斜長石から生成したギブサイトの走査電顕観察―大山および三瓶山降下地積物中の粘土鉱物,その8―

大山降下堆積物中の斜長石のギブサイト化過程を,偏光顕微鏡,X線,示差熱分析,走査型電顕,EPMAを用いて調べた. 斜長石は風化によって,カオリナイト,イライト,ハロイサイト,ギブサイト等を生成することが知られているが,今回,ギブサイト化した斜長石についてのみ検討をおこなった. EPMA分析によれば,一個の斜長石の表面に,Al, Si, Na, Caの多く存在する新鮮な斜長石の部分と,Na, Caをほとんど含まず,多量のAlと,ごく少量のSiを含んでいるギブサイトの部分とが分布し,その境界は, 明瞭であることがわかった（図版2）.それぞれの部分の分析値は第1表のとおりである. 走査型電顕による斜長石の微細形態観察から,下記のことが明らかになった. ①新鮮な斜長石の表面は,平滑かまたは離溶ラメラがみとめられる（図版3-1）. ②風化過程の初期に,水を合んだ非晶質の薄層が,斜長石の表層に生成する.この非晶質薄層の生成にさき立って,斜長石の表面の一部に, ロート状のくぼみが形成される場合がある（図版3-2,3）. ③この非晶質薄層に亀裂が生じる（図版4）.一方, ロート状のくぼみの上にも非晶質の薄層ができ,亀裂が生じる（図版8-1,2）. ④さらに風化が進むと,ラメラ, 亀裂およびロート状のくぼみを部分的に残しながら,-･部には,ギブサイトの結晶が生成する（図版5）. ⑤ギブサイトの結晶は,横1～3μm, 縦2～15μm,　厚さ0.5μm前後の平板状の形態,または,直径15-25μm,厚さ0.5～1μm の円盤上の形態をもつ（図版6）. ⑥ギブサイトの結晶は,平板状のものが数段重なり,集合体をなす場合もあり（図版7-1）,これは,ブラジルのミナス鉱山産のギブサイトの集合状態（図版7-2）とよく似ている. すなわち,斜長石の表面に,風化により,水を含んだ非晶質の薄層ができ,次に,その薄層に亀裂が生じ,イモゴライトの生成をともないながら,直接ギブサイトが結晶すると考えられる. 地名 Okachi 大河内　Hongu 本宮 Kurayoshi 倉吉 Daisen-Cho 大山町 Shuki 秋喜 Hiruzenbara 蒜山

Zoned alternation of gibbsite and clay mInerals in the vermicular gibbsite

Vermicular gibbsite aggregates found in the weathered pumice layer (the Kurayoshi pumice) at Yotsuzuka, western part of Tottori Prefecture, range in size from 5 to lOmm (Fig.1). They are more or less twisted and show some cleavages perpendicular to the long axis. Vermicular gibbsite are milky white colored and usually coated with dark brown color. X-ray diffraction patterns show strong renections for gibbsite, kaoline minerals, hydrobiotite and a relatively small amount of hydrated halloysite (Fig.3), Kaoline minerls are rather abundant at the white part. On the other hand, the dark brown part is rich in hydrobiotite. Differential thermal analysis shows the endothermic reaction for the dehydration of gibbsite at 310℃ and of kaoline minerals, hydrated halloysite and hydrobiotite at 550℃ (Fig.4). Electron microscopy shows that the gibbsite consist of peculiarly warped rods (Plate 1). The clay minerals which are looked like "cracked rice grain" are seemingly kaoline minerals or hydrated halloyslte. By the electron microprobe scanning across the vermicular gibbsite, the triform structure is revealed, such as the gibbsite rich part, the hydrobiotite rich part and kaoline minerals rich part (Fig.5 and 6). Gibbsite and clay minerals (hydrobiotite or kaoline minerals) grow alternately zone by zone (Fig.7). The width of each zone ranges in size from 20 to 40 micron

1.Biominerals

金沢大学大学院自然科学研究科　環境科学Editor : Tazaki, Kazue, Cover:Scanning electoron microscopic photograph of Gallionella sp. in biomats of Aso caldera, Kyusyu, Japan. Various shapes of Gallonella sp. are shown (image:Moriichi, Shingo).COE, 金沢大学 水・土壌環境領域シンポジウム「地球環境における微生物の役割」, 日時：2002年12月4日（水）13：00～, 場所：金沢大学理学部3階第一実験

Circumstances of heavy Oil from Russian Tanker "Nakhodka" in 1997

金沢大学大学院自然科学研究科Scedule:17-18 March 2003, Vemue: Kanazawa, Japan, Kanazawa Citymonde Hotel, Project Leader : Hayakawa, Kazuichi, Symposium Secretariat: XO kamata, Naoto, Edited by:Kamata, Naoto

Preface

金沢大学大学院自然科学研究科　環境科学Editor : Tazaki, Kazue |田崎, 和

Microbial formation of a halloysite-like mineral

Transmission electron microscopy (TEM) has been used to demonstrate the biological formation of a hollow spherical halloysite-like mineral in freshwater systems. The interaction between clays and microbes was investigated in microbial films from laboratory cultures derived from natural sediments. Optical and electron microscopic observations of cultured microbes revealed that thin clay films covered areas of the bacterial cell wall. X-ray diffraction of the thin films after 2 y of ageing showed a 7.13 Å d spacing, consistent with a 7 Å halloysite-like phase [Al 2Si 2O 5 (OH) 4·H 2O]. Fourier transform infrared analysis of the thin film exhibited the characteristic adsorption bands for O-H (3651 cm -1), C-H and C-N (2925, 1454 and 1420 cm -1, respectively), suggesting that the phase was closely associated with adhesive organics. Observation by TEM of the thin films revealed that spherical, hollow, halloysite-like material formed on both coccus- and bacillus-type bacterial cells. Electron diffraction analysis of this material showed 2.9, 2.5, 2.2 and 1.5 Å d spacings. The present investigation strongly suggests that the thin film wall of the spherical halloysite-like material was associated with bacteria as a bio-organic product. This material, referred to hereafter as bio-halloysite, is further evidence for the microbially-mediated formation of clay minerals. The identity of the bacteria responsible for bio-halloysite formation is unknown, but is tentatively assigned to sulfate-reducing bacteria on the basis of morphology and the presence of reducing conditions in the microcosm at the end of the experiments. Copyright © 2005, The Clay Minerals Society

3.Oil pollution

金沢大学大学院自然科学研究科　環境科学Editor : Tazaki, Kazue, Cover:Scanning electoron microscopic photograph of Gallionella sp. in biomats of Aso caldera, Kyusyu, Japan. Various shapes of Gallonella sp. are shown (image:Moriichi, Shingo).COE, 金沢大学 水・土壌環境領域シンポジウム「地球環境における微生物の役割」, 日時：2002年12月4日（水）13：00～, 場所：金沢大学理学部3階第一実験

Ⅰ. Impact assessment of oil pollution

金沢大学大学院自然科学研究科　環境科学Editor : Tazaki, Kazue |田崎, 和