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STUDIES OF BRAZILIAN METEORITES XIV. MINERALOGY, PETROLOGY, AND CHEMISTRY OF THE CONQUISTA, MINAS GERAIS, CHONDRITE
Author(s) -
Keil K.,
Kirchner E.,
Gomes C.B.,
Jarosewich E.,
Murta R.L.L.
Publication year - 1978
Publication title -
meteoritics
Language(s) - English
Resource type - Journals
eISSN - 1945-5100
pISSN - 0026-1114
DOI - 10.1111/j.1945-5100.1978.tb00807.x
Subject(s) - troilite , pyroxene , pigeonite , chondrite , olivine , geology , meteorite , chromite , geochemistry , electron microprobe , mineralogy , augite , plagioclase , astrobiology , quartz , paleontology , physics
The Conquista chondrite consists of major olivine, low‐Ca pyroxene (both ortho‐ and twinned clino‐), troilite and metallic nickel‐iron; minor glassy to microcrystalline material and pigeonite; and accessory chromite, high‐Ca clinopyroxene and hydrous ferric oxides that formed by terrestrial weathering of metallic nickel‐iron. Results of microscopic, electron microprobe, and bulk chemical studies, particularly the compositions of olivine (Fa 17.2 ) and low‐Ca pyroxene (Fs 15.4 ); the contents of metallic nickel‐iron (18.5%) and total iron (25.83%); and the ratios of Fe°/Fe total (0.64), Fe°/Ni° (9.59) and Fe total /SiO 2 (0.69) indicate H‐group classification. The pronounced, well‐developed chondritic texture; the slight compositional variations in constituent phases; the high Ca contents of pyroxene and the presence of pigeonite, glassy to microcrystalline interstitial material rich in alkalis and SiO 2 , and of twinned low‐Ca clinopyroxene suggest that Conquista is of petrologic type 4 .