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Oxygen isotope ratios in magnetite core‐and‐mantle structures
Author(s) -
LINDH ANDERS,
HOEFS JOCHEN,
MALMSTRÖM LARS
Publication year - 1984
Publication title -
journal of metamorphic geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.639
H-Index - 114
eISSN - 1525-1314
pISSN - 0263-4929
DOI - 10.1111/j.1525-1314.1984.tb00594.x
Subject(s) - microcline , geology , magnetite , biotite , geochemistry , mantle (geology) , feldspar , isotopes of oxygen , quartz , mineralogy , paleontology
In a polymetamorphic, felsic, biotite‐bearing gneiss, biotite has reacted to form magnetite and microcline. The resulting structure is a magnetite core surrounded by a mantle of feldspar and quartz normally not exceeding 20mm in diameter. Measurements of oxygen isotope ratios disclose disequilibrium between mantle microcline and mantle quartz and also between mantle and matrix minerals of the same species. A clustering of temperature estimates from the oxygen isotope distribution between magnetite and quartz and between magnetite and microcline in the interval 550 to 600°C suggests an approach to oxygen isotope equilibrium. No signs of a re‐equilibriation of the reacting biotite can be found.