Constraints on the anhydrous precursor mineralogy of fine-grained materials in CM Carbonaceous chondrites

Details Constraints on the anhydrous precursor mineralogy of fine-grained materials in CM Carbonaceous chondrites Constraints on the anhydrous precursor mineralogy of fine-grained materials in CM Carbonaceous chondrites

Nov 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998m%26ps...33.1213b&link_type=abstract

Meteoritics & Planetary Science, vol. 33, no. 6, pp. 1213-1220

Other

7

Scientific paper

Mass balance calculations were performed to constrain the precursor mineralogy of fine-grained aqueously altered materials in CM carbonaceous chondrites. The bulk composition of unaltered fine-grained CM materials was estimated, and then used to calculate phase proportions for several different initial assemblages. All starting assemblages contain relict unaltered Fe-poor phases observed in CM chondrites, plus Fe-sulfides. The original sources of Fe are uncertain, because most primary Fe-rich phases were aqueously altered. Four endmember assemblages are considered by adding Fe metal, Fa50, Fa100, or FeO-rich amorphous materials to the Fe-poor phases. These represent the Fe-bearing phases in CM and/or other chondritic classes. Results indicate that the precursor CM assemblage may have contained a maximum of either ~10 vol% Fe metal, 57 vol% Fa50, ~28 vol% Fa100, or 37.0 vol% FeO-rich amorphous materials. Additional calculations were performed in which Fe metal was added to the various FeO-bearing assemblages. These reveal a strong positive correlation between the ratio forsterite/(forsterite + enstatite) and the amount of FeO-bearing phases that co-exist with metal. If forsterite was more abundant than low-Ca pyroxene in the accreted CM materials, then these materials must have also contained significant amounts of FeO-rich phases, for example at least 36 vol% Fa50, 10 vol% Fa100 or 17 vol% FeO-bearing glasses. Calculated mineral proportions suggest that intact calcium aluminum inclusions (CAI) represent only ~1/2 of the original CAI budget, consistent with previous hypotheses that the initial CAI contents of CM and CO chondrites were similar. Some similarities exist between the primary CM assemblages calculated here and the mineralogies of other chondrite classes, but the initial CM materials do not appear to be represented in our meteorite inventory.

Affiliated with

Also associated with

No associations

Rating

Constraints on the anhydrous precursor mineralogy of fine-grained materials in CM Carbonaceous chondrites 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 Constraints on the anhydrous precursor mineralogy of fine-grained materials in CM Carbonaceous chondrites, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Constraints on the anhydrous precursor mineralogy of fine-grained materials in CM Carbonaceous chondrites will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-803141