Chloride-carbonate nodules in kimberlites from the Udachnaya pipe: Alternative approach to the evolution of kimberlite magmas

摘要: Group-I kimberlites are the crystallization products of low-degree partial melts derived from convective mantle [1, 2]. Since main economic source diamonds, evolution primary kimberlite is great importance for deciphering compositions, melting conditions, and diamond genesis. Most consist a brecciated mixture olivine phenocrysts xenogenic crustal material embedded in fine- or coarse-grained groundmass, which dominated by serpentine, calcite, and, occasionally, dolomite [3-5]. Thus, evolutionary trend magmas controlled Mg silicates (high contents MgO SiO2) carbonates CaO CO2). However, this can be intensely affected interactions during ascent, assimilation xenoliths, syn- postmagmatic alteration most rocks. Almost all studied around world, even aphanitic [6, 7] "uncontaminated" "fresh" ones, were variably these processes [7-10]. In studying kimberlites, special attention was given to one aspect conditions: entrapment country rocks interaction with them [3, 11]. Nodules (peridotites, eclogites, metamorphic sedimentary rocks, as well diamondiferous rocks) usually used estimate physicochemical structural conditions subcontinental lithosphere, properties magma, diamonds. It convenient study Udachnaya pipe Yakutia because large number, diversity, remarkable freshness its nodules [11, 12]. Our focused on new (carbonate-chloride) type recently found at deep levels (>350 km) open-pit mine Udachnaya-Vostochnaya pipes. Host also unique chemical mineral composition. The groundmass predominantly olivine-carbonate-chloride composition shows almost no evidence replacement [13, 14]. presence such unaltered seems not coincidental provides insight into magmas.