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(1)Reports. [Science. Yokohama. the. of. Geological. National. Petrographical. arLd. II, No･. Sect. University,. Studies. 9,. 1962]. the. on. Mountainland. TarLZaW?. Part. II*. By. Keizo 20. Wl'th. MIEA:MI. Illustrations,. Tables. 9. Plates. 5. and. CoNTENTS Petrography.‥…‥‥‥‥‥‥‥‥‥.‥‥‥‥..‥‥‥‥‥‥.. 59. Characteristics Activities of Volcanic Alterations‥‥‥‥.‥‥‥‥‥‥‥.‥‥‥‥‥‥‥.‥‥‥‥‥.. 87. ‥‥‥‥‥‥‥‥‥‥‥. Chemical. CompositiolユS. Igneous. Tectonic. and. Trace. and History. Element Tanzawa. the. of. 89. Contents. ‥. ‥. 96. ‥‥. Mountainland. (Conclusion)‥‥‥‥‥‥‥‥‥...‥‥‥‥.…‥…‥‥‥.‥.102 References‥..‥‥‥.‥‥.‥‥‥‥‥‥.‥‥.‥.‥‥.‥‥‥‥106. PetrograpIly I. The. bulks. characterized is very. graphy. The. to analyse. slgni丘cant during. place in age.. Miocene. the. and the making matrix, hydrothermal intense the identify. to. The. the. nature. his. attention. his. focused. field survey the. jrom. collected 1,000 thin. breccia). were. supplementary Continued. of. having. the. selected studies from. this. of the. pyroclastic. sections. rocks. pyroclastic. 辛. true. requires皿uCh by these. rocks. composition. these. of. are. petro-. volcanisms the. middle. of volcanic ejecta and labour. In addition,. essentially. and. their. and. geosynclinal to Oligocene. displayed feature. textural. their. has. writer. During. rocks.. nearly. section. rocks,. the. described,. already. often. ln. accurately rocks. pyroclastic･. it. make. thin. remains. petrographically.. unknown. were. thin. of. as. latest. the. consist. alterations. Accordingly,. sections.. from. period. of. feature. the. however,. rocks,. pyroclastic. di氏cult. Rocks. Aikawa and groups, of the Tanzawa by the thick accumulation pyroclastic of. took. which. Pyroclastic. on. volcanic. present. been. examined. coarse-grained. type. as. show. many. Samples. different. object that the rocks Sec.. ⅠⅠ,No.. of. 8. this type. (1961), 107.. because are. in. of. these. ejecta. horizons,. stratlgraphic. microscoplCally. (mainly lapilli-tuft. of investigation. the. Reports,. COntained. reglOn,. in. rocks. eJeCta. In and. of:. identical. this. case,. volcanic. (1) Some in petro-.

(2) K.. 60. graphy When. and. ered. the. in. c. and. 1953). these. a. Main. essentially. Constituent. nlng. matrix, is寸ery. of plaglOClase the. normal are. zoning To tion. the. andesite. and. dacite. rock. pigeonitic. encountthe. of. assemblage. common. source.. types. (H. KuNO,. series. mineral. and. the. to allotriomorphic. their. typlCal,. lS. most. indicates. that. volcanic. Some. twins.. the oscillatory-normal. and. -reverse. and. twin-. crystals. is rather. in composition. variation. Albite. crystals･. Carlsbad. with. ejecta. ;. simple types. of. common.. examine. in. variation. of. angles. universal. that. throughout. combined. but. ∑oned,. zoning. it di氏cult. makes. revealed. a. distributed. frequently. are. from. idiomorphic. ln. common,. their. lose. they. altered,. Minerals. It is widely. occurring. and. derived. (2). coarse-tuff)A. certainty.. has. in composition. similarity. Plagioclase: the. with. matrix. investlgation. and. frequently. which. ejecta are the basalt, olivine,all belonging to the. were. ejecta. highly. of these. without. Such. A.. this. their. and. way. types. rock. become. individualities,. ejeCta. this. (1argelyfine-. type. rocks. pyroclastic. mineraloglCal. identify And. Xc. the fine-grained. of. the血e-grained. textural to. those. with. MIIくAMI. stage,. 140. crystals. the. results. An-content. in. the. of. which. the. of plaglOClase, to 010 normal. zone. illustrated. are. maximum. in Figs.. 7 and. I. 14 13. 12■Fd----】. 111ral. ･o!b 9 8 チ. 7 __i. 6. r. 5 4 3 2 1 30. An%. Fig.. 7. of. Range. chert rocks. volcanic. 1 Yadorigi Siomizu 7 Bodai Karasawa. 5(). the. of. 60. composition as. occurring 2. vol,-bre., 5. e]'ecta. Yadorigitu-ff,. 70. of. 80. 3. Mizunasi. c),. vol.-bre･, d Dacites. a. pyroclastic Kansiti 6. Andesites. (Ⅹc).. 9D. plagioclase-phenocrysts in. (Xc. and. rocks.. vol;-bre.,. Kuzuha. vol.･bre., vol.-bre., 9 Nunokawa vol.-bre., 8 Hondani-tuff, ll 0sawa for., 12 Zike for., 13 tuff,. 14 Nakatuky6. (Ⅹc and. 40. 4. vol.-bre.,. vol.1bre.,. 10 Miyagase for.,. c),. extincby the. measured. were. b. Basalts. 8..

(3) Geological. Petrographical. and. Studies. Tanzawa. the. on. 3. Molintainland,. Part. II. 6壬+. a. !d. 2. 1. An%3040506070809O Fig･. 8･. Range. 1 T6gatake 4. As. subgroup,. Aikawa. be. may. fragments. in. seen. the. in the in. common. of. basic. in the. in. ally. pleochroic higher. indices. containing. in the that. the. tuff,. difference. slgnificant. the. ejecta and and. ejecta. in. com-y. plag10Clase-. the. as. matrix. were･. pale. and in petrography. to. ejecta.. crystal-fragment5Lr. are. than. zoned;. the. of small. the. in. those. yellow･. of plaglOClase, found. pyroxenes. slightlypheno-. twined,. ejecta,. pyroxene･ similar. their. ln. often. are. matrix. only. hasp.. rim. monoclinic. in the. differing. the volcanic. and. outer-most. frequently. are. usu-. Some. clusters,. their. They. core･. grains. monoclinic. brownish. usually. Itv is. minerals. in. sometimes. 1arge=. prlSmatic,. groundmass. light. and. often. sometimes. rounded,. 3mm･),. to green. refraction. All. magnetite.. in volcanic. constituent. small-grained. (up. of. crystals. of. is abundant. common. as. either. little amount. a. no. Dacitic. rocks.. or. shades. large. and. is. pyroxene. It is also. occurs. crystals. simple. crysts. Monoclinic. same. it. ejecta,. in. indicates. rocks･. in phenocrysts,. crystals. there. which. :. the. of. In the. figures,. tuff, d. orlgln.. pyroclastic. matrix. basaltic. plagioclase-phenocrysts. Monoclinic勿′roxene the. to. these. matrix,. their. Andesitic. a. group,. between. position. the composition of plagioclasein pyroclastic rocks. 2 0yama 3 Susugaya subgroup, subgroup, of. chert fragments. ′. angular. form. The. 2V. of. were. which. the. crystals,. From. these. monoclinic not. reference. optic. results. plgeOnltlC,. to their. The. those. minerals. clastic. ejecta and. rocks of. of. to. present. compositions.. thus. ejecta in. measured. 486･. 9-10.. their. suggesting. occurring. groundmass. is partly or wholly hydrothermal intense. reglOn;. hypersthene-augite-andesite. dacitic. was. as. commun. sourLce.. have. phenocrysts. larger. the. Rhombic. Rhombic勿′roxene: the. positions,. pyroxenes in. pyroxerle due. units. in Figs.. shown. volcanic. various. facts important : (Ⅰ)The+ out the following pointed found･ in the pyroclastic are rocks mostly of augi･tic二 are invariable in the 2V, of and also values without. monoclinic. than. monoclinic. secondary. are. the. stratigraphic. are. stratigraphic. general, angles. different. of which. pyroxenes. nature,. (2) In. results. in. found. pyroxenes. monoclinic from gathered. pyroxene. is of. altered. Vc),. chlorite. or. in. tne. other･. actions. rare. occurrence. in. it is present. (Type. to. or. small. amounts. in coarse-tuffs. 【pyro-in. either. of andesitic.

(4) K.. E62. MIl{AMl. Phenocryst. -. _--Groundmass. Pigeol-iticー→Augitic. a コく⊃. 8 7 6 5. L. bD. -S (ム. 4 3. DiabaseBasalt●. く勺. andAndesite/一一〈ー-＼一. ■お. /) ム. .bL) :コ. 1. !【/). ■LZ. 0 ll. /o/oo一一ニ/i-ノ:oo:＼;甘o--l＼ 10. ∽ h (U. ,a. E コ. 9 a. ∠○､･. 8 7 6. Andesite. 5 4. 3. :冒･○. 2. ;一. ぷ. 1. O. 0. .A,-oてプoo:Dt＼ヾ. .(β. lF3. 9 8. :F:. ■Ed ○ .1一-I. 7 6. UiabaseandBasalt. CI. 4. 3. :,:::,o;o., L2 1. l. ○//o. 0. /. 9. ●. 8 7. l. 1. Andesite. 6 5. ●●●. 4 3. ●● D. .コ ■O. 1■. 2. O. bD. 1. .a. コ節. 0. /o/o.-;.I:声:七∵｡-:--∴＼､. I一′--∫. A) メ【勺. 9 8. (匂 bJ) lO. 7 6 5. 〔一 /＼＼. Basalt. //●o. 4. //＼ /ooo●わ●＼●. r) I). 2 1. ,/--o'.'7シ?/･･Q･＼｡1:ヾ-●■ E:. 9. 404142434445464748495051525354555657L〕8. 〔十)2V. 9.. Fig.. Frequency. Oyama. (T6gatake,. ln. occurring. pyroxenes. clinic. for. curve. and. 2V. angle. optical. ejecta. VOIcanic. of. of. 皿OnO-. rocks. pyroclastic. Subgroups)･. Susugaya. P】georlitic. 35. 35. ーA1】git]C. ←. 3'). 3し) Diabase.. Basalt,. 25. Aロdesite. aTld. Da(つie. ●. Pher)ocrys(. 15. GTOL)r[drrlaSS. I). =し1. 20. 15. 15. 10. 10. 2O. 21. 22. 23. 24. 25. 26. 27. 28. 29. 3(). 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. ▲18. 49. 50. 5l. LIJ2. 53. 51. (＋r2V. Fig. clinic. 10.. pyroxenes. (Tanzawa. and. Frequency occurring. Aikawa. for. curve ln. VOIcanic. Groups)･. optical. angle. 2V. of. ejecta of pyroclastic. mono-. rocks. 55. +. :乙.

(5) GeologlCal. Petrograpbical. and. In the volcanic. with. ･associated. 2V(-). from. It contains in. small. leach. .replaced In the. quantity･. its. less. mineral. pleochroic light. and. less. or. shades. of. green (Z) ; yellowish imply th･at it is hyper-. augite-grains. more. usually. and. magnetite,. fractured,. partially. chlorite.. rhombic. pyroxene. commonly. that. in. from. alteration the. of. is. in. 63. length). habit,. rounded. characters. optical. this. or. (Y),. plaglOClase-laths,. And. coarse-tuffs, ln. The. infrequently. or. prlSmatic. II. in. 2mm.. (皿aXimum. It is slightly brown. 62o-64D･. values of 2V of hypersthenes. †hose. somewhat. Part. Mountainland,. phenocrysts. pyroxenes･. iron-saponite. by. rdiffering The. a. with. Tanzava. the. on. as. (X), light yellowish. varies. stbene･. occurs. monoclinic. brown. reddish ･its. ejecta, it. microphenocrysts. 二and. Studies. found. in. the. intrusives,. minor. volcanic. are. fragments,. as. ejecta.. hypersthenes,. above-mentioned. found. occurs. together in. shown. Fig.. with. ll. as. a. curve.. ￣frequency Homblende:. Hornblende,. is. 虹quantity, and. ･ejecta. only. in. up. rocks. ･clastic Aikawa. Hondani-gawa. Susugaya. the. Fig.. in the. pyro-. Oyoma. the. forming. the. but. acicular,. brown. 2Vト). of. for. curve. optioc-. pyroxenes. rhombic. rocks. pyrOClastic. found. ￣blendes. and. minor. or. phenocrysts or. brown. ･dacitic pyroclastic -ing in the Susugaya in. the. horn･. of. horn-. intrusives, frequency. a. is. in. the. and. most. basic. matrix. rocks. red-purplish,. Most. in. those. while. hornblendes. the are. 14. ,a. glO. a 8. are 6 curve.. encoun-. is. of. the. pyroclastic. rocks. ノ. 84. 81. 78. †. 75. 72. ト)2V. Though. infrequently. ノ 87. predominat-. subgroup. it. amount,. and. microphenocrysts, rarely hornblendes. embayed, habits.. 2. eJeCta. green. 巴12. those. Quartz. in the. of to. microphenocrystic. 4. Quartz:. varieties occurrence. opacitization.. irregularly. etc.. of. in minor as. to. in. A). 2V. with. in Fig. 12,. colour. of tabular of light. (Ⅹ), greenish. together. as. sometimes. (Z),. two. phenocrystic. sometimes. ._greenish (Y), yellowish green The of values blendes,. subject. in shades. pleochroic,. 二StrOngly. the. is restricted. occur. The. groundmass･. groundmass. present. 62. intrusives.. are. latter. ejecta, always in the ejecta. hypidiomorphic,. tsmall. 65. 68. Frequency. 2V ln. curring. and. there the. although. .greenish faltered volcanic Hornblendes. tered. 71. ll.. angle. cal. the. only. microscope,. brown,. ･shown. also. subgroups.. Under. トare. and occurs. not. but. 2. 74. It. composing. group. 弓4. rocks. pyroclastic. fragments. as. ･occasionally. 昌6 ,工). as. a. the. the. 8. volcanic. occurring. formations,. ･Osawa. some. dacite-tuffs. rocks. making. in. found. in. small. Fig. cal. angle. pyroclastic. 12.. 2V. Frequency. curve. of bornblendes rocks. and. minor. for. opti-. in occurring intrusives..

(6) 64. K.. from. a. less crushed,. quantlty.. small. or. somewhat by. surrounded. Some. groundmass. form,. corroded. dusty. grain-size､. or. materials. of■､ more･. sometimes. of. grains. small. angular. crystals,. generally. in. exceed. ln. vary. and. amount. plag10Clase-ones.. Crystobalite once. those. have. but. present. it is. proportions.. Magnetie. is also. rocks,. l)eak. in the. in. and. proportions.. is. usually. found. and. they. alteration.. in. than. occurrence. in. the. materials. cementillg. matrix. in. the. of. In. subgroup. or. of particles,. be. growing.. group,. the. scat-. pyroclasticl. these. as. in. rocks,. to. Tanzawa. the. 1ess･. aggregates... same. tends. amount. occurs､. plaglOClase. offine-grained. its of. or. sometimes. matrix. and. Susugaya. the. crystals,. horizons. upper. of. hornblende,. the. coarse-tuff,. the. dacite-tuffs the. it is in simple. sizes. towards. more. as. either. intense. to. common. hypersthene,. fragments. as. as丘ne-tuft. and. more. because. probably. due. quartz be. will. augite,. Usually. Glass. more. replaced. in. found. Various. Glass: such. by. magnetite. included. varylng. tering. lacking,. entirely. it In the volcanic rocks, ejecta of pyroclastic <described. in the and grains groundmass; microphenocrysts, small. phenocrysts,. ln. are. been. Probably. already. commonly. tridymite. and. Magnetite:. of. are. grains. ln. range. ejecta. in the. evidence of showing are ln fragments usually Various-sized, In dacitic tuff, the quartz-fragments. The. as. to. crystals. well-rounded. and. in the dacitic. occurring. resorption.. augite,. the. crystals. large. phenocrystic occur in. them or. The. fragments.. as. MIKAMT. it. rocks, main. its. with occurs･. constituents. pumice-fragments. Most. grains mite. glass,. dusty. materials,. of. chlorite. and. in. curately some. of. thin. brown,. I) Vo且canie. bring. clastic. rocks. of. out. of Mafic what. the. types. present. specimen占collected. different 〉Their. also in. be. cannot. interstitially. that. sometimes. The. Mizunasi. the. In many is. which. found. in. a°-. groundmass. basalt.. colour, glass. celado-. determined. ln or. of andesite dark. materials. the. the. due. to. ejecta. of. 1.525･^. measures. volcanic-breccia. Rocks. Minerals of. volcanic the. reglOn, were. ejecta (1951, 1952 and 1954).. tigations of 388. Ⅹc). nature. as. such. minerals. Ejecta. of in these. minerals. dusty. Pyroclastic. ト1) Combinations …To. true. occurs. or. secondary. impalpable. with. indices.. Coarse-grained. B.. their. yellow. of. (Type,. andesite. in refractive. by. replaced. Glass. impregnated. completely. ejecta, particulary. inclusions. augite. or. sections.. volcanic. impalpable. are. ; consequently,. it displays. eases,. however,. of. the. at. stratigraphic units, instense alterations. ways. determined. This. random. the make. rock. of. after. results some. from. ofl Which. specimens. method was. given. the are. pyro-I. ejecta of between. combination the. determination chiefly. the. characterize. ma丘c inves-. of KuNO's thin. on. volcanic shown. still unknown. sections､. breccias in Figs. to. of. 13-15._∼ us,. so,メ.

(7) GeologlCal. 才ar. their. as. as. ways. unknown. ever,. rock. judging augites. their. which is. rock is. these. of the Xc and. rocks. 10. 30. 40. a. Aikawa. group,. take. Basalt. 4. Dacite. 2. Diabase,. 4. (Type. Ⅹc. (Types,. Xc),. *. Except. 14. the. c. the. in. type,. subgroup･. c),. dacite,. of. gravels. rare. 13. constituents. e. occurrence･. 100%. 14. 15. of. the. coarse-. f･, T6ga-. Sizyuhasse-gawa. subgroup･ Andesite (Types,. Ⅹc,. c,. and. Dacite-tuft,. 9. f壬ornbleⅠユde-bearing. 7. dacite-tuff,. 12壬iornblende-quartz-diorite, Liparitic. sedimerT-tary. Vc),. Ⅲornblende-bearing. 6. 15. rock,. 12. pigeonitid. to. importance･. 90. Ⅰ】. the. stratigrapbic units*･ c karasawa-gawa f･, Oyama. subgroup･ 3. 10. in. basalt. the ln. of. 80. 9. main. different. from to. are. series. 8. ejecta. secondary. 70. 7. the. ll Quartz-diorite,. GranopⅠ1yric. for. 6. in. and. 8. Homblende-bearing andesite, Micro-hornblende-diorite, Quartz-porpbyry,. 5. Andesite-tuft,. 5. rock. 60. i., T6gatake. f Yadorigi-zawa. subgroup,. 1. 3. f･, Oyama. d Ⅰiondani-gawa. subgroup,. to. groundmass-. volcanic. belonging. though. 50. illustrating. section. or. of. composition. olivine), both. rocks pyroclastic b Osawa f･, Susugaya. grained. of the in. conclusion, hypersthenic. 2. presence. most. range. reglOn. the. 20. that. results. another to. Columnar. 13･. occasional. (without. c. 1. Fig.. and. how-. rocks,. Xc. be. see皿tO. 14-15. belong. to. composition. them. Figs.. volcanic. 65. II. of alterations･. present. In passing, belonglng. series. that. free. mineral. someof. feature. from. Types. of. least. at. and. partially. wer?. rocks. appear. textural. concluded. pyroclastic. type. rock. in. in. indicated. concerned-as hornblende-bearing. the. Part. Tanz=LWまMountainland,. the. on. are. Besides. series,. from. Studies. combination. type.. this. of. plgeOnitic. dacite. of. rock. most. It. PetTOgraPhical. and. 10 13. rock･ rOCks･. 1 C. 2 3 4 5 6. 6. (. %. olb2b3b4b51o6b7O81o91o1【氾11o21o31o41o50607O80d)100.--1O21o31o4051o61o7rO81o9Ol. E≡∃ Types, Fig.. 14.. a. Columnar rocks. of. Dacite,. b. ･1 Yadorigトzawa. Ⅹc. illustrating. sections Types,. Ⅹc. Andesite,. c. and. and c. c. [コ. Unknown. the. frequency. occurring. as. ejecta. type. rock. occurrence. of in. volcanic. of vole;anic breccias.. Basalt.. f., T6gatake. 3 H〇ndani-gawa･ subgroup, 5 Susugaya oyama subgroup,. subgroup, f･, Oyama subgroup,. 2. Sizyuhasse瑠aWa. subgroup, 6 Aikawa. 4. f., T6gatake. Karasawa-gawa group･. f･,.

(8) 66. E.. MIKAMI. 【≡∃Pigeonitic 卿Hypersthenic. rock. [ニコロnkown Fig. ing. 15.. belonglng. Columnar. tO. series. type. rock. frequency. the. series rock. illustrat_. section occurrence. of. of. rocks､. the. plg･eOnitic series. rock the llyperSt血enic one found and in voト as canic breccias ejecta. 1 Yadorigl-ZaWa f･, 2 Sizyuhasse-gawa f･,. 3. Hondani-gawa. エ 0. /O. SO. p･野40. Ⅰ-2)Principal. Rock. Types. rock. series. (Type. Xc):. Pigeonitic. a). Augite-basalt. 61Qわぁ9bノめ.1. in. encountered. eJeCta. fine-grained,. porphyritic. of. dark. green,. This. In. lath-shaped. the. to. alteration. by. the. while,. whereas. the. in. a. laths. glassy. it. is. being in. shades. brought. are. the. by. out. of. and. the. base丘11ed. typlCally. which. well. or. the. show. remain. also. prismatic. groundmass. In. in-. some. being. free. partially. of. taken chloriti-. fre九. relatively. (Porphyritic. (Pl･ Ⅰ,Fig･ by. augite-basalt,, Quartz occurs in. 5))･. small. interstitial. grains. of augite,. between. grains,. irltergranular,. plaglOClase, chlorite. with of the. and. is in. in. as･. most. are. epidote. auglte as. or. plaglOClase. chloritization. disappear, their place. rimmed as. also,. well-twined,. to. chloritized. usually. and. It alters. and. The. augites. basalts. of･. and. the. pla--. pilotaxitic. to･. graips･. (Type c):. variety. quantitatively. Xc-type. are. of. chlorite. entirely. highly. resorption;. in. are. excess. phenocrysts,. crystals. Crystals. as. groundmass. ones. is. texture,. ones. an. is oscillatory.. phenocrysts. susceptibility augites invariably. a､pglte. large. Albite,. their. crystals,. grourldmass in. in. with amounts,. large. in these.crystals･. case,. rounded. augite,. instances.. So血e. minerals･. occurring. of the. Augite-basalt porphyritic. frequently-. most reglOn,. slgni丘cant. type. commonest. common. in. and. The. of sericitization･. phenocrystic. evidence. trachytic. Ai-. 6. usually. ･coloured, colours. rare. groundmass･. clay. form. in other. : as. The. is. present. hypidiomorphic. as. the phenocrystic. variety. showing glOClase. and. vary. but. forms. Karasawa_. subgroup,. type. the. of. These. ln. only. whose. groundmass. chlorite,. two. zoning,. crystals. altered. rocks is strongly. black･. either. in the. crystals,. zation,. an. occurs. products. granular. stances･. this. of. calcic plagioclase is present in. amounts. the. ln. of. small. sericite. only. These. and. in. evidencing. zoning. purple,. glass. crystals. typlCally. which. addition,. plagioclase. rarely. group.. pyroclastic. composed. is found. The. to. is. rock. quartz. kawa. 4. alterations.. former･. the. f･･ 5 Susugaya. basalt. rock. reddish. intense. their. the. The. i.,. gawa. The. above-mentioned. unimportant,. but. dusty. and. basalt. sometimes. augite. of. this. and. magnetite. materials rock. basalt. is frequently. type. embedded′. (Pl･ Ⅰ,Fig.. 3).. represefltS. Compared found. are. with in. the. a. the. nOn･. latter,∫. pyroclastic/.

(9) Geological. The. Diabase:. they. is. 丘11ed with by. (T37Pe Xc). Augite-andesite. the. of. present. the. of. secondary. minerals,. under tite. the. are. due. idiomorphic. the. in the. seen. the. crystals,. composed. of. The. having. the. in. texture,. clase. laths. stices. are. 1n. in. texture,. lar. 6 and in. The. Xc). is. dark. varietiesVarious^. albiteand/or. theclays;. as. to. epidote･･ manner. to. that. replaced. sometimes. often. same. prismatic. tot. (up. and. chlorite in the. in. occurs. plaglOClase. prehnite･. magne--. and. borders. occurs. en-. green.. less corroded. subordinate. chlorite,. great. augite. The. augite. pyroclastic. veinlets･. plag10Clase,. to. generally. by. granular. of. the. by. aggregates･. plaglO--. minerals･. the. laths. to. or. or. pilotaxitic occur influidal. needles. the. of andesite basalt of the. Type. the. Xc type,. same. plaglOinter-. their. materials･,. glassy. chloritized. the. varia--. which and. orientation,. and. displays. groundmass. hyalopiliれin. haphazard. in. glassy,.. cryptofelsitic It is highly phenocrysts･. is the. common. magnetite,. augite,. or. sometimes as. most. composition. and. to sericitization. subjected. which plagioclase ⅠⅠ, Fig･ Pl･ 1)･ Thus. mineral. purple or. those､. frequently. most. or. more. their. the. calcite･. disposed. are. the. cases,. quartz, are. the. by. occupied. wholly-. with. in the by. groundmass･. composition. mineral. needles. or. together. type,. rock. of. hypocrystalline,. of which. or. some. Fig.. is. same. as. other. and. groundmass. amygdules･. replaced is partly. amygdules. with. surrounded. chlorite. plaglOClase-. augite. and. It isaltered. of which. amount. The. occurrence. phenocrysts. found･. (Type. It is always. clase.. ble. basalt. plaglO-･. thoughsmall by. characterized. in. crystals. rarely. of this. brown,. altered. by minerals such replaced some plaglOClase crystals of as. amounts･. coinUsuallyJ. lath-shaped. crystals･. The. theu. of. principally. quartz･. sometimes. alterations,. reddish. the. well-twinned is. are. occur. microscope,. Zoning. 2mm).. here. in. instances･. common. of. intense. moreover,. embedded. consisting. of. rounded. ejecta. They. to. colours. countered. small. prehnite･. c), are. reglOn･. are. which. colour. in. rare. or. or. The. :. Ⅹc and. (Types,. basalts. of the. of. 67●. Ⅰ, Figs･ト2)I. (Pl･. chlorite. In. albite, and. and/or. calcite, quartz,. chlorite,. replaced. rocks. II. variety. coarse-grained fabric and. ejecta. rocks,. magnetite･ in interstitial. to sericite. altered. occurmig. and. present. a. as. non-porphyritic. augite,. quantlty,. are. minera卜composition. basalt,. the. green,. granular. is.ften. Xc) whose. of. dark. are. clase, in. those. with. type. this. of. rocks. augite-basalt (Type cide. Part. Mountainland,. Tanzawa. the. on. Ⅰ,Fig. 4)･ ejecta (Pl.. as. rocks. Studies. Petrographical. and. trachytic. the. (Pl, Ⅰ,･. trains. is essentially. differing. simiin. only. texture.. when. -equivalent. the. or. augite of. the. Augite-andesite. type. this. of. rocks. individuality,. oglCal mass. the. which. often. type. altered,. it di艮cult. makes one. phenocrystic. highly. are. (Porphyritic. to. lose. their. discriminate. the. they. augite-andesite,. mineraレ. ground-一. an. altered. Xc-andesite)･. (Type. c):. the. phyritic. equivalent. of. texture. prlnCIPally. coincide. The. andesite with. of. rocks. (Type those. of. this. type. Xc). ; their. the. above. seem. to. mineral andesite･. be. the. non-por一･. composition Though. and less･.

(10) 萄8. K.. than. ･com皿On. the. andesite,. (Pl. II, Fig.. they. HyPersthene-augite-andesite. They. large. for. are. An50). :. small. ふTbe hypersthene. in. both. and. closely. amounts. are. in. also. occurs. in. and. small. the. is rather. the. -peculiar They. are. plaglOClase, 二1arge. green not. and. crystals,. usually. some. 'iron-saponite･. 一Zoning. of. lS. and. The. mineral. ･groundmass. めf bluish. crystals dacites. of. in. crystals, are. in. of. them. part. are. the. of occurs. always. their. always. of. occur. as. quartz,. rounded. plaglOClases locally replaced. It to. altered. are. by. and. parting.. and. usually. crystals,. microphenocrystic. amounts･. their. celadonitization.. cleavage. the large. and. of. phenocrysts. are. 5).. most. subgroup,. phenocrysts. rather. small. found. are. because. The. an. with (Pl･ II, Fig.. augite. intense. with. along or. aS. their. or. grains,. occurs. in. also. chlorite. and/or. iron-. rather. glassy,. the. part.. this. type,. the. texture. and. alterations･. Ptilolite. thus and. groundmass. and. some. the. rocks. quartz. also. seems. however,. of which,. Celadonite. extensively･･ green･. occurs. of augite in. or. composition. intense. auglte. tO. moreover･. which･. yellowish. texture,. others. xenocrysts･. the phenocrysts. prlSmatic. whole. しSaPOnite-in In many. ･its. The. short. ･.clusters･. to. chiefly. rocks be. 2V-62｡,. products. Susugaya. the. quartz. (Ptilolite?)･. zeolite. is oscillatory-normal･. sometimes. well-twinned･. sometimes. conked. to. some. type. rock the. its orlgln. The. seem. which. often. along. whole. in the. and. up. from. owes. 53o).. groundmass.. basaltic. making. altered. alteration. plgaioclase dacites of this. auglte･. (2V-51o,. Magnetite. the. porphyritic. occasionally. lath-shaped. in. fresh,. their cleavage.. with Z-light. but. the. the. which. groundmass.. phenocrysts,. brown,. amounts,. as. macroscoplCally colour distinctly. large. groundmassI. rocks. occurs. relatively. crystals. in. coarse-grained･. pyroclastic. distinguished. large. commonly iron-saponite in. small. crystals. the. along. are. to. between relationship Augite-dacite The (Type Xc):. bluish. and. normal (Core : An74, both in the groundmass. yellowish. present. which. groundmass. in. in. consisting. (Optically negative. hypersthene. intergranular. ･abundantly easily ･are. type,. either. only. Y-light. scattered. phenocrysts. The. as. plaglOClase. remain. occurs. prismatic. crystal-ouline. chlorite,. being. rock. rocks. in. running. augite. of augite-grains. the. and. zoning･. The as. large. and. materials. by. Llauglte, roas. augite. parting. replaced. rocks. volcanic-breccla,. crystals. twinned･. form. phenocrysts. occurs. glassy. -Brown. this. of. porphyritic hypersthene･ The. of iron-saponite. phenocrysts. by reaction surrouロded rims Ⅹ-reddish brown･ざ63o･ 64o;. ycleavage,. ejecta. coloured･. and. formation. in. and. The. pyroclastic. Nakatuky6. the. lath-shaped. as. oscillatory-normal･. grains. ･green)･. The. :. and. or. the. of. or. grey. well-shaped. incIPlent. most. 一Margin. Vc) ln. auglte. phenocrysts,. the. Frequently. blackish. plag10Clase･. r,Leither The phenocrysts ･except. (Type. exclusively. commonly of. in. in various. formation.. are. ･essentially. I.as. found. are. Karasawa-gawa. the. found. are. 2).. tLejecta. ニSma11 amounts,. MIKAMI. variety are occur･. are. of. because. obscure chlorite coloured. the. alteration. replace. peculiarly as. of the. in shade minerals.

(11) Geological. more. less. or. the. closely. is. groundmass. auglte. In this. a. ing. of. to. similar are or. that. relatively the. along. b). less. auglte. of alterations, outlines. crystal. the. are. pyroclastic. red. groundmass. They. consist. of. The. amount. of. The. glassy. and. is usually. with On. by. rimmed to. mm.. augite,. are. and. morphic. while. wholly. ophitic augite,. magnetite. texture,. in which. usually. lS. found. only. amounts,. and their. although to. a. type.. glassy a. and. certain. the. augite. these. some. several. Crowed. (Pl.. with. to. it also. X-light. iron. basic. grains. inclusions. occurs. as. hypidiomorphic. ln. ones,. of augite. magnetite. phenocrysts. rounded. intergranular,. lath-shaped. are. grains.. Some linked. altered. petrograpbically. inclusions. with. minerals.. pro-. optlCal. either. rocks. of. micro-. dust.. or. oxides,. 6). These. chlorite. is typlCally. as. Y≒Z-brown. are. materials. grains,. auglte. 76o, 79o ; c∧Z-15o, 21o. tabular usually crystals,. elongated the glassy. The. bornblende,. Its. brown,. greenish. rocks. secondary. the. is. grains. occurs. And. in amount.. is commonly. largely. chlorite,. chlorite.. ⅠⅠ,Fig.. microphenolarge. the. of or. calcite. augite. contain. plaglOClase. consisting. and. of. porphyritic. altering of. of. quartz. Xc). The. Each. by. the. somewhat. often. (Type. groundmass in. amygdules. are. magnetite. 2V(-)-73o,74o,75o,. most. type. magnetite.. or. type. rocks,. but. surrounded. with. commonly. crystals,. partially The. which. this basalt. the. across). aggregate,. the. Partially. of. to. quite above,. in. to hypidiomorphic. by. groundmass,. impregnated. Andesites. is. nature. mentioned. crystalline. groundmass.. in. crystals. opacite. or. chlorite. identical. idiomorphic. replaced. green; yellowish it occurs as occasions. most. consisト. in small. hornblende,. augite. as. tingeof. a. less. a. sometimes. grains. rounded. are. perties. from. exceeds variety, of brown as follows : Pleochroism. commonly. texture,. either. rock. porphyritic. in the. crystals. Small. phenocrystic. this. of. ejecta. indistinctly. both. occurs. to albite,. ln. in. materials.. acicular. altered. wholly. chlorite. formation. of plaglOClase,. plagioclase. crysts. Micro-. occurs. Hondan卜gaWa. in texture,. slightly. mainly. brown.. inclusions,. the. in. light. all this. magnetites;. spe-. diametre,. sen'es. purplish,. varies. and. is also. centimeters. intergranular. although. of the. rocks. commonly. glassy. augite.. Hornblende-augite-andesite: in. plaglOClase-. inclusions. commonly. c). And. (Type. the. which. in the. sporadically. few. a. rock,. grains. in. texture;. basaltic. usually. compact,. of non-porphyritic,. Hj4)ersthenic rock. 69. hairs. of. inclusions,. basalt. the. of. free. II. replacing. type,. this in. scattered. dusty. occurrence. laths,. plaglOClase. are. frequent. it is typlCally. scoplCally,. commonly. rocksof. hyalopilitic. and. or. of the. sandstone-like,. amongthe. magnetites. though. minerals,. above. Part. Mountainland,. 3-4).. hematite. the. Each. noticed.. cially. and. with. variety,. the. crystalline,. grains. Tanzawa. the. on. with. is found. rather. impregnated. base. is. dacites. of. variety. microlites,. associated. (Pl. ⅠⅠ,Figs.. groundmass A. Studies. Petrographical. and. 3-5. (each plaglOClase,. of. to. allotrio-. both. of. them. sometimes. sub-. plaglOClase, augite. together. granular. occurs. in. as a. an. spindle.

(12) K.. 70. The. Hornblende-andesite: diameter,. are. dant. grey-coloured,. occurrence. hnite,. of. the. form. amount,. morphic latter. is frequently The oxides,. blende,. composed a. and. of. small. the. Osawa. formation. ish. brown. colored,. auglte morphic. as. commonly. or. slender. laths. abunas. such. pre-. chlorite. more. less. or. in. idiomorphic or. in. smaller to. allotriothel. sericite, while borders. corroded. and. part.. by. of plaglOClase,. chlorite, needles. iron-. and. epidote. horn--. of actinolitic. of glass. This. :. form. is only. rock in. the. but. part,. usually. in which. phenocrysts.. The. brown. with. altering. a. as. ln. yellow-. greenish. altered. quartz,. plaglOClase,,. plaglOClase. is hypidio-. dusts,. the. and. iron-saponite. to. occurs. by. covered. infrequently. not. and. porphyritic,. lmpregnated. crystals,. found. southern. eJeCta,. invariably. usually. rounded. by. have. epidote. sandstone-like. crystals,. an. though. as. impregnated. celadonite. it is indistinctly. magnetite. and. or. distributed. of MicroscoplCally,. occurs. replaced. replaced. amount. composed. minerals,. hornblende,. former. that. chlorite. Hornblende-augite-dacite. shell. The. crystals. groundmass, is. characterized. with. and. partially. euhedral to. volcanic-breccia. by. being. in They. quartz.. are. altered. Ar5cm.. averaglng. Kuzuha. rocks,. plaglOClase. which. in. occurs. and. type,. rock. the. amygdulesfilled. phenocrysts.. crystals. in. only. and. microscope, the. this. of. porphyritic. veinlets. calcite. chlorite,. Under. e)ecta. found. occasionally. blackish. are. MIKAMI. along. occurs･. augite. its. and. cleavage. crystaトoutline. The. groundmass. consists a. and. and. microlites. Hornblende-clacite: pyroclasic. ejecta. petrography, ring. as. The few. the. they. unless. both. up. phenocrysts. groundmass. Xc),. highly. also. of plaglOClase, base丘11ed with celadonites. glassy. are. closely to. similar. the. in. associated dacite. the. hornblende. green. the. in. occur-. minerals. as. glassy. hornblende. microlites. are. groundmass. of the. found. seldom. They. but. auglte. The･. base.. glassy. are. which. mag-. hairs.. radiating丘bers. the. type. formation.. not as. and is. of. (Type. contain. this. dusty. and. with. in. packed. Osawa. the. dacite. the. of. dacites. glass 丘11ed. vesicles densely. are. The. making. rocks. the. with. which. hairs. hornblende-microlites,. and. of brown. amount. netite-grains, certain texture is spherulitic, in above. of plaglOClase-. and. and. well. rarely. dusty. that. as. of the are. quartz. dacite;. a. inー. scattered. materials.. 2)淑atriⅩ The. matrix. coarse-tuffs, matrix. of. colours, rarely dacitic. the coarse-grained. of has. and. to. andesitic. which. is. quartz,. and,. chiefly. variety. of. pyroclastics. the. quartz-. and. is usually. other and. composed. of. In general,. the･. compositionsI. displays. dark. of fragments. occasionally on. rocks. pyroclastic. of colours. basaltic. composed. pyroclastics,. consisting. a. or. yellowish. auglte,. of plag10Clase, hypersthene or hornblende.. hand,. is commonly. plag10Clase-fragments. of. grey. scattered. magnetite The皿atrix or. green. and of. bluish. green,. in the. glassy.

(13) GecnoglCal. Petrographical. and. basis,. dark. or. green. while. are. matrix. these. minerals,. Breccias. ln. the. 71-. strong. of veinlets. chloritization. and. the･. matrix;. epト. and in. And. celadonitization. fragments of the. replacement. by. the-. variousF･ with. amygdules五11ed. tioned. from. rence. in varylng. in. shown. fine-tuff, are. in. fragments. an. added. latter. The. tuH: Aikawa. the. dacite. of the. in. or,. found. They. breccias.. additiorl,. are. They. wholly. these. by. replaced. quartz,. Chlorite,. of this. by. radiating. tu#:. The. breccias. Osawa. formation,. cm･. across,. are. up. the. Osawa. for-. with. the. associated. is similar. feature. matrix. 4-10. making. intimately. petrographic. instances,. usually. pyroclastics are. their. and. purplish. rock. to. eJeCta that. of. is. replaced. of丘brous. zeolite. usually. aggregates. and. In. instances. rare. fragments. plagioclase. hornblende And. and the. matrix. amygdules丘11ed. in a. added. few. are. by. replaced. partly. or. is commonly. with. chlorite. a. above. largely. former･. the as. vitreous. ejecta of. the. consisting. present. not. also. with. of. are. quartz. promiscuously are. mixed. excess. are. rock. tuffs,. an. (Lithic-crystal-vitric. is partially augite. usually. with. occasionally. this. of. compact. coloured,. hornblende-fragments. scattered. these. by. dark. commonly. tuff). to. the. magnetite,. auglte, are. replaced. to. rocks. calcitel. sericite,. this rock,. of. tuff). The. some. in. and. ploglOClase-. The. or. partially. of. dacitic. group.. Xc),. (Type. infrequently. basalt. are. matrix. breccias. Augite-homblende-dacitic. vitric. to basaltic. chlorite.. scaly. which. matrix. of andestic. or.. tuff).. in the. (Crystal-vitric. celadonite,. epidote.. particles. coarse-. magnetite･ augite and (Crystal-vitric もuff)･ゝd. plag10Clase, vitreous. combinations. found. and. of. below:-. green,. yellowish. occur-･. of. etc･. uncommonly. mation. rocks,. above一皿en--. frequency. is glVen. whic■h. usually. common. the. various. of. Augite-dacitic. by. few. and. 1rOn-SapOnite,. epidote,. the. their. a. fragments. aggregate. not. in. scattered. the. is. rock fragments. (Lithic-crystal-vitric. Both. the. with. their. and. of. petrography. This. angular. are. mingled. breccias,. these. of. 13, the. tu#:. which. sporadically frequently. Not. underlying. types. Fig.. Augite-andesitic. are. strata. pyroclastic. of. proportions.. rock. prlnClpal are. the. breccias. rocks,. pyroclastic. coarse-grained. ejecta The. Rocks. Pyroclastic. of. derived. directly. the. II. Gravels. and. Breccias. 3-1). of. owing. development. the. throughout to. is exclusively. the. the. and. Part. minerals.. 3). or. are. green. found. commonly. secondary. is wide-spread. colours. bluish. the. Mountainland,. Tanzawa. the. on. brown.. alteration. yellowish. dotization,. ferric. or. celadonitized The hydrothermal. Studies. fragments,. (Crystaレ. matrix altered. In. and. andesite. tuff).. chlorite. wholly. and/or altered. Impregnated. or丘brous. with. iron-saponite, to. chlorite. iron. varieties. while. and/or. oxides, of. zeolite･. often.

(14) 72. K. 3-2) Gravels ln. the. 訂enCe. pyroclastic few. a. Of. derived. from. LOf these. gravels,. and. a. ･grains, The green. is of. enclosing. properties. are. by. These. features. that. in. relations. intimate. amount. of. The. X-light. large. Some. -The. of. rock. of. The. often. hornblende green. Y-greenish. brown altered. partially when. showing. a. present, parallel. large by. a. orbi-. 1956),. which. con-. a. small. and. hornblende. 73o, and. and. 75o, 76o ;. is. always. intergrowth. CuⅡ1mingtonite. occurring. with. H. Hornblende,. C. Cummingtonite,. M. Magnetite,. P. PlaglOClase.. green. by. or. within latter. 70o,. And. 75o;. enclosed. 52o,. 55o, 56o.. that. these. directly. from. biotite.. 19o,. c∧Z-17o,. the. Its. follows:. as. Z-pale. and if. present,. form. poikilitically optical. the. (Fig. 16).. auglte, in. of. around. are. any. appears. the. crystals. replaced. the. has. Some. green･. sometimes. The. enclosillg It. Ⅹ≒Y-colourless. clases･. acidic. 20o ; Plechroism. properties. grains. more. zone. c∧Z-18o,. with. always. in small. magnetite.. found. usually. or. crystals,. Z-brownish. to actinolite,. An71),. crystals. narrow. rimmed is in hypidiomorphic. ye11ow･. intergrowtb. grey,. (Average;. plagioclase. in hypidiomorphic. either are. The. 20o;. parallel 二hornblende.. sur-. occurring. magnetite. 2V(＋)-69o,. in. mass. greenish. hornblende,. green. optlCal. Fig･ 16･. H.. are. of the IsHIKAWA,. intrusive. some. of. optical X-pale. quartz-diorite.. 2V(-)-72o,. cummingtonite,. 二bornblende,. from. and/or interstiti?lly･. plaglOClase,. are. derivation. Its. crystals. matrix. and. An69). Ⅶedge-. augite.. crystals. properties: brown,. (K. MIKAMI. a. the. of. small. (Core;. sometimes. Some. green･. in. or. magnetite. Pleochroism. c∧Z-18o;. that. magnetite.. crystals type. 13.. consisting. of. reverse. and. paper. plaglOClase,. (An69)･. core. of plaglOClase. medium-grained. a. be found. can. hornblende. ･of. is. occurs. quartz. -following. the. quartz,. of. grains. ･several. with. cummingtonite. 'welトtwinned, ,grains. than the. is. It. 6)uartz-diorite: largely. rock. this. the. types. Fig.. rock,. large･ crystals,. resemble. previous. shown. small large. been. rock in. amount. of. Z-brownish. and. actinolitic. suggesting. sists. grains. petrographic. in the. zoning. 2V(-)-73o;. hornblende.. described. トCulite. small. brown. a. hypidiomorphic. follows:. as. Y-greenish. rounded. evidence. main. medium-grained. and. occur一. have. which. The are. hypidiomorphic. the. occasional. of. rocks･. occurrence. coloured,. in. either. which. of. an. most. rocks,. its related. honblende. green. hornblende. ones,. grey. greenish. occurs. of. Igneous. their＼frequencies. is. there. stated,. already. quartz-diorite. plaglOClase,. some. as. various. and. ･1argely The plag10Clase. 加ow血,. rocks,. of. It is. of. Rocks. gravels. the. Diorite:. formed. Igneous. of. MrKAMI. angle. of ln. is. small plaglO-. (十)51o,. The. facts indicate above have been torJl gravels the. quartz-diorite. and. r占1ated. rocks. Another type. of. the. quartz-diorite. its.

(15) Geological. is. found. Mt.. as. the. an. containing granular. It is slightly diopsidic augite･. of. a. with. armored. to. (Optically. actinolite. partially X-light. altered yellowish. brown,. brown).. This. of quartz-diorite. the. of. matrix. type. has. and. Y-light. brownish. green. bears. also. (in. a. reactiorr It is. greenish. ､Z-light. to. resemblance. close. facies. one. al. ; Pleochroism,”. and. representing. as. a. c∧Z-37o･. 2V-73o. with. negative. presumably. orbiculite,. 2V(＋)-54o,. in,. occurs. hornblende 58o;. of. rock. above. always. augite. 73:. II. valley. small the. from. The. green. of. shell. hornblende),. green. with. western. different. abundance. crystal. the. of. course. Part. Mountainland,. Tanzawa. the. on. middle. Kiyokawa-mati.. Bukka,. relation. in. boulder. a. Studies. Petrographical. and. the. of. the､. quartz-. diorite.. and. phenocrysts in. embedded. and. rounded less. and. partly. The. the. determine. fairly. basic. the. type. and. iron-saponite.. of. Liparitic. ing are. a. the. oscillation･. altered. in. an. this. The. or. partly. in. gravel. of. this. replaced. glassy. in. by. which base.. to,. t&. rocks rockタ. of the. is. plaglOClase albite, prehnite. is zoned. often. with,. the. and. lacking･. and. plagioc如e-laths. as. either. in. sericiteゝ. breccia. volcanic. formation･. Karasawa-gawa. is in. augite･. (＋)56o･ in. ploglOClase. entirely. occurs. impregnated. or. of. amounts. and. is found. rock, are. impossible. pyroclastic. (An57). augite. rock. porphyritic. minerals The chlorite･. in texture,. small. ones,. rocks. pyroclastic. in the. plagioclase. the. and Y-1ight￣. lS usually replaced kaolinite, etc･ sericite,. with. of. some-. and. coloured,丘ne-grained. lath-shaped. angle. plag10Clase. brown,. it. and. plaglOClase. green. optical. coloured, Ma丘c. altered. oxides,. composition･. make. albite,. plag10Clase. of. yellowish 79o, 84o･. is found. altered. the. to. The. dark. a. in. often. of. rock. It is and. X-light. It is partially. The. brown. crystals, is granular. .scattered. The. phenocrysts･. wholly. rounded mass. dark. (the･ more. colour,. magnetite,. is An46-5.. type. grey. whitish. 2V(-)-78o,. combinations. crystals. between. intercalating. somewhat. iron. with. of quartz･. of. rock･. interstitial.. as. rock:. as. predominantly. however･. this. of. of quartz. large. hypidiomorphic. It is. nature. occurs. quartz. corroded lmpregnated. plaglOClase. alterations,. of variety formation･. largely. consisting. crystals,. being. quantity. has. of various. Nakatuky6. the. The. true. aggregate. an. A of. the. zoning. characteristic. pleochroism brown; Z-greenish. and. evidence. crystals. consisting. small The. hydrothermal. Intense. by. a. hornblende. green,. a. in texture,. hornblende.. actinolitic. occurs. is wholly. displays. containing. actinolitic. brownish. rらck. micrographic this,. only. The. minerals.. well-twinned, in. are. chlorite･. This. besides. of. same. which. quartz. and. large. occurs. groundmass. by. replaced. is indistinctly. times. quartz. The. GranoPhyre:. and,. crystals･. stained. fractured.. Some. the. of. in. rock,. plaglOClase,. composed. COmmOnly. grey. greenish. of intermediate. An35),. and. porphyritic,. groundmass. crystalline. type?).. oscillatory. distinct. a. microphenocrysts. (An｡｡_44. plagioclase. or. a. is. It. Quartz-PorPhyry:. the. magnetite. form-. if. present,. which･ form of. epidote･ and. The. somewhat. ground-. quartz-grains. are.

(16) ′74. MIKAM1. K. Gravels. 3-3) As 二in a. already breccia. lower. of. in question･. ■■blackish grey. blende. is present. ･,quartz occurs. as. a. instances, The. in. of. plagioclase,. Judging. from. the. that. 皿etamOrphic. rocks. 3-4) Gravels Mudstone:. the. upper. in. the. Karasawa-gawa. horizon. pyroclastic rocks. This displays rock altered andesite MicroscoplCally, iron. addition,. plaglOClase. composed. magnetite.. the. occurrence. of. (”, IsⅢIKAWA,. 1955),. its. allied rock be traceable. can. the it is. in. their in. the. Rocks unimportant,. Generally'their. l･5m･. in. amount. kind. length). rock. of. lower,. with. is. along. brown. clay. of. also. arranged. of various. gravels is more. in the. than. characteristic reddish Palaeozoic chert.. rarely. rock. predominant. often bedding. its. and. in. plane. of. like. impregnated. andesite. peak. present. looking. colour,. minerals. this. an. with. basalt. are. amounts.. of Globigerina. and. other. forami-. remains.. Quartzite･ greyu'acke have. rocks. and. In The. and,. gravels. magnetite, augite, and fragments, though in small it contains a little quantity. cases･. porhorn-. mountainland.. it is composed. minute. a. actinolitic. in texture,. or. a. the. and. micrographic. of such. present. commonly. grains.. PlaglOClase,. In many niferan. or. the. up. is distinctly. grains･. granophyre. of the Tanzawagroup formation･ This. (maximum. patches. oxide･ in IPreSent. source. in distribution･. in. ･angular. of. Althoughquantitatively. wide-spread. tare. the. Sedimentary. of. small. Nakagawa. at. are. are. groundmass･. actinolite, chlorite, features from and also. the. of. relic. exposed. and. in. is rather. gravels. composition･. making. which. quartz,. above. those. as. rock. granophyre. ･meta皿Orphosed 血ot unlikely ･orlglnal. this. rock This. gorge.. The the zoning type, of the reverse blastoporphyritic large in crystals, and,. in. rather. rock,. of plaglOClase. and. developlng. is enclosed. groundmass. actinolitic. rocks. diameter,. crystalline. amounts. is. in. compact. consisting. coarse-grained. crystal,. auglte. のf lath-shaped. a. pyroclastic. 6cm･. averaglng. small. rounded hornblende. んaCtinolitic ･rare. in. gravels of Kyuha-zawa. the. of. formation.. minerals. embedded. few. a. the. diabase-looking,. coloured,. Phenocrystic. are. between. Hondanl-gaWa. the. gravels. 二phyritic･. the. is intercalated. horizon The. Rock writer found in the river-bed. pointed out, breccia exposed. volcanic. -volcanic. Actinolitic. of. are. various. been. found. derived in the. proportions･. sandstone･. hard. probably. from. accidental The. s/mle, chert, etc･ : The gravels the Palaeozoic Cretaceous and. pyroclastic. petrography. rocks. of. these. the. of. gravels. Aikawa is. theLee. of. systems, group,. in. in. this. omitted. part.. C. The. Fine-grained constituents. Pyroclastic of. the. Rocks rocks. of this. type. and. their. petrographic. features.

(17) GeologlCal. prlnClpally. in part. rals. is glVen. Basic. description. the. bluish-green,. or. light. or,. rarely. and. 孤agnetite,. iud,. tu#･. well-. is mostly. rock. largely. consists. in. present. often. This. of. augite･ latter･. the. of. of. basalト. plagioclase,. excess. slight. a. as. region. present. (mainly. with. ; Lithic-crystal. Types)). ((principal_Rock. usually. are. materials. glassy. ･chloritized. and. colours,. crystal-fragments. quartz),. types:-. rock. main in. purplish. various. andesite-ejecta, and. and. mine-. secondary. various. the extensively basic丘ne-tuff･ with. associated. usually. strata,. the. of. It is found. coarse-tu#.I. bedded. con-. in whole･. or. Below. dark-. replaced. commonly. aト. ; the. pyroclastics. coarse-grained by impregnated. or. 75. II. Hydrothermal. type･. coarse-grained. in the. than. Part. Mountainland･. Tanzawa. the. on. of the. encountered. more are. stituents. those. with. coincide is. teration. Studies. Petrographical. and. amounts･. small. tu#･ Crystal. Vitric-1ithicICryStal. etc.. Basic. it consists. that. The. fine-tu#:. of this. rock. of. predominantly. Dacitic. and. Osawa. the. of. line-. The. coarse-tu#:. formation,. coarse-tuff,. except. (mainly. plagioclase,. augite. crystaトfragments. instead of ejecta･ magnetite), Rock Types)) ; Crystal-vitric ((principal. and. to the. is similar. type. of. rocks. this. type. tu#･. etcI. bulk. the. constitute strata･. well-bedded. as. occurring. Vitric-crystal. tu#･. in. sometimes. layers.. massive. They. usually. are. sometimes. green,. grey'bluish. brown. yellowish. composed with ferric. packed sporadically and plag10Clase-fragments a are small To fragments unusually base･ these added or glassy celadonitized sometimes of hypersthene of augite amount of particles and/or hornblende, of. ･essentia11y. (pl. V, Figs. in .a. which. quartz-. Dacitic. 5-6)･ manner. sub-parallel. in the. present. small and of plaglOClase in base replaced vitreous. crystals. slender. is often. pumice. by. type･ in. disposed. are. vesicles. this. of. rocks. celadonite. and/or. chlo-. tu#,. Vitric-. rite.. ((principal crystal. tu#,. Rock. Pumice-crystal. tu#,. etc･. 2.. Each width,. of the except. the. blocky. kawa. volcanic-breccia. are basalts lava一色ows series,. found. lava-Bows. for. lavas. And. the. Xc. (Types. Lava-Flows in the. resembling. petrographically. a). Pigeonitic. Basalt. the rock. (Type Xc):. petrography series It is. a. Close. relations. c), which. and the. basalts. This. of the. source. dark-green･. belong. to. fact as. principal. -purplish･. the. Nunothose. pigeonitic as. pyroclastic. rock. the. among. indicates. highly. or. the. found. are. which. with. in. 30m･. than. types. rock. predominant. most. rocks mentioned･ already pyroclastic from been the same ilows have extruded. is given. ln. is less. reglOn. present. occurring. the. Below. tu#, Crystal-uitric. ; Pumice-crystal-vitric. Types)). rock in. ejecta that. these. rocks･. types:-. -brown. coloured,. por-.

(18) 76. K.. ro-ck･ in. phyritic are. the phenocrysts which in the groundmass･ In rare. embedded. in small The. amounts,. some. of which. OCCurS. auglte. several. in. of. shades Tbe. or. in. to in. only. mainly. or. (Quartz-basalt).. crystal. glomeroporphyritic. intergranular,. ones,. It is slightly. often. pleochroic. from. varies. sometimes. of plagioclase-laths,. is present. allotriomorphic, welトtwinned form sericitization. The of. the. crystals. magnetite. 50｡A5｡. in. subophitic and. augite-grains. magnetites. tex-. with. glass.. without A few. 弘ws,. zoned. is typlCally. consisting. rounded. of plagioclase and magnetite･ to light brown, the 2V(＋) and. green. groundmass. large. a. rounded. grains. pale. of plag10Clas▲e, augite and instances, however, quartz. hypidiomorphic. are. either. enclosing. forming. always is in. plaglOClase. crystals,. ture,. MIKAMI. inclusions. offine-tuffis. particularly. the. ln. found. occasionally lavas. blocky. occurring. in. some. the. ln. these. of. Nunokawa. lava一. volcanic-. breccia.. is. All. of the. wholly. or. are. partly and. chlorite. and/or. clay. Veinlets. and. in. found. often. Basalt. the. non-porphyritic. or. phical feature burdensome. of. is. which. repetition, Hypersthenic rock Andesite (Type Ve):. of. the. to. morphic the. most. brown, The and. iron-saponite･. hypersthene. auglte saponite. scattering occurs. of which and. the. in the. exceeds hypersthene. Fig. (Pl. ⅠⅠⅠ,. rod-shaped. Tanzawa. and. a. partly. is. 68o. to. crystals,. to. glassy in granular. chlorite,. and. yellowish. hypersthene,. forming. to. 71o.. ferric. than. zoned,. altered. Y-light. ; plaglOClase,. augite. altered. which it. excess. hypidio-. are. in granular. from. an as. of. brown,. characte-. occurs. Partially. brown,. crystals. and. augite. base.. The･. ones,. the. grains. rarely. Both to. the･. iron-. 3).. 3.射inor The. in. groundmass are. varies. in texture. sporadically. rather. some. reddish. Its 2V. the. save. with. plag10Clase. is always. petrogra-. To. tinge,. hypersthene. and. Aikawa. groups. lntrusives are. notable. for. a. only. section.. yellowish. crystals,. Ⅹ-pale. minerals. the. latter.. the. this. normal･. hypersthene. is hyalopilitic. groun血ass. magnetite. amount. The. a. The. being. zoning. also. represent. basalt,. of. in. plaglOClase. well-twinned. characteristic. are. secondary. types. above. to that. with. phenocrysts･. in pleochroic shades of: Z-light yellowish green.. slightly. grey. in texture;. invariably. the. these. of. of. is glVen. series It is dark. allotriomorphic,. or. sericite. are. descrlption. chlorite. kaolinite,. various. rocks. equal. by. plaglOClase and. augite. typlCal. most. (Pl. III, Figs.ト2).. type. variety. prlnClpally. no. non-porphyritic former. The. coarse-grained. sericite. with丘11ed this. of. Diabase:. b). ristically. amygdules. of. the. the. which. the. of. as. such. lava-flows. (T3'Pe c) and. minerals,. replacements. minerals. hydrother甲ally;. affected. secondary. Partial. by. or. commonly. to. altered. epidote･. epidote,. encountered･ are. are. constituents. their. numerous. occur-.

(19) GeologlCal. rences. Petrographical. and. intrusives,. of minor. The. distribution. types. As. in the. abundant in. these. in basalts. and. rocks. the. and. map. T6gatake. belong. graphically Ⅹenes. the. to. number. are. the. plgeOnitic are. have. pyroclastics 4.. Main. subgroups,. rock. a. fact. this. common. in total.･. of. indicates. them. of. the. are. rocks. most. excepting. and. occurrence.. of. group. T6gatake. Oyama. Susugaya. subgroup. subgronp. subgroup. 25. Micro-uralite-gabbro*. g. ･警. Total. Andesite. .蔓甥 P･巳. num-. group. bers. 46. 21. 1. 1. rock*. Diabase*･Basalt. o'Q'. petro--. intrusiv?･. the. Aikawa. Pyroxenitic. most-. pyro-monoclinic a few crystalsA. that. intrusives. minor. of. frequency. Tanzawa. :a_. rock.. main. orlgln･. types. rock. tbeir. nature,. of augitic All. and. All. series.. the. intrusive. these. table,. 659. to. 7T. II. 4.. in Table. the and Oyama and. Part. Mountainland,. approximates in Fig. 2, and. is shown. (Fig･ 17)･. Table. of which. enumulated. moreover,. rocks, diabases. Tanzawa. the. on. intrusives. frequency. from. seen. the. these. of. their. and. Studies. (Ⅹc. &･. 199. c). 310 1. 2. (Ⅹc)･Augite-andesite. 4. 2. 5 15. 3. 12. 18 1. 1. Augite-dacite. 2. 2. Åug.-byp.-diabase U. Basalt. Andesite. 53,ii. IIornblende-andesite. 那. Atlg.-hor.-andesite. (Vd) 15. 62. 47. U. 1r. Ⅲyp.-nor.-andesite. Minor. 1. facies. Micro-hornblende･diorite. iMicro-quartz-diorite. diorite. 1. 1. 1. 3. 3'1. 3. 3. +. Gabbroic. rock. Granophyric Total The. 251 asterisk. is. considered. 15. 9. 384. basalt. of. equivalents. coarse-grained. 659. Xc)･. Besides. contact. Occurrence. of. the. in dikes. To. an. with. 3-1) Modes. occur. 2. rock. numbers. rock. (Type. obtain. upon. It is clear. micro-quartz-diorite, or. of. representative plotted. 1. of. quartz-. the. 1. 1. 宅読 Ch. 2. 2. (e). ●畠.賀. sheets. these the. were. Schmidt. from. the. than with trend. preferred. dikes the. less. intrusives. determined net. all of the loom. thick. the of the by. in Table. rocks. enumulated locally Although is. surroundings intrusives,. measuring. the. their. usually contact. disturbed,. distinct.. planes. strike. 4. and. of dip,. 208p and. (Fig･ 18)I. projection. that. the. dikes. occurring. ln. the. present.

(20) て8. K.. Pigeoniticpyro:くerlCー. MIKAMI. -→Augiticpyroxene. a コ ⊂〉. 島. こ). AndesiteandDacite. 也 i ぐd. -i 3. ●. =ヨ i. 2. 0●●●. 1. O●○●oo●d●●. LU? q). 害毒 62: 5. Andesite. 4 3. ′ーヽ. の. D. =;. ●. ⊂〉ゝ一. 2. OO■)●●〇Ooof●. I. とd). ぎ忘. 15. 払;;Fd. 14 13. fdEC. 蒜(⊃. 12. 00. ∼. E=てプ. ll. Micro-uralite-gabbro,. (:岳. 10. CI. Diabasea皿dBasalt. 良. ●. ●. (勺 ●OL. (勺ヒ叫 l⊂). ●. ≡二. OO＋4. 6 OOO4. .C). ●●●●●X●. ･1 つ I). c●O●OX●●×xXOO 0●xo＋ ●00. 36. 37. 2. ○〉のOXxOヾ00●●●. 38. 39. 40. 41. 42. 44. 43. 45. 46. 1. 47. 49. 48. (＋ )2V Fig.. 17.. Frequency. are. reglOn. commonly. fact,. This. subject. to. for. by. indicate. may trend. general. optical. occurring. characterized. therefore, the. 52. 53. 55. 54. 56. 57. 58. 王2%cerno.'cu,ryaftte-gabobroGr.undmass. curve. pyroxenes. 51. 50. of. that. the. of. monocliコニiご. intrusives,. minor. predominance. dikes. these. faults. the. (＋)2V. angle. ln. in. found. NE-SW. of. in. occurrence. T6gatake. the. trend.. are. strongly. Oyama. and. subgroups. Rock. 3-2)胡乱in. Types. N. Pigeonitic. a). rock. series. Micro-uralite-gabbro ties. of texture this. of. type-one. equlgranular,. approaching. abases.. They. plaglOClase, small. 18.. ･dikes (208 numbers). 6%, 4%, 2%, per l%. diagram Contours. area. of. for at. most. projection. mal. sphere.. ℃rystals. The or. short. prismatic. ones,. often. pordト of. magnetite of. plaglOClase, Some. stals.. 8%,. other. commonly. consist augite,. idiomor.phic. Orientation. rocks. porpbyritic. amount. The. Fig.. varie-. and ⅠⅠⅠ,. (Pl.. apatite. 4).. Fig.. S. Two in the. medium-grained, the. and. phyritic,. a. :. found. are. to. is in. well-twinned,. allotriomorphic are. crystals. crythe. ∑oned,. being characteristic zoning An76, Margin: (Core: An65). nor-. augite. enclosing. occurs. grains. either. of. as. plagioclase. rounded and.

(21) Geological. Sttldies. Petrograpbical. and. Twinning. (100) is. II. 79. large. Sometimes,. common･. Part. Mountainland,. Tanzawa. the. on. crystals ate 2V than the outermost rim･ their value of ノZOned, with are by hydrothermal type The this affected alterations･ of commonly rocks Augite is usually to sericite ￣plagioclase is partially altered and/or epidote･ 2V-83o ; Ⅹ-light yellowish to (Optically negative with actinolite altered brown, Z-brownish Y-yellowish green, green)･ Chlorite, calcite and quartz. 1magnetite.. on. fairly. core. occur. ･invariably A few. inclusions,. in. -present. these. Below rrocks｡ PlaglOClase. common. some. glVen. 51o,. :. groundmass. hornblende. :. 53o, 57o. 2V(-)-81o,. all the for the. are. colour,. -green. (Types, Xc. Basalt. and. same. ; lath-shaped. ture. The. 皇Of Xc- and These ぢClase and. are. rocks. in found. plaglOClase The. 2V. of. .excess. The lath-. or. in. most. in. (Type Xc). embedded. An67･-69. and. the. and. :. ln. (phenorysts. in these. to. in. rocks,. petrography. in in. crystals. as. partly. or. the. texture. variety. small wholly. rock,. also. and. groundmass,. grains. epidote, in. and. replaced. by. of the groundmass, texture,. or. or. An73),. is usually The quartz･ as. chlorite and/or it is rather not. slight 1)･. Fig･. and. phenocrysts. but. plagio-. a. with. (Pl･ V, (An68. phenocrysts. chlorite,. is hyalopilitic. present. of. composed. amounts. equal. large the. to. sometimes. An69-75. are. glass. either. needle-shaped. regar･d. various. with. amygdulesfilled. porphyritic. approximately and. occurs. crystals,. plaglO-. of. phenocrysts. (＋) 48o, 51o, 52o, 53o. distinct. a. Magnetite. plagioclase. :. inclusion:. It is. augite, usually feldspar.. common. ; veinlets. uralite-gabbro. in inclusion phenocrysts. albite and/or sericite, in the groundmass is both. the. in tex-. the. t｡. -prismatic with. or. uncommon･. rather. of augite. Andesite and. a. being. is that of basic inclusions found association inclusions diabase･ These coincide entirely. common. those. .clase. (diabase). of alterations:. fresh. remain are. minerals less. free. partially. often. augite. ･particularly with. An72. dark-grey. c-basalts).. ･secondary. A. magnetite Pl. IV, Fig･ 1)･. 5-6, and is. of plagioclase. composition. and. augite. blue. of. intergranular. or. ophitic. brown,. in mineral gabbro from (uralite)･ augite. derived. typlCally. (Pl. III, Figs.. base.. pyroclastic. minerals:-. di占playing. rocks,. actinolite. granular. the. tinge. a. above-mentioned. of are. rocks. plaglOClase,. ･in its chloritized. the. as. those. Y-greenish. with. green. c): These. absence. except ･composition, The groundmass of these. brown,. yellowish. and. often. 58o. 83o. z-brownish Diabase. constituent. 2V(＋)-52o, Ⅹ-light. in. ejecta. are. resembles. closely as. the. of. 2V(＋)-50o,. :. phenocryst. Actinolitic. Optical An6｡_68. :. phenocryst. Augite. data. rocks･ across,. centimeters. petrographical both occurring diabase,. and. c). several. character. whose. rocks,. are. less than. these. of. products. alteration. usually. (Type. basalt. のf the. the. as. in the. larger. altered augite. somewhat epidote･. rich in. infrequently. Or. variety; among.

(22) 80. Ⅰく.MIKAMl. the. is found. rocks. is exposed. in. phyistic the. the. It has. texture,. river-si､de. of the. yellowish. grey. a. 1n. Which. quartz,. in. occurs. rock. Yude-gawa colour,. less. dike. a. thick,. Kiyokawa-. is characteristically. and. plaglOClase,. 5m.. than. Yaname,. near. auglte. and. por-. form. magnetite. phenocrysts.. The The. quartz. plaglOClase or. crystals,. augite. iron. An. occasional inclusions. in the. diabase. scattering. ln. or. ; lath-shaped. brown. a. wholly calcite,. prlSmatic short in part.. whole. plag10Clase,. base. glassy. impregnated. the. and. quite. dacite.. And found.. those. uralite-gabbro. This. rock:. is. rock. of. petrography. MIKAMI,. is in this of basic inclusions noticed in fabric to and similar composition. occurrence are. Pyroxenitic. wholly has been. which. by. metamorphosed in. reported. the. the. quartz-dio-. previous. (K.. paper. 1953).. b). HyPersthenic. rock series Augite-hypersthene-diabase: the. closely approximate from the latter; they a. with. chlorite in texture. or. chlorite,. sometimes in. crystals.･. partly. iron oxides,. of rounded,. hyalopilitic. magnetite. crystals,. albite,. or. fractured. oxides.. these. rite,. and. form. the. is rather and. less. or. to allotriomorphic. iron-saponite. to. altered. groundmass. granular with. in. more. corroded,. kaolinite. is. auglte. usually. The. as. by. replaced. The. epidote.. occurs. always. is in idiomorphic. impregnated or. in. (Fig･ 2)･. mura. is usually. groundmass. iron. with oxides. Augite-dacite This (T3'クeXc):. which. The. texture.. trachytic. or. pilotaxitic. impregnated. present. The stals, is found. in. stumpy. small large. some. crystals,. brown. and. augite. usually. 血ed. in. quite. free Basalt. cally. of. plag10Clase, matrix. (An80)･ saponite･. augite. and. magnetite. are. ones･. The. to. is the. of. the. oscillatory. hypersthene. is. in. in shades of pleochroic brown. Its 2V(-) varies. rounded. It. zoning. The. 2V(＋). the. crystals,. noticed. that. the. eastern. area. of. large. to allotriomorphic. dikes Mt･. normal or. rounded X-brown, from. short, Y-light. 69o-70｡. is. of which this. of. Oyama,. type. rock and. crytype. that. The. relatively are. con-. they. are. alteration.. (Type e):. This. non-porphyritic, hypersthene. composed. The. as. distribution of. as. greenish. occurs. idiomorphic. either. slightly. Z-light. (49o, 50o, 51o)･. rocks. predominantly feldspar. In addition,. crystals･. and. small. the. 2). occurs. plaglOClase lath-shaped. or. the. of. slight (Pl. ⅠⅤ, Fig.. more of this type but diabases, differ in composition hypersthen声, and of plag10Clase. appearance,. afore-mentioned. consist. excess. In. plag10Clase. of. brown. is dark. rock. intergranular and. grey. with. in. texture･. magnetite, glass. (Pl. Ⅴ, Fig.. is in lath-shaped. It is almost alwaysaltered The bypersthene occurs. all. as. a. tinge, yellow It consists. sporadically. scattering. largely. of. in. the. 2).. crystals,. fairly. to. and/or. albite,. and. is slightly. and kaolinite. small. typi-. and. grains,. calcic. in composition or. to. iron-. pleochroic.

(23) Geological. in. 2V(-). Ⅹ-light. of:. shades. from. varies. phyritic. rock,. as. minerals. and. evidence. zoning. lCryStals,. occurring. phenocrysts. both. brownish. 70o.. and The. The. Vd,. of. by. crystals, tO. oscillatory rimmed. An46･. 79o, 80｡, 81o, The except. pilotaxitic. not. 82｡, 83o,. diametre,. are. brown, is (-). Y-. 65o, 66o,. or. acicular. are. scattered. in. in. contained. often. basalt. the. of. equivalent occur. has. texture, the. encountered,. this. of. approximately. type. of. equal. occurs. plaglOClase remains. chlorite･. the. Their. or aggregates of various gdules Augite-homblende-andesite:. in. hornblende,. the. with. idiomorphic. to. displayed these. by rocks. combinations This rock. of seems. And. hyalopilitic. (Pl･ ⅠⅤ,Fig･ this. of. or. 78o,. pbenocrysts,. glass･. one. partially. brown. the. is. andesites. follows:. 2V(-)-77o,. black. variety. are. as. Y-light. as. trachytic the. are. green-;. or. usually. crystals,. slender broⅦ･n,. brown. amountsof. of. porphyritic. composition. the most variable; is found infrequently. some. indistinctly. brownish. or. but. but. of. properties. light. common. alterations. grey. hornblende･. phenocrysts. as. optical or. mineral. slgni丘cant. are. rocks. well-twinned,. occur. brown. same. as. fresh. 4), and皿Ore. fresb･ Its composition ranges relatively or is frequently either normal zoned,. hornblende. the. or. in. common. most. these. of. together. magnetite,. and. are. (Table. of sporadic distinctly. green yellowish 88o; 86o, c<Z-18o･. it contains. general,. magnetite. augite. are. yellowish. Z-light. is slightly. texture. In. and/or. groundmass. for. in. presence. they. of. X-light. brown,. greenish. plaglOClase The. Which■1ath-shaped and. a. chlorite･. X-yellowish. andesites described･ Most. plaglOClase. Most. opacite. pleochrois皿Of. 1n. auglte,. andesites. the. and. The. zoning･ by. varies. often. rounded with. of. by. optical angle 53o-54o･. from. in. are. phenocrysts,. replaced of. The. groundmass. (An79). inclusions. non-porphyritic. already. microscope,. hypidiomorphic. are. those. plag10Clase The phenocrysts･. An45. augite. and. as. augite. as. and. shades. green･. and. in which the. the. bornblende-bearing. characterized. texture,. form. a. The the. the. and. partially. in. centimetres. represent. than. under. form. are. and. hypersthene. among. colour,. por-. inclusions.. these. appearance. phenocrysts. contain. often. holocrystalline,. few. Homblende-andesite: occurrence. grey,. base･. a. usually. and. minerals. augite. hypersthene. They. in. the. its altered. although. amounts. in. hypersthene. them. of. is rather. andesite.. Type. 2V. granular. ln sporadically Inclusions,. in. The. grains. groundmass. Both. groundmass. plaglOClase,. this. as. former.. larger. The. apatite, and magnetite, is slightly pleochroic, yellow, and Z-yellowish. bypersthene. Its. green･. both. occurring. crystals,. or. and/or. 67o,. predominantly. (oscillatory?).. the. of. Z-light. green,. type is a dark of this rock hypersthene of 'plaglOClase･. andesite. is in welトtwinned. plaglOClase. excess. brownish. 81. II. 3).. ･(Pl.. The. The. Vd):. consisting. ⅠⅤ,Fig.. Y-light. brown,. Part. M〇untainland,. TaユZaWa. the. on. 69o-71o.. (Type. Andesite. Studies. PetrogTaPhical. and. replaced. rock by. the and. 4)･ type amy･. chlorite, calcite, zeolite, etc･ to be a variety of the above-.

(24) 82. K.. mentioned. hornblende■(maximum. of green the. greenish Under. grey the. hornblende small. microscope,. as. enclosed. chlorite. or. by. highly. riety. of. The. in. and. somewhat. are. type･. The. -79o･. plaglOClase,. This. :. as′･. is partially. rock. largely. magnetite,. the. and. above･. manner.. displaylng. ;. ones. as. to. seems. also a. grey. Whitish. of plaglOClase,. be. another. colour,. magnetite. ∀ar. and. por--. a. and. slender. and. The. green･. small. Z-light. and. of pheno-. oscillatory. positive brown,. is in. phenocrysts. the. of. yellowish. pleochroic. (An6,),.. crystals. optically. hypersthene. slightly. as. large. zoning. of X-light. ; pleochroism. phenocrystic crystals, rounded and brown･ brownish Y-light green･. crystals. evidence. crystals,. labradorite. of The. minerals･ which. of. is in. composition. allotriomorphic. groundmass. Z-light. and. the to. some. c^Z-16o. brown. has. hypidiomorphic. well-twinned, hornblende. 82o･ 84o. greenish. above.. present. are re-ma丘c minerals entirely however, is still preserved-it seemso. sub-parallel. commonly. lath-shaped. crysts. of augite hornblende. The. the. is. The. lath-shaped. It is composed. plagioclase in both. occurring. to. added. hypersthene.. of The. are. amount. certain. texture,. original. which in. a. altered･. hornblende-andesite,. texture･. amount. in･し. embedded. opacite.. Hypersthene-homblende-andesite. phyritic. phenocrysts･. sporadically. in hornblende･. rimmed is. disposed. the. large. which. are. and皿agnetite. Besides,. poikilitically. in. pilotaxitic, are. in. in length). cm･. plaglOClase. phenocrysts･. grains. be. 1. in texture,. groundmass.. to chlorite, altered The groundmass by chlorite･ placed to. is porphyritic. and. andesite,. MIKAMI. Y-light in. rather. shades. micro-. X-1ight-. of. Its. green･. yellowish. 2V. with. 2V(-). is69o. The are. is rather. groundmass. wholly. by. replaced. in. hyalopilitic the. and. chlorite,. texture,. but. base. glassy. the. ma丘c. impregnated. minerals. iron-･. with. oxides.. Granophyric of. side lOm･. in. Two rock: Kurokura-gawa,. the. grey. by. colour. glOClase,. and. of which dike (3m･. theotherasa. width),and. metamorphosed. one. the. texture.. hornblende,. to. seems. in. found. are occur. as. a. the. They. magnetite,. are a. and. small. slightly a. greenish_. largely. composed amount. river_,. (about. sheet. Both ofthemare wide)･ (Table 5), commonly displaying. quartz-diorite. medium-grained. actinolit･ic. type. of this rock. examples. of. of pla--. quartz. and=. biotite. The stals. are. narrow,. forming sometimes biotite. occurs. plaglOClase also. met rim. clear an. more. it. occurs. sodic. as. granoblastic. Both. with･･. aggregate･. is in. as. of. than. them the. are. core･. The. actinolitic. short. prlSmatic. but. crystals, almost. The. hornblende crystals. porphyroblastic. always. quartz. surrounded. occurs. as. is in granular characteristic. cry--. by. small. a. grains,. but. crystals, of. augite.. The. usually associated the small鮎kes, with actinolitic hornblende. Gabbroic A irltruSion less than lOm･ thick rock: gabbroic a crops out at immediately the the Kurokura-gawa point junction north of of an.d the Ku-.

(25) Geo】ogLCal. (Kumaki. the. The. part. main. or. rapidly. gradually boundary.. irregular. an. rather. is. intrusion. surrounding. a. the. with. rocks･. the. y.quartz-diorite,. rocksmetamorphic. of. characteristic. 83Jl. II. pyroclastic by. of composed into a且ne-grained,. changlng The contact. Part. Mountainland･. metamorphosed. appea【､ance. this. of. the. with. is entirely. heterogeneous. Tanzawa. the. on. together. volcanic-breccia),. displaylng. rock,. intrusion,. This. maki-zawa.. Studies. Petrographical. and. gabbroic. coarse-grained･ amphibolitic. with. rock,. is･. surroundin革amphibolites. gTadational.. MicroscoplCally, largely and. of. quartz,. plaglOClase hornblendes. cummingtonic. sociated. the. with. Both. them. of. sodic. latter. the. the. around As. be. being. from. seen. Possibly. orlgin･. or. uralite-gabbro. the. it represents. within orー. within latter･. the. with. this intrusive. is of. rock. ob--. micro二,. above-mentioned. in contact. All. and. Micro-quartz-diorite. of the. so-called quartz-diorite, Hornfels of the diorite･. that. resembling. occur. commonly. and･. both. occurs. the. porphy-. found. are. pyroxenes. of. narrow. rock.. equivalent. closely. variety. The. hornblende. plaglOClase,. intergrowth. a. or. crystals,. hornblende. a. as-. ones･. porphyroblastic by rimmed. granular. description,. actinolitic･. usually interstitial･. always. always. as. either. above. pyroxenitic. the丘ne-grained. being. cores. parallel. ln. Ml･cro-lwmblende-diorite. feature. their occurs. is. sometimes. cummingtonitic. hornblende,. may. scure. The. crystals.. crystals,. consisting･. proportions,. quartz. inclusions several of a few relics of diopsidic. containing. Occasionally,. magnetite.. in varylng. The. texture,. In addition,. hornblende･. present. granoblastic. as. ones,. roblastic. are. in. granoblastic. green. and. zoning; evidence The hornblende. sheath.. are. rocks. hornblende･. green. occurs. plaglOClase. these. all of. bordering. aureoles. :. these. of. their. petrographical. and. its these. some. bodies. of. These. rocks. are. are･. rocks. allied. rocks-. intrusives･-. 3-3) Age-Relations Diabase dominant by:. (1) Almost textural. feature. lava-flows. the. (3) Some hand,. other. It is inferred in. intimate. resemble bulk of of. they. these. occurring. the. with. variety. of. (Fig. 2. and. to. be. the. the. Table. contemporaneous. 4). The with. are. the. cut. by. facts. that. the. a. small. by. date. of. that. of. is con血ed. intrusion. the. of. diabase. these and. pre-. characterized the T6gatake･ composition. those. and,⊃ the. of. andy･. quartz-diorite,. of hornblende-andesiteof these. of and. most. diabase. of. also. the. rocks. took. the. pyroclastic. Oyama. subgroups･. rocks rock : These basalt, representing and. their. to. mineral. and. dike. intrusion. eruptions violent the T6gatake of. occurrence. and. ejecta. rocks･. affected. often. diabase. And. of. pyroclastic. Gabbroic. and. above. latter･. the. deposition. Mzlcro-uralite-gabbro. those. closely. the. in distribution. 4). (2) Their. Table. and. rocks,. the. with. association. intrusive. confined. are. rocks. are. from. during. identical. these. c):. whole. rocks. (Fig. 2. the. composing. and. the. these. of. Subgroups. basalt. on. all. Oya皿a. and and. throughout. type. rock. (Types, Xc. Basalt. and. to. place rocks･. petrographically. are. a. the. rocks, basalt･. coarse-grained said. subgroupsゝ. therefore,. seems▲.

(26) K.. .笥4. Andesite. Dacite. and. ーthe intrusions -rocks,. however,. found. in the. ￣to have. are. taken. Aikawa. place. groups,. pyroclastic. the. intrusion. is. andesite-. of the. represent. the. slightly. dacite-eJeCta. therefore,. deposition. of the. later. the. than. seems. Tanzawa. the. of. intrusive. an. and. phase. Susugaya. eruption. Although. rock:. diabase. whole indicate. its. that. dike. a. such. intrusives,. the. -throughout. subgroup, the dacitic. of. petrographical. is. type. rock. tO. similarlty. alone. all the. basalt. rock. is contemporaneous. diabase. and of the basalt Hornblende-beanng The andesites: of this rocks belonglng tO the bypersthenic rocks ･･､ofthe intrusive. type. make. may. rocks. are. ･other. hand,. some. ℃ontact. found. relation. bution. these. of. amounts. only. during period Hypersthene-bearing. some. to. after. facts. :. invasion. (1) The. LCurrirlg. the. のf metamorphic. eastern. up. took. the. are皿OSt. are. rocks,. most. intrusion. of these. prevailed. rocks. The. certainty. are. makes volcanic. most. COmmOn. And. subgroup.. of these This may. slightly. fact. this. connection. the. with. with. there. the. a. intrusion. AIetamorphic the. is. have. be by. justi丘ed the. pyroclastic mass. of. before from. the. quartz-diorite. rocks granopbyre. of. the oc-. of quartz-diorite.. Rocks. quartz-diorite. of which. great. happened. rocks. affected. in the. abundant. (3) In Nakagawa,. of. subgroup.. rocks. andesites.. rocks. relation. in. present. subgroup.. in close. place. said. however,. series, the Oyama. quartz-diorite.. of these. aureole. with. distri-. subgroup.. are. these. of. occurrence. rock. rocks. 4. ln. of. Probably. gravels. intimate. activity the Oyama. occurs. The. Oyama. the. composing. intrusion. making. of the. dikes. subgroup･ ln. date. always. recognized. the. basalt Oyama. the. of. andesites. the. of The<occasional. :. these. :. rocks. rocks. hypersthenic. that. (2) Granophyric `Oyama. rocks. just-mentioned. of the Granophyric the. deposition. rocks. indicates. activity. のr. the. the. pyroclastic. strongly. pyroclastic facts that. tell their. ･ejecta belonging the. these. diabase,. the. former. to. con血ed hornblende-bearing. the. the. ln. be. can. The. mass.. area. of the. on. while,. same. of. the. is almost. Of. from. to. cut. those. case,. latter. the. the. distribution. in this. by. moreover,. eJeCta. It is evident. impossible. be observed･. dikes. no. by. Some. series.. rock. bulk. the. up. quartz-diorite,. with. rocks i.n the. observed. can. rocks,. the. addition,. ニSmall. as. latter;. the. ICutting. far. of. metamorphosed. of these. is often. So. subgroup･. in. of. mass. great. slightly. dikes. the. of. the. cutting. of them. uralite-gabbro. んand. it. activity. that. these. :at. the. this. of. this. 1n. the. of. rocks.. Pyroxenitic. ･rand -with. of. These. and. andesite,. depositions. the. may. during. of intrusion. the. date. the. occurrence.. occasional. to. during. dacite. prevailing. date. the. The. tell definitely. to. their. of. in petrography. rocks. intermittently. while. volcanisms. ･dacitic ､though. because. rocks,. similar. pyroclastic. It is difBcult. (Type Xc):. these. of. MIKAMI. been. are. developed. derived. from. various. the. kinds. pyroclastic.