craton and the mantle gold flux. Broader impacts include education of a graduate student and international collaboration with the private sector. Placer Dome and Anglogold corporations will provide access, logistic, and some scientific support.