Re-Os dating of micrometric Os-rich alloys and sulfides in mantle xenoliths from the Slave Craton: implication for craton formation processes and the Early Earth evolution

太古宙的古陆是地球表面保存下来的最古老的大陆，它记录了在地球演化早期塑造我们星球的地质过程。它们的生存部分是由于其化学浮力和机械强度强的地幔根。虽然Kaapvaal、西伯利亚和格陵兰的地幔根被认为是通过俯冲作用由岩石圈堆积形成的，但奴隶地幔根（SC）的形成过程仍有争议。该项目旨在获得SC地幔根的确切年龄限制，确定其P-T-t图像，以限制其形成过程，并了解早期地球动力学和热历史。这些目标将通过耦合“最先进的”Re-Os定年和Os主矿物中的高亲铁元素（HSE）分析来实现（即合金、硫化物）。在微钻后，将利用超灵敏电感耦合等离子体质谱（ICP-MS）获得现场Re-Os和HSE数据，使用高性能HP消解装置（Anton帕尔HPA-S）进行化学消解，以有效侵蚀耐火合金和HT硫化物以及超低空白化学;以及通过超灵敏激光烧蚀ICP-MS。

Archean cratons, the oldest pieces of continents preserved at the Earth’s surface, recorded the geological processes that shaped our planet early during its evolution. Their survival is partly due to their chemically buoyant and mechanically strong mantle roots. While mantle roots of the Kaapvaal, Siberia and Greenland cratons were suggested to have formed by lithospheric stacking via subduction, the formation process of the mantle root of the Slave Craton (SC) is still debated. This project aims to obtain firm age constraints on the SC mantle root, determine its P-T-t picture in order to constrain its formation process(es) and understand the early Earth dynamics and thermal history. These objectives will be achieved by coupling “state of the art” Re-Os dating and highly siderophile element (HSE) analyses in Os-host minerals (i.e. alloys, sulfides) in 4 mantle xenolith suites from the SC. In-situ Re-Os and HSE data will be acquired by ultra-sensitive inductively coupled plasma mass spectrometry (ICP-MS) after micro-drilling, chemical digestion using a high-performance HP digestion device (Anton Paar HPA-S) for efficient attacks of refractory alloys and HT sulfides and ultra-low blank chemistry; and by ultra-sensitive laser-ablation ICP-MS.