1. Mg and Si isotopic fractionation patterns in types B1 and B2 CAIs: Implications for formation under different nebular conditions.
- Author
-
Bullock, Emma S., Knight, Kim B., Richter, Frank M., Kita, Noriko T., Ushikubo, Takayuki, MacPherson, Glenn J., Davis, Andrew M., and Mendybaev, Ruslan A.
- Subjects
MAGNESIUM isotopes ,SILICON isotopes ,NEBULAR hypothesis ,MELILITE ,METAL inclusions ,CRYSTALLIZATION ,HYDROGEN - Abstract
Magnesium and silicon isotopic profiles across melilite grains in two type B1 and two type B2 calcium-aluminum-rich inclusions (CAIs) reveal differing but constant enrichments in heavy isotopes everywhere except ≤1000 μm from the CAI margins. There is no close correlation in the B1s or the B2s between isotopic composition and åkermanite content of the melilite, a measure of progressive igneous crystallization, yet such a correlation might be expected in a type B2: without a melilite mantle (as in B1s) to seal the interior off and prevent further evaporation, the melt would have maintained communication with the external gas. These observations indicate a model in which B1s and B2s solidified under differing conditions. The B2s solidified under lower hydrogen pressures ( [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF