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Chemical composition and iron oxidation state of amorphous matrix silicates in the carbonaceous chondrite Acfer 094
Author(s) -
Hopp Timo,
Vollmer Christian
Publication year - 2018
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/maps.12991
Subject(s) - carbonaceous chondrite , chondrite , iron sulfide , silicate , oxidation state , amorphous solid , materials science , chemical composition , chemical engineering , mineralogy , chemistry , astrobiology , meteorite , metal , crystallography , metallurgy , sulfur , physics , engineering , organic chemistry
Nanoscale amorphous silicates are a major component in primitive carbonaceous chondrite matrices and anhydrous interplanetary dust particles. Owing to their metastability and sensitive response to reactions with water, this material is of particular interest in understanding nebular and parent body processes in the early solar system. Here we investigated the amorphous silicate matrix ( ASM ) in the ungrouped carbonaceous chondrite Acfer 094 regarding its texture, chemical composition, and Fe oxidation state. We applied transmission electron microscopy techniques on six, focused ion beam technique‐prepared, electron‐transparent lamellae of Acfer 094 to determine the textures of this material. Furthermore, we used energy‐dispersive X‐ray analysis and electron energy loss spectroscopy to quantify the Fe content and the Fe oxidation state of the ASM . Textural investigations reveal differences in sulfide content, porosity, and distribution of the ASM among the samples, as well as evidence for rare recrystallization of phyllosilicate fibers. The chemical composition reveals mobilization of Fe. Furthermore, the determined Fe 3+ /ΣFe ratios of the ASM in the six samples display a homogeneously high oxidation state (0.66–0.73). This high and homogeneous Fe oxidation state in the ASM of Acfer 094 disagrees with its formation as a primary phase in a reduced solar gas and must have been induced in a later stage process. Most likely, this process was aqueous alteration on the Acfer 094 parent body, which led to hydration and oxidation of the ASM , which is supported by textural and chemical evidence of aqueous alteration.