New Evidence for 26Al in CAI and Chondrules from Type 3 Ordinary Chondrites

Details New Evidence for 26Al in CAI and Chondrules from Type 3 Ordinary Chondrites New Evidence for 26Al in CAI and Chondrules from Type 3 Ordinary Chondrites

Mar 1996

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996lpi....27.1257s&link_type=abstract

Lunar and Planetary Science, volume 27, page 1257

Mathematics

Logic

6

Aluminum-26, Calcium-Aluminum-Rich Inclusions, Chondrites: Ordinary, Chondrules, Chronology

Scientific paper

We have known since 1976 that 26A1 (tl/2 = 7.2 x 105 yrs) was alive in the early solar system, at a level of (26Al/27Al)o z 5 x 10-5 in calcium-aluminum inclusions (CAI). However, several outstanding questions remain. Little evidence for 26A1 has been found in other chondritic material, and none has been found in differentiated meteorites. These results might imply that 26A1 was heterogeneously distributed in the nebula or by mineralogic site in nebular dust, or they might reflect differences in time of formation. There are strict limitations on finding evidence of 26A1 in normal chondrules with bulk Al/Mg ~ 0.1, since even quenched, perfectly preserved, late-stage glasses would have low Al/Mg. Primary plagioclase crystals provide the only possibility, but these only crystallize rarely in melts within the compositional range of normal chondrules. Also, metamorphism can erase the evidence in high-AI/Mg phases. To address these issues, we have conducted a search for chondrules and CAI with high-Al/Mg phases suitable for ion-probe measurement in type 3 ordinary chondrites. Previous work has revealed evidence for 26Al in a plagioclase bearing, olivine-pyroxene class from Semarkona (LL3.0; (26Al/27Al)o = 7.7+/-2.1 x 10-6)), a plagioclase-rich object from Bovedy (L3.7?; 2.5+/-1.2 x 10-7), in separated plagioclase from St. Marguerite (H4; 2.0+/-0.6 x 10-7), an isolated hibonite grain from Dhajala (H3.8; 8.4+0.5 x 10-6), and in Al2O3 and hibonite grains ((26Al/27Al)o = 2-5 x 10-5; [GRH, unpublished]) from acid residues of Semarkona, Bishunpur (LL3.1), and Krymka (LL3.1). We have identified and measured Al-Mg isotope systematics in two CAI and seven chondrules from ordinary chondrites of low metamorphic grade and have found clear evidence for 26A1 in both CAI and in two chondrules.

Affiliated with

Also associated with

No associations

Rating

New Evidence for 26Al in CAI and Chondrules from Type 3 Ordinary 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 New Evidence for 26Al in CAI and Chondrules from Type 3 Ordinary Chondrites, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and New Evidence for 26Al in CAI and Chondrules from Type 3 Ordinary Chondrites will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1614815