Condensation in Dust-enriched Systems, by D.S. Ebel and L. Grossman,
Geochimica et Cosmochimica Acta, 1999

Results: Composition of Feldspar

------------------- Figure 13: Mole fractions of albite (Ab) and orthoclase (Or) in feldspar as a function of temperature at Ptot= 10-3 bar and a dust enrichment of 100x and 1000x. (enlarge)

TThe mole fractions of albite and orthoclase in feldspar are plotted as a function of temperature at 10-3 bar and dust enrichments of 100x and 1000x in Fig. 13. The amount of feldspar and its albite and orthoclase contents increase steadily with decreasing temperature in both cases. Above the temperature of disappearance of liquid, feldspar draws its Na from both liquid and gas but its K from the liquid only. Below this temperature, Na and K continue to condense from the gas into feldspar, increasing their concentrations in feldspar with decreasing temperature. At 10-6 bar and dust enrichments of 100x and 1000x, K contents of feldspar are vanishingly small down to the last temperature step of the computations shown on Table 7. This is also true for Na at 100x, but XAb at 1000x rises to 0.1 at 1200K.

CONDENSATION in DUST-ENRICHED SYSTEMS Denton S. Ebel (1) Lawrence Grossman(1,2) (1) Department of The Geophysical Sciences The University of Chicago 5734 South Ellis Ave. Chicago, IL 60637 (2) Enrico Fermi Institute The University of Chicago 5640 South Ellis Ave. Chicago, IL 60637 Submitted December 22, 1998 to Geochimica et Cosmochimica Acta Revised version submitted June 30, 1999

Abstract Introduction Technique Bulk Composition Method of Calculation Data for Elements and Gas Species Data and Models for Solids Data and Models for Silicate Liquids Test of MELTS: Peridotite KLB-1 Transition Between Liquid Models Results Vapor of Solar Composition General Effects of Dust Enrichment and Total Pressure Oxygen Fugacity Condensation Temperatures and Liquid Stability Condensation at 100x Dust Enrichment, Ptot=10-3bar Condensation at 1000x Dust Enrichment, Ptot=10-3bar Condensation of Oxidized Iron at High Temperature Bulk Chemical Composition of Condensates Composition of Silicate Liquid Composition of Spinel Composition of Clinopyroxene Composition of Feldspar Composition of Metallic Nickel-Iron Metal-Sulfide Condensate Assemblages Discussion Stability of Silicate Liquid in Solar Gas Chondrules in Dust-enriched Systems Conclusions References