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Peridotit xenoliths: a key to understanding exceptional depletion and re-enrichment of the lithospheric mantle beneath Greenland

橄榄岩捕虏体：了解格陵兰岛下方岩石圈地幔异常消耗和再富集的关键

基本信息

批准号：
274106255
负责人：
Dr. Axel Gerdes
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：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/274106255?language=en
关键词：
Peridotit xenoliths key understanding exceptional

项目摘要

The Earths different ancient continental cores (cratons) show significant differences in their composition and structure. However, all cratons archive encrypted information on early Earth dynamics and environments that can be decoded by applying a variety of geochemical tools to exposed crustal samples or to lithospheric mantle samples entrained during sporadic magmatism. The cratonic part of Greenland has been a hotspot of scientific investigation since it was discovered that it contains some of the oldest crust on Earth and that the underlying lithosphere has significant diamond potential. We have in hand a newly recovered suite of fresh kimberlite-entrained peridotite xenoliths that range in lithology from dunites to harzburgites and highly metasomatised wehrlites. Using a detailed petrographic and in situ analytical approach for the acquisition of major and trace elements, as well as multiple radiogenic isotope systematics (Sr, Sm-Nd, Lu-Hf, Re-Os) of mineral separates and in situ, we would like to address the following questions that are directly relevant to early terrestrial dynamics: (1) What is the origin of the exceptional depletion of the mantle lithosphere beneath cratonic Greenland and what was the role of vertical (plumes) vs horizontal (subduction) processes during its nascence? (2) Was the formation of the crust and lithospheric mantle in cratonic Greenland coupled or decoupled? (3) What are the nature and timing of re-enrichment of mantle lithosphere and its link to regional tectonothermal events, in particular the formation of low-volume melts, such as diamondiferous kimberlites?

地球不同的古老大陆核(克拉通)在成分和结构上表现出显著的差异。然而，所有克拉通都将有关早期地球动力学和环境的加密信息存档，这些信息可以通过对暴露的地壳样品或在零星岩浆作用期间携带的岩石圈地幔样品应用各种地球化学工具来破译。格陵兰的克拉通部分一直是科学调查的热点，因为它被发现含有地球上一些最古老的地壳，并且其下面的岩石圈具有巨大的钻石潜力。我们手头有一套新发现的新发现的金伯利岩夹带橄榄岩包体，岩性范围从英安岩到方辉橄榄岩和高度交代的重晶岩。采用详细的岩相学和现场分析方法获取主元素和微量元素，以及矿物分离和原地的多种放射性同位素体系(锶、Sm-Nd、Lu-Hf、Re-Os)，我们想要回答以下与早期地球动力学直接相关的问题：(1)格陵兰克拉通之下的地幔岩石圈异常亏损的原因是什么，在其形成过程中垂直(羽流)与水平(俯冲)过程的作用是什么？(2)格陵兰克拉通的地壳和岩石圈地幔的形成是耦合的还是解耦的？(3)地幔岩石圈重新浓缩的性质和时间是什么，它与区域构造热事件，特别是低体积熔体的形成，如含钻石的金伯利岩？