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

用高亲铁元素和锇同位素追踪岩石圈的形成和演化

• 批准号: 200189580
• 负责人: Dr. Sonja Aulbach
• 金额: --
• 依托单位: Abteilung Petrologie und Geochemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2011
• 资助国家: 德国
• 起止时间: 2010-12-31 至 2012-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/200189580?language=en
• 关键词: Tracing; Lithosphere; formation; evolution; highly

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.

高亲铁元素 (HSE) 与 Os 同位素的结合表明它们是地幔形成和次生叠印（地幔交代作用）的强大示踪剂。正是由于20世纪90年代初精确的铼锇地质年代学的出现，大陆地壳和下伏岩石圈地幔的共同演化首次被广泛证明。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。尽管进行了数十年的深入研究，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尚未确定。这是法兰克福大学正在进行的一项研究工作，Lu-Hf 同位素系统越来越多地被用作获得地壳和地幔样本的精确等时线年龄的有前景的工具。然而，这种方法仅限于地幔部分，其中熔融交代作用可以被证明是最小的。由于锇在地幔中的相容性以及在流体和熔体中的丰度低得多，锇同位素能够独特地“风化”二次叠印。此类叠印的严重性和影响可以通过 HSE 丰度模式进行监控。我正在申请资金，利用已有的设施和仪器将 Os 同位素和 HSE 丰度的测量带到法兰克福大学。一旦开始实施，我将把这项技术应用到来自纳米比亚的一小套橄榄岩捕虏体上，这些捕虏体的年龄迄今为止还没有得到很好的限制，也是正在进行的地幔耦合项目的主题。