Systematic characterization of cosmic symplectites in the Acfer 094 carbonaceous chondrite

• Material Type: 博士論文
• Title: Systematic characterization of cosmic symplectites in the Acfer 094 carbonaceous chondrite
• Author/Editor: 阿部, 憲一
• Author Heading: 阿部, 憲一
• Publication, Distribution, etc.: Hokkaido University
• Publication Date: 2017-03-23
• Publication Date (W3CDTF): 2017-03-23
• Alternative Title: 炭素質コンドライトAcfer 094隕石における宇宙シンプレクタイトの系統的な特徴付け
• Contributor: 圦本, 尚義; 永井, 隆哉; 橘, 省吾; 坂本, 直哉
• Degree grantor/type: 北海道大学
• Date Granted: 2017-03-23
• Date Granted (W3CDTF): 2017-03-23
• Dissertation Number: 甲第12690号
• Degree Type: 博士(理学)
• Conferring No. (Dissertation): 甲第12690号
• Text Language Code: eng
• NDC: 400
• Target Audience: 一般
• Note (General): We describe the petrographic occurrences, abundances, and compositional variations of symplectically intergrown Fe,Ni-sulfides and 17,18O-rich magnetite (Δ17O ~90‰), named cosmic symplectites (COS; Sakamoto et al., 2007), from the Acfer 094 (C3.0) ungrouped carbonaceous chondrite. A total of 314 COS studied in two polished sections of this meteorite are uniformly distributed in its matrix with ~600 ppm surface area abundance. No COS have been identified in the Acfer 094 dark inclusions (chondritic lithic clasts) which appear to have experienced extensive aqueous alteration prior to incorporation into the host meteorite. The structure of COS can be arranged in a hierarchy of four categories (from finer to coarser): (1) symplectite structure composed of nanocrystalline magnetite and Fe,Ni-sulfides, (2) submicron -sized wormy structure composed of nanocrystalline symplectites, (3) micrometer -sized irregular rope-like structure composed of wormy structure, and (4) aggregates of the rope-like structure. COS typically associate with fractured Fe,Ni-sulfides and lack Fe,Ni- metal. Most COS studied have smooth surfaces; four grains contain abundant pores. In a single COS, the pore- rich regions are depleted in sulfur and nickel relative to the pore-free regions, indicat ing that the former are depleted in Fe,Ni-sulfides. Most COS studied contain similar abundances of Fe,Ni-sulfides and magnetite, whereas Ni/(Fe+Ni) atomic ratio in Fe,Ni-sulfides ranges from 0 to 0.4. The lack of Fe,Ni-metal associated with COS supports the formation process proposed by Seto et al. (2008), i.e. oxidation of Fe,Ni-metal and sulfides by 17,18 O-rich water vapor in the outer part of the protoplanetary disk. The similar abundance ratio for Fe,Ni-sulfide and magnetite cannot be simply explained by oxidation processes of Fe,Ni-sulfide precursors after sulfurization of Fe,Ni-metal precursors for COS formation as proposed by Seto et al. (2008).; (主査) 教授 圦本 尚義, 教授 永井 隆哉, 准教授 橘 省吾, 助教 坂本 直哉; 理学院（自然史科学専攻）
• DOI: 10.14943/doctoral.k12690; https://doi.org/10.14943/doctoral.k12690
• Persistent ID (NDL): info:ndljp/pid/10370884; https://dl.ndl.go.jp/pid/10370884
• Collection: 障害者向け資料
• Collection (Materials For Handicapped People:1): テキストデータ
• Collection (particular): 国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文; https://dl.ndl.go.jp/collections/A00014
• Acquisition Basis: 博士論文（自動収集）
• Date Accepted (W3CDTF): 2017-07-03T04:10:06+09:00
• Date Created (W3CDTF): 2017-03
• Format (IMT): PDF
• Access Restrictions: 国立国会図書館内限定公開
• Service for the Digitized Contents Transmission Service: 図書館・個人送信対象外
• Availability of remote photoduplication service: 可
• Periodical Title (URI): http://dx.doi.org/10.14943/doctoral.k12690; http://hdl.handle.net/2115/65400
• Is Referenced By (URI): http://hdl.handle.net/2115/65401
• Data Provider (Database): 国立国会図書館 : 国立国会図書館デジタルコレクション; https://dl.ndl.go.jp

• Summary, etc.: We describe the petrographic occurrences, abundances, and compositional variations of symplectically intergrown Fe,Ni-sulfides and 17,18O-rich ...