Origin of CAI rims by vaporization and metasomatism

Details Origin of CAI rims by vaporization and metasomatism Origin of CAI rims by vaporization and metasomatism

Jul 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994metic..29..526r&link_type=abstract

Meteoritics (ISSN 0026-1114), vol. 29, no. 4, p. 526

Computer Science

3

Aluminum Compounds, Calcium Compounds, Chondrites, Inclusions, Meteoritic Composition, Rims, Vaporizing, Mineralogy, Olivine, Petrology, Scanning Electron Microscopy, Temperature Effects

Scientific paper

On their margins most Ca, Al-rich inclusions (CAIs) contain thin 'rims' comprised of multiple layers. Previous work has shown that the bulk composition of the rims can be explained by a combination of vaporization during flash heating of the CAIs and a metasomatic event that involved an influx into CAIs of Mg and Si. The layering structure of rims may have formed by a coupled reaction/diffusion process during metasomatism. We discuss additional data that better define the interplay between vaporization and metasomatism in forming CAI rims, based on microprobe and Scanning Electron Microscopy (SEM) studies of CAIs in the Vigarano, Leoville, and Efremovka CV3 chondrites. The rim sequence is essentially the same on CAIs of all petrographic types and in CAIs composed of aggregated objects, although individual layers are often missing or very thin. If flash heating alone affected rims, then they should be consistently enriched in refractory elements compared to the CAI interior, but this is not the case. Relative to the mel-rich substrate, bulk rim layers are typically enriched in Ti, Mg, Si, Cr, Fe, Na, and Cl, and depleted in Al and Ca. The enrichment of the refractory element Ti may be ascribed to flash heating, and the enrichment of the volatile elements Na and Cl is certainly caused by alkali-halogen alteration, but the enrichment of non-refractory elements is best explained by their addition to CAIs from an external medium during metasomatism. The average concentration ratio increases in the order Al less than Ti less than Ca is approximately Mg less than Si, which indicates that the inner spinel-rich layer is enriched in refractory elements compared to the outer silicate layers. This gradient can be explained by the addition of nonrefractory 'chondritic' material to rims that had previously undergone volatility-dependent vaporization.

Affiliated with

Also associated with

No associations

Rating

Origin of CAI rims by vaporization and metasomatism 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 Origin of CAI rims by vaporization and metasomatism, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Origin of CAI rims by vaporization and metasomatism will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-822029