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Stable isotope analysis of carbon and nitrogen in angrites
Author(s) -
Abernethy F. A. J.,
Verchovsky A. B.,
Starkey N. A.,
Anand M.,
Franchi I. A.,
Grady Monica M.
Publication year - 2013
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/maps.12184
Subject(s) - carbon fibers , nitrogen , dissolution , isotopes of carbon , isotopes of nitrogen , chemistry , achondrite , mineralogy , geology , environmental chemistry , materials science , astrobiology , meteorite , total organic carbon , chondrite , organic chemistry , physics , composite number , composite material
Angrites are a small group of ancient basaltic achondrites, notable for their unusual chemistry and extreme volatile depletion. No comprehensive study of indigenous light elements currently exists for the group. Measurement of the abundances and isotopic composition of carbon and nitrogen could provide information pertaining to the evolution of the angrite parent body. Bulk‐sample stepped combustion analyses of five angrites and a glass separate from D'Orbigny were combined with earlier data and acid dissolution experiments of carbonates found in D'Orbigny to compile an inventory of indigenous carbon and nitrogen. Indigenous carbon combusted between 700 °C and 1200 °C, with abundances of 10–140 ppm and a mass‐weighted δ 13 C of −25 to −20‰ with the exception of D'Orbigny (δ 13 C approximately −5‰). Nitrogen was released at 850–1200 ºC , 1–20 ppm with a δ 15 N −3‰ to +4‰; again, D'Orbigny (δ 15 N approximately +20 to +25‰) was an exception. We interpret these components as largely indigenous and decoupled; the carbon in graphitic or amorphous form, while the nitrogen is present as a dissolved component in the silicates. No relationship with the textural sub‐classification of angrites is apparent. We suggest that the angrite parent body contains a reservoir of reduced carbon and thus may have undergone a change in redox conditions, although the timing and mechanism for this remain unclear.