Mineralogical characterization of a unique material having heavy oxygen isotope anomaly in matrix of the primitive carbonaceous chondrite Acfer 094

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• 作者：Yusuke Seto ; Naoya Sakamoto ; Kiyoshi Fujino ; Takashi Kaito ; Tetsuo Oikawa ; Hisayoshi Yurimoto
• 关键词：Adhesion ; Composites ; Enzymatic ; Fungi ; Laccase ; MDF ; Paper ; Particleboard ; Peroxidase ; Wood
• 刊名：Geochimica et Cosmochimica Acta
• 出版年：2008
• 期刊代码：27_00167037
• 类别：ear
• 出版时间：1 June 2008
• 卷：72
• 期：11
• 页码：2723-2734
• 文件大小：2247 K

摘要

We report the mineral compositions and micro-texture of the isotopically anomalous (δ^17,18O_SMOW +180‰) Fe–S–Ni–O material recently discovered in matrix of the primitive carbonaceous chondrite Acfer 094 [Sakamoto N., Seto Y., Itoh S., Kuramoto K., Fujino K., Nagashima K., Krot A. N. and Yurimoto H. (2007) Oxygen isotope evidence for remnants of the early solar system primordial water. Science 317, 231–233]. Synchrotron radiation X-ray diffraction and transmission electron microscopy studies indicate that this material consists of the symplectitically intergrown magnetite (Fe₃O₄) and pentlandite (Fe_5.7Ni_3.3S₈) with magnetite/pentlandite volume ratio of 2.3. Magnetite forms column-shaped grains (10–30 nm in diameter and 100–200 nm in length); pentlandite occurs as worm-shaped grains or aggregates of grains 100–300 nm in size between magnetite crystals. Although both the X-ray diffraction and electron energy loss spectra support identification of iron oxide as magnetite, the electron diffraction patterns show that magnetite has a weak 3-fold superstructure, possibly due to ordering of vacancies. We infer that the isotopically anomalous symplectite formed by sulfurization and oxidization of metal grains either in the solar nebula or on an icy planetesimal. The intersite cation distribution of pentlandite suggests that timescale of oxidation was no longer than 1000 years.