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Title: Oxygen isotope characteristics of chondrules from the Yamato‐82094 ungrouped carbonaceous chondrite: Further evidence for common O‐isotope environments sampled among carbonaceous chondrites
Award ID(s):
1658823
NSF-PAR ID:
10032541
Author(s) / Creator(s):
 ;  ;  
Publisher / Repository:
Wiley-Blackwell
Date Published:
Journal Name:
Meteoritics & Planetary Science
Volume:
52
Issue:
2
ISSN:
1086-9379
Page Range / eLocation ID:
p. 268-294
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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  3. Abstract

    We have carried out a SEM‐EPMA‐TEM study to determine the textures and compositions of relict primary iron sulfides and their alteration products in a suite of moderately to heavily altered CM1 carbonaceous chondrites. We observed four textural groups of altered primary iron sulfides: (1) pentlandite+phyllosilicate (2P) grains, characterized by pentlandite with submicron lenses of phyllosilicates; (2) pyrrhotite+pentlandite+magnetite (PPM) grains, characterized by pyrrhotite–pentlandite exsolution textures with magnetite veining and secondary pentlandite; (3) pentlandite+serpentine (PS) grains, characterized by relict pentlandite exsolution, serpentine, and secondary pentlandite; and (4) pyrrhotite+pentlandite+magnetite+serpentine (PPMS) grains, characterized by features of both the PPM and PS grains. We have determined that all four groups were initially primary iron sulfides, which formed from crystallization of immiscible sulfide melts within silicate chondrules in the solar nebula. The fact that such different alteration products could result from the same precursor sulfides within even the same meteorite sample further underscores the complexity of the aqueous alteration environment for the CM chondrites. The different alteration reactions for each textural group place constraints on the mechanisms and conditions of alteration with evidence for acidic environments, oxidizing environments, and changing fluid compositions (Ni‐bearing and Si‐Mg‐bearing).

     
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