Olivine in komatiite records origin and travel from the deep upper mantle

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چکیده

Abstract The deep upper mantle is the main source of high-temperature magmatism, but only known naturally occurring samples high-pressure constituents are mineral inclusions in diamonds. Trace elements olivine crystals from 3.33 Ga Commondale Greenstone Belt South Africa reveal that these formed as phenocrysts, and some perhaps even transition zone (410–600 km) where they began wadsleyite. were entrained within ascending komatiite magma conveyed to surface. have highest contents Al2O3 (0.3 wt%) recorded any terrestrial olivine, which indicative formation at high pressure. gave rise Archean komatiites, extraordinarily hot magmas (up 1700 °C), provide insight into Earth's early evolution most ancient continental oceanic crust. In spite extensive research since their discovery over 50 years ago, origins komatiites remained contentious. Plumes—thermochemical instabilities originating core-mantle boundary—are likely source, no direct evidence a origin has yet been recognized.

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ژورنال

عنوان ژورنال: Geology

سال: 2021

ISSN: ['0091-7613', '1943-2682']

DOI: https://doi.org/10.1130/g49523.1