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Early differentiation of the moon - Evidence from trace elements in plagioclase

Conference · · JGR, J. Geophys. Res., (Sect.) C:; (United States)
OSTI ID:5823210
Bulk samples and plagioclase mineral grains from lunar cataclastic ferroan anorthosites were analyzed for trace elements by instrumental neutron activation analysis. Some pure plagioclase crystals have lower concentrations of Cr, Co, Sc, and heavy REEs than previous analyses indicated. Concentrations of Sr, Eu, Na, Ga, and the REEs in plagioclases from different anorthosites vary in a systematic way, and the trace element patterns of plagioclases from pristine norites and troctolites are very different from the plagioclase pattern of anorthosites. The following model is suggested to account for these observations: (1) melting of a large fraction of the moon, formation of a magma ocean, precipitation of olivine and later pyroxene, followed by flotation of cumulus plagioclase; (2) mixing of KREEP with a mafic component enriched in Mg, Cr, and Co; (3) precipitation of noritic and troctolitic cumulates and metallic iron from this magma; and (4) eruption of these KREEP and Mg-rich lavas and/or distribution of these materials over the front-side of the moon by basin-forming impacts 3.9-4.0 b.y. ago.
Research Organization:
Max-Planck-Institut fuer Chemie, Mainz, West Germany
OSTI ID:
5823210
Report Number(s):
CONF-840385-
Conference Information:
Journal Name: JGR, J. Geophys. Res., (Sect.) C:; (United States) Journal Volume: 89
Country of Publication:
United States
Language:
English