10th Asian Regional Conference of IAEG (2015)

Influence of Mineral Assemblage to form the Groundwater Quality in Altered RockArea
Takehiro OHTA(1), Shuichi HATTORI(2), Yoshihiro KIKUCHI(3) and Dai SHIMOFUSA(4)(1) Railway Technical Research Institute, Japan
E-mail:ohta@rtri.or.jp(2) Japan Railway Construction, Transport and Technology Agency, Japan, (3) JX Nippon Exploration andDevelopment Co.,Ltd., Japan, (4) NS Environmental Science Consultant Corporation, Japan
Abstract
Groundwater geochemistry which is distributed at the Hakkouda Tunnel in the
Sankaku-dake Mountains, Aomori prefecture, was surveyed to understand the mineral
assemblage effecting onto the water quality of groundwater. We collected and analyzed theprimitive groundwater samples that were gushed out from the cutting face and the pilot
drilling. The groundwater geochemical characters were compared with the geological,
petrographical and mineralogical features of the surrounding rock mass. From the results ofthe consideration, we conclude the influences of hydrothermal alteration to the groundwater geochemistry as follows. 1) The groundwater distributed around the Hakkouda
Tunnel is classified into the calcium-bicarbonate type and/or the calcium-sulfate type. 2)
The groundwater in the hydrothermal alteration area shows geochemical feature of thecalcium-sulfate type, and the feature becomes more remarkable as the degree of alteration
increases. 3) At the strong acidic alteration zone in which pyrophyllite are included, thegroundwater exhibits low ion concentration and low pH. 4) The quality of fissure water in
hard rock mass depends on the mineral assemblage of aquifer and is not homogenized ingeochemical by mixing due to groundwater flow.
Keywords: groundwater quality, altered rock, minerals assemblage, hydrothermal alteration
1.

Introduction

heavy metal are occurred in groundwater contacting
ore-vein around the mines. The relationship between
the secondary mineral assemblage and thegroundwater quality are not clear. It is not clear how
much range influence on groundwater quality by thethermal alteration extends to. We have no knowledge
for the difference of water quality between thermal
alteration and diagenesis alteration.
In this report, we will discuss the influence ofmineral assemblage to form groundwater quality fromthe result of comparison between water quality andmineral assemblage in spatial at Hakkouda Tunnel.

Recently groundwater pollution caused by theheavy metal elements from natural rock mass
becomes serious issue, and is widely noticed. It is
well known for example that the seepage water frommines has strong acidity and has high heavy metalelements concentration (Saskatchewan Environment
and Public Safety Mine Pollution Control branch,
1992). It is suggested that the wide area arsenic
pollution of groundwater depend on the hydrogeology
of aquifer (Shimada, 2003). On the other hand, it isafraid that concrete materials such as lining of tunnels
are deteriorated by the long-term seepage of acidgroundwater and that agricultural environment
around tunnels is influenced by constant alkaline
water seepage.
The groundwater quality will be changed by
the reaction between water and minerals and willattain to chemical equilibrium condition in the aquifer.
It is probable therefore that the geology of aquifer
influence to groundwater quality (Seki et al., 1999). It
is expected that acidification and concentration of2.

Geological setting

The Neogene rocks in Kanegasawa Formation,
Yotsuzawa Formation, Wadagawa Formation and
Ichinowatari Formation distribute around the
Hakkouda Tunnel, and the Neogene igneous rocks
intrude into these formations (Fig.1). The Quaternary
pyroclastic flow deposits from the Hakkouda volcano
cover these Neogene rocks. Mudstone distributes
mainly in Yotsuzawa Formation and Wadagawa

1

10th Asian Regional Conference of IAEG (2015)

Volcanic rock

DioritePyroclastics

DaciteIchinowatari F.

Andesite.

Wadagawa F.

.

Yotsuzawa F.

Vein Ore.

Kanegasawa F.

Kuroko Ore

Fig.1 Geological map around the Hakkouda Tunnel
Formation. Yotsuzawa Formation was formed at thesame time as Nishi-Kurosawa Formation that is
known as the "Kurokou" formation. Wadagawa
Formation was deposited simultaneously with
Onnagawa Formation that contains oil. Kanegasawa
Formation that is the lowest formation in this area
distributes around the summit of this tunnel. The
upper formations distribute to the west and east
entrances of the tunnel. Therefore, the structure of the
Neogene formations around this tunnel is an anticline
to extend the axis from north to south at the summitof this tunnel.
There are many abandoned mines, e.g. theKitakami Mine, around this tunnel. The abandoned
mine to be distributed over less than 3km from thistunnel is 11 mines, e.g. the Taisei Mine (Fig.1). Theseabandoned mines classified as ore vein type mines,
which consist of pyrite, chalcopyrite and sphalerite
mainly, distributed at Kanegasawa Formation,
Yotsuzawa Formation and Wadagawa Formation.

100%

Is（市ノ渡層 砂岩）（×）
Ichinowatari
Formation

80

80
SO 42-

Ca 2+

Ⅲ

+

+

Mg 2+

C -

Ⅴ

20
0

20

Ⅰ

0

Ⅳ

100%

100%
20

80

20

Ⅴ
Na +

SO 42-

K+

Mg

Ⅱ
80

80

20
0
100%

80

HCO3 -

+
2+

20

100%
80

20

Ca2+

0

20

0

Fig.2 The Piper diagram of the groundwater in
Ichinowatari formation
Wlt（和田川層100%

火山礫凝灰岩）（○）

lapilli tuff
火山礫凝灰岩）（×）

Wlt（和田川層8080

basalt玄武岩）（○）
SO安山岩）（×）andesite+Wbt（和田川層 玄武岩質火砕岩）（○） Cbasaltic
pyroclastics
Wb（和田川層

24

2+

Ca

Ⅲ

Wa（和田川層

+
Mg2+

-

Ⅴ

20

20

0

Ⅰ

0

Ⅳ

100%

100%

3.

0
100%

80

C -

Groundwater quality in each Formation

20

20

Ⅴ

80

80
Na +
+

Mg

We already reported the groundwater quality ineach formation distributed around the Hakkouda
Tunnel (Shimofusa et al., 2003). The summaries ofthe feature of groundwater quality are as follows:
The groundwater in Ichinowatari Formation isclassified into calcium-bicarbonate type, andindicates 7.5 to 8.5 in pH (Fig.2). In Wadagawa
Formation, the groundwater quality is different ineach rock type. If the aquifer consists of basaltic
rocks, the groundwater shows the features ofcalcium-sulfate type, and if tuff breccias thegroundwater is classified into calcium-bicarbonate
type (Fig.3). The pH of the groundwater in
Wadagawa Formation shows from 7.5 to 9.0. The
groundwater in Yotsuzawa Formation, which shows
8.0 to 9.0 in pH, is rich in sulfate and is classified as
calcium-sulfide regardless of rock type (Fig.4). If the2+

HCO3 KSO 42-

+

Ⅱ
80

80
20

20
100%

0

100%

80
Ca

Wst（和田川層

0

20

100%

0

100%

成層凝灰岩）（○）

layered成層凝灰岩）（×）
tuff

80

80

デイサイト）（○）

daciteデイサイト）（×）

SO4Wd（和田川層

2-

Ca

Ⅲ

2+

+

+

凝灰角礫岩）（×）
tuff breccia
Wm（和田川層 泥岩）（対象外）
mud stone
Wtb（和田川層

Mg 2+

C-

Ⅴ
20

20

0

Ⅰ

0

Ⅳ

100%

100%
20

20

Ⅴ

80

80

Na+

HCO 3-

+
Mg

80

-

C

Wst（和田川層
Wd（和田川層

020

2+SO 42-

K+

2+

Ⅱ
80

80
20

20
100%

0

100%

80
Ca

2+

20

0

0

20
C

-

80

100%

0

Fig.3 The Piper diagram of the groundwater in
Wadagawa formation2

10th Asian Regional Conference of IAEG (2015)
100%

An（貫入岩Yt（四沢 層2-SO 4An（貫入岩Yt（四沢 層Da（貫入岩Yb（四沢 層

+

+

2+

Mg

-

C

Da（貫入岩玄武岩）（ ○）

basaltYb（四沢 層 玄武岩）（ ×）Ba（貫入岩20SO4玄武岩）（○）

Ⅰ

Mg

20

0

Ⅰ

Ⅴ

100%

80

20

+
K

SO 4

-

HCO 3
+

Ⅱ

Mg

2-

+

2+

SO 4

K

Ⅱ

80

80

80

Na+

2-

+

20

Ⅴ

80

HCO3 -

2+

0

Ⅳ

100%

20

+

2+

Ⅴ

100%

Na
Mg

+

C

20

100%
20

2+

0

Ⅳ

80

Ca

Ⅲ

-

20

0

2-

+

basalt玄武岩）（×）Di（貫入岩閃緑岩）（○）
dioriteBa（貫入岩Ⅴ

80

80

デイサイト）（○）

daciteデイサイト）（×）

2+

Ca

Ⅲ

100%

安山岩）（○）

andesite
安山岩）（×）凝灰岩）（ ○）

tuff 凝灰岩）（ ×）

80

80

20

20

80

80

100%

20
0

100%

80
Ca

20

2+

0

20

0

C

100%

80

-

0

Yｄ（四沢層（○）

daciteデ イサイト）
mud泥岩）（
stone対象外）
Ylt（四沢層 火 山礫凝灰岩）
lapilli tuff
（×）
四沢層 安山岩～玄武 岩および同
andesite - basalt
質火砕岩

100%

20
100%

0

100%

80
Ca

2+

20

0

0

20

-

80

100%

0

C

Ym（四沢 層

80

80
2-

SO 4

2+

Ca

Ⅲ

+

+

Fig.6 The Piper diagram of the groundwater in
intrusive body

Mg2+

-

C

Ⅴ
20

20

4
Ⅰ

0

Ⅳ

Rank of diffracted intensity

0

100%

100%
20

20

Ⅴ

80
Na

80

+

HCO3

-

+
Mg

2+

K

2-

+

SO 4

Ⅱ
80

80

20

20
100%
0

100%

80
Ca

20

2+

0

20

0

C

80

-

100%

0

Fig.4 The Piper diagram of the groundwater inYotsuzawa formation
100%
80

80
2-

SO 4

2+

Ca

Ⅲ

+

+
C

0

Ⅰ

0

Ⅳ

100%
20

20

Ⅴ

80

80
Na +
+

Mg 2+

HCO3
K

-

2-

+

SO 4

Ⅱ
80

80
20

20
100%

0

100%

80
Ca

2+

20

0

0

20
C

-

80

100%

0

Fig.5 The Piper diagram of the groundwater in
Kanegasawa formationaquifer consists of tuff and tuff breccias in
Kanegasawa Formation, the groundwater featureshows calcium-bicarbonate and/or calcium-sulfate
and is in range from 8.0 to 9.0 in pH (Fig.5). The
major groundwater in intrusive body shows thefeatureofcalcium-sulfate
type
and/orcalcium-bicarbonate type, and sodium-sulfide inminor (Fig.6). These ground waters are in range from
8.0 to 9.5 in pH.
4.

Mineralqualityassemblages

and

2

1

645

640

635

The representative samples were examined by
X-ray powder diffraction (XRD) in order to grasp theinfluence of the mineral assemblage on the
groundwater quality. We examined 580 rocksamples.
The diffracted intensity of each mineral detecting
in samples by X-ray powder diffraction is divided
into 4 grades qualitatively. Fig. 7 indicates the spatial
distribution of the diffracted intensity of each mineral.
In this figure the diffracted intensity shows asproximity average grade of 20 samples approachingit. Because it is not a sampling of the equal distance,
the proximity average of the number of the uniform
samples does not express correct qualitative grade.
However we can understand the distribution of thediffracted intensity of minerals in a large sense at thewide spatial range shown in Fig. 7.
Chlorite and smectite are distinguished in thesection between 636km and 639km, at 641km to
645km the rock mass is enriched in smectite
including zeolite. Chlorite excels from 646km to theend of the tunnel generally. Sericite is included in thesection from 646km to 650km. Smectite andlaumontite are included in the section between
651km and 654km, and at the end part of tunnel from654km, sericite and calcite are included. I In theseareas, the mineral assemblages show the feature of

20

100%

650

calc iteFig.7 Spatial distribution of mineral assemblage

andesite 3
Klt（ 金ヶ沢層 火 山礫凝灰
lapilli tuff
岩）（○）

Ⅴ
20

655

di aspore
pyrit eseric ite
epid ote
epi stilb iteSta.（km）

KAｎ（金ヶ沢 層 斑目状安 山
岩 貫入岩層 ）（○）

2+

Mg

-

pyro phil lit ech lori telaumon tite

3

0
660

安 山岩）
andesite1
Kpr（ 金ヶ沢層
安 山岩）
andesite2（×）
Ktb（ 金ヶ沢層 凝 灰角礫岩）
tuff breccia（○）
Kpr（ 金ヶ沢層（○）

kaoli nite
sme ctit estil bitegroundwater

4.1 Spatial distribution of mineral assemblages

3

10th Asian Regional Conference of IAEG (2015)

pH

10

pH

140

ＥＣ

9

120

8

100

7

80

6

60

5

40

4

20

3
660

655

65 0

64 5

EC (mS/m)the neutral altered zone with the feature of alkaline
altered, therefore diagenesis was the dominantalteration process.
Acidic alteration minerals such as kaolinite andpyrophillite are enriched remarkably in 639km to
640km, 645km to 646km. Then the rock masses inthese areas are affected by hydrothermal alteration
notably. The rock masses at 640 – 641km, around642km, 646 – 650km, 653 – 656km and 658 –
659km include many pyrites. It is considered thatthese rock masses were affected by hydrothermal
alteration with diagenesis as dominant alteration
process, because pyrite is a dominant phase in the orevein distributed around the Hakkouda Tunnel.

0
635

640

Sta. (km)Fig.8 Spatial distribution of pH and EC ingroundwater

4.2 Spatial distribution of groundwater quality
We collected and analyzed 1,006 primitive
groundwater samples that were gushed out from thecutting face and the pilot drilling to confirm thespatial distribution of the groundwater quality.
To understand the spatial distribution ofgroundwater quality in a large sense, we illustrate thespatial variation of proximity average values of pH,
electrical conductivity (EC), cations and anions
concentrations of 10 samples coming close to in
Figs.8-10. The groundwater distributed in the area inwhich diagenesis was the dominant alteration process
is in range from 8.0 to 9.0 in pH and ranges from 10
to 30 mS/m. At the areas affected by bothhydrothermal alteration and diagenesis with many
pyrites the EC of groundwater exceed 40mS/m. If therock masses include calcite with pyrite at the samelevel especially, e.g. 640 to 641km, 648 to 650km,
around 655km, the groundwater has more than 80
mS/m of EC. On the other hand, the groundwater inrock masses affected by remarkable acidic alteration,
645 to 646km, indicates strong acidity, lower than
4.0 of pH. The pH of groundwater at 639 to 640km
including acidic alteration minerals becomes lower
than that of peripheral groundwater.
Comparing the concentration between the four
major cations, Na+ and Ca2+ are dominant in the
groundwater and there is much Mg2+ next. K+
concentration in the groundwater is very low atstudied area. If the calcite and pyrite of quantity atsame level are contained in rock mass, theconcentration of Ca2+ and Mg2+ in the groundwater
becomes higher than peripheral area. The
concentrations of Na+, Ca2+ and Mg2+ in the
groundwater are slightly low at the area in which themineral assemblages of neutral to alkaline alteration,such as zeolite, are recognized.
It is only sulfate that a remarkable concentration
change is seen in anions. SO42- concentrations ingroundwater become high at the area in which acidic
altered minerals distribute and at the diagenesis
alteration area which contain many pyrite. SO42concentration in the groundwater at neutral and

10
1

9

10

7
-1

6

10

pH

ion (mmol/L)

8
100

5
10-2

Na
Ca
pH

-3

10

660

65 5

65 0

645

K
Mg

4

3
6 35

6 40

Sta. (km)Fig.9

Spatial distribution
groundwaterofcations

in
10

1

9

10

7
10-1

6

pH

ion (mmol/L)

8
100

5
10-2

SO4
Cl
pH

HCO3

4

-3

10

660

65 5

65 0

645

3
6 35

6 40

Sta. (km)Fig.10 Spatial distribution
groundwaterofanionsinalkaline alteration zone indicates low value.
5.

Discussion

From the comparison between mineral
assemblages and groundwater quality, it is clear thatthe ion concentration in the groundwater become
higher at the section affected by hydrothermal
alteration, which formed pyrite vein in rock mass. If
the rock mass suffer strong acidic hydrothermal
alteration which precipitate the acidic alteration
minerals, many elements in rock mass are dissolved

410th Asian Regional Conference of IAEG (2015)

throughout alteration process. Therefore, thegroundwater in this rock mass shows low
concentration in ions and becomes acidic with low
pH. On the other hand, at the rock mass that is
affected by alkaline alteration precipitating zeolite
during diagenesis process, ion concentrations ingroundwater become low. From this fact, it isassumed to absorb ions into zeolite.
Comparing between the spatial distribution ofmineral assemblages and groundwater quality, we canconfirm that the distribution of groundwater affectedby hydrothermal alteration is limited at or near thehydrothermal alteration area. Therefore, the water
quality of fissure water in hard rock mass such as themountain around the Hakkouda Tunnel depends onthe mineral assemblage of aquifer and is nothomogenized in geochemical by mixing due to wider
groundwater flow.

low ion concentration and low pH.
4) The quality of fissure water in hard rock massdepends on the mineral assemblage of aquifer and is
not homogenized in geochemical by mixing due togroundwater flow.

6.

Saskatchewan Environment and Public Safety Mine
Pollution Control branch (1992): Mine Rock
Guidelines, Design and Control of Drainage Water
Quality, Steffen Robertson and Kirsten (B.C.) Inc.
Seki, Y., Kanai, Y., Kamioka, H., Tsukimura, K.,
Hamasaki, S., Kanazawa, Y. and Nakajima, T.
(1999): Relationship between geology and water
quality of rock seepage from quarries – A case study
around the Yamizo Mountains -, Bull. Geol. Surv.
Japan, Vol. 50, No. 11, pp. 683-697.
Shimada, N. (2003): Arsenic in groundwater: The
chemical behavior, source and relevant problems,Shigen-Chishitsu, Vol. 53, No. 2, p. 161-172.
Shimofusa, D., Ohta, T. and Hattori, S. (2003): The
relationship between groundwater qualities from the
Neogene formations in the Hakkouda Tunnel andtheir geology, Proceedings of the JSEG 2003.

Acknowledgements
The authors are indebted to all staffs, Japan
Railway Construction, Transport and Technology
Agency and every joint venture for constructing of
the Hakkouda tunnel, for convenience at explorationand sampling. We also appreciate to Mr. A.
Hasegawa, Mr. T. Urakoshi, Railway TechnicalResearch Institute for a lot of discussion.
References

Conclusions

We examined the relationship between themineral assemblage and the groundwater quality tounderstand the influence of mineral assemblage toform the groundwater quality. From the results of theconsideration, we conclude the influences ofhydrothermal alteration to the groundwater
geochemistry as follows.
1) The groundwater distributed around the
Hakkouda Tunnelisclassified
into
thecalcium-bicarbonate type and/or the calcium-sulfate
type.
2) The groundwater in the hydrothermal alteration
area
shows
geochemical
featureofthecalcium-sulfate type, and the feature becomes more
remarkable as the degree of alteration increases.
3) At the strong acidic alteration zone in which
pyrophyllite are included, the groundwater exhibits

5