J. Japan. Assoc. Min. Pets. Econ. Geol. 79, 503-508, 1984

Calcian serandite in a magnesioriebeckite-quartz schist from the Mitsuishi district, Hidaka Province, Hokkaido

TOSHIROMORIKIYO Departmentof Geology,Faculty of Science, Shinshu University,Matsumolo 390, Japan

Calcian serandite was found in a magnesioriebeckite-quartz schist from Mitsuishi, Hidaka Province, Hokkaido. The schist is composed of magnesioriebeckite, epidote, calcian serandite, albite, aegirine and quartz. Chemical composition and physical properties of the mineral are presented together with the results of chemical analyses of magnesioriebeckite, pectolite and the host whole rock. The calcian serandite seems to be formed as a primary metamorphic mineral judging from its mode of occurrence. It is assumed that the appearance or disappearance of the mineral in the crystalline schist depends on the chemical composition of the host rock under the condition of the epidote-glaucophane schist facies. This is the first finding of calcian serandite from metamorphic rocks.

From the magnesioriebeckite-quartz

Introduction schist, I found calcian serandite. In this paper,

Serandite is the manganese analogue of the mode of occurrence, physical properties and

pectolite, and calcian serandite has an interme chemistry of the mineral are presented. diate composition between pectolite and seran Description of the rock samples dite. Pectolite has been already reported as a

vein mineral in the epidote-amphibolite from Calcian serandite-bearing specimen was

the Mitsuishi district, Hidaka Province, Hok taken from a block on mountain slope 3km

kaido, by Suzuki et al. (1974) and Harada and north-northeast of Mitsuishi (1 in Fig. 1). The

Hariya (1984). rock is dark green and very fine-grained. It is

In this district, various kinds of metamor rather homogeneous, and schistosity or bedding is not recognized. Original texture such as phic rocks are exposed as xenolithic blocks in the serpentinites as shown in Fig. 1. The clastic or igneous one is not observed, but it

metamorphic rocks are grouped into the follow seems to be a kind of ferruginous siliceous

ing types: epidote-amphibolite (hornblende+ sedimentary rock. Under the microscope, the

epidote+albite+chlorite•}muscovite•}gar rock is composed of magnesioriebeckite,

net•}biotite), greenschist (actinolite+epidote+ quartz, albite, aegirine and calcian serandite

albite+chlorite+muscovite•}riebeckite with a subordinate amounts of epidote, magnet ite and clay mineral. Magnesioriebeckite is a •} aegirine•}stilpnomelane•}pumpellyite),

magnesioriebeckite-quartz schist (magnesio small acicular and columnar crystal with the

ribeckite+quartz+epidote+calcian seran- size less than 0.01•~0.06mm. Its color is vivid bule-green to violet. Calcian serandite is an dite+albite+aegirine+magnetite), metagab- euhedral and prismatic crystal, and is scattered bro (chlorite+albite•}prehnite•}pumpellyite).

(Manuscript received July 9, 1984) 504 Toshiro Morikiyo

Fig. 2. Photomicrograph of calcian serandite from specimen 73081203 in plane light. Bar: 0.1mm. Cs, calcian serandite; Mr, magnesioriebeckite; Qz, quartz.

the quarry at the south of Horai-san (2 in Fig. 1). The rock is a dark green medium-grained epidote-amphibolite and contains large radiat Fig. 1. Geological map of the Mitsuishi district ing aggregates of pectolite. This consists of and localities of the specimens studied. blue-green hornblende, epidote, albite, chlorite, pectolite, muscovite and pumpellyite with a 1: calcian serandite-bearing rock (speci men 73081203). subordinate amounts of sphene, rutile and 2: pectolite-bearing rock (specimen apatite. Pectolite is a colorless large poikilo 78100801). blastic crystal with a length of several centi Compiled after Ishibashi (1939) and Mori meters and includes hornblende, albite and kiyo (1979). pumpellyite. Aggregates of dull yellowish in the fine-grained matrix composed of green chloritic mineral have been formed along magnesioriebeckite, quartz and albite as seen in the periphery. Pumpellyite forms aggregates

Fig. 2. It is colorless and average grain size is of wedge-shaped grains and occurs as veinlets.

0.16•~0.04mm. Many tiny inclusions of low The original mineral assemblage seems to be

index material, which can not be identified, are musc ovite-chlorite-albite-epidote-hornblende, contained, and the periphery of crystal is some which is for the albite-epidote-amphibolite times altered to brown clayey minerals. facies (Morikiyo, 1979). Pectolite, pumpellyite

Epidote is present but is a very small amount. and chloritic mineral would be formed in the

Quartz is abundant and shows a saccharoidal later stage of the metamorphism, of which texture. These minerals do not show any reac condition seems to be lower than that of the tion texture among each other, except for albite-epidote-amphibolite facies. between calcian serandite and clayey minerals.

Therefore, magnesioriebeckite, quartz, albite, Mineral description and discussion aegirine and epidote are in equilibrium with Calcian serandite was separated from the calcian serandite during the metamorphism, other minerals in the powdered sample by which seems to be in the epidote-glaucophane means of the heavy liquids with a centrifuge. schist facies. Densities of the heavy liquids were measured

Pectolite-bearing rock has been found from with the specific gravity indicators, and the Calcian serandite from Mitsuishi district 505

Table 1. X-ray diffraction data

1: Pectolite (Schaller, 1955).

2: Pectolite from Mitsuishi (specimen 78100801).

3: Manganoan pectolite (Schaller, 1955).

4: Calcian serandite (Schaller, 1955).

5: Calcian serandite from Mitsuishi (specimen 73081203).

s: strong, ms: moderately strong, mw: moderately weak.

Experimental condition: CuEa 40kv, 20mA, scanning speed 0.5•‹/min.

densitiy of calcian serandite was measured to ite. Mn/Ca ratio of calcian serandite exceeds

be 3.15•}0.02. 1. There is no compositional difference from

X-ray powder data of calcian serandite grain to grain. Whether a crystal is chemi and pectolite are presented in Table 1 together cally zoned or not could not be determined

with the data of Schaller (1955). The data for because of the small size. Pectolite is almost

pectolite is in good accord with Schaller's data, free from MnO and is very close to the end and that of calcian serandite from this district member of pectolite. ƒÂD value of this pectolite

shows an intermediate value between man has been reported to be -314% by Kuroda

ganoan pectolite and calcian serandite by et al. (1979). Schaller. Pectolite usually occurs as a hydrothermal

Refractive indices of calcian serandite mineral in serpentinites and in dolerites. It is

were determined to be ƒ¿=1.641, ƒÀ=1.648, also reported in alkaline igneous rocks and in

ƒÁ =1 .675. 2Vz is about 48•‹ and the elongation kimberlites. However, it has rarely been re

is nearly parallel to Z and extinction angle is ported from metamorphic rocks except for

usually small. some calcium-rich rocks and skarns (Deer

Calcian serandite and magnesioriebeckite et al., 1978).

were chemically analysed as shown in Table 2. Occurrence of calcian serandite and

The analytical result of pectolite from locality serandite is rare and they have been found

2 in Fig. 1 is also presented in Table 2. Atomic mainly from alkaline igneous rocks, such as

ratios of the minerals were calculated on the nephelin syenite in Greenland (Winther, 1901),

anhydrous basis of O=17 for calcian serandite phonolite in Queensland, Australia (Carr and

and pectolite, and O=23 for magnesioriebeck Phillips, 1976), lujavrite in Lovozero, Kola pen 506 Toshiro Morikiyo

Table 2. Chemical analyses

Fig. 3. A(Al+Fe+3-3K)-C(Ca)-F(Fe+2+Mn+ Mg)-N(Na) diagram. Abbreviation for minerals: Pect, pectolite; Cal Ser, calcian serandite; Ser, serandite; Ab, albite; Aeg, aegirine; Rie, riebeckite; Gl, glauco phane; Tr, tremolite; Act, actinolite; Parag, paragonite; Pump, pumpellyite; Ep, epidote; Chl, chlorite. Minerals are indicated by atomic ratios of A-C-F-N. Star, chemical composition of calcian se randite-bearing rock. Triangle: calcian serandite-free riebeckite-quartz schists * EPMA analyses. and riebeck ite-al bite-epidote-actinolite ** Calculated based on the assumption that Fe+3/Fe+2=1. schist.

insula (Semenov et al., 1976) and sodalite riebeckite-albite-epidote-actinolite schist from syenite in St. Hilaire, Canada (Semenov et al., Mitsuishi and that of riebeckite-quartz schist

1976; Philpotts, 1974). Recently, pure seran from other areas of the Kamuikotan dite has been reported from the stratiform metamorphic belt are also plotted in the dia manganese ore deposits of the Tanohata mine, gram. These rocks are considered to belong to

Japan, and its crystal structure has been deter the epidote-glaucophane schist facies and the mined (Takeuchi et al., 1976). Calcian seran paragenesis, epidote-albite-riebeckite is stable. dite has not yet been found from metamorphic Chemical composition of calcian serandite rocks. bearing schist is plotted in the N side of the Metamorphic minerals, which are common plane Ep-Ab• Aeg-Rie• Gl, whereas those of in the epidote-glaucophane schist facies rocks calcian serandite-free schists are plotted are shown in the A (Al+Fe+3-3K)-C(Ca)- between A and the plane. From this figure, it

F(Fe+2+Mn+Mg)-N(Na) diagram (Fig.3). is considered that the appearance or disappear

Mineral paragenesis of the calcian serandite ance of calcian serandite depends on the chemi bearing rock is indicated by the triangular cal composition of the host rock, especially Na pyramid (Ep-Rie•EGl-Ab• Aeg-Cal Ser) content under the condition of the epidote within the diagram and chemical composition glaucophane schist facies. of the host rock is plotted within the pyramid.

For comparison, chemical composition of Acknowledgements: I would like to Calcian serandite from Mitsuishi district 507

Table 3. Chemical analyses of whole

1: Calcian serandite-bearing magnesioriebeckite-quartz schist (Specimen 73081203). 2: Riebeckite-bearing albite-quartz schist from Kamietanbetsu

(Suzuki and Suzuki, 1959).

3: Aegirine augite-bearing riebeckite-quartz schist from

Kamuikotan (Suzuki and Suzuki, 1959).

4: Aegirine-bearing riebeckite-albite-epidote-actinolite schist

from Mitsuishi (Ishibashi, 1937). express my appreciation to Prof. Y. Kuroda of Ishibashi, M. (1937), On the metamorphic rocks of

Shinshu University for helpful suggestions and the Mitsuishi district, Hidaka Province. J. critical reading of the manuscript. I am also Geol. Soc. Japan, 44, 487-489 (in Japanese). grateful to Dr. K. Tazaki of Instiute for Ther Ishibashi, M. (1939) On some metamorphic rocks of the Mitsuishi district, Hidaka Province. mal Spring Research, Okayama University and Bull. Geol. Surv. Hokkaido, No. 10, 7-34 (in Dr. M. Inomata of Geological Institute, Tokyo Japanese). Nogyo Daigaku for their help in the analytical Kuroda, Y., Suzuoki, T. and Matsuo, S. (1979), The work. lowest ƒÂD found in hydrous silicate, pectolite. Nature, 279, 227-228.

Morikiyo, T. (1979), Zonal structure of garnet from References the metamorphic rocks in the Mitsuishi dis Carr, G.R. and Phillips, E.R. (1976), An occurrence trict, Hokkaido. J. Assoc. Min. Petr. Econ. of eudialyte and manganoan pectolite in a Geol., 73, 27-35 (in Japanese). phonolite dyke from southeastern Queensland. Philpotts, A.R. (1974), The monteregian province. Mineral. Mag., 40, 853-856. In The Alkaline Rocks (Soerensen Ed.). John Deer, W.A., Howie, R.A. and Zussman, J. (1978), Wiley, New York, 293-310. Rock-Forming Minerals, Vol. 2A: Single Schaller, W.T. (1955), The pectolite-schizolite-se Chain Silicates (2nd ed.). pp. 668, Longman, randite series. Amer. Mineral., 40, 1022-1031. London. Semenov, E.L, Maksimyuk, I.E. and Arkangels Harada, Z. and Hariya, Y. (1984), Minerals in kaya, V.N. (1976), On the minerals of the Hokkaido. pp. 327. Geol. Surv. Hokkaido (in pectolite-serandite group. Zap. Vses. Min. Obshch., 104, 154-163 (in Russian). Japanese). 508 Toshiro Morikiyo

Suzuki, J. and Suzuki, Y. (1959), Petrological study Japanese). of the Kamuikotan metamorphic complex in Takeuchi, Y., Kudoh, Y. and Yamanaka, T. (1976), Hokkaido, Japan. J. Fac. Sci. Hokkaido Univ., Crystal chemistry of the serandite-pectolite Ser. IV, 10, 349-446. series and related minerals. Amer. Mineral., Suzuki, M., Arita, K. and Niida, K. (1974), Guide 61, 229-237. book for the geological excursion: Mitsuishi Winthr, Chr. (1901), Schizolite, a new mineral. - Cape Erimo-Hiroo. Geol. Soc. Japan, 29pp (in Medd. om Gronland, 24, 196-203.

北 海 道,日 高 三 石 地 方 の マ グ ネ シ オ リ ー ベ ッ ク 閃 石 片 岩 か ら, カ ル シ ア ン セ ラ ン ダ イ トの 産 出

森 清 寿 郎

北 海 道,日 高 三 石 地 方 の マ グ ネ シ オ リー ベ ッ ク閃 石 一 石 英 岩 か ら,カ ル シ ア ン セ ラ ン ダ イ トを発 見 し た 。 母 岩 は,マ グ ネ シ オリ ー ベ ック 閃 石,緑 レ ン石,カ ル シ ア ン セ ラ ン ダ イ ト,曹 長 石,エ ジ リ ン,石 英 な ど か ら 成 る 変 成 岩 で,原 岩 は 鉄 に 比 較 的 に富 む 珪 質 堆 積 岩 と思 わ れ る。 そ の 全 岩 組 成 は, Alに 対 し て Naに 當 み, Mn量 も比 較 的 多 い。 カ ル シ ア ン セ ラ ン ダ イ トは産 状 か ら み て,緑 レ ン 石 一 藍 閃 石 片 岩 相 の 変 成 鉱 物 と 思 わ れ る 。 こ の 鉱 物 は,今 ま で アル カリ 火 成 岩 か らの み 発 見 され て い た が,今 回 の 発 見 に よ り, 変成岩中で も母岩の化学組成が適 当であれば出現可能 であ ることが判明した。