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 (REE) 的相对丰度，是破译矿物和岩石的起源和地质历史的重要工具，尽管这些特征和相关过程对于地壳物质和岩石圈上地幔来说是众所周知的。关于地球深层的直接数据仍然很少。对具有超深起源（软流圈上地幔、过渡带和下地幔）的钻石内含物的稀土元素的研究表明，CaSiO3-钙钛矿可能是对于大多数岩石化学来说，CaSiO3 相仅存在于与下过渡带和下地幔深度相关的压力下。已经表明，在超深钻石中发现的至少一些 CaSiO3 夹杂物起源于上地幔，最有可能来自碳酸岩熔体。在本提案中，我们计划应用各种非破坏性方法“原位”技术，特别强调我们小组开发或改进的新型先进同步加速器 X 射线束技术。主要任务是确定碳质子集的稀土元素和微量元素库存，因此可能富含稀土元素。具有建议的超深层起源的钻石中的矿物和流体包裹体的目标是描述和比较具有各种建议的起源深度和过程的不同子集，其中包括可能具有下地幔的包裹体套件。 (CaSiO3+MgSiO3+-MgO)、过渡带(CaSiO3+Ringwoodite)或上地幔(CaSiO3+Ca2SiO4)成因，以及CaSiO3-CaTiO3共生体、碳酸钙、磷酸钙和相关的富稀土流体。与之前的任何努力相比，基于我们在 DESY（汉堡）和 ESRF（格勒诺布尔）的新技术开发，我们现在能够以远低于 1 微米的空间分辨率定量测定仍困在钻石主体内的所有 REE，这使得能够测量非常微小（低于 1 微米）、非常脆弱（如碳酸盐）或非常复杂的内含物，并且这种类型的测量可以通过使用新型板检测器技术来实现，该技术能够以高空间分辨率（约 100 nm）和低检测限（<由于稀土元素和微量元素模式对于破译矿物和岩石的地质历史至关重要，因此可能有助于限制其在异质地幔内的起源和来源区域。