Computer Science
Scientific paper
Jul 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994metic..29r.492l&link_type=abstract
Meteoritics (ISSN 0026-1114), vol. 29, no. 4, p. 492-493
Computer Science
Alkalies, Chondrites, Evaporation, Meteoritic Composition, Planetary Evolution, Abundance, Depletion, Gravitational Effects, Pressure Effects, Temperature Effects, Vapor Pressure
Scientific paper
Differentiated meteorites and planets show characteristic volatile-element depletions relative to chondrites. If differentiated bodies formed from chondritic matter they should have inherited chondritic abundance patterns. Although it cannot be excluded that the accreting material was already depleted in volatiles, an undifferentiated meteorite analog is missing in our meteorite collections. However, if chondritic matter accreted to form smaller bodies, which differentiated and in turn formed larger planetary bodies, evaporative loss from the intermediate-sized bodies may have been responsible for the observed alkali-element depletions in planets. Two factors are important for alkali loss by volatilization during large-scale planetary differentiation. Temperatures must rise sufficiently high to evaporate alkali-element compounds. The gaseous compounds must leave the gravitational field of the planetary body. Gas composition and vapor pressures depend mainly on the temperature reached during planetary differentiation and on the redex state given by refractory solids and liquids. Because of their incompatibility, the heavier alkali elements can concentrate in melts and be transported more efficiently to the surface. We model alkali-element loss as hydroxide gases. The evaporation sequence with increasing temperature is CsOH is greater than RbOH is greater than KOH is greater than NaOH is greater than LiOH. For planetary differentiation, temperatures of greater than 1270 K are required. Jeans loss from an atmosphere is governed by the escape velocity and the thermal velocity of the particles in the gas. Assuming that surface temperatures reach 1300 K during differentiation, the vapor pressures increase and alkali elements can be lost. The extent of alkali-element fractionation then depends on the fraction of alkali elements in the gas and the time period when alkali elements are evaporated. Loss of alkali elements from Mars-sized bodies heated to magmatic temperatures requires a few billion years and is highly unlikely.
No associations
LandOfFree
Retention of alkali elements during planetary accretion and differentiation does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Retention of alkali elements during planetary accretion and differentiation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Retention of alkali elements during planetary accretion and differentiation will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-822344