The mineralogy, chemical composition, and physical properties of cratonic mantle eclogites with oceanic crustal protoliths can be modified by secondary processes involving interaction with fluids and melts, generated in various slab lithologies upon subduction (auto‐metasomatism) or mantle metasomatism after emplacement into the cratonic lithosphere. Here we combine new and published data to isolate these signatures and evaluate their effects on the chemical and physical properties of eclogite. Mantle metasomatism involving kimberlite‐like, ultramafic carbonated melts (UM carbonated melts) is ubiquitous though not pervasive, and affected between ~20% and 40% of the eclogite population at the various localities investigated here, predominantly at ~60–150 km depth, overlapping cratonic midlithospheric seismic discontinuities. Its hallmarks include lower jadeite component in clinopyroxene and grossular component in garnet, an increase in bulk‐rock MgO ± SiO₂, and decrease in FeO and Al₂O₃ contents, and LREE‐enrichment accompanied by higher Sr, Pb, Th, U, and in part Zr and Nb, as well as lower Li, Cu ± Zn. This is mediated by addition of a high‐temperature pyroxene from a UM carbonated melt, followed by redistribution of this component into garnet and clinopyroxene. As clinopyroxene‐garnet trace‐element distribution coefficients increase with decreasing garnet grossular component, clinopyroxene is the main carrier of the metasomatic signatures. UM carbonated melt‐metasomatism at >130–150 km has destroyed the diamond inventory at some localities. These mineralogical and chemical changes contribute to low densities, with implications for eclogite gravitational stability, but negligible changes in shear‐wave velocities, and, if accompanied by H₂O‐enrichment, will enhance electrical conductivities compared to unenriched eclogites.

中文翻译：

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地幔榴辉岩中的超镁铁质碳酸盐融解和自变质作用：成分效应和地球物理后果

具有地壳原生质的克拉通地幔榴辉岩的矿物学，化学组成和物理性质可以通过涉及与流体和熔体相互作用的次级过程进行修改，这些过程包括俯冲（自变质作用）或放置于克拉通后的地幔交代作用与各种平板岩性产生。岩石圈。在这里，我们结合新的和已发布的数据来隔离这些特征，并评估它们对榴辉石的化学和物理性质的影响。涉及金伯利岩状，超镁铁质碳酸盐熔体（UM碳酸盐熔体）的地幔交代作用普遍存在，尽管并不普遍，并且在这里调查的各个地方影响着约20％至40％的榴辉岩人口，主要是在约60-150 km的深度，重叠的克拉通中石圈中部地震不连续性。₂，FeO和Al ₂ O _3减少含量，LREE富集伴随着更高的Sr，Pb，Th，U，部分Zr和Nb以及更低的Li，Cu±Zn。这是通过从UM碳酸盐熔体中添加高温辉石，然后将该成分重新分布到石榴石和斜环茂铁中而介导的。随着斜柏基-石榴石微量元素的分布系数随石榴石总成分的减少而增加，斜柏基是交代签名的主要载体。UM在大于130-150 km的碳酸盐熔融成岩作用破坏了某些地区的钻石库存。这些矿物和化学变化导致密度低，影响榴辉岩的重力稳定性，但剪切波速的变化可忽略不计，如果伴有H ₂与未浓缩的榴辉岩相比，O浓缩会增强电导率。