To provide new insights into the origin of garnet megacrysts and evolution of kimberlite melts, we studied in detail the polymineralic and monomineralic inclusions and their host garnets from the Grib kimberlite (Arkhangelsk diamond province, Russia). Low-Cr and high-Cr garnet megacrysts and eclogitic garnets contain abundant polymineralic and rare monomineralic inclusions. Monomineralic inclusions presented by clinopyroxene, ilmenite, olivine replaced by serpentine, were found exclusively within the low-Cr megacrysts. The composition of clinopyroxene exhibits geochemical equilibrium with the host garnet, indicating its primary origin during the formation of the megacryst assemblage. The low-Cr garnet–clinopyroxene mineral assemblage formed as a result of high-temperature, melt-associated mantle metasomatism by failed kimberlite within the lithospheric mantle (T = 1150 °C and P = 5.5 GPa). Polymineralic inclusions are characterised by a silicate or silicate-sulphate matrix. The central part of the silicate inclusions is filled by serpentine and contains ilmenite, spinel, perovskite, calcite and apatite. At the contact with host garnets, phlogopite, spinel and amphibole occur as reaction minerals. Composition of spinel and other minerals within inclusions with silicate matrix suggests that kimberlite melt was trapped at mantle pressures. Inclusions with silicate matrix were found in all garnets. The matrix of silicate-sulphate inclusions consists of silicate cryptocrystalline phases and sulphate minerals (celestine–barite) and contains calcite grains. The inclusions are distributed in some low-Cr garnet megacrysts and eclogitic garnet. The silicate-sulphate inclusions were crystallised from the late-stage kimberlite melt. Diverse reaction textures are evidences of disequilibrium between the host crystals and polymineralic inclusions and indicate that garnet and the hosted inclusions reacted with the ascending kimberlite melt. The silicate-sulphate inclusions with a thin rim of epidote within eclogitic garnets indicate that a kimberlite melt invaded the garnet and induced partial melting. The studied inclusions allow us to propose three stages of the Grib kimberlite evolution: 1) generation of garnet megacrysts and primary inclusions due to melt metasomatism, 2) reaction of the high-Ti kimberlite melt with garnet megacrysts (including their dissolution) and 3) alteration of the inclusions in garnet after kimberlite ascent.

中文翻译：

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从 Grib 金伯利岩（俄罗斯阿尔汉格尔斯克地区）石榴石巨晶中的包裹体推断的金伯利岩熔体的多阶段演化

为了对石榴石巨晶的起源和金伯利岩熔体的演化提供新的见解，我们详细研究了来自 Grib 金伯利岩（俄罗斯阿尔汉格尔斯克钻石省）的多矿物和单矿物包裹体及其寄主石榴石。低铬和高铬石榴石巨晶和榴辉岩石榴石含有丰富的多矿物包裹体和稀有的单矿物包裹体。由斜辉石、钛铁矿、被蛇纹石取代的橄榄石呈现的单矿物包裹体仅在低铬巨晶中发现。单斜辉石的组成与寄主石榴石表现出地球化学平衡，表明其主要来源是在巨晶组合形成期间。高温下形成的低铬石榴石-斜辉石矿物组合，岩石圈地幔内失败的金伯利岩与熔体相关的地幔交代作用（T = 1150 °C 和 P = 5.5 GPa）。多矿物包裹体的特征在于硅酸盐或硅酸盐-硫酸盐基质。硅酸盐包裹体的中心部分被蛇纹石填充，含有钛铁矿、尖晶石、钙钛矿、方解石和磷灰石。在与寄主石榴石接触时，金云母、尖晶石和角闪石作为反应矿物出现。含有硅酸盐基质的包裹体中的尖晶石和其他矿物的组成表明金伯利岩熔体被困在地幔压力下。在所有石榴石中都发现了具有硅酸盐基质的内含物。硅酸盐-硫酸盐包裹体基质由硅酸盐隐晶相和硫酸盐矿物（天青石-重晶石）组成，并含有方解石颗粒。包裹体分布在一些低Cr石榴石巨晶和榴辉岩中。硅酸盐-硫酸盐包裹体是从后期金伯利岩熔体中结晶出来的。各种反应结构是寄主晶体和多矿物包裹体之间不平衡的证据，表明石榴石和寄宿包裹体与上升的金伯利岩熔体发生了反应。榴辉岩中带有薄绿帘幕边缘的硅酸盐-硫酸盐包裹体表明金伯利岩熔体侵入了石榴石并引起了部分熔融。所研究的包裹体使我们能够提出 Grib 金伯利岩演化的三个阶段：1) 由于熔体交代作用产生石榴石巨晶和初级包裹体，