Page 1 地調月報Bull．GeoLSurv。Japan，voL30 ，p。645＿674

地調月報Bull．GeoLSurv。Japan，voL30㈱，p。645＿674，1g7g
549．2 553．21／．24 （524）
Ne⑬ge聡㊧M；量醜《踏鼠量量忽認電量⑰麗し⑪￡電恥e Te量賦e−G賊電⑪se亘》量s重窟量c寛，
We舘Ho購置鯉⑪，」聯徽
Junkichi YAJIMA＊
Aめs瞭ac醜The zonal distribution of metallic ore deposits around Jozankei quartz porphyry is
recognized in the Teine−Chitose district．Toyoha mine is one of the representative le＆d−zinc
deposits in the inner Pb−Zn zone，while Chitose mine is the typical gold−silver deposits in the
outer Au−Ag zone．
The temperature乱nd salinity of fluid inclusions丘om Chitose deposits are200。一300。C
and O．0−3．6percent，respectively，and vapor pressure＆nd density ofthe fluid at the lowest leveI
ofdeposition are estimated as84。9atm and O。7349／cc which correspond to the depth of lo50
meters．
At Toyoha deposits，decreasing tendency in temper＆ture and salinity offluid inclusions
as well as mineral zoning are observed ffom east to west among earlier veins and f士omsoutheast
to northwest among later ones。Taking account of heat source at southeastem deeper zone，
thc sequence ofmineralization in space and time was deduced fbr Toyoha deposits。
亘鵬騰《葺聰c意量⑪聡
The Teine−Chitose mining district is well known fbr the occurrence ofmany epithermal ore
deposits ofNeogene period，such as Teine，Toyoha，Todoroki and Chitose mines．The district has
produced by the end of1977，a total of34tons of gold，1，684tons of silver，345，000tons of lead and
846，000tons ofzinc metall this occupies an important portion ofthe mineral production in Japan．
Ofthis total，however，79percent ofsilver and99。9percent oflead and zinc aref士om Toyoha mine，
and the bulk ofgold丘om Chitose mine。Most mines in this district have been closed during the
past ten years due to the exhaustion of ores．Toyoha and Chitose are the exceptions・
Alargenumberofstudiesontheseoredepositsandonthegeologyofthisdistricthavebeen
carried out fヒom various view points，such as mineralogy，structural geology and metallogeny．
They are introduced in each related chapter of this paper．It should be noted here that NAR皿A
8♂α」．（1965a）reveεし1ed a cle＆r zonal distribution of metallic ore（ieposits at Sh抗kotan Peninsula，
and in the Teine−Chitose district，AKIBA（1958）pointed out the arrangement of ore deposits in
two belts on both sides ofthe Jozankei quartz porphyry。Also YAJIMA and OKABE（1971）pmposed．a
concentric zoning around quartz porphyry such4s inner Pb−Zn zone and outer Au−Ag zone．
The present author attempts to cl乱ri鯨in this work the fbrmation conditions ofthese zonally
arranged deposits also their mutual relation丘om the view point of geologic structure，mineral
paragenesis and fluid inclusion study。Detailed discussion is made with special refbrence to the
results of the detailed study on Chitose and Toyoha deposits．
L o麗臨㊤o亘geo亙⑪gy
LI G磯e翻琶e⑬亘⑪gy
Hokkaido is divided into three geologic units f｝om a geotectonic view point，namely，west，
＊Hokkaido Branch
一645一
BulL GeoL Surv．Japan，Vol．30，No。12
central and east Eokkaido which are bounded by the Sapporo−Tomakomai Iowland belt and the
eastem margin of Tokoro−Toyokoro tectonic belt（MINATo6知」。，1965）。West Hokkaido is
geologically the northern extension of the imer zone of northem Honshu．There occur thick
volcanic fbrmations ofMiocene period，which constitute the“green tuffregion”，on the basement
rocks of Paleozoic to lower Mesozoic strata．In contrast，the centra田okkaido is characterized by
geosynclinal sedimentation ofJurassic to Cretaceous periods and the subsequent Hidaka orogenic
movement（MINATo66αZ．，1956）。
The west Hokkaido is divided f巳rther into three sub−provhlces by the nature ofsediments and
tectonic fヒatures．The癒st one，characterized by出e terrestrial sediments of Fukuyama stage，
covers the areas fヒom M乱tsumae to Kudo and around Shimamaki．The second sub．province is
upheaved areas composed of much pyroclastics of Miocene age which appeared in patches at
Shakotan Peninsula，Shizukari−Toyoura，Otam−Muroran and Kameda Peninsula（II in
Fig．1）。The third is a sedimentary basin with a thick pile ofnomal marine fbrmation ofMiocene
age which is distributed丘om Kmitomi，Toya to Hakodate and Sapporo to Shikotsu：Lake（III
isFig。1）．
The Teine−Chitose district is situated at the northem part ofOtaru−Muroran area ofthe
second sub−province．Th蛤district is underlain by basement rocks of Paleozoic to Mesozoic age，
vast volume ofpyroclastic rocks of Miocene and Pliocene age and ofQμatemary volcanic rocks．
The basement rocks are sporadically distributed along the so−called Shakotan direction at
Sangaidaki，Kyogoku and Kunitomi，and are mainly composed ofpelitic schist oflow grade and
quartz diorite，Neogenefbrmations are classified into Jozankei Group，Toy・oha Group andToyama
Group of Miocene age and Nishino Formation of Pliocene age in ascending order（SA皿06知乙，
1972−75）（Table1）．
The Jozankei Groupwhichis composed ofaltered andesite and pyroclastics is distributed along
Shirai，MigimataりShiramizu and Pepenai Rivers，and it is correlated to Fukuyama Formation
（NAGAo and SAsA，1934）or Kayanuma Formation（TANAI，1961）。The Toyoha Group is sub一
Table l Correlation ofNeogene Tertiary fbrmations in west Hokkaido．
West HokkQido
（NAGAO qnd SASA l934）
Jδzqnkei
（SAITO e†ql．1972−75）
Se↑qnα F。
ToyohG Mine
H弟HIMoTo e↑α1，1977）
Nishino F。
Kuromqtsunσi F。
Toyqmq G．
Yqkumo F．
OtqrunqigqwG F．
OeyqmG F．
Sqnbonmqtq F．
o￡o＞Oト
Kunnui F，
ー
Tqkinosqwq F．
ShirGigGwq F．
？
NGgqto F．
Motoyqmq F．
⊂）。
KoyqnGgizqwq E
Pre−Ter†iqry
x⊂oNoつ
一6
Fukuyqmq F．
Shirqmizugqwq F．
F．
Usube†su
一646一
Noruo F．
Bifue F．
⊂）e
Yoshiokq F．
Chi†ose Mine
FUJIWARA l954）
？
Neogene Minerαhzation ofthe Teine−chitose D蛤trict，West H：okkaido，Japan（．∫．YAJ陥）
divided into Shiraigawa，Takhlosawa and Otarunaigawa Formations。Shiraigawa Formation，which
covers the Jozankei Group discordantly with basal conglomer乱te，is located at Shirai River，a
neighbou血g area of the Chitose mine and upper streams of Shiribetsu and Yoichi Rivers．
Takinosawa Formation consists ofdacitic to rhyoliticpyroclastics，and Otamnaigawa Formation of
shaleラaltered andesite，rhyolite and their pyroclastics，The Takinosawa Formation shows a wide
distribution at westem to southem parts of this district and，narrower occurrence at eastern sid，e．
Otarunaigawa Formation occ皿s almost throughout the district．Toyama Group is a rather thick
unit consisting mainly of sandstone and mudstone at Yunosawa River and northem or southem
areas ofShikotsu：Lake．Atthe central and northernparts ofthis district，thesamefbrmation，though
being intercalated with normal sediments in its upper part，changes into andesitic volcanic
breccia which occupies a vast area around Otarunaigawa Formation．Nisl血o Formation is com．
posed of sandstone，mudstone and dacitic pyroclastics and distributed not only at Zenibako−
Yoichi sea−coast but also at the basaユpart ofQμatemary volcanoes，such as Mts．Asari and Izari
with an altitude ofabout800meters above sea IeveL
Qμatemary period is characterized by violent volcanism。It fbrms Hαt lava plateau（L9m．y．，
SuMI6厩1．，1978）at Mt。Muine．The eruptive activity continues to recent at Mts．Tarumae，
Eniwa and USU。
1410
1400
％σ
」σρσρ
0〆
＼
，！／輸≧，、．
咲健傭聾
1 ￥o◎ ，！1
懸
轡1り『、Te，Bl￥
Hl／／『O麟△やSAPP・R・
齢曝亀ノ
Mo圏
430
鱗
￥
夢鞠醸いll・
懸 Cu−Pb−Zn dep・
￥
G’、、15’＼
皿 副も会Bi1￥
￥
￥
II ／ ’
亜鎗、、
縢難
Te，BilSn￥
＼
y4
智M・II
O Cu−Pb−Zn−Mn dep．
△ Au−Ag−dep．
Kurokoor
講 mGssive bori↑e dep．
麟…懸△’ハ8 ￥
喚
￥
△
III￥
△△
￥
＼
￥
￥
⑱
び㌧野￥￥、
口 Mossive pyri↑e dep・
恥AcidiCin↑rusiverock
聡左3一、ノ∩ ￥
曽1、簿＼
￥
σMURORAN
Fig．1 Zonal distribution ofbase metal deposits in west Hokkaido．
Zonal distribution of deposits is indicated by smaller dashe（1hnes，Geological sub−province is
bordered by dotted lines．II：the second sub−province，皿：the third sub−province．Names of
minαs are asfbllows；1：Suttsu，21Kutosan，3：Toyoha，4＝Akaiwa，5；Matsukura，61Me蟻i，
7：Todoroki，8：Teine，9：Kobetsuzawa，10：0toyo，11：Inatoyo，12：Toyohiro，13＝Jozankei，
14：Toyotomi，15：Koryu，161Eniwa，17；Cbtose，18：Shiraoi，191Morino，20：Minami−
Shiraoi．
一6些7一
BulL GeoL surv．Japan，VoL30，No．12
1・2 亘9齪しの⑰腿s題c琶量v量電y
The characteristics of tke igneous activity in this district are summ乱rized as fbllows。At the
stage of the Jozankei Group，terrestrial volcanism which often includes alkalic rocks（IKEBE6砲1。ラ
19711HAsEGAwA and OsANAI，1978）occurred accompanied by block movements。In the fbllowing
earlier stage of transgression，basic volcanic rocks of tholeiitic series appeared at the Shiraigawa
stage，Bimodal volcanic activity belonging to calc−alkali rock series developed at the marginal part
of the sedimentary basins of the Takinosawa stage。At the Otarunaigawa and Toyama stages，
violent volcanic activities of calc−alkali rock series occurred around volcanogenic collapsed basins
tofbrm出esommastructures批tJozankei，Mt．AmemasuandAkaigawa。Thebiggestintrusivebody
in this district，the so−called“Jozankei quartz porphyry，，，intruded at the latest stage of Otarunai−
gawa Formation（8．5m，y．，Sum6地1。，1978），cutting above．mentioned collapsed structure in
NNW direction．
L3Tec⑳謡c鵬oveme醜鋤通ageo蛋謡盟er謹盟重io醜
The Otaru−Muroran area，the second of the three sub．provinces within west Rokkaido，is
situated between normal sedimentary basins，and it is an elevated unit accompanied by violent
volcanisms and structural movements of early to later Miocene periods。The composite fbld
structure ofN−S trend is developed in the third sub−pro願nce and this structure is also maintained
in volcanogenic sediments of the uplifted sub．province．On the other hand，the volcanogenic co1−
1apsed basin structure is observed in this area and three basins are arranged in the so−called
Shakotan direction fピom Jozankei to Amemasu and Akaigawa。The collapse is recognized fピom
middleMiocene，andthedistributionofvolcanicrocksofOtarunaigawastagerepresentsacollapsed
caldera and surrounding somma lava structure．The age ofcollapsed basins become younger f士om
southeast to northwest．In the youngest Akaigawa caldera，Kunitomi Formation（SAITo6知1。，
1969−1971，corresponding to Takinosawa Formation）fbrms a deep volcano−sedimentary basin乱nd
its topographical fヒatures together with the distribution of Q』μatemary volcanic rocks retains
distinct色atures of a caldera．
Nishino Formation covers the Miocene system with an unconfbrmity and shows a fbld
structure ofE−W trend in clear constrast with that ofunderlying fbrmations．
As fbr mineralization，two epochs are discriminated in the Teine一αゴtose district with
refヒrence to the above−mentioned stages of volcanic activities and tectonic movements。The五rst
epoch corresponds to the upper Takinosawa stage when stratabound type kuroko and massive
barite deposits were fbrmed in intimate association with the basin structure of Takinosawa or
Kunitomi Formation andwith bimod．al volcanic activities．The second is the latest stage ofOtaru−
naig＆wa Formation whenmany polymetallic vein−type ore deposits were gener乱ted in a clear zonaI
distribution around quartz porphyry intrusive bodies。
2。 幽eraし1量zat置o聡置麺重he Te直蝕e一一C瞳重ose d亘stlr量ct
2・1M伽1亙⑭ge戯c騨ov賊ce蝕west脇臨窺湿o
WestHokkaido is de五ned notonly as one geologicunit but also as onemetallogenicprovince
（SAITo6孟α1．，19673BAMBA，1977）。This metallogenic province is divided fhrther into three sub−
provinces which approximately correspond to such geological sub−provinces as mentioned in the
一648一
Neogcne Mineralization ofthe Teine−Chitose District，West Hokkaido，Japan（」．YAJIMA）
preceding chapter・
Inthe且rstsub−province at M乱tsumae−Kudo and Shimamaki areas，Au−Ag−Cu−Pb−Zn−Fe
vein．type and replacement−type deposits occur around basement blocks．The examples are
Kudo，Jokoku，Imagane and Sanklei mines．The second sub−province（II in Fig。1）characterized．
by violent volcanisms and upheaval movements includes many polymetallic ore deposits of
￡ssureGIling type which are zonally arranged around Shakotan dome（NAR．ITA6地1．，1965a）or
Jozankei quartz porphyry（YAJIMA and OKABE，1971）。The sedimentary basin of the third sub−
province（III in Fig。1）has plenty of exhalative−sedimentary manganese ore deposits，as well as
bedded iron and dolomite deposits especially at the westem side of Suttsu−Hakodate line．At the
eastem side of the same tectonic line，kuroko and massive barite deposits occur and they are
distributed sporadically at the marginal parts of the basins。Thus，the mineralization of Neogene
period is a伍ected by a subsiding movement of basement rocks，fbrmation of basin stmcture and
igneous activity，and yield characteristic ore deposits in each sub−province．The mineralization
continued to Qμatemary period and fbrmed sulphur and iron sulphide ore deposits（IGARAsHI，
1976）。
The Teine−Chitose district includesシamong these groups of deposits，several famous mines3
Toyoha mine fbr its large amount of ore reserves，Teine mine fbr the occurrence of gold．silver
㌻ellurides or teineite and Todoroki mine fbr todorokite、About twenty mines are known in this
district，twelve ofwhich have records ofproduction（Table2）．Only two，Chitose and Toyoha，are
working at present．
Table2Metal production in the Teine−Chitose mining district．
MinGmi−
ShirGoi
Period
1957−77
Au（k9）
Chi↑ose
1935−77
て6803
Ag（？）
73
Cu一（↑）
40
Eniwq
Koryu ¶oyoromi
1951−42 1937−56
726
5．1
83
1．5
1933−37
1
0．12
■oyoho
Toyohiro
Teine
1937−77
1945−52
可931−72
3186
1337
O．18
10404
0．73
で63
75608
0．8
Pb（↑）
て，5
345108
133
Zn（↑）
7
8449↑7
150
BqSO4（↑）
167193
¶odoroki
1906−77
2571
104
Meiji
AkGiwo
Mq↑suku
1913−45 ，956−72
Q33
1935−40
O．3
Q．22
0．7
π￡
一
一
4．5
2．O
1069
323173
3．4
2．2 ⊂】鼠我ss量最c箆電量⑪聡⑪童職e霊鍵盟童c o暫e《畳⑲互》os且愈s
Many investigations have been carried outsince19320n the minerals and ore deposits in this
district，including the classic works byWATANABE，M．（1932，1933，1934），WATANABE，T．（1936a，
b，1943）and by YosHIMuRA（1934，1936）which marked the begiming of the microscopic studies
of ore minerals in Hokkaido．All mineral species described in the district until today are
summarized in Table3肋m many papers which are indicated by a notation（＊）in re蝕ences．
Since BowIE and TAYLoR（1958）established the new method ofore mineral identi分cation by
reHectivityandhardness，ithasbeenadoptedwidelyinthe且eld oforemicroscopy（UYTENBoGAARDT
and BuRKE，1971）．YAJIMA（1976）examined some minerals f士om this district by the method，the
result ofwhich is shown in Fig．2。
As it is shown in Table3，all deposits haveverysimilar paragenesis，namelymonoparagenetic
association．Consequently the classi且cation in this paper is established considering the fbrm ofore
bodyandthemajorcomponents expressedinmineralparagenesisorinquantityofmetalproduction。
The metal production is shown in Table2，0re deposits in this district are classi且ed into the
fbllowtng three types：
1．Kuroko type＿＿＿Akaiwa，Matsukura，Me弓i，Shiraoi，Minami・Shiraoi，Morino．
一649
Bull．GeoL Surv。Japan，vo1．30，No。12
90
○・一丁OYOHA
△・一TEINE
80
ロー・CHITOSE
elec↑rum
7Q
／
1
60
／
−
／
／
−
／
／
nG卜Te
／
／
／
pyrite
ろ
／ IV
ぷ
／／
50
＞
←
〉
ろ
／ bismu↑hinl↑e
ろ
←
り
L』
」
L 40
］
匡
30
轡蹴．…慕・
／／
20
spholeri↑e ／
ll 奇脅／ V
／
10
10
／
20
30 40 50 100 200 500 400
700 1000
2000
VICKERS HARDNESS NUMBERS
L metals，II＝sulphidesJII：sulphosalts，IV：Ni−Co−Fe sulph量des，
V：oxides．（BowIE and TAYLoR，1958）
Fig、2
Distribution of ore minerals飾om the Teine−Chitosc district
on the basis of their reflectivity and hardness．
2．Au−Ag vein type＿＿＿TeineラTodoroki，Koryu，Eniwa，Chitose，Kobetsuzawa．
3。Pb−Zn vein type ＿＿＿Otoyo，Toyohiro，Inatoyo，Toyoha，Jozankei，Toyotomi．
Type l includesmassiveometworkbaritedeposits of Matsukura，Minami−Shiraoi，Akaiwa，
Shiraoi and Mo血o mines which are accompanied byvery little sulphide minerals．Occurrence of
these workable barite deposits is one ofcharacteristic fヒatures in west Hokkaido as comp翫red with
the sulphide−predominant㎞roko deposits ofHokuroku district（IGARAsHI6施1．，1974）．The major
components of t五is type are Pb，Zn，Cu and Ba。As fbr the minor element，Me弓i mine五as an
isolated small mercury deposit ofdissemination type（HAsEGAwA6麺乙，1976）．The ore minerals are
ch皿abar and marcasite w五ich are excluded in Table3．No other indicative minor constituent is
observed in this type．In Table3，a small amount of Au and Ag are indicated in Akaiwa mine
which are listed not fヒom a mineralogical description but fyom a production record．
Type2represents vein．type deposits of gold．and silver with abundant quartz as a gangue
minera1ラwhich is usually called as“gold−bearing quartz vein，’．Todoroki，Koryu，Eniwa and．
Chitose mines comprise the typical deposits of this group。The ores of Teine mine are dif琵rent
倉om typical gold一『uartz vein．The deposits consist ofthree groups ofvein swarm which are called
Bamosawa，Mitsuyama and Koganesawa．The latter two vein groups contain，in addition to the
650
1
Table3
Mineral association oforedepositsin theTeine−Chitose district．
Kurokoイype
Cu5（As，Sb）S4
luzonけe
Cu3（As，Sb）S4
bismu†hinite
Bi2S3
emplecti†e
CuBi s2
schqpbqchite
AgBi s2
pe†zite
Ag3AuTe2
rickqrdi†e
Cu7Te5
sylvqnite
AuAgTe4
hessi『e
Ag2τe
qltqi？e
PbTe
M
M
m
m
m
m
m m m
m
m
m
m
m
m
Te
αguilqri†e
Ag4SeS
ber↑hieri†e
FeSb2S4
5PbS2Sb2S5
bouIGngeri†e
r
m
m
m
M
M
m
m
m
m
m m
m m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
dyscrqsite
Ag3Sb
Grsenopyri†e
reolger
FeAsS
AsS
orpimen†
As2S3
no†ive qrsenic
As
cossi†eri†e
SnO2
stqnni↑e
Cu2Sn（FeンZn）S4
CGnfieldi†e
4Ag2SSnS2
woifrqmife
（Fe，Mn）WO4
m
m
m
r
m
m
m
m
r
m
m
r
m
m
m
m
m
m
m
m
r
m
Sio2
CαCO5
bαrite
BqSO4
rhodochrosite
MnCO5
rhodoni†e
MnSio5
αdulqrio
KAISi308
m
m
m
m
m
m
m
m
r
Sb2S3
cqlcite
M
M
M
m
stibni†e
quqrtz
m
m
m
m
4PbSFeSSb2S3 m
r
r
m
m
r
m
m
M
m
m
M
m
m m
m
m M
m
M
M M M
M M
m
m
m
m
m
m
m
m
m
r
m m
M
m
m m
m
m m
m
M
m
m
m
m
r
m
M
m
m
m
m
m m
M m
m m
m
inesite
secondqry Ag
m
m
Mn
m
下e
Pb
m
m：minOr consti↑Uenち
r＝rGre
m
M
m
m
m
mqjOr minerqlS7
m
M
M
M
m
m
m
m
m
m
r
lqmesonite
Cu
m
m
m
m
m
m
r
m
m
m
m
m
no↑lve ↑e目urium
m
M M M
M M M
r
M
freibergi↑e
M
m
m m
m
m
m
r
m
EO↑o＞、O↑
enqrgite
m
m
m m
Φと⊂oNOつ
Cu3（S㌧As）S3．25
m
m
m
m
m
m m m
m m m
m m m
M M M
QEコNH
te†rqhedrite
m
m
m M
m
■ 『
o＞
、Oの
CuFeS2
r
＝も
OE，﹃Lo工
chqIcopyri†e
m
oE： o↑
Fe205
隆 一
o＞、O↑O⊂H
hemq†i†e
m
m
OL， ︸￡O＞、O卜
Fe304
m
m
M
M
O＞、o↑○
mqgneti†e
m m
m m
m m
M
M
コo
TOyOhq
…：
o
N⊃o↑ΦnOと
Fel−x S
m
m
m
σ の
o
I E
o⋮
pyrrho†ite
m
m
m
①≧
⊂二〇
の↑． 一Σ
mqrcαs汁e
FeS2
FeS2
pyri†e
M
M
M
M M M
M M M
M
m
m
m
m
m
m m m
I o
ooと
golenq
M
M
M
Φ9りo↑辱 一￡Q
ZnS
PbS
M
M
m
m
03， 一⊂田
sphderi†e
E三
uの
■ 一
コ＞LOと
Ag（Sb，As）S
、＿ L
とoLOuo↑
Ag sulPhosqけs
m
m
Teine
9 −O
1 σ
⊆， 一Σ
Ag2S
O⊂一 ﹃﹂OΣ
Ag sulphide
●一
：二’
〇σ﹂， 一￡の
（AuフAg）
『 一
ΦΣ
nq†ive gold
o≧■ 一〇xく︹
composifion
oL
コxコo↑oΣ
chemicql
minerqlS
Ieqd−zinc
gold−silver
r
m
m
m
m
m
m
m
r
萎
Neogene Minerallzation ofthe Teine−Chitose Dlstrict，west Hokkaido，Japan（J。YAJ週A）
募
華
common Au−Ag paragenesis，菖an abundant copper as Cu−Sb sulphosalts，not as chalcopyrite，
with quartz and barite in Mitsuyama group while sphalerite−galena−realger−orpiment with qu＆rtz
and calcite in Koganesawa Group（SuGIMoTo，1952）．It may be regarded as an intermediate
characterbetween gold−quartz and lead−zinc mineralization．However，the major component ofthis
type is always gold and silveL The description on Kobetsuzawa mine does not include native gold，
so important portion of gold content of the mine may be derived．from gold tellurides（lsHIBAsHI，
1956）．Characteristic minor elements are tellurium，bismuth and selenium in Chitose，Teine and
Kobetsuzawa mines．
Type3is lead−zinc deposits including Toyoha mine。The particular situation of Otoyo mine
which contains no other minerals than Iuzonite，bismuthinite and pyrite might be explained as an
intermediate type between Teine and Toyo五a deposits（SuGIMoTo，1958）．Silver，tin and tungsten
are important minor constituent in Toyoha mine（YAJIMA，19771NARITA6知Z。ラ1977）．The rare
occurrence of schapbachite is reported in an intemal publication of Toyoha Mining Co。and a
血rther discovery ofbismuth mineral is expected。
Other minor constituents occur血g in t五is district are antimony，arsenic and manganese．
2。3 Zo甑題量d遥s宣r韻》腿重畳⑰躍【⑰宜⑬re《量e験os量愈s
There are many reports regarding the zonal distribution of ore deposits in west Hokkaido．
AKIBA（1958）studied，the relation between igneous activities and，metallogenic province in west
Hokkaido，commenting on the two belts arranged on both sides ofJozankei quartz porphyry，that
is，Au−Ag belt on the east side and Cu−Pb−Zn belt on the west sid，e．In Shakotan Peninsula，
NARITA伽1．（1965a）showed a zonal arrangementaround Tertiary granitoids，such批s Mn一（Cu）一
Pb−Zn zone，Cu−Pb−Zn zone，massive iron sulphide and barite zone fヒom imer to outer side
（Fig。1）。Gold and silver are dispersed throughout the area in this zonation．
Several other examples of zonation are known in west Hokkaido，though being rather com−
plicated or irregular in distribution and smaller in scalel Date−Eorobetsu district（SuGIMoTo
and YAMAGucHI，1955），Kameda Peninsula（SAwA6渉α1。，1958），Suttsu−Oshamambe district
（AKIBA，1958），Shimamaki−lmagane（NARITA6緬1．ジ1965b），Kudo（YAMADA and YAMAYA，1962），
Yakumo（SuGIMoTo，1962），and Jokoku（SAwA6砲1。，1965）．They are always accompanied by
aCidiC intrUSiVe rOCkS．
Besides the above−mentioned zonations，it is said that manganese is rich in westem side of
Yoichi−Hakodate line（SAITo6緬1．，1967），where exist many workable manganese deposits of
both vein and stratabound types・As fbr the indicative minor elements，IsHIBAsHI（1958）stated
that Snand Mo arerichinthewestempart，whileTe，：Bi，Sb andAs arerelativelyabundantinthe
eastem part ofwest Hokkaido．
In the Teine−Chitose d，istrictラthe well arranged zonal distribution around quartz porphyry is
observed．Pb−Zn vein type deposits are situated in the central part surrounded by the outer belt
of Au−Ag vein type deposits（Fig。1）。Kuroko and massive barite deposits occur at the outer
periphery but it is notable that they were fbrmed in a dif艶rent geological environment and in an
earlier stage than these vein type deposits as mentioned in the岱st chapter．
The relation between igneous activity and mineralization together with zonal distribution of
metals is summarized by SMIRNov（1976）．亘e says that，at the later stage of post．magmatic ore
deposition related to granitic magma，there occurs，in genera1，the fbllowing zonation：
Mo−w／sn／cu−Pb−zn−co−Bi／Au／sb−Hg
ThezonationintheTeine−Chitosedistrictisconsistentwiththisgeneralizedmode1．SnandW
651
Bun．Geo1。surv．Japαn，vo1。30，No。12
are fbund in the center of this concentric zoning．An arrangement of Pb−Zn（Toyoha），Cu−Sb
sulphosalt（Otoyo），Au−Ag−Cu−Sb−Bi（Teine）and．gold，一quartz（Chitose，Todoroki）is observed
丘om imer to outer．There are two mineralization stages of antimonyl one accompanied with
Cu−Pb−Zn stage fbrming a tetrahedrite group and silver sulphosalt minerals，and the other，1atest
stage after a main sulphide deposition which brought stibnite，jamesonite and berthierite at
Toyoha d，eposits．Jozankei quartz porphyry，including such rock facies as granite porphyry，
granodiorite porphyry and dacite，is regarded as one of Neogene granitoids（NIsHIKAwA，1977）．
Furthermore，theaf田iationbetweenthis granodioriteporphyryandoresofToyohadepositsisshown
filling↑emperαure
− r9 し』
O O O
O o o8
MiyOZGWO（71）
Ben曾en一一一一匿一一
Ko量suro et ol〔711
Fukujin一一一一日一一一一一一一咽一
FukuIin
Miyozowol71）
Shikozono〔74》
Tojimo一一一一一ロ
Tolimσ
Izumo
Hcrimo一
SOyo一一一一一一
一TokinosowO
騨一Bqnnosowo
Wo↑onobe
−Hossoku
Yonedo e曾ol（78）
Fig．3
Chue曾su−
Chue曾5u一一一一一一一
Shue†su一一一
Filling temper翫tures of nuid inclusions fンom the district。
一652一
Neogene Mineralization ofthe Teine−Chitose District，West Hokkaido，Japan（」．YAJIMA〉
by IsHIHARA and SAsAKI（1978）ffom sulphur isotopic study。On the basis ofthese evidences，it may
be reasonable to set the zonation ofmetallic ore deposits around quartz porphyry。
Other occurrences oftin minerals in the neighbouring district are known at Suttsu（IsHIBAsHI，
1952）and Kutosan mines（KINosHITA and TAKIMoTo，1944）．They are also regarded to have
fbrmed at the central part ofthe zonal distribution，though smaller in scale．
2．4 璽覗麗量dl量舩c1閾s量⑪n stu忍dly
Du血g the past twenty years，the study offluid inclusions in minerals has been established as
an ef琵ctive method in petrologyタmineralogy，geochemistry and especially in the research of
economic mineral deposits to investigate the nature ofmineral−fbrming solutions and the condition
of fbrmation（DEIGHA，19551RoEDDER，19671YERMAKov6勘1．，1965）。Thermometry by fluid
inclusion is now prevailing in the various branch．es ofgeological sciences and is believed to be one of
reliable methods among many geological thermometers．
In order to study the nature of ore solution，it is indispensable to analyse the content of liquid
in inclusions but the method has not been well established yet to use in a routine work（RoEDDER．，
1958三R．oEDDER．6∫α」。，1963）・Now the cryoscopy of fluid inclusion is generally used in place of
rather dif丑cult chemical analysis，by which we can estimate the salinity offluid in each inclusion as
expressed，by NaCI equivalent percent（RoEDDER，19623TAKENoucHI，1970，1975−1976）。Thus
many data on minera1−fbrming solutions have been accumu1翫ted recently（RoEDDER，19721ENJoJI
and TAKENoucHI，1976）．
In this chapter，the result of fluid inclusion thermometry is briefly mentioned．The detailed
description of thermometry on Chitose and・Toyoha samples are given in the third and fburth
chapters．
The result of temperature measurements of ore deposits in this distr玉ct is shown in Fig。3．
The pressure correction fbr the盒11ing temperature is about10。C degreesラassuming a vapor
pressure of200atm with5percent NaCl solution（LEMMLEIN and KLEvTsov，1961）。As will be
shown in the next chapter，the vapor pressure related to the fbrmation ofFuk両inzawa deposits of
the Chltose mine is estimated to be about85atm at the lowest level ofdeposition．Much higher
pressure may be unlikely in the case ofβssure−Blling type epithermal ore d．eposits，So the￡11ing
temperature is used here without pressure correction．
Filling temperatures measured by quartz and．sphalerite ofvein type deposits areinthe range of
about1500−300。C．The lower range under150。C ofTeine and Todoroki mines are obtained丘om
barite and calcite oflater stage．As the temperature range of2500−300。C is observed in a limited
area，that is，in the deepest level ofboth Chitose and Toyoha mines，孟t is more suitable to say that
the important portion ofthese deposits were fbrmed in the range of150。一250。C．
The lowest temperature in Minami−Shiraoi，Me単and Matsukura mines are obtained fωm
barite．So these temperature might not be considered to represent the whole range of fbrmation
temperature especially in Me茸i mine。It is reported that the fbrmation temperature ofkuroko in
Hokuroku district isin the range of2000−300。C（UR．ABE and SATo，1978）and most probably in
2000−250Qc（sATo，1973／1974）．Main ore body ofMe勾i deposits and sulphide minerals ofMatsu−
kura，Akaiwa and Minami−Shiraoi might be fbrmed at about the same temperature range with
those of kuroko in Rokuroku district．The fbrmation temperature of barite ore body itself is less
than1000C．
653
BuIL Geo1。surv．Japan，vol．30，No．12
3．G・1d・silverdep・sits・fC臨・sem蝕e
3。且Ore謹epo曲s
Chitose mine is the representative gold−silverdepositslocated atthesouthem endoftheAu−Ag
zone．It is composed oftypical gold．quartz veins whic五are known fbr its high Au and Ag content．
Detailed and fhll description on geology and ore deposits are fbund in the papers by IGI and HATA
（1954），FuJIMoTo（1961），H：uNAHAsHI and AKIBA（1970）and IKEDA and NAGAMATsu（1975），so
only a briefcomment is given here．
The mine is situated at the westem side of Shikotsu ILake in the area composed of altered
andesite，andesitic pyroclastics and tuf溢ceous mudstone which are correlated to Takinosawa and．
Otarunaigawa fbrmations。Several ore deposits are fbund there arranged in northeast direction。
Each one consists ofvein sw＆rm三the Fuk両inzawa deposits ofthe most productive one fbr example，
include more than ten veins．At the upper levels ofFukujinzawa vein swarm，veins show parallel
arrangement ruming f士om east to west with subordinate veins ofNE trend，and at the lower level
they are gradually comected each other showing occasionally a cymoid loop and unite into one
vein at the lowest360m：L．Daikoku Sango vein，the champion vein of the mine is750meters in
strike length and460meters in dip length with a mean thickness of O．8meters（IKEDA and
NAGAMATsu，1975），and in its upPer half』gold and s旦ver are especia，11y concentrated．
The vein is usually composed ofquartz ofthree stages which takes a lbrm ofbanded structure。
Porcelain quartz ofthe且rststage accompanies ad．ularia and verylittle gold．The second stage is that
ofmain mineralization乱nd includes clear crystal ofquartz and sulphide minerals associated with
adul＆ria and chlorite。Bεしrren quartz at the central part of the vein represents the third stage．
HuNAHAsm（1961）examined these vein quartz by petrofabric analysis and commented on the
dif溌rent tectonic conditions which prevailed between wall rock and veins during its fbrmation．
The amount ofquartz decreaseswhile chlorite increases at thelowerpart below150m：L ofpai−
koku Sango vein，and also relative＆mount ofsilver decreases fヒom Au：Ag ratio of1：10−20at the
shallower levels to the ratio of1：1−5，in ad．dition to the general tendency of decline of gold and
silver content at the lower levels。In Daikoku Nigo and Shimpi veins，high grade ore is｛brmed even
at deeper levels，IKEDA and NAGAMATsu（1975）proposed the How direction ofore．fbrming solutions
on the basis ofiso−grade contour map（Fig．4）．
Regarding wall rock alteration，H：uNAHAsHI and AKIBA （1970）classified six facies around
Fukujinzawa vein swarm and pointed out the玉ntimate association of sericite−quartz assemblage
with the ore shoot。
3。2 0買ξ》曲eぜ麗星s
All minerals described丘om the mine are listed in Table3．Mineral assemblage is，in genera1，
electrum−Ag minerals．sphalerite．galena−chalcopyrite−pyrite−tetrahed．rite−quartz．Aggregations of
且ne−grained sulphide minerals fbrm banded．black streaks called“ginguro”（＝silver black）in the
quartz veins．In the ore shoot，electrum in of毛en observed by the unaided eyes displaying tabular，
scaly or d．endritic fbrms・It contains21。4to27．2weight percent（YAJIMA and ONoDERA，1973）or
29。4to33。8percent（YAMAoKA，1971）ofsilver．Rare examples ofidiomorphic crystal ofelectrum
are reported by YAJIMA and ONoDERA（1973）。They have recognized several crystal fbrms such as
octahedral，dodecahedral and also flattened，one on（111）with triangular pits（Fig，5）．
一654一
Neogene Minera五zation ofthe Teine−Chitose District，west Hokkaldo，Japan（J。YAJ㎜）
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6＝intersection between veins，7：fault，8：fiow d丘ection of ore−fbrming solution
Fig．4 Au assay contour map ofFuk両inzawa deposits（1瓶DA and NAGAMATsu，1975）．
一655一
Bull．Geol．Surv．Japan，vol。30，No。12
灘
冊懸、
細，
臓
Fig。5 1diomorphic crystals ofelectrum丘om Chitose mine．Daikoku Nigo vein，一210mL．
聾越．
難
Fig．6
Microphotograph showing electr㎝（bright
Fig．7
Microphotographshowinghessite（hs），gale．
white），galena（white）and sphalerite（grey）
na （gn）， altaite （a1）， sphalerite （sp） and
without anysilverminerals．DaikokuShimpi，
chalcopyrite（cp）。B血e vein，一180n正．
一240mL．
656
嚢
Neogene Mineralization ofthe Teine−Chitose District，West Hokkaido，Japan（」．YAJIMA）
藝
Numerous silver minerals have been identi盒ed fヒom the mine such as argentite，f士eibergite，
polybasite−pearceite，proustite−pyrargyrite，stephanite and sternbergite．Pyrargyrite is especially
concentrated at the top of Hyakunen N’igo vein under a cap rock of tu価ceous mudstone。As
mentioned earlierラrelative amomt ofsilver decreases towards lower levels ofthe veins and electrum
is often seen without乱ny silver minerals（Fig，6），Characteristic occurrence of tellurium−and
selenium．containing silver minerals is described by YAMAoKA and NEDAcHI（1971），Petzite，虹essite
and aguilarite f士om the ore of Daikoku Nigo vein coexisting with sphalerite，galena，chalcopyrite
and pyrite were determined。Silver minerals fヒom Bifhe veinラlocated at500meters north to
Daikoku Sango vein，are almost always hessite（Fig，7）with a minor amount of argentite and
altaite but the di伍ciency in gold content makes the vein unworkable．
FeS content of sphalerite coexisting with electrum and argentite is analysed by YAMAoKA
（1971）。A temperature estimation by an electrumtamish method．using Ag content in electrum and
FeS content in sphalerite of electrum−argentite−sphalerite−pyrite assemblage，was made by him
whichshowedagoodcoincidencewiththatmeasuredbyahomogenizationmethodofHuidinclusions．
3。3 F置朋畳d量聡c量麗s量o既st朋dξy
Inclusions mainly in quartz ofthe sulphide stage and some in the quartz oflater barren．stage
were examined．In addition to normal two−phase Huid inclusions，gaseous ones were often observed．
Rock crystals in vugs often include splendid negative crystals ofgaseous inclusions which are easily
recognizable macroscopically（Fig。8），This heterogeneity is explained as a boiling phenomenon in
a hydrothermal fluid system．
To detect gases underpressure ininclusions，the crushingstage methodwhichhad been devised
by DElcRA（1950）and was improved by：RoEDDER（1970），was applied。The result of crushing
experiment ofquartz grains showed more or less t五e presence ofgas underpressure and it is in色rred
Fig．8 Negative crystals of gaseous inclusions．
Lower halfofeach crystal is rich in normal two−phase Hquid inclusions．Daヨkoku Nigo vein，一270mL、
一657一
蒙
糠
BuH．Geol．Surv．Japan，Vol。30，No．12
十30L
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＋30L
30L
−30L
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200
250
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15
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一360L
L
150 200 250 300。C
Fig．9
F皿ing temperatures offluid inclusions ffom Fuk雨inzawa deposits of Chitose mine．
Left：Daikoku Sango and Kita Ichigo veh｝s．Right：Hyakunen Ich圭go and Nigo，Daikoku
Nigo，Daikoku Shimpi and Maehi veins。
658
Neogene Mineral三zation ofthe Teine−Chitose District，West Hokkaido，Japan（J．YA那MA）
KITA ICHIGO AND DAlKOKU SANGO VEINS
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Fig・10 Temperature distribution on pro且1es of Fuk雨inzawa veins of Chitose mine．
659
Bull。Geo1．surv．Japan，voL30，No．12
KlTA iCHIGO AND DAIKO卜くU SANGO VEiNS
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Fig．11
Distribution of salinities of fluid inclusions on pro丘les of Fuk両inzawa ve三ns of Oh孟tose mine．
一660一
Neogene Mineralization ofthe Teine−chitose District，wes田：okkaido，Japan（J．YAJIMA〉
to contain a small quantity of carbon dioxide，In the course of the study of about2000nuid in−
clusions，neither halite nor any daughter mineral was observed，
Measurements of且11ing temperature were carried out by using a heating stage，Type1350，
：Leitz。Temperatures were calibrated against the melting point ofsalophen（191。C）and saccharin
（2280C）。The￡lling temperature was determined with an accuracy of±1．5◎C．
The result of measurement is皿ustrated in：Fig．9，Histograms in the Ggure demonstrate the
gradual increase offilling temperature towards lower levels．Data倉om every sampling points are
prqjected on the profile ofthe veins in Fig。10．The temperature range is clearly dif琵rent between
the upper half and the lower parts，and at the middle180mLラthe temperature of2500C is
dominant．It can be said that the upper halfofFukujinzawa deposits was fbrmed at temperatures of
2000−250。C and the lower half at250。C−300。C．
Homogenizationtemperaturesoffluid．inclusionsinsphaleritewerealso determinedfromseveral
samples．The results were in the uppermost temperature range obtained f｝om inclusions in quartz．
YAJIMA and ORTA（1977）reported the salinity o田uid inclusions fヒom the mine．The result is
presentedherewithsomemodi五cations。Measurements o伍eezing temperaturewere carriedoutby
the fyeezing microscope stage，Type NE，Nikon。Some amelioration was perfbrmed in order to
minimize the temperature gradient within the sample chamber（OHTA and YAJIMA，1977b），and
the uncertainty in the fヒeezing temperature determination generally came to±0．10C．
Published data about the salinity of且uid inclusions ffom gold−quartz veins in Japan show
rather low values in the range ofO・O to2・5percent（ENJoJI and TAKENoucHIラ1976），Similar result
was obtained at Chitose deposits，where the measured salinity was in the range of O．O to3。6
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Fig・12 Distribution of temperatures and salinities in a single clystal of quartz丘om Chitose mine．
661一
Bul1．Geol．S皿v．Japan，Vol．30，No．12
％
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filling temperoture
D3−Daikoku Sango vein，NfKita Ic屈go vein，H1−Hyakunen Ichigovein，H2−Hyakunen Nigo vein，
Dm−Daikoku Maehi，Ds−Daikoku Shimpi vein，D2−DaikokuNigovein．Markswith＆crossrepresent
the data丘om the highest grade part in Fig．4，Lower parts encircled by dashed lines include the
data ffom the lowest grade part in the same丘gure．
Fig．13
Temperature−salinity relation of且uid inclusions丘om Fuk両inzawa deposits，Ohitose m圭ne．
percent equivalent NaCl and more than90percent of the measured values fbll within O．O to2．O
percent。The results of the meas皿ements are illustrated in Fig。lL The close relation between
high salinity and ore shoot is observed，though the data regarding the upPer half of Daikoku Sango
vein are not sumcient。It might be also pointed out that the distribution pattem of salinity is
generally consistent with the flow direction of ore solution proposed by IKEDA乱nd NAGAMATsu
（1975）．
Afもw examples oftemperature and salinity measurements in a single crystal ofquartz is shown
in Fig。12。Although the crystals belong to those ofthe third stage，且11ing temperature ofinclusions
in cores ofeach crystal is coincident with that which is measured on the second stage quartz ofthe
same position．
Fig。13showstherelationshipbetweenfillingtemperatureandsalinity。Arathersteepinclination
of the distribution pattem圭s observed as a whole．Two encircled areas in each figure includ．e the
points which correspond to the highest and the lowest grade parts in Fig。4．
The maximum temperature dif琵rence between the deepest and the shallowest parts was
measured to be1000C and its vertical distance is about400meters。Thus the temperature gradient
in the hydrothermal fluid system is about2．5。c／lo m．
3．4 E⑪饗職題電量⑪髄c⑪蝕d鐘髄⑪亘且
Fluid inclusion study ofquartz from Euk両inzawa deposits showed the temperature of3000to
一662一
Neogcne Mineralizationofthe Teine−chitose District，west Hokkaido，Japan（J、YAJ臨）
0
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4 90 100 110 120 130 140 150
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200
250
500
TEMPERATURE （OC）
Fig．14 Boiling．point curves for H201iquid（O percent）and fbr brine ofconstant composition given in
wt percent Naσ1（HAAs，1971）．
200。C and the salinity of3．6to O．O percent．Active boiling was evidenced by gaseous inclusions．
One of the possible reasons fbr boiling is a sudden depression in pressure which can be caused by
openedffactures．Abundance ofgaseous inclusions might be explained by a geyser−1ikephenomenon
withinahydrothermalHuidsystem。HAAs（1971）calculated theef驚ctofsalinityonthe temperature−
depth relations of a brhe of constant composition at hydrostatic pressure．Provided that the de−
position occurred in open fyactures，the temperature of3000C and the salinity of2。O percent which
were measured at the lowest level ofthe deposits，correspond to the depth ofabout1050meters on
his boiling−point curve（Fig．14）．The vapor pressure and the density of this point are calculated．
as84。9atm and o。7349／cc，respectively．with the assumption that open倉actures existed at the
time，it can be said that Fukゆnzawa deposits were fbrmed at the depth between1000and500
meters。
The recent investigations on the geochemical environment at the time ofgold−silver deposition
revealed that oxygen fαgacity of Au−Ag deposition most probably was higher than that fbr
Pb−Zn mineralization and oxidation process seem to have occurred（SHIKAzoNo，1973，1974）．
Oxidation could be caused by the mixing with sub−sur飴ce waters．A steep distribution in the
relationship between salinity and temperature also implies the mixing ofthe fluid with cold water。
According to the geophy「s1cal study on the terrestrial heat flow in Hokkaido（EHARA and
YoKoYAMA，1971），an extremely high heat flow region is known in west Hokkaido。Chitose mine
together with Eniwa and Koryu mines，is Iocated at the eastem fyinge of this region and，thus，is
not far fヒom a low heat How region of the Sapporo一一Tomakomai lowland belt．Furthermore，
thermal sp血gs at Chitose mine show very low temper批ture（SAKo6麺1．，1977）contrary to those
一663一
BulL GeoL Surv．Japan，vo1．30，No．12
of Toyoha mine located at the high heat How area。Fuk両inzawa deposits are situated at the
distance of15kilometers f士om a southermlost outcrop of Jozankei quartz porphyry，and it is
possible to say that the site ofore deposition was initially farffom the heat source in addition to the
critical situation to bc located at the boundary between high and low heat flow regions。
Gold fbrms very stable complexes as chloride and，thus，is expected to be transported a long
distance批nd．to be deposited after precipitation of most other metals（H肌GEsoN and GARR肌s，
1968）。This model of transportation and deposition agrees well with the fbrmation of zonal
distribution in the Teine−Chitose district．The gold−containing hydrothermal fluid might have
been carried飯r f士om its source and deposited as a result of the relatively rapid decrease in
temperature at the low heat flow region。It may be accelerated by mixing ofcold meteoric water
and the mixing kas played still important role to result anincrease ofoxygen fUgacity。
4． Le剛量嘱量臨c de夏》⑪s量ts o宜丁⑪yo翫a盤醒魍e
4・童o鯉想e脚s竜s
The mine is situated at the central part of this district where sediments，pyroclastic rocks
and lavas ofJozankei Group and Toyoha Group occur as their typelocality．Koyanagizawa Forma−
tion，correlated to upper Jozankei Group，is composed of altered basaltic andesite and rhyolite
lavas。Motoyama Formation corresponding to lower Shiraigawa Formation consists oftuf財ceous
snt，mudstone and sandstone，and it overlies Koyanagizawa Formation with basal conglomerate．
Nagato Formation corresponding to㎡ddle Shiraigawa to Takinosawa Formations is characterized
by a large quantity of pyroclastics and lavas of altered andesite，dacite and rhyolite．These three
fbmations are the host rocks ofore deposits（AKoME and亘ARAGucHI，1963，1967三MIYAJIMA6渉α1．，
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Fig，15 Disposition ofveins at Toyoha deposits。
一664一
乙4
Neogene Mineralization ofthe Teine−chitose District，west Hokkaido，Japan（J、YAJIMA）
19713HAsHIMoToθ」α1。，1977）。
Epithermal fissure一五11ing type ore deposits of the mine are mainly composed of sphalerite，
galena and pyrite accompanied by minor amount of hematite，magnetite and silver minerals．
Morethan’15veins areknownandthey areclassi且edinto three丘acturesystemsas E−W，NW−SE
andN−S（Fig。15）．Tajima，Harima，ChikugoandBizenveinsbelongtoE−Wsystem。TheNW−SE
system includes Oshima，Hiy＆ma，Soya，Soyabunki and Izumo veins。Sorachi vein ofN−S trend is
economically important because of its high grade ore．Ishikari and Nem』uro veins are grouped
here in the N−S system despite their NW trend as they are branch veins of Sorachi and have
similar mineral paragenesis with that ofSorachi．Theveins ofNW−SE andN−S systems cut across
those ofE−W trend，so the mineralization at Toyoha deposits is divided into the earlier and the
laterstages．
As fbr the w乱11rock alteration，OKABE and BAMBA（1976）discriminated fb皿色cies around
Tajima vein and reported that sericite−quartz−pyrite assemblage had a close relation to the
mineralization．
4．2 0即e宜聡量聡er譲浬s
Pyrite，sphalerite and．galena are the predominant ore minerals throughout the deposits and
they are usually accomp＆nied by minor amounts ofchalcopyrite，tetrahedrite and pyrrhotite。How．
ever，the earlier and thelaterveins have contrasting mineral assemblages，
The earlier veins have a spotted occurrence ofhematite−magnetite and argentite−native silveL
A little amount of arsenopyrite，wurtzite and graphite is known at lower levels of Harima vein．
Galena in the earlier veins rarely contains silver sulphosalt minerals．Rare occurrence ofcassiterite
and jamesonite（Fig。16）in Tajima and wo1丘amite in Harima are also known．It is con鉦med
that reduction of hematite to magnetite and deposition of argentite，jamesonite，cassiterite and
wolfヒamite in the earlier veins were all caused by the later mineralization（YAJIMA and OHTA，in
press）。
Among the later veins，a zonal distribution ofminerals is observed。The veins ofeastem side，
Sorachi and Izumo，include large amounts of pyrrhotite，arsenopyrite，marcasite and wurtzite
together with wolfyamite，cassiterite，stamite group minerals，silver sulphosalts，1ead sulphosalts
Fig．16 0ccurrence ofjamesonite in vugs。Each Hbre has a diameter ofone to fivemicron。丁勾imaveinシ
ー350mL．
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Bul1。GeoL Surv。Japan，voL30，No。12
and graphite，while the westem side veins，SoyaヲHiyama and Oshima，are characterized by
mang乱nese carbonate minerals as well as antimony and arsenic minerals，Argentite is rare in
these veinsラwhereas silversulphosalt minerals such as miargyrite，polybasite，pyrargyrite，fピeibergite
and stephanite，are usually fbund in galena and sphalerite（photo l in Fig。17），Stannite group
minerals（photos2，3，4，5in Fig．17）and lead sulphosalts are not well determined yet。
Furthermoreりstibnite，berthierite and native arsenic are recognized（OHTA，1979）．
Coaly substance and rutile are foundまn ores of Ishikari，Sorachi，Izumo and Soyabunki veins．
They are confirmed to be derived from their host rock，black mudstone，and sometimes coaly
50μ
1：Miargyrite in galena，2：Aton・like stannite in sphalerite，3：Zonal growth ofstannite and chalcopyrite in
sphalerite，4：Collo￡ormtextureofzincianstannite（imer）andsakura韮te−like曲eral（outer）insphalerite
with dotted chalcopyr三te，5：Exsolved chalcopyrite in stannite，6：Graphite圭n wurtzite，lefトopen nicol，
right−crossed nicoL Rutile is血cluded at the core ofgraphitc．
Fig。17Microphotographs showing occurrence ofsome minerals鉦om Toyoha deposits．
666
Neogene Mineralizationofthe Te量ne−ChitoseDistrict，West Hokkaido，Japan（J．YAJIMA）
substance changed into graphite by the influence ofhydrot五ermal solution（YAJIMA，1978）（photo
6inFig．17）．
4．3 距巳亘魍且題蜘臨c昼聡s量o聡s電腿認y
Several reports on fluid inclusion study ofToyoha deposits have been published and they were
summarized by ENJoJI and TAKENoucHI（1976）・EL SRATouRY6渉α1．（1975）studied fluid inclusions
in quartz phenocrysts of r五yolite倉om the mine，suggesting a mもdng of meteoric water with
hydrothermalsolutionαtleastintheveinsofE−Wtrend・YAJIMAandOHTA（inpress）madedetailed
studies o田uid inclusions in Taj㎞a，Harima and Izumo veins，so only a briefdescription is given
here according to their result．Temperature乱nd salinity of ore−fbrming solutions at the time of
deposition ofthe major three veins are reported as fbllows：
Izumo vein．．．．．＿，．．．＿．．．．。．300。一2000C，4．2−1．O percent
Har㎞a vein ．＿．＿。．．．．．＿2500−200。C，2．2−LO percent
Tajima vein．．．．．＿＿＿＿＿．250。一150。C，L5−0．2percent or lower
Soya vein is considered to havc about the same condition in temperature and salinity with those of
T句im乱（SHIKAzoNoシ1974，1975）。
Boiling of fluid as expressed by the existence of gaseous inclusions is occasionally observed in
samples ofores and gangues fピom Toyoha mine，contrary to the case ofC1亘tose．
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150 200 250 3000C
fi川ng temperO↑ure
Fig。18
Distribution of temperature and salinity of fluid inclusions翫om epithermal（Chitose and
Toyohaンthis study），mesotherma1（Taishu，IMAI，1978）and hypotherma1（Takatori，ENJoJI，
197231MAI，1978）deposits．Crossed lines represent the ranges measured by those in rhyolite
丘om Toyoha mine（EL SHATouRY6砲」．，1975）．
一667
BulL Geo1．Surv．Japan，vo1．30，No。12
Distribution of temperature and salinity of inclusions are illustrated in Fig．18together with
those of Chitose，Takatori（hypotherma1）and Taishu（mesotherma1）deposits。Temperature and
salinity ranges ofinclusions in rhyolite（EL SHATouR．Y6砲」．，1975）are also shown in the same且gure
by crossed lines．Fluids in rhyolite show close similarity with those related to hypothermal and
mesothermal deposits。Rowever，the condition at which mineralization actually occurred at Toyoha
deposits is still in the range ofepithermal condition。
4。農 For職題重量0舩C⑪臨d匿重io醜
．Recently YAJIMA and OHTA（1979）examined geological environment，mineral zoning among
veins oftwo stages and also the result offluid inclusion study，and suggested that the mineralization
proceeded，on the one hand，貸om Harima to Tajima and Chikugo at the earlier stage and on the
otherhand，fヒom Izumo to Sorachi and丘om Izumo to Soya and Oshima at thelaterstage，and that
deposition ofmost ofthe sulphide minerals occurred under reducing conditions，
Takingaccountofsubterraneanthermalstructureinthis district（EHARAandYoKoYAMA，19711
TAKEucHI6厩♂．，1975），they considered．that ore−fbrming solution came up fピom southeastem deep，
andproposed a modelfbr the fbrmation ofToyoha deposits．The model explainswell the occurrence
of overall minerals and the behaviour of some elements in the mine，fbr example，occurrences of
argentite，cassiteriteラwo1貸amite and antimony sulphosalt minerals in the earlier veins and also the
reduction ofhematite to magnetite。It is said that the ores fbrmed at出e later stage may be superior
to those deposited at the earlier stage both in amount and in quality。
They showed that both sulphur and oxygen fhgacities at the time of deposition are not much
dif琵rent between earlier and later veins，fbr instance，f亀was between10−10and10−17，while￡02
had the range of10−35to10−45，respectively．Thus，the decrease in temperature might be an
important factor whic五controlled mineral deposition．Compared to the fbrmation process of
：Fuk両inzawa deposits ofChitose mine，Toyoha deposits are thought to be fbrmed under rather slow
and gradual changes in temperature because they are located．atvery high terrestrial heat flow area。
Extensive secondary alteration of ores（SHIKAzoNo，1975）might be caused by the geothermal
conditions which changed very little to this⊂1ay．
s朋贈灘躍y
（1）WestHokkaidoisdividedintothreegeologicalsub．provinceswhichcanbecorrelatedwith
re乱sonable closeness to metallogenic sub−provinces．The趾st sub−province is characterized by the
terrestrialsedimentsofearlyMioceneageandincludespolymetallic vein．t四eandreplacement−type
ore deposits．The second one is an upheaved area where enormous quantity of pyroclastic rocks
together with polymet＆11ic vein．type ore deposits are fbund，In subsiding through ofthe third sub−
province，stratabound，type（leposits ofmanganese occur as well as kuroko type deposits．
（2）The Teine−Chitose district is in an upheaved area where pyroclastic rocks ofMiocene
age and Pliocene to qμatemary volcanic rocks spread over older basement rocks associating with
quartz porphyry intrusives．Neogene fbrmations of the district are classified as Jozankei，Toyoha，
Toy乱ma Groups and Nishino Formation in ascending order。The fbrmer two groups provide the
site of ore deposition．A number of polymetallic deposits in this district show a distinct zonal
arrangement aroundJoz批nkei quartz porphyrywhichis considered to be one ofNeogene granitoids．
Toyoh乱mineis arepresentativedeposits of the inner Pb−Zn zone．The outerAu−Ag zoneinc玉udes
Todoroki，Teine，Chitose mines and others．Tellurium is a characteristic element in the Au−Ag
一668一
Neogene Mineralization ofthe Teine−Chitose District，west Hokkaido，Japan（」．YAJIMA）
zoneりwhereas，tin and tungsten are known in the Pb−Zn zone，SbシAs and Mn are distributed
throughout the district in variable amounts。It is concluded that there are zonation ofbase metal
deposits in this district fyom geologica1，mineralogica1ラgeochemical and geophysical evidences．
（3） Kuroko and㎞roko−type barite deposits occur around this zonation，but they are fbrmed
in an earlier stage than the vein−type deposits and also in a di飾rent geological environment．
（4） Teinedeposits demonstrate a prominent琵ature with regard to metal content and mineral
paragenesis．The deposits differ f士om that of Chitose and Todoroki in the small amount ofquartz
and丘om Toyoha deposits in翫bundance of coppeL This characteristic was interpreted as an
intermediate character between Au−Ag and Pb−Zn deposits。
（5） Formation temperaturewas measured byHuid inclusions。An importantportion ofthe ore
deposits in this districtwas concluded to be fbrmed at temperatures between150。and2500C except
massive barite deposits．Much higher temperature was observed at deeper levels of Chitose and
Toyoha deposits．Barite deposits have been fbrmed at temperatures lower th乱n1000C．
（6） Chitose mine is situated at the southem end ofthe zonation and consists oftypical gold−
quartz veins。In Fuk両inzawa deposits，fbrmation temperature and salinity measured by fluid
inclusions批re in the range of2000−3000C and of O・O to3・6percent，respectively．Assuming the
existence ofopen行actures，the deposits were fbrmed at depths between500and1000meters．The
steep distribution in temperature−salinity diagram suggests the mixing ofsaline solutions with cold．
meteoric water。The hydrothermal solution was transported to a distance and encountered．cold
meteoric water at about the boundary area between the high and low heat flow regions，and
precipitated gold and silver to fbrm the veins of Chitose mine。
（7） Toyoh批mine is Iocated at the center ofthe zonation and includes typical lead．zinc vein．
typedeposits．Morethan15veinsoccurinm両orthreedirectionssuchasE−W，NW−SE andN−S．
Veins of E−W trend were fbrmed earlier than those of：NW−SE and：N−S trend．Decreasing
tendency in temperature and salinity ofHuid inclusions towards the west is apparent and mineral
zoning was recognized in both vein groups。The sequence of mineralization in spacc and time
was d．ed．uced fヒom these observations together with the subterranean thermal structure。
Adk餌ow艮e岨ge鵬e就
This study is a，part ofthe authors doctor批1thesis presented at the Faculty ofScience，Hokkaido
University．The author thanks Profbssor T．BAMBA fbr his continued encouragement and guidance
since he had been the chiefgeologist in the author，s laboratory，Fluid inclusion study was initiated at
Hokkaido University on the suggestions ofPro艶ssors M．HuNAHAsHI and M。MINATo，The author
appreciates their guidance which were very essential to this study。The author is also gratefhl to
Profヒssors Y。KATsul and S，HAsHIMoTo of Hokkaido University fbr their sincere guidance on the
problems ofvolcanism and plutonism in Vest Hokkaido fヒom the petrological view point。
The author thanks DL K SAwAMuRA and DL E．NAR皿A ofGeologic31Survey ofJapan，Hok−
kaido Branch，fbr reviewing manuscript with valuable suggestions。He is also indebted to his
colleagues，Dr．T．IGARAsHI，Messrs．：K．OKABE and E。OHTA fbr discussions and supports in
experimental work。It is recorded with sadness and a great免eling ofloss that during the course of
the preparation of this paper，Dr。T．IGARAsHI passed away af㌃er a year’s fight against a desease．
The author respectfhlly expresses his condolence and．also s血cere thanks fbr his constant guidance
since the author joined Geological Survey ofJ翫pan．
The cooperation ofmany personnel of Chitose and Toyoha Mining Companies duringβeld
一669一
Bul1。GeoL Surv．Japan，vo1．30，No。12
workisgreatfα11yac㎞owledged．
Re郵e騰鵡ces
The languages used in each paper are indicated in parenthesis with abbreviations as follows．（J）＝written in
J’apanese。（JwE）：written in Japanese with Eng五sh abstract。（F）：written in French．The paper without such
indications arewritten in English．References w三th a notation（＊）are thosefor Table3。
AKIBA，C。（1958） Some problems on the ore deposits in the southwestem part of Hokk翫ido．C6nozo26R65．，
voL27，P。22−31，（」）．
AKo皿，K．and HARAGuGHI，M。（1963）Geology and ore deposits ofToyoha mine．M2痂g O60ム，voL13，
p．93−99，（JwE）．
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Bull．GeoL Surv．Japan，VoL30，No．12
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470．
地名英和対応表
Akaiwa 赤 岩
Chitose
千 歳
Eniwa
恵 庭
Kobetsuzawa 小別沢
Matsukura
松 倉
Inatoyo
稲
豊
Jozanke三
定山渓
Koryu
光
竜
KutOS我n
倶登山
Me茸i
明
治
Minami．Shiraoi
南白老
MQrino
白 老
盛 能
Otoyo
大
豊
Shakotan
積 丹
Sh丘＆oi
Suttsu
寿
都
Teine
手 稲
Todoroki
轟
Toyoha
豊
羽
Toyohiro
豊 宏
Toyotomi
豊 富
西部北海道，手稲一千歳地域における新第三紀鉱化作用
矢島 淳吉
要 旨
西部北海道の東部に位置する手稲一千歳地域には，定山渓石英斑岩を軸として分布する金属鉱床の累
帯配列が認められる．豊羽鉱山は内側の鉛亜鉛帯における代表的な鉛亜鉛の鉱脈鉱床であり，千歳鉱山
は外側の金銀帯に属する典型的な含金石英脈鉱床である．
千歳鉱床の流体包有物から得られた温度，塩濃度はそれぞれ200。一300。C，0．0−3．6％であり，鉱床の
最下部において得られたデータから見積もられた熱水溶液の蒸気圧，密度は，それぞれ84・9気圧，0・7組
9／ccであった．静水圧のみが働いてv・たと仮定すれば7この値は1，050mの深度を与える．
豊羽鉱床においては，前期鉱脈では東側から西側へ，後期鉱脈においては南東側から北西側へ，それ
ぞれ，流体包有物の温度，塩濃度の低下及び鉱物の累帯分布が認められる．この事実と，鉱山東南方深
部に推定されている熱源の存在とから，豊羽鉱床の形成過程に関するモデルを構築した．
地質学的背景，鉱物共生関係，流体包有物の解析結果などに加えて地下の熱構造を総括的に検討した
結果からみても，本地域に金属鉱床の累帯配列を設定することは妥当であると思われる．
（受付：1979年4月17日1受理31979年6月8目）
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