Elucidating Eoarchean geodynamic processes by multiple sulfur isotopes

太古代地球动力学过程的类型以及早期陆壳形成的地球动力学背景是目前备受争议的问题。基于一组来自格陵兰岛> 3.7 Ga Isua表壳带及其邻近地区的具有良好特征的始太古代样品，我们将研究太古代早期地壳循环过程如何运作。我们使用大量的岩石和在现场的多种硫同位素组成的始新世洋壳，地幔橄榄岩和大陆地壳的跟踪再循环的物质，与海洋-大气系统的相互作用，进入地幔和熔融过程进入早期大陆地壳。通过对岩石和硫化物的原位硫同位素组成以及岩相学观察，我们检验了独立于质量的分馏硫（MIF-S）是否在热液蚀变的洋壳中被掺入，然后被转移到地幔中，并随后被掺入可能来自加厚的原弧壳的早期陆壳中。因此，我们放置在太古代早期的岩浆和热液硫循环的限制和调查，如果地壳循环过程相当于今天的俯冲操作。

The style of Archean geodynamic processes as well as the geodynamic setting of early continental crust formation are currently highly debated. Based on a well-characterized set of Eoarchean samples from the > 3.7 Ga Isua Supracrustal Belt and adjacent areas in Greenland, we will investigate how crustal recycling processes operated in the early Archean. We use bulk rock and in situ multiple sulfur isotope compositions of Eoarchean oceanic crust, mantle peridotites and continental crust to trace recycling of material, which interacted with the ocean-atmosphere system, into the mantle and by melting processes into early continental crust. By performing bulk rock and in situ sulfur isotope compositions of sulfides together with petrographic observations, we test if mass-independent fractionated sulfur (MIF-S) was incorporated in hydrothermally altered oceanic crust, then transferred into the mantle and subsequently incorporated in the early continental crust that possibly sourced from thickened proto-arc crust. Thus, we place constraints on the early Archean magmatic and hydrothermal sulfur cycle and investigate, if crustal recycling processes comparable to present-day subduction were operating.