In-situ characterization of the trace element signatures, with special emphasize to the REE pattern, of Ca-rich mineral and fluid inclusions in diamonds from a super-deep source.

对超深层钻石中富钙矿物和流体包裹体的微量元素特征进行原位表征，特别强调稀土元素模式。

• 批准号: 427321448
• 负责人: Professor Dr. Frank Erich Brenker
• 金额: --
• 依托单位: Department of Earth and Atmospheric Sciences
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/427321448?language=en
• 关键词: situ; characterization; trace; element; signatures

Trace element pattern, including the relative abundance of rare earth elements (REE), are an important tool to decipher the origin and geological history of minerals and rocks. Whereas these signatures and related processes are quite well known for crustal materials and the lithospheric upper mantle, direct data on the deeper Earth are still scarce.Studies of REE of inclusions in diamonds with a suggested super deep origin (asthenospheric upper mantle, transition zone and lower mantle) demonstrate that CaSiO3-perovskite might be the main host of these trace elements within the deep Earth. For most rock chemistries, it is experimentally demonstrated that a CaSiO3-Phase will only exists at pressures related to depths of the lower transition zone and the lower mantle of the Earth. However, it was already shown that at least some of these CaSiO3-inclusions found in super deep diamonds originate in the upper mantle most likely from carbonatitic melts.In this proposal we plan to apply a variety of non-destructive “in-situ” techniques, with special emphasize to novel advanced Synchrotron X-ray beam techniques developed or improved by our group. The main task will be to determine the REE and trace element inventory of a subset of carbonaceous and therefore potentially REE-rich mineral and fluid inclusions in diamonds with a suggested super deep origin. The goal will be to characterize and compare different subsets with various suggested depths and processes of origin. These include inclusions suites with likely lower mantle (CaSiO3+MgSiO3+-MgO), transition zone (CaSiO3+Ringwoodite) or upper mantle (CaSiO3+Ca2SiO4) origin, as well as CaSiO3-CaTiO3 intergrowths, Ca-carbonates, Ca-phosphates and related trapped REE-rich fluids.In contrast to any effort before, based on our new technical developments at DESY (Hamburg) and the ESRF (Grenoble), we are now able to quantitatively determine all REE with a spatial resolution of well below a micron, of inclusions still trapped within the diamond host. This enables to measure very tiny (below 1 micron), very fragile (like carbonates) or very complex inclusions and attached fluid films. This type of measurement is possible by the use of a novel plate detector technology, which enables fast and simultaneous wavelength dispersive X-ray fluorescence analyses of all REE at high spatial resolution (~ 100nm) and low detection limits (< 1ppm). As REE and trace element patterns are crucial to decipher the geological history of minerals and rocks it might help to constrain their origin and source region within the heterogeneous mantle.

微量元素模式，包括稀土元素的相对丰度，是解释矿物和岩石成因和地质历史的重要工具。然而，这些签名和相关的过程是相当有名的地壳物质和岩石圈上地幔，直接的数据在地球深部仍然是稀缺的，在超深起源（软流圈上地幔，过渡带和下地幔）的金刚石包裹体的稀土元素的研究表明，钙钛矿可能是这些微量元素在地球深部的主要主机。对于大多数岩石化学，实验证明，CaSiO 3相只存在于与地球下过渡带和下地幔深度相关的压力下。然而，它已经表明，这些超深金刚石中发现的CaSiO 3-夹杂物中至少有一些起源于上地幔最有可能从碳酸盐melt.In本提案中，我们计划应用各种非破坏性的“原位”技术，特别强调新的先进的同步辐射X射线束技术开发或改进我们的小组。主要任务将是确定一个子集的碳质，因此可能稀土丰富的矿物和流体包裹体的钻石与建议超深起源的稀土元素和微量元素的库存。其目标将是描述和比较具有各种建议深度和起源过程的不同子集。这些包体可能含有下地幔（CaSiO 3 + MgSiO 3 +-MgO），过渡区（CaSiO 3 +Ringwoodite）或上地幔（CaSiO 3 + Ca 2SiO 4）成因，以及CaSiO 3-CaTiO 3共生体、Ca-碳酸盐、Ca-磷酸盐和相关捕集的富稀土流体。（格勒诺布尔），我们现在能够定量确定所有稀土元素的空间分辨率远低于一微米，夹杂物仍然被困在钻石主机。这使得能够测量非常微小（小于1微米），非常脆弱（如碳酸盐）或非常复杂的夹杂物和附着的流体膜。这种类型的测量是可能的，通过使用一种新的板检测器技术，使快速和同时波长色散X射线荧光分析的所有稀土元素在高空间分辨率（~ 100 nm）和低检测限（<1 ppm）。由于稀土元素和微量元素模式对解释矿物和岩石的地质历史至关重要，这可能有助于将它们的起源和源区限制在非均匀地幔内。