Sublithospheric diamonds and the inclusions they may carry crystallize in the asthenosphere, transition zone, or uppermost lower mantle (from 300 to ∼800 km), and are the deepest minerals so far recognized to form by plate tectonics. These diamonds are distinctive in their deformation features, low nitrogen content, and inclusions of these major mantle minerals: majoritic garnet, clinopyroxene, ringwoodite, CaSi perovskite, ferropericlase, and bridgmanite or their retrograde equivalents. The stable isotopic compositions of elements within these diamonds (δ11B, δ13C, δ15N) and their inclusions (δ18O, δ56Fe) are typically well outside normal mantle ranges, showing that these elements were either organic (C) or modified by seawater alteration (B, O, Fe) at relatively low temperatures. Metamorphic minerals in cold slabs are effective hosts that transport C as CO3 and H as H2O, OH, or CH4 below the island arc and mantle wedge. Warming of the slab generates carbonatitic melts, supercritical aqueous fluids, or metallic liquids, forming three types of sublithospheric diamonds. Diamond crystallization occurs by movement and reduction of mobile fluids as they pass through host mantle via fractures—a process that creates chemical heterogeneity and may promote deep focus earthquakes. Geobarometry of majoritic garnet inclusions and diamond ages suggest upward transport, perhaps to the base of mantle lithosphere. From there, diamonds are carried to Earth's surface by eruptions of kimberlite magma. Mineral assemblages in sublithospheric diamonds directly trace Earth's deep volatile cycle, demonstrating how the hydrosphere of a rocky planet can connect to its solid interior. ▪Sublithospheric diamonds from the deep upper mantle, transition zone, and lower mantle host Earth's deepest obtainable mineral samples.▪Low-temperature seawater alteration of the ocean floor captures organic and inorganic carbon at the surface eventually to become some of the most precious gem diamonds.▪Subduction transports fluids in metamorphic minerals to great depth. Fluids released by slab heating migrate, react with host mantle to induce diamond crystallization, and may trigger earthquakes.▪Sublithospheric diamonds are powerful tracers of subduction—a plate tectonic process that deeply recycles part of Earth's planetary volatile budget.

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岩石圈下钻石：来自地球最深地幔样本的板块构造


岩石圈下钻石及其可能携带的内含物在软流圈、过渡带或最上部下地幔（从 300 公里到 ∼800 公里）结晶，是迄今为止板块构造公认的最深的矿物。这些钻石的独特之处在于其变形特征、低氮含量以及以下主要地幔矿物的内含物：主要石榴石、斜辉石、环木石、CaSi 钙钛矿、铁方长石和布里奇曼石或其逆行等价物。这些金刚石中元素的稳定同位素组成（δ11B、δ13C、δ15N）及其内含物（δ18O、δ56Fe）通常远超出正常的地幔范围，表明这些元素要么是有机元素 （C），要么在相对较低的温度下被海水蚀变 （B、O、Fe） 修饰。冷板中的变质矿物是有效的宿主，可将 C 以 CO3 的形式传输，以 H2O、OH 或 CH4 的形式在岛弧和地幔楔形下方传输。板坯的加热会产生碳酸盐岩熔体、超临界水流体或金属液体，形成三种类型的亚岩石圈金刚石。金刚石结晶是通过流动流体通过裂缝穿过主地幔时的运动和还原而发生的，这一过程会产生化学异质性，并可能促进深聚焦地震。主要石榴石内含物和钻石年龄的地压测量表明向上迁移，可能到地幔岩石圈的底部。从那里，钻石通过金伯利岩岩浆的喷发被带到地球表面。岩石圈下钻石中的矿物组合直接追踪了地球的深度波动循环，展示了岩石行星的水圈如何与其固体内部相连。 ▪来自深上地幔、过渡带和下地幔的岩石圈下钻石拥有地球上最深的可获得矿物样本。▪海底的低温海水蚀变在表面捕获有机和无机碳，最终成为最珍贵的宝石级钻石。▪俯冲作用将变质矿物中的流体输送到很深的地方。板加热释放的流体迁移，与主体地幔反应以诱导钻石结晶，并可能引发地震.▪岩下层钻石是俯冲的强大示踪剂，俯冲是一种板块构造过程，深度回收了地球地球波动预算的一部分。