A New Approach to the Archean Sulfur Cycle from Marine Carbonates

从海洋碳酸盐中研究太古代硫循环的新方法Jess Adkins，Woodward Fischer摘要大气中氧气从原本减少的行星表面上升是地球历史上的中心问题。人们普遍认为，地球海洋和大气的氧化是以突然的步骤发生的。太古宙-元古界的大氧合事件是这些深部时间跃变中研究较好的事件之一，主要是通过稳定硫同位素的质量无关分馏(MIF)。然而，大多数证据来自于硫的还原形式，主要是在MIF信号中富含黄铁矿。目前的理解假设，互补光MIF信号此时驻留在海洋硫酸盐中，这是碳酸盐中的一种痕量相，到目前为止还无法分析到。PIS将使用一种新的MC-ICPMS方法，将目前太古宙碳酸盐中硫酸盐的检测下限降低三个数量级以上。通过对特定结构的微观钻探来揭示晚太古宙岩石中硫酸盐和硫化物相的同时演化，将被用来更好地理解早期地球是如何从缺氧的大气过渡到具有大量分子氧的大气的。PIS将在南非坎贝兰德平台的野外活动中收集新的露头和钻探岩心样本，并对这些样本进行数百次新的硫同位素测量。他们的目标是在地球历史上的这个关键时刻创造一部海水硫酸盐演化的历史。

A New approach to the Archean sulfur cycle from marine carbonatesBy Jess Adkins, Woodward FischerABSTRACTThe rise of atmospheric oxygen from an originally reduced planet surface is a central problem in Earth history. It is widely believed that the oxygenation of the Earth's oceans and atmosphere occurred in abrupt steps. The Great Oxygenation Event at the Archean-Proterozoic boundary is one of the better studied of these deep-time jumps, chiefly through the mass independent fractionation (MIF) of the stable sulfur isotopes. However, most of this evidence comes from the reduced forms of sulfur, chiefly pyrite being enriched in the MIF signal. The current understanding assumes that the complementary light MIF signal resides in oceanic sulfate at this time, a trace phase in carbonates that has been analytically inaccessible until now. PIs will use a new MC-ICP-MS method that lowers the current detection limit for sulfate in Archean carbonates by over three orders of magnitude. Micro-drilling of specific textures to unravel the simultaneous evolution of the sulfate and sulfide phases in Late Archean rocks will be used to better understand how it is that the early earth transitioned from an anoxic atmosphere to one with substantial amounts of molecular oxygen. PIs will collect new outcrop and drill core samples during a field campaign to the Campbellrand Platform in South Africa and make hundreds of new sulfur isotope measurements on these samples. Their goal is to create a history of seawater sulfate evolution during this key moment in earth history.