Reduced amphibolite facies conditions in the Precambrian continental crust of the Siberian craton recorded by mafic granulite xenoliths from the Udachnaya kimberlite pipe, Yakutia

Perchuk, A.L.; Sapegina, A.V.; Safonov, O.G.; Yapaskurt, V.O.; Shatsky, V.S.; Malkovets, V.G.

Авторы: Perchuk A.L., Sapegina A.V., Safonov O.G., Yapaskurt V.O., Shatsky V.S., Malkovets V.G.
Журнал: Precambrian Research
Том: 357
Год издания: 2021
Издательство: Elsevier BV
Местоположение издательства: Netherlands
Номер статьи: 106122
DOI: 10.1016/j.precamres.2021.106122
Аннотация: It is widely accepted that granulite xenoliths from kimberlites provide a record of granulite facies metamorphismat the basement of cratons worldwide. However, application of the phase equilibria modeling for seven representativesamples of mafic granulites from xenoliths of the Udachnaya kimberlite pipe, Yakutia, revealed that agranulitic garnet + clinopyroxene + plagioclase ± orthopyroxene ± amphibole ± scapolite mineral assemblagewas likely formed in the middle crust under amphibolite facies conditions (600–650 ◦C and 0.8–1.0 GPa) in adeficiency of fluid. Clinopyroxene in the rocks is characterized by elevated aegirine content (up to 10 mol.%)both in the earlier magmatic cores and in the later metamorphic rim zones of the grains. Nevertheless, the phaseequilibrium modeling for all samples indicates surprisingly reduced conditions, i.e. oxygen fugacity 1.6–3.3 logunits below the FMQ (Fayalite-Magnetite-Quartz) buffer. In contrast, the coexistence of Fe-Ti oxides indicatestemperatures of 850–990 ◦C and oxygen fugacity about lg(FMQ) ± 0.5, conditions which correspond to earlierstages of rock evolution. Reduction of oxygen fugacity during cooling is discussed in the context of the evolutionof a complex fluid. The reconstructed P-T conditions for the final equilibration in the mafic granulites indicatethat temperatures were ~250 ◦C higher than those extrapolated from the continental conductive geotherm of35–40 μW/m2 deduced from peridotite xenoliths of the Udachnaya pipe. Although the granulites resided in thecrust for a period for at least 1.4 Ga, they did not re-equilibrate to the temperatures of the geotherm, likely due tothe blocking of mineral reactions under relatively low temperatures and fluid-deficient conditions
Добавил в систему: Перчук Алексей Леонидович

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Reduced amphibolite facies conditions in the Precambrian continental crust of the Siberian craton recorded by mafic granulite xenoliths from the Udachnaya kimberlite pipe, Yakutiaстатья

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