The Ni, Fe and Co contents of metal phases in the Allende, Holbrook and Nuevo Mercurio chondrites

• Main Authors: Yasunori Miura, Dorian G.W. Smith, S. Launspach
• Format: Report
• Language: English
• Published: Department of Mineralogical Sciences and Geology, Faculty of Science, Yamaguchi University 1983
• Subjects: Mercurio; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=1561; http://id.nii.ac.jp/1291/00001561/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=1561&item_no=1&attribute_id=18&file_no=1

The Ni, Fe and Co contents of metal phases in the Allende, Holbrook and Nuevo Mercurio chondrites have been obtained using an automated electron microprobe fitted with both wavelength and energy dispersive spectrometers. The variation patterns of Ni-Fe-Co metal used in this study are discussed from the standpoints of the volume percentage and average composition of each region, and the overall average composition of the metal phases. An advantage of random selection of many analytical points is that bulk composition of plessite becomes apparent even when the scale of intergrowth is generally less than the beam diameter. Co contents of kamacite in these chondrites are inconsistent with those reported previously, but the general tendency of Co to increase in the kamacite in chondrites from H, L to LL groups, is supported by this study. Although the variation patterns of Ni-Co observed so far for L4,H5 and CV3 chondrites are simple, six L6 chondrites, including those reported previously, show significant difference in Co contents and the concentration and abundance characteristics of Ni-Fe-Co patterns of the metal phases. The great similarity of composition of each region of these patterns obtained from two samples of Holbrook and two samples of Allende which came from different collections, indicates that the variation patterns of Ni-Co in the metal phases provide a means of characterization or "fingerprinting", as do the great differences in the variation patterns of Fe-Ni-Co which occur from one chondrite to another or even within the same group and petrologic type.