Инд. авторы:	Sokol A.G., Kruk A.N.
Заглавие:	Conditions of kimberlite magma generation: experimental constraints
Библ. ссылка:	Sokol A.G., Kruk A.N. Conditions of kimberlite magma generation: experimental constraints // Russian Geology and Geophysics. - 2015. - Vol.56. - Iss. 1-2. - P.245-259. - ISSN 1068-7971. - EISSN 1878-030X.
Внешние системы:	DOI: 10.1016/j.rgg.2015.01.018; РИНЦ: 24019172; SCOPUS: 2-s2.0-84925326729; WoS: 000351312200018;
Реферат:	eng: Melting and multiple saturation experiments with systems simulating primary kimberlite magma compositions at 5.5-6.5 GPa provide constraints on magma generation conditions. The liquidus of model kimberlitic systems exceeds the hottest temperatures of lithospheric mantle (1400 degrees C) but is 150-200 degrees C lower in systems with lower CO2/(CO2 + H2O) ratios. The high melting points require additional heat sources for the generation of kimberlite magmas. Multiple saturation of experimental melts and the stability of individual near-liquidus phases depend on both major-element contents and XCO2 (as the CO2/(CO2 + H2O) molar ratio) in the starting composition. Generally, olivine-bearing assemblages are stable at XCO2 < 0.5, while an increase in MgO/CaO from 1.8 to > 4.0 leads to progressive changes in the equilibrium assemblages: Ol + Grt + Cpx -> Ol + Grt + Opx + Cpx -> Ol + Grt + Opx. The results of geochemical reconstructions and multiple saturation experiments indicate partial or complete wehrlitization of the kimberlitic source regions. Most of primary magmas with XCO2 < 0.5 may have been derived from carbonated garnet lherzolite. Some highly calcic (MgO/CaO < 2) magmas with XCO2 < 0.5 likely originated from carbonated garnet wehrlite. A probable scenario is that melts and/or fluids repeatedly metasomatized and oxidized the protolith (caused its carbonation and phlogopitization) and thus provided conditions for buffering CO2 and H2O fugacities in the forming kimberlitic magma, at least early in the melting history. During later magma generation, water was, likely, extracted from nominally anhydrous minerals having hydrated (OH) defects in the structure. (C) 2015, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.
Ключевые слова:	SOUTH-AFRICA; DIAMOND FORMATION; OXYGEN FUGACITY; O-H FLUID; GROUP-II KIMBERLITES; H2O STORAGE CAPACITY; CARBONATE-SILICATE MELTS; SUBSOLIDUS PHASE-RELATIONS; UDACHNAYA KIMBERLITE; nominally anhydrous minerals; alkali-rich carbonatite; magma; metasomatism; kimberlite; mantle; experiment; CONTINENTAL LITHOSPHERIC MANTLE;
Издано:	2015
Физ. характеристика:	с.245-259