Elucidating Eoarchean geodynamic processes by multiple sulfur isotopes

太古宙地球动力学过程的样式以及早期大陆地壳形成的地球动力学背景是目前争论较多的问题。基于格陵兰岛> - 3.7 Ga Isua上地壳带及其邻近地区的一套特征良好的太古代样品，我们将研究太古宙早期地壳再循环过程的运作方式。利用太古宙洋壳、地幔橄榄岩和陆壳的大块岩石和原位多硫同位素组成，追踪了与海-气系统相互作用的物质进入地幔并通过熔融过程进入早期陆壳的再循环过程。通过岩石体和硫化物原位硫同位素组成以及岩石学观测，我们验证了质量无关分馏硫（MIF-S）是否在热液蚀变的海洋地壳中掺入，然后转移到地幔中，随后掺入可能来自加厚的原弧地壳的早期大陆地壳中。因此，我们对太古宙早期岩浆和热液硫循环进行了限制，并研究了与当今俯冲作用相当的地壳再循环过程是否存在。

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.