Calcian Analcime" in Ophiolite from Sugasima, Mie Prefecture, Japan by Kazuo HARADA*' and Kin-Ichi SAKURAI* * (Comm

No. 9] Proc. Japan Acad., 43 (1967) 889

196. A "Calcian Analcime" in Ophiolite from Sugasima, Mie Prefecture, Japan By Kazuo HARADA*' and Kin-ichi SAKURAI* * (Comm. by Jun SUZUKI,M.J.A., Nov. 13, 1967)

Introduction and occurrence. A specimen of "calcian analcime" was collected by K. Sakurai from a working quarry of ophiolite, in Sugasima, Toba City, Mie Prefecture, Japan. According to Iizuka (1923) and Fujimoto (1942), weakly metamorphosed, thick sequences of pelitic, siliceous-psamitic, basic tuffaceous and calcic rocks belong- ing to Carboniferous to Permian geosynclinal sediments are developed near Toba City. These strongly folded sediments generally strike NE and dip 20-70° SE, separated many blocks by dominant faults. These sediments belong to lower-temperature metamorphic or nearly non-metamorphic part of the Nagatoro (Sanbagawa) glaucophanitic metamorphic belt originated from the Sakawa (Alpine) orogeny in Japan. This lower grade part of the Nagatoro metamorphic terrane has been called the Mikabu zone. The large masses of metamor- phosed gabbroic rocks and serpentinites intrude these sediments of the Mikabu zone along the strike direction. In the veinlets of the meta-gabbro (ophiolite) "calcian analcime" has been discovered. The "calcian analcime"-bearing veins are up to 2-3 cm in width and are almost free from other zeolites and quartz, except very minor amounts of natrolite fibers. The host rocks cut by the "calcian analcime" veins are gabbroic rocks, generally decomposed into albite- clinozoisite-blue actinolite-pumpellyite-prehnite-chlorite assemblages with calcite and without quartz. Physical properties. The compact zeolite veins are composed of anhedral "calcian analcime" grains up to 0.5cm across. Only associated zeolite is natrolite fibers of up to 1 cm in length, which is less than 2 % of volumetric amounts. "Calcian analcime" is white with a dull vitreous luster. Specific gravity = 2.27 as the average of three measurements by pycnometer. Hardness = 5.5. This mineral is color- less and two sets of twinning lamellae, intersecting at almost right angles, are observed. Cleavage or parting is {001} (pseudocubic cleavage) which is more distinct than in normal analcime. It is biaxial with 2 V = large and, in Na light, a =1.487 ± 0.002, 7 =1.489 ±0.002, 7-a=0.002, dispersion very weak r > v about Z.

*) Section of Geology and Mineralogy , Chichibu Museum of Natural History, Nagatoro, Nogami-machi, Chichibu-gun, Saitama Pref., Japan. * * ) Department of Geology , National Science Museum, Ueno Park, Tokyo. 890 K. HARADA and K. SAKURAI [Vol. 43,

Table I. Chemical analysis of calcian analcime (Analyst: K. Nagashima and K. Nakao, 1967)

Fig. 1. DTA data for analcimes and wairakite. Upper: Analcime from Maze, Niigata Prefecture. Middle: Analcime (calcian analcime) from Sugasima, Mie Prefecture. Lower: Wairakite from Onikobe, Miyagi Prefecture. Rate of heating 10°C/min; reference junction 0°C; thermocouple Pt/Pt-13%oRh; reference material A1203. No. 9] CalcianAnalcime from Sugasima 891

Chemical data. About 2 g of pure sample of "calcian analcime" separated by hand-picking was carefully analysed chemically by the normal wet method, with the result as in Table I. Recast in terms of structural formula, this corresponds to: (r ~0.246N"1.7O8)1•954(Fe0~009A11.94913.949)5.939.012.2.050 H2O This formula is comf ormable well with those of analcimes, although a considerable content of lime is confirmed. Differential thermal analyses. DTA curves were obtained by an automatic thermal analyser at a heating rate of 10°C per minute for "calcian analcime", together with analcime from Maze (Shimizu, 1915) and wairakite from Onikobe (Seki, 1966a and 1966b) as given in Fig. 1. The endothermic peaks at 360°C and 750°C for analcime from Maze are coincident with those given by Koizumi (1953). The shape of DTA curve of "calcian analcime" somewhat resembles that of analcime. But, detailed observation reveals endothermic peaks at 375°C and 580°C correspond to the peaks of wairakite. wairakite shows endothermic peaks at 380°C and 570°C respectively. X-ray data. X-ray powder data were obtained of "calcian analcime" together with analcime as shown in Table II. The "analcimes" were indexed based on the cell data and space group by Beattie (1954) for analcime and by Coombs (1955) for wairakite, respectively. The X-ray powder data of the analcime from Maze are well coincident with those of anisotropic analcime given by Hashimoto (1964), and agree well with the cubic cell and space group. The following analcimes from various localities of Japan collected by K. Sakurai are also of cubic type: a) Hizaka, Shizuoka Pref., b) Koyabe-machi, Yokosuka-city, Kanagawa Pref., c) Himo- sashi, Hirato-shima, Nagasaki Pref., d) Yamasaki, Taira-city, Fukushima Pref. The "calcian analcime" has extra peaks presenting d-spacing as 6.86 A, 3.25 A, 2.344 A, and 2.292 A respectively, which correspond well to monoclinic wairakite (Steiner, 1955; Coombs, 1955, p. 701; Seki, 1966a). Based on the monoclinic indexing, accurate cell dimensions were determined for "calcian analcime" from powder data with quartz as an internal standard: a =13.70, b =13.69, and c =13.66, all ± 0.01 A. 9 angle was determined by trial and error adjustments of dQ within ± 5 as 90° 10'. Those values are com- f ormable with the data for wairakite, although ,9 angle is smaller and c-dimensions are larger than those of normal wairakite. The "calcian analcime" is apparently monoclinic and agrees with the

0 space group as C h - C2/c or C - C2, but 3.45 A peak of "calcian analcime" does not show paired ref ractions, and 1.709 -1.717 peak 892 K. HARADA and K. SAKURAI [Vol. 43,

Table II. X-ray powder data for analcimes

is paired. Dublet peaks of wairakite around 26° 28CUKn( 3.4 A) is indexed as 400 and 004 respectively (Seki, 1966a) which become less distinct as the Ca weight % decreases and Na weight % increases (Surdam, 1967, p. 144). With electron microprobe analyses, Surdam (1967, p. 144-155) has confirmed the existence of complete Na for Ca substitution in analcime-wairakite series. Discussion. Coombs et al. 1959, p. 60) presented the following stage in zeolite facies including stable calcium-zeolite associations progressively deeper in sequences: Stage 1. Heulandite-analcime stage. Stage 2. Laumontite stage. No, 9] Calcian Analcime from Sugasima 893

Stage 3. Prehnite-pumpellyite stage. Then, Coombs (1960, p. 340-342; 1961, p. 204-206) defined stage 3 as prehnite-pumpellyite metagreywacke facies. Recently, Utada (1965, p. 214) recognized the clinoptilolite-mordenite-opal- montmorillonite zone above Coomb's stage 1. Furthermore, Seki (1966b) and Surdam (1967, p. 140-143) recognized a wairakite zone between prehnite-pumpellyite metagreywacke facies and Coombs' stage 2. Subsequently, Croock (1961), Seki (1966, oral comm.), Harada, Tomita, and Sudo (1961), and Harada and Tomita (1967) recognized the stilbite zone above Coombs' stage 1 closely associated with clinoptilolite. In the light of the above data, the following schematic stages of zeolite assemblages can be represented along the progressively rising grade of alteration or metamorphism at a relatively shallow depth, with excess silica and water vapor. Stage 1. Clinoptilolite-mordenite-stilbite stage. Stage 2. Analcime-heulandite-mordenite stage. Stage 3. Laumontite stage. Stage 4. Wairakite stage. Stage 5. Prehnite-pumpellyite metagreywacke facies. Wairakite is stable at relatively high temperature but at low pressure (Coombs, 1960, p. 457; 1961, p. 212; Seki, 1966b, p. 34; Surdam, 1967, p. 142; Harada, Tomita and Sudo, 1966; Harada and Tomita, 1967). If temperature is the dominant physical factor affecting the formation of wairakite, there arises a possibility that analcime-wairakite might be utilized as a rough geothermometer ranging from the writers' stage 2 to stage 4. Acknowledgments. The writers wish to express their healtfelt thanks to Prof. T. Sudo of the Geological and Mineralogical Institute, Tokyo University of Education and Prof. Y. Seki of Saitama Uni- versity for helpful comments. Thanks are also due to Prof. K. Nagashima and Mr. K. Nakao of Institute of Chemistry, Tokyo University of Education for chemical analyses. Dr. J. G. Liou of the Institute of Geology and Geophysics, University of California, Los Angeles has kindly sent us PhD dissertation of Univ. Calif, Los Angeles in 1967. Special thanks are also due to Prof. Emeritus H. Fu jimoto of the Geological and Mineralogical Institute, Tokyo University of Education for helpful suggestions on geologic setting of the locality.

References Beattie, I. R.: The structure of analcime and ion-exchange forms of analcime. Acta Cryst., 7, 357-359(1954). 894 K. HARADA and K. SAKURAI [Vol. 43,

Coombs, D. S.: X-ray observations on wairakite and non-cubic analcime. Mineral. Mag., 30, 699-708 (1955). Lower grade mineral f acies in New Zealand. Rept. 21st Internat. Geol. Congr., Part 13 (petrographic province, igneous and metamorphic rocks), 339-351, Copenhagen (1960). Some recent work on the lower grade of metamorphism. Austr. J. Sci., 24, 203-215 (1961). Coombs, D. S., Ellis, A. J., Fyfe, W. S., and Taylor, A. M.: The zeolite facies, with comments on the interpretation of hydrothermal syntheses. Geoch. Cosmoch. Acta, 17, 53-107 (1959). Crooke, K. A. W.: Vein minerals from Tamworth and Parry Group (Devonian and lower Carboniferous) N.S.W. Am. Mineral., 46, 1017-1029 (1961). Fujimoto, H.: On the geology of the Toba district, Mie Prefecture. J. Geol. Soc. Japan, 49, 262-263 (1942). Harada, K., Tomita, K., and Sudo, T.: Note on the conversion of stilbite and heulandite into wairakite under very low saturated water vapor pressures. Proc. Japan Acad., 42, 925-928 (1966). Sodian stilbite from Onigajo, Mie Prefecture, Japan with some experimental studies concerning the conversion of stilbite to wairakite at low water vapor pressures. Am. Mineral., 52, No 9-10 (in press). Hashimoto, M.: Analcime-veins in mudstone, 2703 m beneath the surface of Kasukabe, Saitama Prefecture. J. Geol. Soc. Japan, 70, 226 (1964). Iizuka, Y.: Geological Map of Toba and the Explanatory Text. Tokyo (1923). Koizuma, M.: The differential thermal analysis curves and the dehydration curves of zeolite. Mineral. J. (Tokyo), 1, 36-47 (1953). Seki, Y.: Wairakite in Japan. I. J. Jap. Assoc. Miner. Petr, and Econ. Geol., 55, 254-261 (1966a). Ditto. II. Ibid., 56, 30-39 (1966b). Shimizu, S.: Analysis of analcime from Maze. Echigo Province. Beitr. Mineral. Japan, 5, 295 (1915). Steiner, A.: Wairakite, the calcium analogue of analcime, a new zeolite mineral. Mineral. Mag., 30, 691-698 (1955). Surdam, R. C.: Low-grade metamorphism of the Karumutsen group, Battle Lake area, Vancouver Ireland, B.C. PhD dissertation of Univ. Calif. Los Angeles (1967). Utada, M.: Zonal distribution of authigenic zeolite in the Tertiary pyroclastic rocks in Mogami district, Yamagata Prefecture. Sci. Paper Coll. General Educ. Univ. of Tokyo, 15, 173-216 (1965).