PETROLOGICAL STUDIES ON THE VOLCANIC ROCKS FROMJAPAN, WITH SPECIAL REFERENCE TO THE“HORNBLENDE-ANDESITE” : Summary of theoriginal paper in Japanese

九州大学学術情報リポジトリ

Kyushu University Institutional Repository

PETROLOGICAL STUDIES ON THE VOLCANIC ROCKS FROM JAPAN, WITH SPECIAL REFERENCE TO THE

“HORNBLENDE-ANDESITE” : Summary of the original paper in Japanese

Taneda, Sadakatu

Faculty of Sciences, Kyushu Imperial University

http://hdl.handle.net/2324/1524099

出版情報：九州帝國大學理學部紀要 : Series D, Geology. 3 (1), pp.19-62, 1947-04-20. 九州帝國大 學理學部

バージョン：

権利関係：

Memoirs Of the Faculty of Science， Ky亘sy亘Imperial University，

       Ser． D， Vo1． III， No．1．1947

PETROLO（ilCAL STUDIES ON THE VOLCAMC     ROCKS FROM JAPAN， WTH SPEqAL

    REFERENCE TO THE HORNBLENDE■

       ・ANDESITE，，

一 Summary of the original paper in Japanese一

By

Sadakatu TANEDA

（Received Sept．11th，1946）

Contents。

CHAPTER I．

   、1．ユ．General introduction and acknowledgements．

    1．2．On the estimation of chemical compositions of rock−forming         mineralS．

CHAPTER II． General properties of the Pyroxene・andesite of Japan．

   II．1． General description．

   II．2． Special treatise．

CHAPTER III． Studies on the Hornblende・andesite ．   III．1． Introduction．

  III．2． Special，treatise．

⁝  

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129﹂4に﹂

 

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．

 

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 ・Tユー1τ且丁﹂I

ITlIT﹄1﹂I TユTlT工IIぎー

Rocks from the Har皿a volcno．

The homblende・andesite from the Ata caldera volcano．

The hornblende−andesite from the Sambe volcano．

The hornblende・andesite from the Hutago volcano．

The hornblende−andesite from the other districts．

        Rernarks and sUmmary．

CHAPTER IV． Comparative studies on the phenocrysts and ground・

     mass in the volcanic rocks， with special reference to the relations      between the Hornblende・andesite and the Pyroxene−andesite ．   IV・1． Special treatise，

  IV．2． Comparative studies．

CHAPTER V． Sammarisation and consideration．

20 Sadakatu TANEDA

   V．1． Discussion on the characteristic properties of the         blendeandesite ．

   V・2． Special discussion on lnagnetite．

   V．3． Significance of coτnparison of phenocrySt with the         mass mineral．

   V．4， Conditions of the crystaU三zation of hornblende．

Additional Remarks．

Horn一

grOund一

CHAPTER L

1． 1．  6enefal Introdllction。

   Japanese Quaternary volcanic rocl（collta｛ns two rock types，

one of which is the Pyroxelle・andesite at、d allother the Hor1レ blende・andesite ．

    The both rock types are apparelltly very different in their various properties fr（）m each other；but by thc detailed examina−

tion it becomes conceivable that thじhol nblende−alldesfte is de1 ivable from a pyroxlene−andesite（magma）chieny by the fractional crystal−

lization and gas actioll in a certai11（geological and othcr）c（mdition．

    Inもhis report・theα1tline of the petrological studies on the hornblellde・andesite i◆given， witll special reference to the l・clation of it to the pyroxene−andesite． The details should be read ill thc品 original paper， in Japanese， that will be printed in the near fultur隼     Note： Figure Nos． and Table Nos． in this report refer to the original paper in Japanese．

   ザ

Ack伽wledgements。

    The writer wishes to explless his sincere thanks to Prof．

Se｛taro TsuBol， Prof． Ken−ichi SuGI， Prof． Hisashi KuNo and otller seniors and friends， who were constant in giving llim encouraging guidance alld kind help．

    The writer is also much indebted to the Scientific Research

Expenditure of the Department of Education， the T6sh6gu Tercentenary Memorial Endowment and the Imperial Acaderlly of

Japan．

  本篇は原著旧本文）の抄録であるので，原著から摘録した表及び説明圏には原著に於   ける番號をその儘附して％る．從つて飛び飛びの番號になつてゐる．

Homblcllde andesite froln Japan

21

1・2・ On the estilwation of chellli（〜al compositiolls of       rock・forming minerals．

   The chemical compositions of the rock・folmi！〕g nlinerals dealt

with in this work， excepting some analysed ones， were estimated from their optical constants． For this purpose were used the optical prope頃es−chcmical compositions variation diagrams which are enumerated below：

1． Plagioclase：S． TsuBoI s diagrarn was used．

     Cf， S． TsuBoI；Proc， Inlp． Acad．， Vol． XI， No．10，1935．

2．Monoclinic pyroxene：H． KuNo s diaglam was used．

     Cf． H， KuNo；Jap． Journ． Geol． Geog．， Vol． XIII， Nos．1−2，

       1936．

3．Oliville：A， N． WINσIELI／s diagram was used． cf． Elements of     Optical Illilleralogy、

4

5

6

7

Rhombic pyroxene：．The wrlter s diagram was used．

  Cf． S． TANEDA； Variations in chemical composition and optic     properties ill rhombic pyroxelles（Joum． Geo1． Soc． Japan，

    under printing）． Abstract is given irp the preceding pages     （S．TANEDA：Mem． Fac． Sci． Kyusyu Inlp． Univ．， Ser． D，

    Vol． II【， No．1， p．14）．

Hornblende：The writer s diagram was used．

  Cf． S． TANEDA；Journ． Jap． Assoc． Min． Petr．＆Eco．、

    Geol．， Vol． XXIX， No．5，1943． Abstract is given in the

    preceding pages（S：TANEDA；Mem． Fac． Sci． Kyusyu

    Imp． Univ．， Ser． D Vol． III， No．1， p．1）．

Biotite：The writer s diagram was used．

  Cf． S． TANEDA； Journ． Jap． Assoc． Min． Prtr，＆Eco．

    Geo1．， Vo1． XXIX， No．3，1943． Abstract is given in the

    prcceding pages（S． TANEDA； Mbm． Fac． Sci． Kyusyu

    Imp． Univ．， Ser． D Vol． III， No．1， p．1）．

Glass：0． G， WILLIAM s diagram was used．

  Cf．0． G． WILLIAM；Journ． Geol．， Vo1．32，1924．

    S．TANEDA；Mem Fac． Sci． Kyusyu Imp． Univ．， Ser． D，

    Vol． II， No，1，1943．

22 Sadakatu TANEDA

CHAPTER II。

6eneral properties of the  pyroxeme田andesite，， of Japan．

II． 1．  （ieneral description．

    The pyrdxene・andesite is the general name given｛o the

pyroxene・andesite， basalt， bandite， miharite，．etc．， which are con−

sidered to be the most abundant types of Japancse Quaternary volcanic rocks． It is characterized by pyroxenes and plagioclase

（calcic bytownite−labradorite）， with or w▲thout olivine． The ground・

mass is constructed of pyroxene（two pyroxene or monoclinic

pyroxene ollly）， plagioclase， magnetite， anorthoclase， silica minerals，

etc，，

    It is・corresponding to the typical pyroxene andesite in the world in its silica percentage（50−62％）， the proportion of plagib−

clase to ma6c minerals and its texture， but in detail it differs from the Iatter． Some notable points are given below：

1）Plagioclase is toQ rich in An content， compared with plagio・

clase expected frorn the Silica cqntent．2）In the bulk composition

CaO is much， and Na20＋K20 is，little，3）In the norm Quartz is

c㎝siderably large and Q／F＞禮．噛

    The difference of groundmass minerals from the phenocrysts should be noted in this part， because the relation between the

both is very different in the  hornblende−andesite ．

    The remarkable points are as follows：

1） Plagioclase：The groundmass plagioclase is nfore Ab rich， to

some extent， than the phenocryst．（It is abbreviated in this report to enumerate the examples）．

2）Pyroxene：，The groundmass pyroxene is more Fs rich than

the phenocryst， （Ditto）．

3）PropOrtion of felsic minerals and femic ones in quantity：

Generally saying the groundmass is littlc（melanocratic）than the

phenocryst in the fe1／fem ratio．（Ditto）．

   The above 3 markable facts are幽realised ln the norm also．

Hornblende andesite from Japan

23

ll．2． Special treatise．

   Descriptions on some pyroxene−andesites may convince olle of the above・mentioned facts， but it is not given in this part， due to・the lack of spacel （Cf． the original paper in Japanese）．

CHAPTER m．

Studies on the Homblende．andesites，，。

lll． 1．  lntroduction．

1） The general name  hornblende−andesite  is given to・the comparatively acidic andesite characterized by the phenocrysts of hornblcnde and intermediate plagioclase with or without pyroxenes

and biotite．．It is， megascopically， constructed of loose and gray

matrix and prominent phenocryst of Plagioclase and mafic minerals

scattering in it． It constructs the dome not皿commonly．＊

2） The diStribution of the  hornblende−andesites  is notable，

that is to say it occupies the inner zone of Islands of Japan，

where latteral pressure has been comparatively large through the Quaternary（perhaps）．

3） In the next Section petrographic descriptions qn the important representatives of the hornblende・andesite  of Japan are giveh．

Ill．2． Special treatise．

III．2．1． Rocks from the Haruna＊＊volcano．

   The Haruna volcano is made up of two bodies， the older and

the younger． The former is composed of pyroxene・andesite to・

gether with a few hornblende砲ndesites and the latter is composed of hornblende・andesite． Besides the above both rρck types （the pyrox（…ne・andesite and the hornblende−andesite） there is an inter−

mediate andesite， that is caUed the Himuroyama type．

   The Haruna s rocks are classi6ed， according to their ferroma−

gnesian silicates，・both as、phenbcryst and in the grbundmass， as follows（Table VIII）：

  苦 The hornblende・andesite does not mean all the hornblende−bearing rocks．

  繰榛名

24 S劇akatu TANEDA

      ￠㈱㌣蘭γ

診端幽亀イ

》き』烏嶋Rぱ5伽ノらρ島冗

豊 圏

〆9

e穆80鍋●

塾v縛ザぬw槻 綱●鍋自繭成G畠 灘ワ輪＝・▲e紡 ¶アρ￡ご乱鰺館

z8翼eイ ーt己4

  話〆徽〆A酢㌢∀ 縮心持議5 fW汚ジ鴻浦一弼yム芦8θ ぜ ・碗）

擾﹁㌻麿 曙繊

φ 獅

シ、∴デ

け

ピ一﹁

パ

﹂

∨

    ︑

≠ 

轡弊 蒲

／1、

∴：

：、

、㌧．

 ， 、  ∴・．

、  「、

N →

Fig． L Distribution of the Quaternary volcanic rockざin Japan．．（Scale 1／16．000．000）

1

T1つI

         Table Vflla

Classification of Haruna s rocks．

Olivine ：±二

R

R＋（M）

5γ

 4

r＞．m  2

●

 3

r十m

2

●  2

●

ソ﹈

m

2

ぞペー㎏20

く ー

r

 1 n〕

1，2

0

1，2

0

Hornblende andesite from Japan

25

   III  R＋M         2，4   3，4，6  3，4  3，．4

       。    ○    ○    ◎

   IV  R十M十H   ・9  8，9，（5）  7

       ●     O     V  R十（M）＋H   10，11  10，11        0     ●    VI   R＋H       10，11

       0

 ◎Predominating  O Rather abundant  ）Poσr  ●Very poor

 Figures 1，2＿11， refer to the Table VII（cf． the writer s previous paper有）．

R，r：rhombic pyroxene， M， m：Monoclinic pyroxene， H：hornblende． Large letters are concerned with phenocryst and small ones with groundmass， and（ ） shows microphenocryst．

   Notable features of Haruna s rocks that have been described in the writer s previous papers＊are summarized as follows：

1．Olivine（about Fa 34−49 in Wt．％）is often resorbed with formation of corona made up of hypersthene grains and prisms

（sometimes up to l mm in Iength）， and in some instance§is enclosed in the hypersthene phenocryst． The composition of

hypersthene is riCher in En content than the hypersthene occurring as isolated phenocryst．

2．In the rock， the groundmass pyroxene of which is pigeonite or pigeonitic augite， phenqcryst of hypersthene is surrounded by

an aggregate of minute granules of．pigeoniticオOgite and pigeonite．

The peripheral monoclinic pyroxenes are cρn6ned to the margin of each hypersthene crystal where the latfer is in contact with the groundmass．

3．In the rock that carries two pyroxenes， rhombic and mono−

clinic， in the groundmass， the phenocryst of hypersthene is usually free from the peripheral monoclinic pyroxenes．

4．If the groundmass pyroxene is monoclinic pyroxene al（）ne， it is pigeonite and pigeonitic augite， that are plotted in the  pigeonite

field．

    If the groundmass pyroxene consists of two kinds， rhombic

and monoclinic， the latter is augite， sometimes with subordinate

pigeonitic augite． The． compositions of the augite， hypersthene

  苦S．TANEDA：Mem． Fac． Sci，1〈yusyu Imp． Univ．， Ser． D， Vols、1＆II，1941−

1943，etc．（It is supplemented（revised partly）in this paper）．

   S．TANEDA：P．13 in this vo1． III．

26 Sadakatu TANEDA

and the mixtUres of the two pyroxenes are within the two

pyroxene field ．

5．When rhombic pyroxene forms parallel intergrowth with mono・

clinic pyroxene， the former is always inside the latter． The paraUel intergrowth is not uncommon in the microphenocryst，

while it is not abundant in the phenocryst． Besides the parallel

intergrowth， there are some cases that rhombic pyroxene is attached or enclosed partly or wholly by monoclihic pyroxene．

In this case also the former is inside the latter．

6．Monoclinic pyroxene varies in composition from（diopsidic）

augite to pigebnite in the pigeonite 6eld continuously．

 ぺ

7、In the pyroxene・andesite rhombic pyroxene as a whole varies

in composition from Fs 25士（core of phenocryst）to Fs 50±（marginal

zone and groundmass）．       ・

    The composition of the most predominating＊phenocryst is

different in a different kind． Especially important points are noted as follows：

    1）In hypersthene・andesite of II．1kind， that colltains micro・

phenocryst of augite or pigeonitic augite， the most predominat垣g＊

hypersthene as phenocryst is the same as ill the two・pyroxene−

andesite IIL 1（Fs 36−39．5）， and more Fs rich than in the hypers−

thene・andesite I．1（Fs 32．5−34）

    2） Concernin亀to two−pyroxene・andesites， III．1， III．2 and III．3， it is more En rich in kind III．2， the groundmass of which carries augite and much less●hypersthene， than in kind III．1， the ground−

      モ      タ

       pigeonite or pigeonitic augite， and it

mass pyroxene of which is

is moreover En rich in kind III．3， with augite and hypersthene in the groupdmass．

8．In the hornblende・andesite rhombic pyroxene as a whole Varies

in composition from Fs 49士（core of phenocryst）to Fs 24士（marginal

zone and groundmass）．

   The most predominating＊phenocryst、 is more En rich in VI，

that is free from monoclinic pyroxene， than in IV and V that

carry augite as phenocryst， microphenocryst or in the groundmass．

   For comparison the compositions of the most predominating＊

hypersthene in each kind are givell in、 Table VIII． b．

9．In the Himuroyama andesite as a whole the gro皿dmass hypers一

  枠 See Table VIII． b．

      Table VIII． b

Optical angle of hypersthene in the both rOck types， the pyroxene・andesite and the horn

blende・andesite， from Haruna， and their chemical compositions（in Wt．％）as estirnated

from the former． It is・variable but in this part are shown the values of the maxi伽nl point ln the frequency curve in each kfnd of rock．

I R

II R＋（M）

IIIa R＋M

IIIb R十M

IV  R＋M＋H

V R十（M）十H

VI R十H

︷

（一）2V    Fs

（一）2V

︷

  FS．

（一）2V

︷

  〜Fs．

︷ ︷ ︷

（一）2V Fs．

（一）2V Fs．

     5        

Ph MPh＆Gr

（一）2V  61°：L Fs． 39．5±

∫（一）2v

l Fふ

69°土 29．5士 61°−63° 67°−6g°

39．5−36   32−29．5

    4    r＞m

Ph MPh Gr

66°−64°

32．5−34 61°士 39．5士

61°−63°

39、5−36 580−60°  670−6go 44．5−41  32 −29．5

      3     r十m

Ph MPh＆Gr

67°士 32土

6go−670 630−55°

29．5−32  36−49

Ph

64°

34ゴ   2  r《m

M・Ph＆Gr

66°−64°

32．5−34

      1      m

Ph MPh＆Gr

66°−64°

32．5−34

63°−610  60《〕−55つ 36 −39．5 41 −49

630−610 60°−580 36 −39．5 41 ご44．5

Cf． Table VIIIa．

o日窪ゆaoき阜︒苔⑦怜o目㌃冨b

N

や

28 Sad歌atu TANEDA

thene is more En rich than the phenocrystic one， while the both are variable in Composition and zonal structure， say the latter is in three types， reversal， normal and oscillatory．

    The composition of hypersthelle as phenocryst， estimated from β，is the most Fs rich（up tp Fs 54）of three rock types， the pyroxene−andesite， the hornblende−andesite and this type．

10．In the pyroxene・andesite phenocryst and microphenocryst of rhombic pyroxene that form parallehntergrowth with monoclinic pyroxenes are魑

richer in Fs content than isolated phenocryst， while

in the hornblende−andesite the relation is slightly reversed． In

       セ

the Himuroyama andesite rhombic pyroxene is variable in com−

position throughout the intergrown and the isolated ones． ・

11．In the hornblende・andesite the groundmass pyroxene is

hypersthene alone， or hypersthene and much less augite．

12．Although each kind of Table VIII is variable in acidity， generally

saying it increases from I towards VI and from l towards 5 in

Table VIII， along with the decrease of colour 1 atio in the ground−

mass． That is in order of olivine・hypersthene・andesite I．1， two・

pyroxene−andesite III．1， two・pyroxene−andesite III．3， augite−bearing

hypersthene・hornblende・an．desite IV．4and hypersthene−hornblende・

andesite VI．5．

13，The composition of groundmass pyroxene decreases in Wo content and increases in En content along with increase of the

acidity of rock．

14．Although the amOunt of phenocrysts of hypersthene元augite

and hornblende is variable， there seems to be some regularity as to their relative abundance， i．e：

    1） In the pyroxene・andesite hypersthene is predominating

over augite， the former being 4−10％ （Vol．）， while the latter less than 2．5％（Vol．）．

・ −2） In the hornbler頂e−andesite hornblende is in excess， usually 7％（Vol．）， in amount， while hypersthene−is less than 3％ （Vol．），

and augite much less．

    It should be noted that the rocks＊ that carry augite as pheno・

cryst are superior in the amount of hypersthene and inferior in the

amount of hornblende to the rocks＊which are free from augite

phenocryst． ＊hornblende・andesite．

Hornblende andesit6 from Japan

29

      Table XIII

Relative amounts of some porphyritic minCrals in the

     hornblende−alldesite from Haruna volcano．

Hypersthene Augite Hornblende

Average of IV 3．8in Wt．％

0．4  ，，

6．2  ，，

Average of V and VI    2．7in Wt．％

   0．0    7．8  ，，

Fig．10． The mode of variation of An content ill zoned plagioclase  of Haruna s rocks．

         1−IX， concerned with hornblende・andesite          X−XIII， concerned with pyroxene andesite

30 Sadakatu TANEDA

than in the hornblende−andeslte

    2）The ratio groundmass

Iarger ill the pyroxene・andesite than ln the hornblende・andesite．

   Magnetite as inclusion in hypersthene is rare ih the horn

blende・andesite． It is not abundant in the pyroxene・andesite also．

16．Hornblende occurs as isolated phenocryst except some cases

in which hypersthene is attached or enclosed・partly by the former．

The hypersthelle is similar or slightly richer in Fs content com−

pared with phenocrystic or microphenocrystic one．

17． Plagioclase as a whole is less calcic in the hornblende・andesite

than hl the pyroxene・andesite． Zoning in the hornblende・andesite is prominently oscillatory（in many cases can be divided into two 15．Magnetite occurs as phenocrystic and groundmass millerals．

Although pehnocξystic magnetite as well as groundmass one is

variable in amo皿t through all rocks， a teudency is that：

    1） Total amount in the pyroxene・andesite is more菱bundant

       maglletite to phenocrystic one， is

grotlps， say lnner even normal and outer

irregular， oscillatory even groups）；while it normal in the pyroxene・andesite． Cf． Fig．10．

18． Quartz phenocryst is confined to the

Tridymite occurs釦lterstitially in all rocks．

eVen， rarely WaVe

is generally simple

hornblcnde・andesite．

Wo

Fig．12．

2・・

   ／   乙・＿

 細

Diagraln showing the proportions of Wo， En ferromagnesian silicates of Haruna s rocks．

P1，2：

＼

．△

   臼

and Fs contents in the

Concernillg with Pyroxene・andesites（belonging to the Kind III】（P】、

and III3（P2、 ill Table VIII．）

Blank、cirde（P 1，2） Phenocryst（hypersthelle and augite）

Black circle（P 2）  Groundmass（hypersthene and augite）

        （P1）  ρroundmass（pigeonite）

H  Concerning with Hornblende・andesites

Blank circle（H） Phenocryst（homblende and hypersthene）

Black circle（H）Groundmass（hypersthene）

Hornblende ande⑨ite from Japan

31

19． In the coarse・textured autolith of hornblende−andesite，・plagio−

clase carries hornblende as incluslon in the sodic marginal， or

rarely internal， zone、（calcic andesite）， while it is not found in the core（bytownite−sodic labradorite）．

20．Hornblende shows two types of opacitizatiol1 phenomena，

that iS the pyroxellic type and the black one． Sometimes

the both typeミ are found in the sarr｝e crystal， the  pyroxenic

type being〃outside the black type。

  III．2。2， The Homblende andesite，， of thel Ata＊volcano．

    The properties of the hornblende・andesite from the Ata caldera volcano are same as those from 〔he Haruna volcan（，， alld the

relation of the hornblende・andesite to the pyroxene・andesite in

8．至         4e

44

、

ト：＿

σ

與 動

 ・ 抑ψ御 砂

一

     ，

一

〉

｝

θθ8060〆．旬釦仰幻

︐      

一

      

、

Fig．14， The mode of variation of An content in zoned plagioclase in the  hornblende，andesite of the Ata volcano．       ．

       8．1−Nabeshima・dake   4d＆4e−Senda

苦 阿多．

32 Sadakatu TANEDA

the same volcano is also similar to that found

types from Haruna lust mentioned．

   ＊Cf． S． TANEDA l Journ． Jap． Assoc． Min．

Vo1． XXXII， No．4，1943．

in the both rock Petr．＆Eco． Geol．，

III．2．3． The Hornblende andesite，， of the Sambe volcanq．＊＊

      （Biotite・hornblende−quartz・andesite）

    It is porphyritic， with feldspar， hornblende， biotite， quartz and

magnetite scattering in the五ne・grained matrix． Microphenocrystic

ノ勉。？5η5η．5η可

00 00

●Oの0

励

？0

D︑0▼．

ロ

75

グ50一〇

go

但 知

        1

「、＿T」『げ

尺

一

 一。皐∨ 皿

一一

⌒

声

＿二

『』■

皿

‖

句

50｝

％

51ノ

卯．

一卓卓畠■へ

ゴ

一・〉三「一    OS爪

】

門一一阿

︑

で

一）rJr、

）W

一

●Lノ「一

ノ」・〜庖

一

』｛陣一

コ「コ｛コー ∫

〔「し〜｛＿r

〔

，    ：F■「

 ．A        ，  d 一   匂●

●

■

一一見「

rへコ〜

己

  Fig．16． The mode of variation of An content in zoned plagioclase in the    Sambe s rock．

    1．−STSb 24，  II．−STSb 26   m．−STSb 37   1V．−STSb 25     V．−STSb BO．1 VI．−STSb BO．2  VII．−STSb 19  VIII。−STSb 23．1    1X．−STSb 23．2

 繰三瓶，Cf． S． TAN￡DA：Journ． Jap． Assoc． Min． Petr．＆Eco． Geol．， Vo1． XXXII．

No．5，1944．

Hornblende andesite from Japan

33

constituents are plagioclase， hornblende， magnetite， apatite， and

hypersthene．

    The groundmass is felsitic to hyalopilitic in texture． The conStituent minerals are plagioClase， qUartz， magnetite hypersthene，

apatite， and anorthoclase．

1） Zoning of plagioclase is as a rule， prominently oscillatory， and in some cases can be divided into two gr◎ups， say inller normal

group and outer oscillatory one． The outmost zone is usuaUy more calcic than the continuous imler zone． Micl℃phenocrystic

and groundmass plagioclases are similar ill An colltent to the pheno−

crystic one．

2） Afthough it is little in amount， biotite occurs as phenocryst，

sometimes being resorped with formation of the a恒gregate of

hornblende prisms． So far as the measured valu（鰹are concerlled，

the former is slightly lower in refraction than the latter． Biotite as inclusions ill hornblende is also f◎und not uncommonly．

3）Sometimes hornblende carries a colourless patch in the core，

which is believed to be a member of cummingtonite．

4）．As to hornblende there is a tendency that optic angle 給 slightly smaller in the phenocryst，than in the rnicrophenocryst and groundmass one．

5）Biotite with high refractive index seems to be accompallied by hornblende with high refractive indexP This relation is found

in rocks， being completely free from oxidation．

6） Zonal structure is pronounced in some crystals of hornblende，

in which tremolitic and cummingtonitic zones develop at the

margin and sometimes within the inner zo1宝e of green hornblende．

7） In tlle massive lava opacitization of hornblende and biotite is

commonly found at their marginal zones， the black type 、being predominant except few cases where the pyroxene type de・

velops partially．

8） Ferromagnesian mineral in the groundmass is rhombic pyroxene

except a few hornblendeS．−It is variable in optic angl（ご， say in composition， but as a rule more magnesian than Fs 43．

9）The ratio of magnetite to ferromagnesian minera6 is much large in the whole of the groundmass and microphenocoryst than

in the phenocryst．

10）The proportions of Wo， En and Fs in the hornblende， biotite，

cummingtonitic hornblende and rhombic pyroxene， each of which

34

^．

Sadakatu TANEDA

iS estimated from the optical data，

diagram as shown in Fig．19。

are plotted in a triangular

瑚）．

Fig．19．

 rocks．

    H：

   Hm：

  趣         F邊

The pyroxene components in the ferromagnesian silicates in Sambe・・

氏 BR

Hornblende phenocryst

Microphenocryst and㎡argin of hornblende phenocryst

（Occasionaly cummingtonitic）

Cummingtonite occupying the core of ho】mblende phenocry3t Biotite phenocryst       

Rhombic pyroxene occurring as microphenocryst and in the grQund・

 maSS         1

    The remarkable points in the chemical composition are noted as follows：

1） Although it is nearly constant throughoUt the rock as a whole↓

thC whole of microphenocryst and groundmass and the groundmass

alone， in detail the ratio MgO／FeO（Total）of the whole of micrio・

phenocrysts and groundmass is slightly less than that of rock as awhole， the ratio of the groundmass alone is slightly larger than the．latter．

2） The normative feldspars of the groundmass and of the Whole of the microphenocrysts and groundmass are not prominently・

enriched in Ab content， comparing with that of the rock as a

whole， though the enrichment of Ab content in the groundmass

is prominent in the ordinary pyroxene・andesites from Japan．

Hornblende andesite fron！Japan

35

3）The quantity of normative femic minerals is less in the groundmass and Iargest in the whole of microphenocrysts and

groundmass． This relation is also reversed in basalts and pyroxene−

andesites of other districts．

4）Normative pyroxene wants Wo content throughout the gro皿d−

mass， the microphenocryst and the phenocryst．

    The normative corundumm is less in the rock as a wholeand

most abundant in the groundmass alonq．

5） In§pite of the above facts the ratio，（whole CaO）／（whole FeO

＋MgO）， is notably large in the groundmass comparing with the

rock as a whole， though it is in the whole of mic拶bphenocrysts and groundmass slightly less than in the latter．

III．2．4， The Homblende ande5ite，， of the Hutago＊volcano．

   The properties of the hornblende・andesite from the Hutago volcano are・similar to those of the hornblende・andesite from

      〜、ア吐n       P蛤91◎

Fig．20． Mode of variation of An content in zoncd plagioclase in the rocks  from the Hutago volcano．

苦爾子

36       Sadakatu TANEDA

the Sambe volcano， sequently the descriptiδns

this parL

      See the original paper（in Japanese）．

       Tables XVIII＆XXI Mode（in

Hornblende Biotite Hypersthene Augite Magnetite Apatite．

Plagioclase Anorthoclase Quartz Tridymite Cristobalite Glass Total

     1．

 1．

Pheno・

    cryst    12．2    0．1     十     十    1．0    0．1    17．2

   0．1

HUtagOyama laVa，

   the Hutago volcano

戸一■一一一一一■一一印《一一」・一一一へ

31．7

 Micro

         ground・

pheno・

       maSS     cryst

   O．9      十    十      3．2    十

   十

 1．7−0．5      ］※5−2．8    0．1．    nd．

   f．o   nd．

      nd．

   十

       nd．

        （1n㌫。h）

    ノ

 3．7−2．5    65．6−66．8

      ．of、 priロcipal

A＆B．

are abbreviated in

 2．

       Micro pheno・

         pheno・

    cryst

       cryst    8．0      1．9    1．6      十

 0．5 0．1 20．0

0．4

Wt．％）．

（：）kudaiyama lava，

  the Hutago volcano

1．5−1．0

．0・1

2．6

 十

gro加d−

    maSS    1．8

1．5−2．O

nd，

nd．

nd．

       Optical propertle3 1isted as the Tables

       Table A．13iotite・bearing・hornblende・quartz−andesitel   』        Hutagoyama lava， the Hutago volcano．

       Phenocryst         Micro−phellocryst    Groundma■s Hornblende  α（min．）＝1．655      、

  （green）   β＝4．668−1．672        γ（max．）＝1．683

       （一）2V二81°，77°，77°，76°，    （一）2V・＝79°，79°，．、．，．．，＿77°，78°，80θ，

      ρ＜ひ      95°，

B▲otlte     γ＝1．645一工659       rエ1．630−・1．635（士0．004）

       （±0．002）

  30．、6      6．1−5。6、    63．3−63．8

rock−formillg minerals are

Plagioclase

Hornblende

Biotite

Plagioclase

Hornblende andesite from Japan

max・ext・angle o11 ［010］

   420−−270 An 72   47 zoned， oscillatory

max． ext． angle on［010］

         37°  315        An 64   55

37

Table B． Biotite・hornblende−quartz・andesite，

  Okudaiyama laVa， the Hutago volcano．

  Phenocryst      Microp丘飽otryst， Groundnlass

  α（min．）＝1．655   β＝1．667−1．672

  γ（max．）＝1．680      （一）2V＝836，810，796．

   （一）2V＝83°，81°，79°，78°，

     −71°  75°（1ight・coloured margin）

  ρ＜ひ 7g°一一76°（        ，，       ）       730   910（        ，，       ）

  γ＝1．644−1．660 （士0．002∫

    rarely 1．664

  max． ext． angle on IO10］・      max． ext． angle on・［010］

    380−1go       30°−256   An 66L36      An 53−44−

   zoned， oseillatory

   2．Chemica「compOsition， the norm， Total pyroxene com・

porlent， etc． are discussed in the original paper（in Japanese）， com・

paring the rock as a whole with the groundmass alone．

   See CHAPTER IV in this report．

m．2．5．The hornblende andesite，，丘om the other distficts。

   The descriptions are not given in this part due to the lack of space．

       lll．3。 Remarks

   The general character of thc mariZed as follows l

and Summary．

hornblende・andesite  is sum一

38 Sadakatu TANEDA

1）Ferromagesian silicate minerals occurring in the groundmass are rather poor in Wo and Fs contents in their pyroxene com・

       ノ

ponents comparing with phenocrystlc ones．

2）Normative pyroxene of the groundmass is also poorer in Wo

and Fs contents than that of rock as a whole（Bulk composition）．

3）Plagioclase shows prominent oscillatory zonal structure， the

outer zone being∫ comparatively An rich． The groundrnass plagio−

clase is not so rich in Ab content comparing with the phenocrys−

tlc one．

4） Normative plagioclase of the groundmass is not so Ab rich

       ロcomparing with that of the rock as a whole．

5）The glass in the groundmass is considerably lower in its

refractive index than that of the pyroxene・andesite ．

6） In the Total pyroxene components which are calculated out

from the whole CaO， MgO and FeO（in detail FeO＋Fe203（as． FeO）

＋MnO）， the groundmass is richer in Wo， and less（sometimes

slightly richer）in Fs， than the rock as awhole，

CHAPTER IV。

COmparatiVe StUdieS On the phemCryStS and grOUndmaSS in the

volcanic rocks， with special reference to the relations between   the holrnblende宗andesite， and the pyr ）xene＝andesite．，，

lV．1． SpeCial treatise．

    The

are glven

No． 1

No．2 No．3

  （Appendix to Tables XXIV， XXVI XXXVIII＆XXXIX）

  descriptions on each sample and  the litera｛ures cited   in the original paper in Japanese．

Hypersthene・bearing olivine・anorthite・bas三dt， Okada， Oshima， Idu．

Dyke in the older volcanic body．

Augite・bearing olivine・bytownite−basalt， the upper・most lava of

      ずう

the Taga volcano， NW of Usami， Idu．

Hypersthene・aug三te・01ivine・bytownite−basalt， Tateiwa， Aziro， Idu，

Alava in the Ajiro bed．

『No．4e cf． CHAPTER V，（V．．4）， in this report．

Hornblende andesite from Japan

39

No．5 Hypersthene−augite−olivine−bytowniterandesite， upper part of the         middle lava of the Taga volcano， SW of Shimotaga， Idu．

No．6 01ivine・bearing augite・hypersthene−1abradorite・andesite， Middle         part of middle lava of the Taga volcano， between Usami and         Kameishi， Idu．

No．7 Augite−hypersthene・labradorite−andesite，， upper part of the lava         of the older somma of the Hakone volcano．

No．8 Augite・hypersthene・andesite， Kurohuyama lava， the Asama

        volcano．

No．9 01ivine−beaing hypersthene−augite4abrdorite・andesite， Hutagoyama         lava， the Hakone volcuno．

No 10 Quartz・and hornblende−bearing augite−pigeonite・hypersthene−labra−

        dorite・andesite， An upper me叩ber of the lavas of the older         somma， the Hakone volcano， Hakone pass， SW of Hakone town．

No．1101ivine・augite・hypersthene・labradorite−andesite， Wada lava， A lower         member of the lavas of the Taga valcano， W． of Wada， Atami

        town， Idu．

No．12 Augite・hypersthene・bytownite・andesite， An upper member of the          somma lavas of the HakOne volcano．

No．1301ivine−bearing two−pyroxene・andesite， Maekakeyama lava of the

         Asama volcano．

No．14 01、ivine−bearing hypersthene・augite−labradorite−andesite， Tenmei

         lava of the Asama volcano．

No．15 Two・pyroxene・andesite， Akaigawa pumice， the Komagatake

         volcano， Hokkaido．

No．16 （Augite−hypersthene・and）biotite・bearing hornblende・quaftz−

         andesite， Hutagoyama， the Hutago volcano．

No．17 Biotite・hornblende・quartz−andesite， Okudaiyama， the Hutago

         volcano．

No．18 Hypersthene・bearing biotite−hornblende−quartz−andesite， the Sambe

         volcano．

No．19e Hornblende−bearing two・pyroxene−quartz−andesite， Ko・asama， the          Asama volcano． cf． CHAPTER V，（V．4）．

No．20e Hornblende−bearing two・pyroxene−quartz−andesite， Hotokeiwa， tlle          Asama volcano． cf． CHAPTER V，（V．4）．

    Groundmass 16． Obtained when the whole of phenocrystic magnetite and microphenorystic magnetite is considered to be 2．7％in Mode（Rock No．16）．        −

    Groundmass 16 ． Obtained when magnetite as above mentioned is 1．5タ6irr Mode．

    Groundmass 17． Obtained when magnetite as above mentioed is 2．0％in Mode（Rock No．17）．

    Groundmass lg ． Obtained when magnetite as above mentioned is

1．5タ6in Mode．、、

ぷoo

鰭

40

Sample mmber

     SiO。

｛   

﹁

 但シ織和糖〔TotaD

  線FeO十MgO

AI203＋Na20＋K20   Fe203（as FeO）

    総FeO

     AI203

0ρ O

M

^頭αの

一^・︒ ｝

ωψ

d付

ロロ ロコ◎﹂︷︶

   Na◎0十K⑲0     線FeO      MgO      FeO      MgO      A1203    Na。0十K。O

〆    Sio2   但シ褐和（Tot母1）

  総FeO十MgO

lAl，・，＋N・，・＋K，・

  Fe203（As FeO）

    線FeO

     A120し、

     CaO      Na20      K20      CaO    Na20＋K20

＿＿線FeQ．一＿．一      MgO      FeO      MgO      At203

、  NaΦ0十K。O    Sio。 差

 2426 10200  8052  40寸19ロ   ー

Ω

M

媛 別 品 ロ ω

      1   OO  9● QハU4829Q仕5α 4021  1

H

Ω 稲 田

U

臼 珊

Sadakatu TANEDA

  Table XXIV Volcanic rocks described

50．45   51．10   5L68   52．35   55．83   56．11   57．07 99．67  100．24   99．56  100．41   99．67   99．99   99．97 14．39   14．88   13、51   13．15   1196   11．41   11．88 21．53   21．36   21．96   2341   21．28   22．74   20．85

0．19    0．33    0．26    0．22    0．23    0．23    0．29

 L73    L75    1．83    2．10    2，06   226    2．00 5．30    6．69    6．06    6．23    5．42    3．67    5．38

5．40    4．39    4．77    3．03    2．44    2，09    2．64 2．86    L59    2．26    2．54    2．07    1．92    2．04

2．25    1．30    1．63    L68    1、54    1．45    1．41

9．35    7．68    ＆72    6．36    5．03    4．73    5．22

53．5    53．4    55．4    55．1    60．6    57．78   62．7 99．9   100．0   100．0   100．0   100．0   100．00  100．3 20．37   18．69   18．29   17．48   12，7    10、60   12，ii

15．5    17．2    16．5    18．0    17．7    22．56   17．7

0．19    0．35亀  O．28    0．23    0．28    0．2U    O．21

1．54    L62    1．73    1242    2．05    2．38    2．26

5．00    6．00    5．75    4．67    3．20    2．73    3．88

︑

3．54    3．18    2．96    2．03    1．57    1．89    1．56

307 2・28 2・66 2・59 2・51 2・44 1・95

2．48    1．47    1．92    1．92    1．82    1．87    1．54

5．46    5．14    5．11   ．4．29    3．21    4、50    3．54

．3ユ     2．3    3．7    2．8    4．7    1．7    5．6

差三（The difference between the rock and the groundmass）

糖、FeO−FeO＋Fe203（expressed as FeO）十MnO

Hornblende andesite from Japan

41

  め  1n

 10 57．22 100．13 12．59 21．08   0．28

  2．20

  3．83

  2．19

  2．34

  1．63

  6．36

CHAPTER

 11 57，85 100．04 11．80 20．86   0．27

  2．17

  5．33

  1．99

  1．72

  1．22

  4．32

   IV．

12 59．77 100．04 11．80 20．91   0．28

  2．41

  5．31

  1．80

  3．54

 2．50   4．35

（1）．

 13 60．01 100．29 10．98 20．65   0．22

  2．22

  3．18

  1．76

  1．95

  1．44   3．89

14 60．28 99．34 10．34 20．69 0ユ8 2．32 2．89 1．71

1．74

1．37

3．97

15   16

 61．41   63．13 100．26  100．31   9．65    8．01 21．24   21．51   0．33    0．41

 2．34    2．89

  4．29    L92

  1．15    095、

  3．12．   2．03

 2．11    L18   2．65    2．76

16 ！7

64．46 100．62   6．38 22．50   0．45

  3．06

  1．94

  0．85

  1．59

  2．87

  2．61

17 18

66．54 100．81  4．84 23．21   0．56

  3．66

  2，19

  0．86

  2．67

  1．05

  3．15

60．5 100．10

12．57 19．00   0．32

  2．24

  2．50

  1．57

  2．81

  1．91

  3．52   33

  608888250 5⑨482235刀4⑮7

（りQ∨−凸−▲ 63．6 100．1  9．91

19．7

  0．23

  2．59

  5．29

  1．34

  3．71

  2．86

 ，3．48   3．8

m

99 鈎 四

鵠 Ω ぷ 溺 皿 憩 田

B

60∨ーエー       

^64．00

99．99 3．81 19．40 0．02 2．44 1．75

1。57 0．18 1．60

3．83 3．4

74．07 100．54  2．17 18．89   0．65

  2．81

  5．90

  0．71

  7．68

 2．68   2．01 12．4

70．02 100．00  4．49 20．34   0．02

  4．13

  1．33

  0．55

  0．90

  0．88

  2．26   6．7

7L30

100，00  2．86 20．71   0．39

  4．13

  1．33

  0．55

  2．03

  1．26

  2．26   ＆0

71．41 100．00  2．10

20．92   0．08

  3．60

  1．20

  0．64

  0．35

  0．32

  2．31   7．4

70．64 100．OP  3．09 20．70   0．46

  3．60

  1．20

  0．64

  1．01

  055   2．31   6．6

76．16 100．OP  O．66 20．16

   00   5．73

  1．28

  0．49

  2．14

    0

  2．82 10．1

42

Sample number

       Q

 ／︑ぷuO

oo ω 閃貝℃已口O﹄ぴ︶ 日﹄O

】

50

日﹂O   ；

  ：

  Wo   En   Fs

   肩8↑

OAぐA QFM rbn

恥

命

恥

輪

恥

臼

−廿6238 280  1ふ8 631乙 243

47．6 24．4 28．0

2

45 53

523  合﹂6 091333

37．0 27．1 35．9

Sadakatu TANEDA

 7て19臼 2  63 302一  27 7．67・ −←34

44．1 18．3 37．6

−一45 144 587・  35

17 35 48

29．7 21．9 48．4

Table XXV Volcanic rocks described

3

6．5

へ

61．0 32、5

398  26 000 9白5nj

41．6 24．2 34．2

415

1⊥4τ4

613  54

32 41 27

32．1 25．7 42．2

 839 5  62 361  9錫7

15 45 ω

44．2 21．3 34．5

488 ーエ43 514 721み  45  144 5nδ6 035 324τ  7°76 6 

〃

02  36 442 037・

−

⊥﹂4︑4

42．3 20．4 37．3

−nJρ0 15nO 7●40︼  44

11 46 43

28．3

／

25．6 46．1

 127 604 7・−ρ09句   45

ρ0

7ワ

寸

143

41．6 23．5 34．9

7・30 153

1ふ500

1

307・9臼43 1ーム8

32．5 24．0 43．5

  

 0∨ρ05 8  62 802  45 2Q∨0σ −凸43

41．6 24．5 33．9

352 169ω OQ∨− 055 ーエつ05 1⊥44

42．2 20．9 36．8

 406 91▲62 5Q∨6 88λマ 35 ーエ4nJ

42，3 23．3 34．4

ーユ∩4ワσ 只りー←−←

252  54

16 47 37

33．1 27．8 39．1

Total Wo， En＆F3＝Proportions of CaSiO3， MgSK）3＆FeSiO3， calculatedg  from total

Hornblende、andesite fro，m Japan

43

1n 10 13 61 26

893  3PO 9臼7・1 14▲4

38．5

229

38．6

CHAPTER IV。

121⊥7・ −⊥162 569  4﹂4 622153

39．1 27．2 33．7

2820

ーム ー 6 ワ一

6一b9  z4ぷ笹 ウ80

1

﹂35

41．5 16．5 42．0

（1）．

13 14 61 25

OPO5 144 8尾Uワ． 143

39．8 25．0 35．2

46唱13 11ρ0ワ一 127・14望4

4 ワ・ 9

1 4 

りδ

40．2

26、5 33．3

5343 1 1 6・2 028 10ワ● 62ウH 333

41．4 18．0 40，6

6947 1⊥−b− 802

ーロU内δ

4﹂管9● 162

40．2 24．2 35．5

16 ^噌

1161 7974 802153 172261

44，6 25．8 29．6

17

126 143 81 8578 596 037

50．5 17．3 32，2

866

1⊥POワ●

ウ一53 144 7・49 1⊥4ηδ

  34．6   21．6   43．8

CaO，

60V5 15ウ9 712  54 7．03 153

    36，9      25．7     37．4

MgO and

ワ●nδ0 25ウ臼 ワ・30  ロ﹂4 253 1つ05

37、9 16・9 45．2

dh

O 7

2 一b

2

749

唱

143 143

OU︵δδ6

35，0 26．5 38．5

FeO respectively．

Oり

¶13虜4 ウ︼59臼 144

パ

bー 587 0戸り5

5

の8 3

6

 4 2

9 36．

380V 35 983  7・− 550 45

68．7 4．8 26．5

10∨0

（

651 2FO2 7・21⊥ Om21

42．8 23．2 34．0

208

δ百

6

7・ワ一1 2一b2 091⊥

 7・ウρ

52．8 28，7 18．5

217・ 36 87一b24凸2

 0 1no

  O

62．6 29．9 7．5

118 36 77・6

ワ臼4ワ臼

064  9

54．8 26．2 19，0

541 45 7・85 24ワ一

 0 100  0

79．5 8．13 12．4