TY - JOUR
T1 - Matrix mineralogy of the Lancé CO3 carbonaceous chondrite
T2 - A transmission electron microscope study
AU - Keller, Lindsay P.
AU - Buseck, P R
N1 - Funding Information:
.-icknoM?/edg~enf.s-Twhoisr k was supported by NASA Grant NAG 9-59. We thank Dr. E. Olsen of the Field Museum ofNatural History for providing samples of Lance and Kainsaz and Dr. C. Francis of the Harvard University Mineralogical Museum for a sample of War-renton. We thank Dr. Jung Ho Ahn for assistance with the JEOL 4OOOEX and Jim Clark for assistancew ith the SEM and microprobe. We also thank Tom Sharp, Kazu Tomeoka. and Jung Ho Ahn for useful discussions. The manuscript benefited from reviews by Wolfgang KlSck and two anonymous reviewers.E lectron microscopy was performed at the Facility for High-Resolution Electron Microscopy in the Center for Solid State Science at Arizona State University. establishedw ith support from the National Science Foundation (NSF) Grant No. DMR-86-11609. The microprobe was obtained with funds provided by the Earth Science division of the NSF (Grant #EAR-8408 163).
PY - 1990/4
Y1 - 1990/4
N2 - The Lancé CO3 carbonaceous chondrite (CC) is less altered than the CI and CM chondrites and so provides a view of the mineralogy and textures resulting from the earliest stages of aqueous alteration of CCs. Matrix olivine in Lancé has been partly altered to fine-grained, Fe-bearing serpentine and poorly crystalline Fe3+ oxide, a process that required both hydration and oxidation. Serpentine occurs as discrete packets separated from the olivine surfaces by the Fe3+ oxide. The Fe released during the dissolution of olivine was partly incorporated into the serpentine; the remainder was oxidized to form Fe3+ oxide. Matrix metal was also altered to produce Fe oxides, leaving the residual metal enriched in Ni. Olivine grains in Lancé matrix contain channels along their [100]and [001]directions. The formation and convergence of such channels resulted in a grain-size reduction of the olivine. The alteration was pervasive but incomplete, suggesting a limited availability of fluid. A brief study of two other CO chondrites, Kainsaz and Warrenton, shows that these meteorites do not contain phyllosilicates in their matrices, although both contain Fe3+ oxide between olivine grains. Prior to its alteration, Lancé probably resembled Kainsaz, an unaltered CO3 chondrite. The alteration assemblage in Lancé is only slightly different from that in Mokoia and essentially the same as that in C3 xenoliths from Murchison. Alteration products in Lancé show greater similarities to CI than to CM chondrites.
AB - The Lancé CO3 carbonaceous chondrite (CC) is less altered than the CI and CM chondrites and so provides a view of the mineralogy and textures resulting from the earliest stages of aqueous alteration of CCs. Matrix olivine in Lancé has been partly altered to fine-grained, Fe-bearing serpentine and poorly crystalline Fe3+ oxide, a process that required both hydration and oxidation. Serpentine occurs as discrete packets separated from the olivine surfaces by the Fe3+ oxide. The Fe released during the dissolution of olivine was partly incorporated into the serpentine; the remainder was oxidized to form Fe3+ oxide. Matrix metal was also altered to produce Fe oxides, leaving the residual metal enriched in Ni. Olivine grains in Lancé matrix contain channels along their [100]and [001]directions. The formation and convergence of such channels resulted in a grain-size reduction of the olivine. The alteration was pervasive but incomplete, suggesting a limited availability of fluid. A brief study of two other CO chondrites, Kainsaz and Warrenton, shows that these meteorites do not contain phyllosilicates in their matrices, although both contain Fe3+ oxide between olivine grains. Prior to its alteration, Lancé probably resembled Kainsaz, an unaltered CO3 chondrite. The alteration assemblage in Lancé is only slightly different from that in Mokoia and essentially the same as that in C3 xenoliths from Murchison. Alteration products in Lancé show greater similarities to CI than to CM chondrites.
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U2 - 10.1016/0016-7037(90)90446-R
DO - 10.1016/0016-7037(90)90446-R
M3 - Article
AN - SCOPUS:0025262725
SN - 0016-7037
VL - 54
SP - 1155
EP - 1163
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
IS - 4
ER -