Some Petrological Aspects on Stilpnomelane in Glaucophanitic Metamorphic Rocks

J. Japan. Assoc. Min. Petr. Econ. Geol. 70, 377-387, 1975

SOME PETROLOGICAL ASPECTS ON STILPNOMELANE IN GLAUCOPHANITIC METAMORPHIC ROCKS

MITSUOHASHIMOTO NationalScience Museum, Tokyo KEIICHIROKANEHIRA Departmentof Earth Sciences, Chiba University, Chiba Under the glaucophaniticmetamorphic conditions, stilpnomelane appears in schists whose grade rangesfrom the pumpellyitezone to the biotitezone. Theparageneses of stil pnomelanein these schistsare rather simple,and the mineralis associatedcommonly with quartz, chloriteand calcite and rarely with epidote, pumpellyiteand actinolite. The apparentwide range of chemicaland mineralogicalcompositions of stilpnomelane-bearing schistsis due to small-scaleheterogeneity of rocks, but not due to their suitablebulk chemicalcomposition.

INTRODUCTION the Sangun (Miyakawa, 1961, 1964; Nureki, Stilpnomelane is a common mineral in 1967; Hashimoto, 1968a, 1968b; Nishimura crystalline schists of the glaucophanitic 1971), Sambagawa (Kojima, 1944; Seki, metamorphic terranes. The mineral has 1958; 1961, Hide, 1961; Iwasaki, 1956, been reported to occur in various kinds of 1963; Banno, 1964; Kanehira, 1967; Ernst rocks of pelitic, psammitic, quartzofeldspa et al. 1970; Toriumi, 1971; Tanaka & thic, basic, quartzose and calcic composi Fukuda, 1974), Kamuikotan (Banno & tions, but has not been found in highly Hatano, 1963; Tazaki, 1964; Shibakusa, 1974; Herve, 1975) and other (for example, magnesian rocks. In spite of its wide oc Kanisawa, 1964) glaucophanitic metamor currence, however, most papers describe merely the presence or absence of this phic terranes of Japan (see also Miyashiro, mineral in rocks and do not give details of 1961, 1967; Hashimoto et al., 1970). The mineral has been found also in Paleozoic and the parageneses. Only a few excellent Mesozoic greenstones and associated rocks studies by Zen (1960) and Brown (1971) of the Tamba (Hashimoto & Saito, 1970), have discussed the mineral associations of Chichibu (Hashimoto & Kashima, 1970; stilpnomelane-bearing schists. This paper Suzuki 1972, Ishimoto 1974), Kitakami deals briefly with the modes of occurrence (Moriya, 1972) and other areas (Seki et al., and paragenetic relations of stilpnomelane 1964). Katada & Sumi (1966) reported in the glaucophanitic and allied low-grade stilpnomelane in association with biotite in metamorphic rocks mostly of Japan. a basic tuff of the non-glaucophanitic Ryoke STABILITY RANGE OF STILPNOMELANE belt. IN GLAUCOPHANITIC METAMORPHIC In these Japanese metamorphic dis ROCKS tricts the stability range of stilpnomelane A number of papers have reported extends from the pumpellyite zone to the occurrences of stilpnomelane in schists of biotite zone as shown in Fig. 1. Most

(Manuscript received, October 3, 1975) 378 M, Hashimoto and K. Kanehira

Fig. 1. Appearance and disappearance of stilpnomelane in various localities of glaucophanitic metamorphism in Japan. Numbers or names of zones of stilpnomelane occurrence are in rectangles. authors state that stilpnomelane becomes stability of pumpellyite in basic rocks, in the stable first in the pumpellyite zone where Kanto Mountains Sambagawa terrane. The pumpellyite appears in basic rocks but acti low temperature limit of the stability of nolite does not. Seki (1961),however, reports stilpnomelane in the rocks now considered, the occurrence of stilpnomelane in a zone therefore, may be in the pumpellyite zone. whose metamorphic grade is so low that The frequency of occurrence of stilp even pumpellyite does not crystallize in nomelane in schists seems to increase in basic rocks. But it is not indisputable that zones of the pumpellyite-actinolite and the mineral so identified under the micro epidote-glaucophane facies. The mineral scope is truly stilpnomelane, because the has been reported to occur in nearly all identification of such fine-grained and kinds of rocks of these facies zones excluding micaceous minerals in poorly recrystallized magnesian rocks such as talc schist and rocks is not easy. On the other hand, highly chloritic schist. In much higher Toriumi (1971) has not found stilpnomelane grade zones stilpnomelane becomes less in rocks of his Zone I, which is a zone of the common again. But it persists further into zeolite facies and defined by the associa zones whose grades are higher than the tion of laumontite and quartz in sandstones garnet isograd of the glaucophanitic meta and further characterized by the in morphism, and in some areas it is found Some petrological aspects on stilpnomelane in glaucophanitic metamorphic rocks 379 even in rocks of the biotite zone, particularly in the Alpine metamorphic belt of Switzer in rocks of psammitic and quartzose com land is located in the anchimetamorphic positions (Miyakawa, 1964; Ernst et al., zone, in the lower grade part of which the 1970). Thus the higher temperature limit mineral is sometimes associated with of the stilpnomelane stability range in the glauconite. The mineral facies of this Japanese glaucophanitic belts seems to anchimetamorphic zone is assigned by the exceed the biotite isograd. authors to the prehnite-pumpellyite facies. Stilpnomelanehas been found widely in Niggli (1960, 1970) states that stilpnomelane rocks of the chlorite and biotite zones of the is found in rocks of his stilpnomelane zone Alpine and Otago Schist belts of New Zea and of the lower part of the chloritoid zone. land (Hutton, 1940; Mason, 1962; Brown, Although the mineral facial characteristics 1967, 1971; Kawachi, 1970; Bishop, 1972). of the Swiss Alpine belt are unusual as The mineral appears first in greywackesof the compared with any other metamorphic Chl. 1 zone (e.g., Hutton, 1940; Kawachi, terranes of the world, the above-mentioned 1970), which is a zone of the prehnite two zones may be of the glaucophane schist pumpellyite facies. The stability of stil facies in a broad sense. Stilpnomelane pnomelane increases in the higher grade becomes unstable in the higher grade part zones, and in the Chl. 3, Chl. 4 and Biotite of the chloritoid zone and in much higher zonesin the eastern and western Otago dis zones it disappears. tricts at least a third of rocks studied by Meisl (1970) described in detail the low Brown (1971) carry this mineral. The temperature metamorphic rocks of the above-mentioned three zones are all con Soonwald and Taunus districts, southwest sidered to be of the greenschist facies. Germany. Stilpnomelane, pumpellyite and Finally, stilpnomelane disappears in the actinolite along with subordinate crossite, garnet zone of the epidote amphibolite all being the characteristic minerals of the facies. In contrast with the Japanese pumpellyite-actinolite facies, are found glaucophanitic metamorphic terranes, the over the whole area. Furthermore, stil garnet isograd is located at the higher tem pnomelane in rocks of the quartz-albite perature side of the biotite isograd in the muscovite-chlorite subfacies or the glauco New Zealand schist belts, as in the case of phane schist facies are reported to occur the classical Barrovian zones of Scotland. also from the Turkish glaucophanitic ter The pressure of metamorphism would have ranes by van der Kaaden (1966, 1969) and been lower in the New Zealand than in the cogulu (1967). It occurs, according to the Japanese belts. authors, in quartzose metamorphic rocks Similar wide occurrence of stilpnome associated with metavolcanic and meta lane is reported from the outer zones of the sedimentary rocks. Occurrences of stilp metamorphic belt of the Swiss Alps (Niggli, nomelane in similarly low temperature and 1960, 1970; Martini & Vuagnat, 1970;Frey moderately high pressure metamorphic et al., 1973; Frey et al., 1974 and many rocks have been reproted from the Carpa other papers). According to Frey et al. thians by Streckeisen (1968), Krautner & Medesan (1969) and Maier (1969), from (1973)and Frey et al. (1974),the lowertem Spanish Cordillera by Nijhuis (1964) and perature limit of the stilpnomelanestability 380 M. Hashimoto and K. Kanehira

from Calabria by de Roever (1972). The pressure condition of metamorphism is In the Franciscan blueschist belt of considered to have been higher in the latter western United States, metaclastic rocks than in the Japanese and probably in the and metachert are the principal types of European Alpine metamorphic belts (Ernst rocks in which stilpnomelane is a stable et al., 1970; see also Hashimoto, 1972). mineral (e.g. Coleman & Lee, 1963; Ernst, Wide occurrence of stilpnomelane in 1965; Ghent, 1965; Ernst et al., 1970). argillaceous phyllites are reported by Zen

According to Ernst & Seki (1967), Coleman (1960) from the Castleton area, which is in (1967), Ernst et al. (1970) and others, the a greenschist facies zone of the Barrovian selected areas of the Franciscan terranes type metamorphic belt of the Appalachians. are classified into two or three parts or Except this study, however, the occurrence zones, which are considered to represent of stilpnomelane in the Barrovian kyanite different grades of metamorphism. Pum sillimanite type terranes has not been pellyite is the characteristic mineral in documented well (see also Mather & Ather metavolcanic rocks in the seemingly lower ton, 1965; Mather, 1970). grade zone, which is said to be a"high In conclusion, it can be said that the pressure" pumpellyite zone, because it is a stability field of the mineral stilpnomelane part of the exceedingly high-pressure jade in the regional metamorphic rocks extends ite-glaucophane type of fades series of this over the physical conditions of the higher belt. On the other hand, metavolcanic temperature part of the prehnite-pumpellyite rocks of the higher grade zone contain facies, the higher pressure part of the green epidote, glaucophane, actinolite and garnet. schist facies and the lower pressure part of The fades of the latter zone seems to be the the glaucophane schist facies. In other glaucophane schist facies. There is a words, the conditions of the pumpellyite transitional part between the two zones, actinolite and epidote-glaucophane facies where metabasalts carry lawsonite, glau may be the most favorable for the formation cophane and metamorphic aragonite along of stilpnomelane in schists. with pumpellyite. Jadeitic pyroxene is a characteristic mineral in metagreywackes MODES OF OCCURRENCE AND PARA there. This transitional zone is also of the GENETIC RELATIONS OF STILPNOME typical glaucophane schist facies. LANE IN THE JAPANNESE GLAUCOPHA NITIC METAMORPHIC ROCKS Stilpnomelane occurs in both metagrey wackes and metacherts of all the above It has been stated above that stilpno mentioned zones, though it is less common melane occurs in nearly all kinds of rocks in the higher grade than in the lower grade which have been recrystallized under the zones. On the other hand, little stilpno conditions of low-temperature and mode melane is found in metabasalts of the rately high-pressure regional metamorphism. However, most descriptions about mine Franciscan terranes. Consequently, in this ralogy of these low-grade rocks show merely typical high-pressure metamorphic belt the presence or absence of this mineral in stilpnomelane is stable in metasedimentary rocks, using a simple . designation such as rocks of the "high-pressure" pumpellyite •}, and do not give details of the modes of zone and the glaucophane schist facies zone. occurrence and parageneses. We examined Some petrological aspects on stilpnomelane in glaucophanitic metamorphic rocks 381 a number of thin sections of stilpnomelane these low-grade basic metamorphic rocks bearing rocks mostly from the Sangun, indeed frequently carry stilpnomelane. But Sambagawa, Chichibu and Tamba terranes careful observation of thin sections reveals of Japan. Special attention has been paid that stilpnomelane is found usually in rocks in interpreting the textural relationships of derived from tuff or tuff breccia but not in the newly formed metamorphic minerals so those of the massive crystalline rock origin, as to list up minerals truly associated with and that in these greenstones or green stilpnomelane in the rocks. Particularly in schists it occurs only in thin lenticular felsic heterogeneous rocks such as those derived seams pararell to the schistosity of the from pyroclastic rocks, small-scale domains rocks (Fig. 2) or clean-cut or network of uniform composition were studied in veinlets consisting mainly of quartz, feld detail. In what follows the results of the spar, chlorite and calcite. Stilpnomelane examination are given along with brief is seldom associated with the principal discussions under the heads classified by metamorphic minerals such as epidote, rock types. pumpellyite and actinolite in the matrix of 1) Greenstones and greenschists: - these basic rocks. On the other hand, when Many papers point out the wide occurrence epidote or pumpellyite occurs in the felsic of stilpnomelane in greenstones and green parts, they are almost always strongly xen schists, which are considered to have been omorphic and are being replaced by stil derived from lavas and pyroclastic rocks of pnomelane as shown in Fig. 3. The co basaltic and andesitic compositions and existence of actinolite with stilpnomelane is are characterized by the common associa rarely observed in highly ferromagnesian tion of calciferous amphiboles and Ca-Al rocks or parts of rocks. The observed hydrous silicates. There is no doubt that stable mineral assemblages of the above

Fig. 3. Photomicrograph of stilpnomelane-epidote Fig. 2. Photomicrograph of stilpnomelane-bearing quartz vein in greenschist. The host rock lens in greenschist. The lens consists of consists of epidote, chlorite, quartz, albite stilpnomelane, chlorite, quartz and mus and opaque minerals with no stilpnomelane. covite and is free from epidote. On the Epidote in the vein is being replaced by other hand, the matrix is composed of stilpnomelane and divided into a few iso chlorite, quartz, albite and muscovite lated grains which are in the optical con with abundant epidote and sphene, but tinuity and brought to an extinction at carries no stilpnomelane. Length of bar: the same rotating position under the cro 0.5mm. ssed nicols. Length of bar: 0.5mm. 382 M. Hashimoto and K. Kanehira mentioned felsic seams and veinlets are melane-bearing parts of the pelitic and summarized as follows. psammitic rocks are, therefore, the same as Stilpnomelane (monomineralic veins) those in the felsic seams or veins in basic Stilpnomelane+chlorite rocks. Stilpnomelane+quartz 3) Impure limestone: -Iwasaki (1956) Stilpnomelane+ chlorite+ quartz emphasized that stilpnomelane occurs dom Stilpnomelane+ chlorite+ calcite inantly in calcareous layers closely inter Stilpnomelane+ quartz+ calcite calated within sedimentogenous green Stilpnomelane + chlorite + quartz + calcite schists in the Samgabawa terrane. Stil Albite and muscovite may be the additional pnomelane-bearing impure limestone is not phases, and in the higher grade zone rocks rare also in the regional metamorphic dis garnet rich in spessartine and/or grossular tricts other than the Sambagawa in Japan. molecules and rarely biotite are the other Common parageneses in these rocks are assemblage minerals. stilpnomelane+quartz+calcite with or 2) Pelitic and psammitic rocks: -It without chlorite and feldspar, essentially is generally accepted that stilpnomelane is the same as those observed in small-scale a common mineral of pelitic and psammitic stilpnomelane-bearing parts in basic, pelitic schists in the glaucophanitic metamorphic and psammitic schists described above. terranes. Actually, however, frequency The actual modes of the minerals are greatly distribution of stilpnomelane in the observed variable, and some rocks are very rich in ordinary clastic rocks is rather low, parti calcite while others are not. CaO of these cularly in the fine-grained and homogeneous stilpnomelane-bearing highly calcareous schists is mostly fixed as calcite, and the pelitic schists. Higashino (personal com munication, 1974) found by means of the rocks are practically free from this oxide in electron probe microanalyser that brown terms of the silicate paragenesis. No Ca-Al micaceous minerals in pelitic and psammitic hydrous silicate is associated with stilpno schists of drill cores obtained in the Besshi melane in this kind of rocks, in spite of mining district, which is a part of the Sam their high CaO contents (Table 1). bagawa metamorphic terrane, are mostly Rocks that are very rich in stilpno oxydized chlorites (Chatterjee, 1966) and melane and are to be called stilpnomelane not stilpnomelane, and that the latter schist are frequently occur as beds of a mineral is exceedingly rare in ordinary considerable thickness (several centimeters pelitic schists of the district. When to a few meters) in the Sangun, Sambagawa stilpnomelane is found in pelitic schists and other glaucophanitic terranes of Japan. studied by the present writers, it occurs The mineral assemblages of these stilpno usually in thin seams whose composition melane schists are rather simple and com deviates from that of the host rock and parable with those of impure limestones and becomes favorable to the formation of thin felsic seams in greenschists mentioned stilpnomelane as in the case of greenstones above. The principal constituents are and greenschists. Matrix of sandstones is stilpnomelane, chlorite, quartz and calcite another host of stilpnomelane. with subordinate feldspar, garnet and The mineral parageneses of stilpno opaque minerals. The rocks mentioned in Some petrological aspects on stilpnomelane in glaucophanitic metamorphic rocks 383

Table 1. Chemical analyses of stilpnomelane ones that have attracted the attention of quartz-calcite schist (Hashimoto 1975) petrologists and mineralogists because of their unique mineralogy. Minerals such as piemontite, pistacitic epidote, riebeckite, aegirine, spessartine garnet and hematite, often being specularite, are found in many of quartz schists of this type. Stilpnomelane occurs in all these types or groups of quartz schists. Its parageneses in the first group are similar to those observed in felsic seams and veins in basic, pelitic and psammitic schists mentioned above. The calcite-rich stilpnomelane bearing assemblages in the second type rocks are like those of metamorphosed impure limestones. On the other hand, in rocks of the third group stilpnomelane is often associated with minerals characteriz 1. Stilpnomelane-quartz-calciteschist, Oda, Koda ed by high contents of Fe2O3 such as riebec ma-machi, Saitama Prefecture, Japan. The kite, aegirine, pistacitic epidote and he rock is composed of stilpnomelane, quartz, calcitewith minor garnet, chlorite, biotite and matite. The stilpnomelane itself is usually opaque minerals. a ferric variety (e.g. Onuki & Ernst, 1969; 2. Stilpnomelane-quartz-calciteschist, Nagatoro, Ernst et al., 1970; Kawachi 1970). Saitama Prefecture, Japan. The rock consists Zen (1960) and Brown (1971) discussed of stilpnomelane,quartz and calcite with minor chlorite, epidote and opaque minerals. that stilpnomelane in crystalline schists and phyllites may have been formed first as Table 1 are examples of such stilpnomelane a ferrous mineral and subsequently oxydized schist. and transformed into a ferric one. One 4) Quartz schists: -On the basis of of the evidences given by the latter author mineralogical characteristics, three types of for this theory is that brown stilpnomelane quartz schists are discerned in the glauco is associated with minerals indicating low phanitic metamorphic terranes. The first oxygen pressure during metamorphism and type rocks are those characterized by the scarcely with highly ferric minerals. But association of muscovite, chlorite and as Brown himself (1971) mentions one feldspar with abundant quartz. They are example from Washington State, of stil considered to have been derived from pnomelane-hematite-magnetite-riebeckite- siliceous clastic sediments or acid volcanic spessartine-carbonate schist, the associa rocks. The second type rocks contain a tion of stilpnomelane with high Fe2O3 min large amount of calcite but otherwise are erals is not rare, particularly in quartz similar in mineral paragenesis to those of schists of the thrid group. In these rocks the first type. They are derivatives of stilpnomelane may have been primarily siliceous limestones or calcareous cherts. crystallized as a ferric mineral (see also Liou, Ho & Yen, 1975). Quartz schists of the third type are the 384 M. Hashimoto and K. Kanehira

In any case, however, the mineral par content of iron as to crystallize stilpnome ageneses of quartz schists, especially of the lane under the conditions of glaucophanitic third type discriminated here, in the metamorphism, resulting in the scarcity of glaucophanitic metamorphic terranes have this mineral in them, though the ratio Fe/ not been studied so well and the relevant Mg is usually higher in pelitic than in basic data are still insufficient. rocks in bulk composition of hand sped men. Furthermore, stilpnomelane does not DISCUSSIONS seem compatible with Ca-Al hydrous sili cates such as epidote and pumpellyite in The parageneses of stilpnomelane in rocks of the glaucophanitic metamorphic most rocks excluding again the third type regions are rather simple, excepting those in of quartz schists. Poorness of CaO of the rocks would be favorable to the formation quartz schists of the third type. The common assemblages are those given in the of stilpnomelane. On the other hand, this foregoing paragraphs on greenstones and mineral is commonly found in calcite-rich schists derived from impure limestone. In greenschists (see page 382). The apparent wide occurrence of stil the latter case the high content of CaO is mostly fixed in calcite with high COs, and pnomelane in greenstones and greenschists derived from basic pyroclastic rocks is not the rocks become practically free from CaO attributable to the suitable bulk chemical for the silicate mineral paragenesis. Con compositions of the rocks, but to the small sequently, it is concluded that stilpnomelane scale heterogeneity in the rocks. The would be formed when rocks or parts of stilpnomelane-bearing parts of these schists rocks are actually poor in CaO, or, even if are not similar to their hosts in chemical rich in CaO, all of this oxide is combined composition, but they are perhaps relatively with CO2 to form calcite and is removed richer in iron and poorer in magnesia and from the silicate part of the rocks. lime. On the other hand, the ordinary The paragenetic relations discussed pelitic schists have commonly not so high above are tentatively illustrated with ACF

Fig. 4. ACF diagrams for stilpnomelane parageneses. Shaded areas indicate the composition field of stilpnomelane-bearing rocks. Some petrological aspects on stilpnomelane in glaucophanitic metamorphic rocks 385 diagrams of Fig. 4. In the diagrams we J. Geol. Soc. Japan, 69, 388-393. adopt Zen's assumption (Zen 1960) that all Bishop, D. G. (1972), Progressive metamorphism from prehnite-pumpellyite to greensichst ferric iron in the stilpnomelane analyses facies in the Dansey Pass area, Otago, New represents oxydized ferrous iron of the Zealand. Geol. Soc. America Bull., 83, 3177- original mineral. Ferric and ferrous iron 3198. Brown, E. H. (1967), The greenschist facies in part are to be combined together, and the total of eastern Otago, New Zealand. Contrib. iron is regarded as FeO in the diagram. Mineral. Petrol., 14, 259-292. Under this assumption, the plot of stilpno Brown, E. H. (1971), Phase relations of biotite and stilpnomelane in the greenschist facies. melane is located closer to the corner F of Contrib. Mineral. Petrol., 31, 275-299. ACF diagram than that of chlorite, owing to Chatterjee, N. D. (1966), On the widespread occur the lower Al content of the former mineral. rence of oxidized chlorites in the Pennine zone of the western Italian Alps. Contrib. Mineral. The two ACF diagrams of Fig. 4 indicate Petrol., 12, 325-339. that two tie lines, actinolite-epidote and cogulu, E. (1967), Etude p6trographique de la actinolite-chlorite, are to be broken by region de Mihaliccik (Turquie). Schweiz. mineral. that of stilpnomelane-calcite through the petrogr. Mitt., 47, 683-824. Coleman, R. G. (1967), Glaucophane schists from reactions expressed by the following ap California and New Caledonia. Tectonophysics, proximate equations under the high CO2 4, 479-498. Coleman, R. G. and Lee, D. E. (1963), Glaucophane pressure, stabilizing stilpnomelane in rocks bearing metamorphic rock types of the of the wider range of chemical composition. Cazadero area, Claifornia. J. Petrol., 4, 260- 3 actinolite+2 epidote+8H2O+10CO2= 301. 3 chlorite+10 calcite+21 quartz (1) Ernst, W. G. (1965), Mineral parageneses in Francis can metamorphic rocks, Panoche Pass, Cali Actinolite+7 chlorite+31 quartz+2 CO2 fornia. Geol. Soc. America Bull., 76, 879- =5 stilpnomelane+2 calcite+2 A1203 914. +4.H20 (2) Ernst, W. G. and Seki, Y. (1967), Petrologic com parison of the Franciscan and Sanbagawa Finally, the stilpnomelane-actinolite metamorphic terranes. Tectonophysics, 4, association would become stable in uncomm 463-478. on rocks fairly rich in both iron and Ernst, W. G., Seki, Y., Onuki, H. and Gilbert, M. C. (1970), Comparative study of low-grade magnesia over a wide range of metamorphic metamorphism in the California Coast Range conditions. and the outer metamorphic belt of Japan. Acknowledgements.-Unpublished data were Geol. Soc. America Mem., 124. Frey, M., Hunziker, J. C., Frank, W., Bocquet, J., given by Dr. T. Higashino. The manus Dal Piaz, G. V. Jager, E. and Niggli, E. (1974), cript was reviewed by Prof. Y. Seki and Alpine metamorphism of the Alps: a review. Prof. S. Banno. Our thanks are due to Schweiz. mineral. petrogr. Mitt., 54, 247-290. Frey, M., Hunziker, J. C. and Roggwiller, P. (1973), these persons. Progressive niedriggradige Metamorphose glau konitfiihrender, Horizonte in den helvetischen Alpen der Ostschweiz. Contrib. Mineral. REFERENCES Petrol., 39, 185-218. Ghent, E. D. (1965), Glaucophane-schist facies Banno,S. (1964),Petrologic studies on Sanbagawa metamorphism in the Black Butte area, nor crystalline schists in the Bessi-Inodistrict, thern coast range, California. Amer. J. Sci., central Sikoku, Japan. J. Fac. Sci., Univ. 263, 385-400. Tokyo,11, 15, 203-319. Hashimoto, M. (1968a), Sangun metamorphic ter Banno, S. and Hatano, M. (1963), Zonationof metamorphic rocks in the Horokanaiarea of rane of the Asahi-cho area, Okayama Pre the Kamuikotan metamorphic belt in Hok fecture (in Japanese with English abstract). kaido (in Japanese with English abstract). J. Geol. Soc. Japan, 74, 433-437. 386 M. Hashimoto and K. Kanehira

Hashimoto, M. (1968b), Glaucophanitic metamor Kanehira, K. (1967), Sanbagawa crystalline phism of the Katsuyama district, Okayama schists in the limori district, Kii peninsula. Prefecture, Japan. J. Fac. Sci., Univ. Tokyo, Japan. J. Geol. Geogr., 38, 101-115. II 17, 99-162. Kanisawa, S. (1964) Metamorphic rocks of the Hashimoto, M. (1972), Metamorphic facies series of southwestern part of the Kitakami mountain the high-pressure intermediate group. Rept. land, Japan. Sci. Rept. Tohoku Univ., III 9, 24th IGC, Sec. 2, 75-80. 155-198. Hashimoto, M. (1975), Two manganiferous stilpn Katada, M. and Sumi, K. (1966), Stilpnomelane omelanes from Kanto Mountains Sambagawa coexisting with biotite in a Ryoke metamor crystalline schists. Bull. Natn. Sci. Mus., phic rock. J. Geol. Soc. Japan, 72, 543-544. Ser. C, 1, 131-135. Kawachi, Y. (1970), Geology and metamorphism Hashimoto, M., Igi, S., Seki, Y., Banno, S. and near the head of Lake Wakatipu. Thesis, Kojima, G. (1970), Metamorphic facies map of Univ. Otago. Japan: scale 1:2,000,000. Geol. Surv. Japan. Kojima, G. (1944), On stilpnomelane in greenschists Hashimoto, M. and Kashima, N. (1970), Metamor in Japan. Proc. Imp. Acad., (Japan), 20, phism of Paleozoic greenstones in the Chi 322-328. chibu belt of western Shikoku (in Japanese Krautner, H. G. and Medesan, A. (1969), On stil with English abstract). J. Geol. Soc. Japan, pnomelane in some Romanian Carpathian 76, 199-204. crystalline formation. Tsch. miner. petrogy. Hashimoto, M. and Saito, Y. (1970), Metamor Mitt., 13, 203-217. phism of Paleozoic greenstones of the Tamba Liou, J. G., Ho, C. O. and Yen, T. P. (1975), Petro plateau, Kyoto Prefecture. J. Geol. Soc. logy of some glaucophane schists and related Japan, 76, 1-6. rocks from Taiwan. J. Petrol., 16, 80-109. Hervd, F. (1975), Petrography of the Kamuikotan Maier, O. W. (1969), Stilpnomelangesteine des metamorphic belt at the Ubun-Orowen cross Locva-Kristallins (Rumanien). N. Jb. Miner section, central Hokkaido, Japan. J. Fac. Abh., 110, 199-209. Sci., Hokkaido Univ., IV, 16, 453-470. Martini, J. and Vuagnat, M. (1970), Metamorphose Hide, K. (1961), Geologic structure and metamor niedrigst temperierten Grade in den Westal phism of the Sambagawa crystalline schists pen. Fortschr. Miner., 47, 52-64. of the Besshi-Shirataki mining district in Mason, B. (1962), Metamorphism in the southern Shikoku, southwest Japan (in Japanese with Alps of New Zealand. Bull. Amer. Mus. English abstract). Geol. Rept., Hiroshima Natur. His., 123, 215-247. Univ., 9, 1-82. Mather, J. D. (1970), The biotite isograd and the Hutton, C.O. (1940), Metamorphism in the Lake lower greenschist facies in the Dalradian rocks Wakatipu region, western Otago, New Zea of Scotland. J. Petrol., 11, 254-275. land. N. Z. Dept. Sci. Ind. Res. Geol. Mem ., Mather, J. D. and Atherton, M.P. (1965), Stil 5. Ishimoto, N. (1974) pnomelane from the Dalradian. Nature, 207, , Regional metamorphism of 971-972. the Yawatahama district in western Shikoku , Meisl, S. (1970), Petrologische Studien im Grenz Japan. Sci. Rept. Tohoku Univ., III 12, 279- bereich Diagnese-Metamorphose. Abh. Ness. 330. L. -Amt Bodenforsch. 57, 1-94. Iwasaki, M. (1965), A note on the occurrence of the Miyakawa, K. (1961), General considerations on minerals of stilpnomelane group in the the Sangun metamorphic rocks on the basis Sambagawa crystalline schist region , Japan. of their petrographical features observed J. Gakugei, Tokushima Univ., 7, 1-17. in the San-in provinces, Japan. J. Earth Sci., Iwasaki, M. (1963), Metamorphic rocks of the Nagoya Univ., 9, 345-393. Kotu-Bizan area, eastern Sikoku . J. Fac. Miyakawa, K. (1964), A peculiar porphyroblastic Sci., Univ. Tokyo, II, 15 , 1-90. albite schist from Nichinan-cho , Tottori Kaaden, G. van der (1966), The significance and Prefecture, southwest Japan. J. Earth Sci., distribution of glaucophane rocks in Turkey . Nagoya Univ., 12, 1-16. Bull. Min. Res. Expl. Inst. Turkey , 67, 36-67. Miyashiro, A. (1961), Evolution of metamorphic Kaaden, G. van der (1969), Zur Entstehung der belts. J. Petrol., 2, 277-311. Glaukophan-Lawsonit- und glaukophaniti Miyashiro, A. (1967), Orogeny, regional metamor schen Griinschiefer-Fazies, Gelandebeobacht phism and magmatism in the Japanese islands. ungen and Mineralsynthesen . Fovtschr. Miner., Medd. fra Dansk Geol. For., • 17, 390-446. 46, 87-136. Moriya, S. (1972), Low-grade metamorphic rocks of Some petrological aspects on stilpnomelane in glaucophanitic metamorphic rocks 387

the northern Kitakami mountainland. Sci. English abstract). J. Japan. Ass. Miner. Rept., Tohoku Univ., III, 11, 239-282. Petrol. Econ. Geol., 52, 73-89. Niggli, E. (1960), Mineral-Zonen der alpinen Shibakusa, H. (1974), Glaucophane schists in the Metamorphose in den Schweizer Alpen. Rept. Kamuikotan metamorphic belt of the Horo 21st IGC 13, 132-138. kanai area, central Hokkaido (in Japanese Niggli, E. (1970), Alpine Metamorphose und alpine with English abstract). J. Geol. Soc. Japan, Gebirgsbildung. Fortschr. Miner., 47, 16-26. 80, 341-353. Nijhuis, H. J. (1964), Plurifacial alpine metamor Streckeisen, A. (1968), Stilpnomelan im Kristallin phism in the south-eastern Sierra de los der Ostkarpathen. Schweiz. miner. petrogr. Filabres south of Lubrin, SE Spain. Thesis Mitt., 48, 751-780. Univ. Amsterdam. Suzuki, T. (1972), Volcanism and metamorphism Nishimura, Y. (1971), Regional metamorphism of of the Mikabu Green Rocks in central and the Nishiki-cho district, southwest Japan. western Shikoku (in Japanese with English J. Sci. Hiroshima Univ., C 6, 203-268. abstract). Res. Rept. Kochi Univ., 21, 39-62. Nureki, T. (1967), Finding of axinite-schist in the Tanaka, K. and Fukuda, M. (1974), Geologic Sangun metamorphic zone at Mitake, Yamag structure and metamorphic zoning of the uchi Prefecture, southwest Japan. J. Sci. northern extremity of the Sanbagawa meta Hiroshima Univ., C 5, 241-253. morphic terrane in the Kanto Mountains, Onuki, H. and Ernst, W. G. (1969), Coexisting sodic with special reference to the occurrence of amphiboles and sodic pyroxenes from blue biotites (in Japanese with English abstract). schist facies metamorphic rocks. Miner. Soc. J. Japan. Ass. Miner. Petrol. Econ. Geol., 69, America Spec. Publ., 2, 241-250. 313-323. Reover, E. W. F. de (1972), Lawsonite-albite facies Tazaki, K. (1964), Alkali amphibole-bearing metamorphism near Fuscaldo, Calabria metamorphic rocks in the Kamuikotan belt of (southern Italy), its geological significance and the south-west part of Asahikawa, central petrological aspects. Thesis Univ. Amsterdam. Hokkaido (in Japanese with English abstract). Seki, Y. (1958), Glaucophanitic regional metamor Chikyu Kagaku, 71, 8-17. phism in the Kanto Mountains, central Japan. Toriumi, M. (1971), Sanbagawa metamorphic Japan. J. Geol. Geogr., 29, 233-258. rocks of the Onishi-Manba area, Kanto Moun Seki, Y. (1961), Pumpellyite in low-grade metamor tains, Japan. Thesis Univ. Tokyo. phism. J. Petrol., 2, 407-423. Zen, E-An (1960), Metamorphism of Lower Paleo Seki, Y., Oba, T., Mori, R. and Kuriyagawa, S. zoic rocks in the vicinity of the Taconic (1964), Sanbagawa metamorphism in the cen Range in west-central Vermont. Amer. tral part of Kii peninsula (in Japanese with Miner., 45, 129-175.

藍閃変成岩におけるスティルプノメレンの岩石学的諸問題

橋本光男

藍閃変成作用の条件下では,スティルプノメレンはパンペリー石帯から黒雲母帯におよぶいろいろな岩石に出現する。その共生関係は簡単で,石英・緑泥石および方解石と伴うことが普通であり・緑れん石・パンペリー石およびアクチノ閃石と共存することは少い。スティルプノメレンを含む岩石の種類が多様に見えることは,標本の総化学組成が適当であるためではなくて,標本内の細かな不均質によって,スティルプノメレンを生ずる化学的条件が局部的に生ずるためである。なお,スティルプノメレンと方解石の組合せは,炭酸ガスの圧力が十分に高い場合に生成する。