J. Japan. Assoc. Min. Petr. Econ. Geol. 71, 238-247, 1976.

HYDRATED FROM CHICHIJIMA, THE OGASAWARA ISLANDS, JAPAN

SHIGERU SUZUKI, HIROTSUGU NISHIDO AND RYOHEI OTSUKA Department of Industry, School of Science and Engineering, Waseda University, Tokyo

wollastonite. These mentioned INTRODUCTION above have the following characteristics in

The name hydrated talc or hydrated common. The X-ray powder patterns form of talc were used previously by many suggest a talc-like mineral with a high investigators (Foshag and Wherry, 1922; degree of stacking disorder. The first

Strunz, 1941; Faust and Murata, 1953). basal reflection appears near 10 A, showing

However, there exist some confusions among the considerable shift towards the low-2Į

them. Recently, several papers about angles from that of normal talc, which usu

naturally occurring hydrated talc have ally appears at 9.3-9.4 A. The basal

been published. Maksimovic (1966) des reflections are broadened and do not form a

cribed ƒÀ-kerolite and pimelite from Goles rational series. They are not swollen after

Mountain, Yugoslavia. They occur in a treatment of water, ethylene glycol, glycerol,

fossil laterite formed by weathering of etc. The H20 (+) content is considerably

fresh harzbargite. He showed that these in excess of that of normal talc. Also, there minerals form a series of solid solution, are deficiency and excess in cations in the

where fl-kerolite stands as a magnesium end tetrahedral and octahedral positions.

member and pimelite as a nickeliferous end Hydrated talc was obtained from gels

member. He also suggested that 19-kerolite with appropriate chemical compositions

and pimelite represent a hydrated and a (Caillere et al., 1963; Otsuka et al., 1972) nickeliferous form of talc, respectively. In and by treatment of naturally occurring

their extensive studies on the nature of minerals under hydrothermal conditions

garnierites, Brindley and Hang (1973) (Frank-Kamenetsky et al., 1969; Otsuka et considered an end member having the al., 1974; Sakamoto et al., 1975a).

chemical composition of 3MgO.4SiO2.2H2O During an extensive study of the min

in a series of 10A , and called it eralogy of Chichijima, the second author

talc monohydrate. They suggested that (H. N.) noted a pale brownish clayey the additional H20 in this monohydrate may material in association with zeolites, filling

occupy interlayer positions in a 10 A type cavities in pillow lava. Our laboratory layer structure, as K+ in phlogopite. work showed that this material corresponds

Imai et al. (1973) described "hydrated talc" to hydrated talc mentioned above. In this

from the Akatani mine, Niigata Prefecture, paper, the mineralogical data obtained on which occurs as an alteration product of this material are presented.

(Manuscript received, April 22, 1976) Hydrated talc from Chichijima, the Ogasawara Islands , Japan 239

Fig. 1 Location map of Chichijima, the Ogasawara Islands

island, and especially pillow structures are OCCURRENCE well observed near Hatsuneura. Pillow The Ogasawara Islands (Bonn Islands), lava at the central region of Minami situated about 1000-1500 km SSE of Hatsuneura consists of pillows of 20-40cm Tokyo, consist of about thirty islands in diameter, having many amygdaloidal (Mukojima Is., Chichijima Is., Hahajima Is., cavities. etc.). They are widely distributed in the This material occurs as irregular fillings region of longitude 141•‹16'-142•‹26'E and in cavities in the middle part of individual latitude 24•‹14'-27•‹45'N in the Pacific Ocean pillows, associated with idiomorphic heu (Fig. 1). landite, erionite, phillipsite and green clayey Chichijima, located in the middle part material (Fig. 2). of this region, is considered to be an ancient volcanic island or submarine volcano GENERAL DESCRIPTION AND OPTICAL formed during Early Tertiary, and is com DATA posed of andesite and basaltic lavas (= boninite) and pyroclastics. Sedimentary A hand specimen containing this rocks such as sandstone and limestone are material is pale brown in colour and compact distributed locally in the south western area clayey aggregates with weak greasy . and some other small areas (Iwasaki and In thin section, it is seen to consist almost

Aoshima, 1970). Pillow lavas are widely entirely of platy or fibrous aggregates of a distributed on the eastern coast of this talc-like mineral with very small amounts of 240 S. Suzuki, H. Nishido and R. Otsuka

opaque minerals. Refractive indices deter

mination using immersion liquids and Na

ught gave the values of ƒ¿=1.525-1.530, ƒÁ =1.550-1.555, ƒ¿-ƒÁ=0,03 at 20•Ž. This

material is colourless in thin section, and has

almost straight extinction and positive

elongation.

Fig. 2 Photographs showing the mode of occur rence of hydrated talc from Chichijima

Fig. 4 X-ray diffraction patterns of hydrated Fig. 3 X-ray diffraction patterns of hydrated talc from Chichijima, both heated and talc from Chichijima, both treated and untreated (oriented specimens) unheated (oriented specimens) 1: H2O treated, 2: NH4+-saturated, 1: Heated to 1000•Ž, 2: Heated to 800•Ž, 3: K+-saturated, 4: Glycerol treated, 3: Heated to 700•Ž, 4: Heated to 400•Ž, 5: Ethylene glycol treated, 6: Untreated 5: Heated to 225•Ž, 6: Unheated Hydrated talc from Chichijima, the Ogasawara Islands , Japan 241

The first basal reflection appears at 10 A, X-RAY DIFFRACTION DATA showing a spreading towards smaller angles. X-ray powder diffraction patterns were Also, the basal reflections are broad and obtained with a "Geigerflex" X-ray form a non-rational series. Including the diffractometer using Ni-filtered CuKa basal reflections, only a few reflections are radiation. Diffraction patterns of the recognized. The 020 reflection appears as untreated and treated materials are shown a diffuse band with a spreading towards in Fig. 3 and Fig. 4, and the powder data higher angles, showing a two-dimensional for the untreated material are tabulated in reflection effect. The 132 and 132 reflec Table 1, together with those for well tions are not well resolved and spread. The crystallized Manchurian talc and related 060 reflection appears at 1.525 A, indicating minerals. Though the patterns of this the trioctahedral nature of this material. material show a similarity to those of talc, After heated at 225•Ž for 1 hr. and the following differences are recognized. cooled to room temperature in air, the 10 A

Table 1 X-ray diffraction data for hydrated talc from Chichijima and related minerals

(1): Hydrated talc, Chichijima, this study.

(2): "Hydrated talc", Akatani mine (Imai et al., 1973). (4): White ,ƒÀ-kerolite, Goles Mountain, Yugoslavia (Maksimovic, 1966). (4): Well-crystallized Manchurian talc (Imai et al., 1973). b or B: broad 242 S. Suzuki, H. Nishido and R. Otsuka

Table 2. Chemical analyses and structural formulae of hydrated talc from Chichijima and related minerals

(1): Hydrated talc, Chichijima, this study (analyst: Suzuki). (2): "Hydrated talc", Akatani mine (Imai et al., 1973). (3): White ƒÀ-kerolite, Goles Mountain, Yugoslavia (Maksimovic, 1966). (4): Fibrous stevensite, Ohori mine (Otsu et al., 1963). (5): Stevensite, North Tyne, England (Randall, 1959). (6): Talc (Pask and Warner, 1954). (7): Calculated from ideal talc of chemical composition Mg3Si4O10(OH)2. * ƒ°Oct .=ƒ°(R2++3/2R3+). ** O/T=Octahedral/Tetrahedral cation ratios . Hydrated talc from Chichijima , the Ogasawara Islands, Japan 243 reflection shifts to 9.8 A (Fig. 4). With Table 3. Cation exchange capacity and exchang increasing temperature, this reflection eable cations of hydrated talc from Chichijima changes gradually to 9.5 A at 800•Ž. No

appreciable changes are observed on the

peak profiles. The structure is completely destroyed and enstatite is formed at 1000•Ž.

The treatments of this material with water,

NH4+, K+, and glycerol do not give any no

ticeable changes in the X-ray patterns

(Fig. 3). Only when treated with ethylene lenberger's method is 28.6 m.e./100g.

glycol, the 10 A reflection is contracted to This value agrees closely with 29 m.e./100g 9.8 A. These results are consistent with of ƒÀ-kerolite (Maksimovic, 1966). The

those of Maksimovic (1966), Brindley and analysis of exchangeable cations in the

Hang (1973), and Imai et al. (1973). extract is given in Table 3. The values of

these cations calculated as oxides agree

closely with those obtained by the chemical CHEMICAL ANALYSIS analysis (Table 2). This fact indicates that

The chemical analysis of this material all amounts of alkali metal of this

is listed in Table 2, together with those of material occupy exchangeable positions. related minerals in the literature. The

formulae recorded in Table 2 have been THERMAL ANALYSIS calculated based on a combined tetrahedral TG and DTA curves were simultane +octahedral cation valence of 22. In these ously recorded with a Thermoflex (Rigaku formulations, Mg, Mn, Fe2+, and Fe3+ are Denki Company) at a programmed heating considered to occupy octahedral positions rate of 10•Ž/min. in air, as shown in Fig. 5. and B (octahedral cations) is taken as S The TG curve indicates three steps of weight (R2++3/2R3+) (Brindley and Hang, 1973). loss, indicating that the dehydration of this The chemical composition of this material proceeds in three steps, provided Ogasawara material agrees closely with that the weight loss takes place only upon those of related minerals, except that of dehydration. The initial rapid weight loss normal talc. The formula indicates that of 7.6%, corresponding to mainly loss of there are deficiency and excess in cations in

the tetrahedral and octahedral positions,

respectively. The H20(+) value equals to

1.74, which is much higher than that of

normal talc, 1.00. As shown in Table 2,

similar behaviours can be recognized in "hydrated talc" (Imai et al ., 1973), j

kerolite (Maksimovic, 1966), fibrous steven

site (Otsu et al., 1963) and stevensite (Rand

all, 1959).

The cation exchange capacity of the Fig. 5 Simultaneous TG and DTA curves of Ogasawara material determined by Schol hydrated talc from Chichijima 244 S. Suzuki, H. Nishido and R. Otsuka

hygroscopic water, occurs below 120•Ž. curve is characterized by two endothermic

The gradual weight loss of 1.9% in the tem effects; the low temperature peak (extra perature range from 120 to 780•Ž arises polated onset, Te.o. 45•Ž; peak tem mainly from elimination of interlayer perature, Tp 100•Ž) and the high tem water. The final weight loss of 4.1 % due perature peak (Te.o. 818aC; Tp 852•Ž). to dehydroxylation occurs rapidly between The results of the thermal analysis are

780 and 865•Ž. However, no clear separa consistent with those of #-kerolite (Maksi tions can be found between the loss of movic, 1966), "hydrated talc" (Imai et al., hygroscopic water and that of interlayer 1973) and stevensite (Faust and Murata, water, and between the loss of hydroxyls 1953; Faust et al., 1959; Randall, 1959, and that of interlayer water. The DTA Imai.et al., 1970; Sakamoto et al., 1975b).

Fig. 6 Infrared absorption spectra of hydrated talc from Chichijima , both heated and unheated. 1: Heated to 1000•Ž, 2: Heated to 700•Ž, 3: Heated to 225•Ž , 4: Unheated Hydrated talc from Chichijima, the Ogasawara Islands , Japan 245

disappears. The Si-O stretching absorp INFRARED ABSORPTION ANALYSIS tion appears around 1010cm-1 as a strong The infrared absorption spectra of this and very broad band. In the 400-800 material, both unheated and heated at cm-1 region, there is a strong doublet band various temperatures were obtained with a at 450 and 465cm-1 with shoulders at 534 Hitachi Infrared Spectrometer of grating and 424cm-1. This doublet band is type (EPI-G2). The spectra in the region characteristic to normal talc, and was 400-1300cm-1 were obtained by a KBr assigned to a Mg-O vibration by Wilkins and disk method, while those in the regions Ito (1967). In addition, a strong and sharp 3000-4000cm-1 and 1500-1800cm-1 were band at 668cm-1 is recognized. obtained by a Nujol paste method in order The IR spectra of this material did not

to avoid absorption of water. As shown show any noticeable differences from normal in Fig. 6, the spectrum in the OH stretching talc in the literature except for the appea region (3000-4000cm-1) of the unheated rance of the 3620 and 3425 cm-1 bands due material gives a strong and sharp band at to interlayer water.

3675cm-1 and weak and broad bands at 3620 and 3425cm-1. On heating to ELECTRON MICROSCOPY 225•Ž, the spectrum does not show any Transmission and scanning electron noticeable changes, but when heated to micrographs of this material were taken 700•Ž, the 3620 and 3425cm-1 bands almost with a Hitachi electron microscope (model disappear. The 3675cm-1 band disappears HU-11D) and a JEOL scanning electron at 1000•Ž. In the 1500-1800cm-1 region, microscope (model JSM-U3). The rep an absorption band caused by H2O deforma resentative transmission micrograph shows tion vibration appears at 1630cm-1 as a that the material consists of thin plates and single band. It decreases in intensity and irregular fluffy masses (Fig. 7-a). The SEM

shifts to 1625cm-1 when heated to 225•Ž. micrograph shows an aggregation of

After heating to 700•Ž, this band almost undulating lamellae irregularly outlined

Fig. 7 Transmission (a) and scanning (b) electron micrographs of hydrated talc from Chichijima 246 S. Suzuki, H. Nishido and R. Otsuka

(Fig. 7-b). further interpretations are impossible of its very complex nature, and due to the lack of

the data available. DISCUSSION AND CONCLUSIONS Hydrated talc and related minerals

The present investigation indicates reported up to the present occur as that the Ogasawara material closely weathered (Maksimovic, 1966) and hydro resembles ƒÀ-kerolite (Maksimovic, 1966), thermally altered products (Randall, 1959; "hydrated talc" (Imai et al ., 1973) and Mg Otsu et al., 1963; Imai et al., 1973). In case end member of 10 A garnierite (Brindley of the present Ogasawara material, however,

and Hang, 1973) in mineralogical properties. its mode of occurrence, geologic environ

They all represent a talc-like mineral with a ments and the experimental data obtained

high degree of stacking disorder. They above suggest that - this material would have much more water than normal talc probably be hypogene, and that it might be and exchangeable alkali metal cations at precipitated from hydrothermal solution at interlayer sites. Their structural formulae the latest stage of crystallization. indicate that there are deficiency and excess

in cations in the tetrahedral and octahedral ACKNOWLEDGEMENTS positions, respectively. It is suggested The authors express their sincere thanks that hydration of talc and the presence of to Professor N. Imai of Waseda University exchangeable cations are due to some for the kind advice and criticism during the defects in the layer structure. Probably, course of this study. Thanks are also due water molecules and alkali cations are to Dr. M. Shiraishi of the National irregularly distributed at interlayer sites, Research Institute for Pollution and due to the lack of uniformity in the Resources for providing us the opportunity structure of each layer. Brindley to use a scanning electron microscope, and and Hang (1973), in their extensive studies to Mr. J. Yasui of Waseda University for on 10 A garnierites including fl-kerolite, taking the electron micrograph. suggested two structure models consistent The authors are grateful to the finanical with the chemical relations. One of them support in part by a Grant-in-Aid for represents a hydrated 2:1 talc-like layer Fundamental Scientific Research from the with a defective silica sheet in which water Ministry of Education in Japan, by which molecules are placed where silica is missing. this work was greatly facilitated. The other is obtained by removing part

of the lower tetrahedral sheet and placing REFERENCES at the upper tetrahedral level, as shown in Brindley, G. W. and Hang, P. T. (1973), The nature their paper. This corresponds to a hydrat of garnierites-I, Clays and Clay Minerals., 21, ed 2: 1 talc-like layer, with an excess 27-40. hydrated sheet. Additionally, Caillere, S., Henin, S et Esteoule, J. (1963), Nou velles etudes sur la synthese des mineraux they suggested that interstratifications and argileux a partir de gels, Clay Miner. Bull., segregations of the 2: 1 and 1: 1 layer may 5, 272-278.

exist. The structure of the Ogasawara Faust, G. T. and Murata, K. J. (1953), Stevensite, redefined as a member of the montmorillonite material could be considered on the basis group, Amer. Mineral., 38, 973-987. of their concepts. However, at present, •\, Hathaway, J. C. and Millot, G., (1959), Hydrated talc from Chichijima, the Ogasawara Islands , Japan 247

A restudy of stevensite and allied minerals , Bull. Geol. Surv. Jap., 14, 591-599. Amer. Mineral., 44, 342-370. Otsuka, R., Imai, N. and Sakamoto, T. (1972), Foshag, W. F. and Wherry, E. T. (1922), Notes on Stability of stevensite under hydrothermal the composition of talc, Amer. Mineral., 7, conditions, Memo. Sch'l. Sci. Eng'ng., Waseda 167-171. Univ., 36, 37-56. Frank-Kamenetsky, V. A., Kotov, N. V. and Klo •\, Sakamoto, T. and Hara, Y. (1974), chkova, G. N. (1969), Phase transformations Phase transformations of sepiolite under of sepiolite and palygorskite at different hydrothermal conditions (in Japanese), "Nendo pressures under hydrothermal conditions, Kagahu" (Jour. Clay Sci. Sco. Japan.), 14, 8- Geochemistry, 1, 14-21. 19. Imai, N., Otsuka, R., Nakamura, T. and Tsuna Randall, B. A. O. (1959), Stevensite from the Whin shima, A. (1970), Stevensite from the Akatani Sill in the region of the North Tyne, Min. mine, Niigata Prefecture, Northeastern Japan, Mag., 32, 218-225. Clay Sci., 4, 11-29. Sakamoto, T., Suzuki, S., Otsuka, R. and Imai, •\,(1973), "Hydrated talc" -An alteration N. (1975a), Hydrothermal treatment. of woll

product of wollastonite by reaction with astonite and pectolite with MgCl solution (in magnesium-bearing hydrothermal solution, Japanese),, "Nendo Kagahu" (Jour. Clay Clay Sci., 4, 175-191. Sci. Soc. Japan.), 15, 9-22. Iwasaki, Y. and Aoshima, N. (1970), The nature •\, Otsuka, R. and Imai, N. (1975b), Steve of the Bonin and the volcano islands (in nsite from the Kamaishi mine, Iwate Prefe

Japanese), ed. by Higher Education and Science cture, Japan,. J. Japan. Assoc. Mim. Petr. Bureau, Ministry of Education and Cultural Econ. Geol., 70, 1-11. Properties Protection Division, Agency for Strunz, H. (1941), Mineralogishe Tabellen, 278, Cultural Affairs, 205-221. Leipzig, A kad. Verlags, Beher and Erler, Maksimovic, Z. (1966), fl-kerolite-pimelite series Kom. -Ges. from Goles Mountain, Yugoslavia, Proc. Int. Wilkins, R. W. T. and Ito, J. (1967), Infrared Clay Conf., 1, 97-105. spectra of some synthetic tales, Amer.

Otsu, H., Shimazaki, Y. and Ohmachi, H. (1963), Mineral., 52, 1641-1661. On stevensite from Ohori mine (in Japanese),

小笠原父島産加水タルクについて

鈴木 滋 ・西戸裕嗣 ・大塚良平

東 京 都 小 笠 原 父 島 北 東 海 岸 の 初 寝 浦 付 近 に は,無 人 岩 の 枕 状 溶 岩 が 広 く分 布 し て い る。 筆 者 ら の 一 人(西 戸)

は そ の 空 隙 を うめ て,キ フ ッ石,モ ウ フ ッ石,カ イ ジ ュ ウ ジ フ ッ石 な ど の フ ヅ 石 お よ び 緑 色 粘 土 を 伴 な っ て 産

ず る淡 褐 色 の 粘 土 を 見 い 出 し た 。 そ の 後 の 室 内 研 究 に よ り,こ の 粘 土 は 加 水 タ ル ク を 主 と し,極 く 少 量 の 不 透 明 鉱 物 を 伴 な う こ と が 明 ら か に さ れ た 。 そ の 粘 土 の 化 学 分 析 の 結 果 か ら, 22の 陽 電 荷 を も とに し て 求 め た 構 造

式 は 以 下 の 通 りで あ る 。 (Mg2.87Mn0.022+Fe0.093+) (Si3.95Al0.01)O10(OH)2・Ca0.03・Na0.05・K0.01・nH2O. こ の 論 文 で は,こ の ほ か に そ の 陽 イ オ ン 交 換 能 お よ び 交 換 性 イ オ ン, X線 回 折 デ ー タ,熱 分 析 デ ー タ,赤 外

吸 収 ス ペ ク トル,電 子 顕 微 鏡 像 が 示 さ れ て い る。