Extended time scales of carbonaceous chondrite aqueous alteration evidenced by a xenolith in LaPaz Icefield 02239 (CM2)

LaPaz Icefield (LAP) 02239 is a mildly aqueously altered CM2 carbonaceous chondrite that hosts a xenolith from a primitive chondritic parent body. The xenolith contains chondrules and calcium‐ and aluminum‐rich inclusions (CAIs) in a very fine‐grained matrix. The chondrules are comparable in mineral...

Full description

Saved in:
Bibliographic Details
Published in:Meteoritics & planetary science 2023-05, Vol.58 (5), p.672-687
Main Authors: Lee, Martin R., Floyd, Cameron, Martin, Pierre‐Etienne, Zhao, Xuchao, Franchi, Ian A., Jenkins, Laura, Griffin, Sammy
Format: Article
Language:English
Subjects:
Aluminum
Carbonaceous chondrites
Composition
Ice fields
Inclusions
Isotope composition
Isotopes
Lithification
Meteorite parent bodies
Meteorites
Meteors & meteorites
Mineralogy
Oxygen
Planet formation
Protoplanetary disks
Rims
Serpentine
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:LaPaz Icefield (LAP) 02239 is a mildly aqueously altered CM2 carbonaceous chondrite that hosts a xenolith from a primitive chondritic parent body. The xenolith contains chondrules and calcium‐ and aluminum‐rich inclusions (CAIs) in a very fine‐grained matrix. The chondrules are comparable in mineralogy and oxygen isotopic composition with those in the CMs, and its CAIs are also mineralogically similar to the CM population apart for being unusually small and abundant. The presence of serpentine demonstrates that the xenolith has been aqueously altered, and its phyllosilicate‐rich matrix has a comparable oxygen isotopic composition to the matrices of CM meteorites. The xenolith's chondrules lack fine‐grained rims, whereas the xenolith itself has a fine‐grained rim that is petrographically and chemically comparable with the rims on coarse grained objects in LAP 02239 and other CM meteorites. These properties show that the xenolith's parent body was formed from similar materials to the CM parent body(ies). Following its lithification by aqueous alteration, a piece of the xenolith's parent body was impact‐ejected, acquired a fine‐grained rim while free‐floating in the protoplanetary disc, then was accreted along with rimmed chondrules and other materials to make the LAP 02239 parent body. Subsequent aqueous processing of the LAP 02239 parent body altered the fine‐grained rims on the xenolith, chondrules, and CAIs. The xenolith shows that the timespan of geological evolution of carbonaceous chondrite parent bodies was sufficiently long for some of them to have been aqueously altered before others had formed.
ISSN:1086-9379
1945-5100
DOI:10.1111/maps.13978