Mineralogical and thermobarogeochemical studies allowed us to reveal the crystallization conditions of plagioclase in volcanic complexes of Sulawesi Island (Pacific Ocean). The composition of plagioclases indicates the presence of three types of melts, which were involved in the formation of plagioclase phenocrysts in basalts, andesites and dacites, as well as crystallites in the groundmass of andesites and dacites. The analysis of glasses of heated melt inclusions in plagioclase indicates the involvement of two contrasting melts (mafic and felsic) in crystallization of phenocrysts. At the final stages of volcanic processes, plagioclase in matrix of andesites and dacites formed from another felsic melts with maximum alkali content. The presence of primary syngenetic melt and fluid inclusions in plagioclase phenocrysts indicates the phase separation of felsic magmas, which led to the crystallization of feldspar phenocrysts of different composition during the formation of dacites. Computational modeling in a program (Putirka, 2008) based on the composition of plagioclases, glasses of heated inclusions and glasses from the groundmass allowed us to estimate the crystallization temperatures of feldspar phenocrysts in basalts (1160–1120 oС), andesites (930–890 oС) and dacites (1020–950 oС), as well as the feldspar microcrystals in the groundmass of andesites (875–810 oС) and dacites (890–850 oС).

Keywords: crystallization conditions, plagioclase, melt inclusions, Sulawesi Island, Pacific Ocean.

Received 12.03.2023, accepted 14.03.2023

A.V. Kotlyarov, Institute of Geology and Mineralogy, SB RAS, pr. Akademika Koptyuga 3, Novosibirsk, 630090 Russia; kotlyarov@igm.nsc.ru

N.V. Dmitrieva, Institute of Geology and Mineralogy, SB RAS, pr. Akademika Koptyuga 3, Novosibirsk, 630090 Russia;

V.A. Simonov, Institute of Geology and Mineralogy, SB RAS, pr. Akademika Koptyuga 3, Novosibirsk, 630090 Russia;

I.Yu. Safonova, Institute of Geology and Mineralogy, SB RAS, pr. Akademika Koptyuga 3, Novosibirsk, 630090 Russia; Novosibirsk State University, 2 Pirogov St, Novosibirsk 630090, Russia;

N.S. Karmanov, Institute of Geology and Mineralogy, SB RAS, pr. Akademika Koptyuga 3, Novosibirsk, 630090 Russia;

I.R. Nizametdinov, Institute of Geology and Mineralogy, SB RAS, pr. Akademika Koptyuga 3, Novosibirsk, 630090 Russia

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