Diamond formation in Earth's mantle: Role of C-O-H fluid composition and host rock lithology.

地幔中的钻石形成：C-O-H 流体成分和主岩岩性的作用。

• 批准号: 338400084
• 负责人: Dr. Christopher Beyer
• 金额: --
• 依托单位: Bayerisches Forschungsinstitut für Experimentelle Geochemie und Geophysik (BGI)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/338400084?language=en
• 关键词: Diamond; formation; Earth; mantle; Role

The central goal of this study is to identify the mechanisms of diamond formation in sublithospheric environments, which is an important step towards the understanding of Earth s deep carbon cycle. Deciphering the coupling between diamond formation, redox state, and mantle lithologies will aid to improve the understanding of regional differences in diamond inclusions and their association with upwelling and downwelling regimes in Earth s. The very recently discovered strong affinity of diamond inclusions from depth below 300 km to pyroxenites is of peculiar interest. Up to the present, only little attention has been payed to the role of pyroxenites in the formation of diamonds. Hence, this study will focus on the mechanisms that are responsible for the formation of pyroxenites and the syngenetic precipitation of diamonds under conditions of the lowermost upper mantle and Earth s transition zone. This also involves the systematic analysis of C-O-H fluids reacting with oxidized eclogites and derived partial melts. Finally, to understand the striking difference in diamond yields, we will investigate the effect of isochemical decompression and cooling of C-O-H fluids and the capability to isochemically precipitate macroscopic diamonds independent from the host rock s composition. This process would explain high yields of large diamonds in harzburgitic rocks, that otherwise lack the oxygen buffer capacity to crystallize diamonds.

这项研究的核心目的是确定在跨石层环境中钻石形成的机制，这是迈向理解地球深碳循环的重要一步。解释钻石形成，氧化还原状态和地幔岩石学之间的耦合将有助于提高对钻石包裹物的区域差异的理解，以及它们与地球s的上升和下降状态的关联。最近发现，钻石夹杂物从300公里以下到辉石的深度具有很强的亲和力。直到目前，只有很少关注辉石在钻石形成中的作用。因此，这项研究将集中于负责在最低地幔和地球的过渡区域的条件下，导致辉石的形成和钻石的合成沉淀的机制。这还涉及对与氧化的eclogites反应和衍生部分熔体反应的C-O-H流体进行系统的分析。最后，为了了解钻石产量的引人注目的差异，我们将研究C-O-H流体的等化学解压缩和冷却的作用，以及与宿主岩石组成无关的等化沉淀的宏观沉淀的宏观沉淀的能力。这个过程将解释哈尔茨堡岩石中大钻石的高产量，否则缺乏氧气缓冲能力来结晶钻石。