High-Alumina Daughter Phases in Olivine-Hosted Melt Inclusions from Kudryavy and Menshiy Brat Volcanoesv (Medvezhia Caldera, Iturup Island)

IF 0.9 4区地球科学 Q4 GEOSCIENCES, MULTIDISCIPLINARY

Russian Journal of Pacific Geology Pub Date : 2024-08-09 DOI:10.1134/s1819714024700131

I. R. Nizametdinov, S. Z. Smirnov, A. Ya. Shevko, D. V. Kuzmin, A. A. Kotov, V. S. Sekisova, T. Yu. Timina

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Abstract

For the first time, high-alumina mineral assemblages including rare minerals of the rhönite–kuratite series were found in postcaldera lava flows of the Kudryavy and Menshiy Brat volcanoes (Kuril Islands). These lava flows consist of olivine-bearing basalts and andesite-basalts of the calc-alkaline series. Partially crystallized olivine-hosted melt inclusions in these rocks contain high-alumina daughter phases. Residual glass with up to 25 wt % Al₂O₃, Al-pyroxenes, and spinel with minerals of the rhönite subgroup were identified. The rhönite–kuratite series minerals are characterized by strong variations in Al, Fe²⁺, Fe³⁺, Mg, Si, as well as very low Ti, which makes it possible to call it a low-Ti Fe²⁺ analogue of rhönite with the formula (Ca,Mg,Na)₄(Mg,Fe,Fe, Al,Ti,Mn)₁₂O₄[Si_8.2Al_3.8O₃₆]—(Ca,Na,Mg)₄(Fe,Mg,Al,Fe,Ti)₁₂O₄[Si_6.78Al_5.22O₃₆]. It is assumed that high-alumina daughter phases form in olivine-hosted inclusions via water accumulation in trapped melts during crystallization of the host olivine on the walls of melt inclusions. Water-rich melts can inhibit early crystallization of plagioclase, which promotes enrichment of the residual melt in Al₂O₃.

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库德里亚维火山和门希布拉特火山（伊图鲁普岛梅德韦日亚火山口）橄榄石包裹体中的高铝子相v

摘要在 Kudryavy 火山和 Menshiy Brat 火山（千岛群岛）的破火山后熔岩流中首次发现了高铝矿物组合，其中包括菱铁矿-栗铁矿系列的稀有矿物。这些熔岩流由钙碱性系列的含橄榄石玄武岩和安山岩玄武岩组成。这些岩石中部分结晶的橄榄石托管熔体包裹体含有高铝子相。经鉴定，残留玻璃中含有高达 25 wt % 的 Al2O3、铝辉石和尖晶石以及菱铁矿亚群矿物。菱铁矿-绢云母系列矿物的特征是 Al、Fe2+、Fe3+、Mg、Si 的强烈变化以及极低的 Ti，因此可以称其为菱铁矿的低 Ti Fe2+ 类似物，其化学式为 (Ca,Mg,Na)4(Mg,Fe,Fe,Al,Ti,Mn)12O4[Si8.2Al3.8O36]—(Ca,Na,Mg)4(Fe,Mg,Al,Fe,Ti)12O4[Si6.78Al5.22O36].据推测，橄榄石寄主包裹体中的高铝子相是在熔融包裹体壁上的橄榄石寄主结晶过程中，通过被困熔体中的水分积累而形成的。富水熔体可抑制斜长石的早期结晶，从而促进残余熔体中 Al2O3 的富集。

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来源期刊

Russian Journal of Pacific Geology 地学-地球科学综合

CiteScore

1.30

自引率

37.50%

发文量

审稿时长

>12 weeks

期刊介绍： Russian Journal of Pacific Geology publishes the results of research on the Earth crust and mantle composition and provides articles on the geological structure and patterns of distribution of mineral deposits in the Pacific Ocean, marginal seas and continental margins. It discusses the topics of stratigraphy, sedimentology, magmatic activity, and seismicity. The journal deals with the problems of lithosphere plates tectonics, and offers the results of neotectonic, geomorphological, geodesic, environmental and mining studies in the Pacific region. The journal accepts theoretical, methodical and philosophical articles covering general issues of geology, geophysics, geochemistry, geoecology and mining. The journal also publishes critical notes and comments, and reviews.