Tracing Lithosphere formation and evolution with highly siderophile elements and Os isotopes

高亲铁元素（HSE）与锇同位素的结合显示了它们自身作为地幔形成和二次叠加（地幔交代）的强有力的示踪剂。90年代初精确Re-Os年代学的出现，首次广泛地揭示了大陆地壳与岩石圈地幔的共同演化。大陆的形成和演化是地球科学最基本的方面之一，与生命演化、矿石成因、地球物质循环等问题密切相关。尽管经过了几十年的深入研究，但关于最早的大陆核如何形成、壳幔耦合何时发生以及大陆岩石圈如何演化的细节仍有待确定。这是法兰克福大学正在进行的一项研究工作，该大学越来越多地使用Lu-Hf同位素系统作为获得地壳和地幔样品精确等时线年龄的有前途的工具。然而，这种方法仅限于地幔部分熔体交代作用可以被证明是最小的。由于锇在地幔中的相容性和在流体和熔体中的低丰度，锇同位素可以独特地“风化”二次叠印。这种叠印的严重性和影响可以通过HSE丰度模式来监测。我正在申请资金，利用现有的设施和仪器，将Os同位素和HSE丰度的测量带到法兰克福大学。一旦建立，我将适用于一个小套橄榄岩捕虏体从纳米比亚的年龄是到目前为止不好的约束，这是一个正在进行的项目壳幔耦合的主题。

Highly siderophile elements (HSE) in combination with Os isotopes have revealed themselves as powerful tracers of mantle formation and secondary overprint (mantle metasomatism). It was owing to the advent of precise Re-Os geochronology in the early 90ies that the co-evolution of continental crust and underlying lithospheric mantle was first broadly demonstrated. The formation and evolution of continents is one of the most fundamental aspects of Earth Sciences that is closely related to questions of the evolution of life, ore genesis, the Earth’s material cycle, among many others. Despite decades of intensive research, the details of how the earliest continental nuclei formed, when crust-mantle coupling occurs and how the continental lithosphere evolves have yet to be determined. This is an ongoing research effort at Frankfurt University where the Lu-Hf isotope system is increasingly used as a promising tool to obtain precise isochron ages on crust and mantle samples. However, this approach is restricted to mantle portions where melt-metasomatism can be shown to be minimal. Because of the compatibility of Os in the mantle and much lower abundances in fluids and melts, Os isotopes can be singularly able to “weather” secondary overprints. The severity and the effects of such overprints can be monitored by HSE abundance patterns. I am applying for funds to bring the measurement of Os isotopes and HSE abundances to Frankfurt University, using facilities and instrumentation already available. Once instituted, I will apply the technique to a small suite of peridotite xenoliths from Namibia whose age is so far ill-constrained and which are the subject of an ongoing project on crust mantle coupling.