SILICA-RICH OBJECTS IN ACFER 182: A SIMS STUDY.

VARELA M.E.; ZINNER E

Houston

Conferencia; Lunar and Planetary Science Conference; 2012

The carbonaceous chondrite Acfer 182 and paired meteorites (Acfer 207, 214), are mem-bers of the CH group, as introduced by [1]. CH chon-drites - closely related to CR and CB chondrites (the so-called CR-clan, [2]) - are among the least altered chondrites known. The CH chondrites have high metal contents (20 vol. % FeNi-metal) with significant amounts of Cr. The chemical zoning patterns in some of these metal grains is indicative of formation by con-densation at temperatures from 1370 to 1270 K [e.g., 3]. These chondrites are also very rich in small chon-drules (<90 ìm) and chondrule fragments (70 vol. %) [e.g., 1, 4, 5]. A few of these objects have very high SiO2 contents [6, 7]. The silica-bearing objects – more common in UOC (e.g., 8) - are very rare in carbona-ceous chondrites [6, 7]. Here we report the results of major and trace element studies of some silica-bearing objects in Acfer 182. ìm) and chondrule fragments (70 vol. %) [e.g., 1, 4, 5]. A few of these objects have very high SiO2 contents [6, 7]. The silica-bearing objects – more common in UOC (e.g., 8) - are very rare in carbona-ceous chondrites [6, 7]. Here we report the results of major and trace element studies of some silica-bearing objects in Acfer 182.