Formation of refractory inclusions by evaporation of condensate precursors

摘要: Berman’s (1983) activity-composition model for CaO-MgO-Al2O3-SiO2 liquids is used to calculate the change in bulk chemical and isotopic composition during simultaneous cooling, evaporation, crystallization of droplets having compositions reasonable condensate precursors Types A B refractory inclusions CV3 chondrites. The degree evaporation MgO SiO2, calculated be faithfully recorded zoning individual melilite crystals, directly proportional rate, which a sensitive function PH2, inversely droplet radius cooling rate. When are partially melted pure hydrogen at peak temperatures vicinity initial temperature melilite, their evolve into fields inclusions, mass-fractionated Mg, Si, O produced that range natural profiles result similar those observed real inclusions. For 0.25 cm evaporating PH2 = 10−6 bar, containing 8 13 wt.% 20 23% SiO2 objects compact Type rates 2 12 K/h, depending on precise starting composition. Precursors 14 23 26% with characteristics B1 1.5 3 K/h. relatively SiO2-poor members B2 group can from 16 27 33% 15% than found any condensation curve. fluffy including reversely zoned only understood context this if they contain relict melilite.