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Symplectic exsolution in olivine from the Nakhla martian meteorite
Author(s) -
MIKOUCHI Takashi,
YAMADA Ikiko,
MIYAMOTO Masamichi
Publication year - 2000
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/j.1945-5100.2000.tb01483.x
Subject(s) - olivine , augite , meteorite , geology , martian , astrobiology , magnetite , geochemistry , plagioclase , mars exploration program , physics , quartz , paleontology
Abstract— The Nakhla meteorite, commonly accepted to have originated from Mars, is a cumulus clinopyroxenite with ∼10 vol% of Fe‐rich olivine. Almost all olivine grains in Nakhla contain dark lamellar inclusions (less than 2–3 μm wide). High‐resolution scanning and transmission electron microscopy revealed that the inclusions are complex intergrowths of augite and magnetite. Such a symplectic intergrowth of augite and magnetite in olivine was known in some terrestrial rocks, lunar rocks, and a few meteorites. The inclusion in Nakhla olivine is the first symplectite found in a martian rock. Apparently, the presence of Fe 3 + in olivine under an oxidizing condition on Mars caused symplectic exsolution at high temperature (>900 °C) during cooling.