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Geology and mineral resource of Southern Tohoku, Japan:

Insights from Hosokura polymetallic deposit, Itaya zeolite,

Adatara volcano and Ishikawa pegmatite

August 5-7, 2019

Society of Economic Geologists

Akita University Student Chapter

(SEG-AUSC)

FIELD REPORT-2019

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1.0. Introduction

A Three-day field excursion was conducted between August 5th and 7th, 2019 in Miyagi,

Yamagata and Fukushima prefectures of southern Tohoku, Japan (Fig. 1). This year’s

travelling team was constituted by sixteen (16) students (both undergraduate and

graduate), a guest and Professors Yasushi Watanabe and Antonio Arribas (Table 1). The

main objective of the field excursion was to explore and get a practical experience on the

geology and mineral resources of southern Tohoku by appreciating epithermal to

mesothermal vein-type deposits of Hosokura Mine (closed), non-metallic deposits in

form of Itaya zeolite and Ishikawa pegmatite as well as hydrothermal alterations and H2S

fumarolic hot springs from the Adatara volcano.

Figure 1. Location map showing the route and stops during the field excursion.

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Table 1. List of participants for the field excursion

No. Name Status Academic position

1 Antonio Arribas Industrial advisor Professor

2 Yasushi Watanabe Academic advisor Professor

3 Amogelang Kooganne Member, Treasurer PhD student

4 Beny Sumaryono Member MSc student

5 Hugo Arribas Guest Guest

6 Ishizu Takumi Student MSc student

7 Maki Birukawa Member BSc student

8 Manuel Nopeia Member MSc student

9 Mika Kitamura Member, Vice-president MSc student

10 Mpho Keediste Member, President PhD student

11 Mukuka Simusokwe Member PhD student

12 Paolo Martizzi Member, Executive member PhD student

13 Patthana Bounliyong Member, Secretary PhD student

14 Renaldi Suhendra Member MSc student

15 Reza Firmansyah Hasibuan Member PhD student

16 Takumi Imura Student PhD student

17 Teruhiro Suzuki Student PhD student

18 Wataru Tachi Student BSc student

19 Yuho Fujimaki Student MSc student

2.0. Field stops

Three (Hosukura Mine Park, Adatara Volcano and Ishikawa pegmatite) main stops and

one geo-tourism site (Hiraizumi temple) made up the field excursion. Table 2 below

shows the complete field trip itinerary. At least one hour was allocated for every stop,

depending on the stop the following sequence was followed; induction, outcrop

investigation and sample collection.

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Table 2. Complete itinerary of the field excursion.

Date Time Activity

Day 1

Aug 5

06:30 –

09:00 Depart from Akita University to Hiraizumi temple

09:00 –

10:30 Understanding the history of gold at Hiraizumi Temple

10:30 –

11:30 Depart from Hiraizumi Temple to Hosokura Mine Park

11:30 –

13:30 Understanding the ancient metals mining activity

13:30 –

15:30

Depart from Hosokura Mine Park to the Itaya zeolite deposit

Yamagata

15:30 –

17:30

Brief induction and introduction about Itaya zeolite deposit,

followed by mine and factory tour

17:30 –

18:30 Depart from the Itaya zeolite deposit to Hotel in Fukushima City

Day 2

Aug 6

09:00 –

10:00 Depart from the hotel to Adatara volcano

10:00 –

16:00 Geological and mineralogical investigation in Adatara volcano

16:00 –

17:00 Depart from Adatara volcano to hotel in Fukushima city

Day 3

Aug 7

07:30 –

09:50 Depart from hotel to Ishikawa pegmatite deposit

09:50 –

11:00 Geological and mineralogical investigation of the pegmaties

11:00 –

11:10

Depart from Ishikawa pegmatite mine to the Museum of History

and Folklore in Ishikawa town, Fukushima

11:10–

12:00

Tour at the Museum of History and Folklore in Ishikawa town,

Fukushima

12:00 –

18:00 Depart from Ishikawa town to Akita University

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Day 1

2.1. Konjikido Temple in Hiraizumi, Iwate

The team received an overview on the history of the temple and origin gold that makes

the temple unique. We learned that the Hiraizumi-temples, gardens and archeological sites

representing the Buddhist Pure Land were registered as UNESCO world heritage sites in

2011. The Konjikido temple (Fig. 2a; one of the temples) was completed in 1124 by Oshu-

Fujiwara clan and was built to represent the Buddhist Pure Land and to console the souls

of all those, whether friend or enemy, who died in two major conflicts at the end of the

11th century. The inner sanctuary (Fig. 2b; photography is prohibited) of the Konjikido

temple is lavishly decorated with gold sprinkle representing the pinnacle of Heian

Buddhist art. Most importantly, we learnt during the trip that the gold used to decorate

could have been placer gold primarily from orogenic gold deposits from northeastern

Japan.

Figure 2. a) Konjikido temple. b) The inner sanctuary of the Konjikido temple lavishly

decorated with gold. Source: https://www.japan-guide.com/e/e5001.html.

a

b

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2.2. Hosokura Mine Park

The group made a tour of some of the main shafts in the Hosokura Mine Park which is

located in Uguisuzawa town, Miyagi Prefecture. This park used to be one of the largest

epithermal to mesothermal polymetallic (Pb-Zn-Ag-Cd) vein-type deposits in Japan

(Urabe, 1977). The mine commenced operations in the 16th century (closed in 1987) and

produced 26 Mt of ore at 4.12% Zn, 1.59% Pb and 12.8 Moz of Ag. The main ore hosted

within altered sedimentary and volcanic rocks is vein-type galena and sphalerite

overprinted by late calcite veins which are often rimmed by chlorite -smectite alteration

(Fig. 3d).

Figure 3. a) Entrance of the Hosokura Mine Park. b) Group photo in the mine. c) Prof. Arribas

explaining about vein-hosted sphalerite-galena and late calcite veins. d) Calcite vein with galena

and sphalerite rimmed by chlorite-smectite alteration.

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2.3. Itaya zeolite deposit in Yamagata (ZEEKLITE Ltd.)

The Itaya zeolite deposit (Fig. 4) located in Yonezawa city, Yamagata Prefecture, is one

of the largest zeolite deposits in Japan. The company management gave a safety induction,

introduction on mine operations and geology. This was then followed by mine and factory

tours. We learned about the Itaya deposit, mining history, characteristics, application, and

products of the Itaya zeolite. The ZEEKLITE Ltd. was established in 1936 as a kaolinite

mining project which operated until 1995. Now the company is mining the 70 Mt reserve

zeolite deposit which according to the mine has thousands of years life-span. The zeolite

deposit was formed subsequent to submarine volcanic eruption during the Neogene age.

Because of its unique properties, the zeolite is used for different purposes one of which is

to absorb ammonium from sludge/wastewater. Recently it has been used to fix the soil

system at the Fukushima nuclear plant, post 2011 nuclear accident. The company

produces different sizes and shapes of zeolite products depending on client demands (Fig.

4d). The Itaya zeolite has white color, homogenous (massive) with little to no impurities

(Fig. 4a, b). From the factory (Fig. 4c) tour we witnessed the following sequence of

events; Crushing → Drying → Secondary crushing depending on client’s requests →

Packaging.

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Figure 4. a) white and homogeneous outcrop of the Itaya zeolite deposit. b) Massive zeolite which

is mainly composed of clinoptilolite. c) Inside of the ZEEKLITE Ltd. factory. d) one of the

products made from the Itaya zeolite.

Day 2

2.4. Adatara volcano

Adatara is an andesistic stratovolcano overyling the Tertiary sedimentary rocks and whose

volcanic eruptions occurred in a series of 3 episodes approximately 250,000, 200, 000

and 120, 000 years ago (Yamamoto and Sakaguchi, 2000). The team started hiking the

mountain from 10 am and got back to base at 4 pm. The volcano is well-known for its hot

springs and fumaroles. Various lithologies can be observed within the volcano, for

example Lava flow (Fig. 5a), andesitic rocks (Fig. 5b) and silicified rock (sometimes

mineralized with fine-disseminated pyrite) (Fig. 5c). The hot spring water has pH less

than 3. The group felt more than fulfilled to make it to the summit where we saw the

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Numanotaira crater (Fig. 5f) within which the last eruption of Adatara took place in the

1900, unfortunately ~72 miners died at the time since they were mining sulfur directly

from the crater.

Figure 5. a) Lava flow covered by the alteration part. b) Whitish orange-colored altered part in a

slope (left side) and rolling boulder-sized volcanic rocks (right side). c) Silicified rock enriched

with very fine-grained pyrite. d) hot and acidic (pH=2.2) water from the hot spring. e) oxidized

water table (=water has pH 3.2). f) The Numanotaira (the sulfur river) crater viewing from the

top.

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2.5. Ishikawa pegmatite mine in Fukushima

We visited four pegmatite closed mines in Ishikawa town, Fukushima prefecture. Mr.

Aida who is local person guided us to these preserved ore bodies. The first orebody is

underground mine which has a height of 15 m and length of 25 m (Fig. a, b). It has been

mined for feldspar and quartz which were necessary for ceramic and clay making. Big

crystals such of quartz, feldspar, and mica were observed. The second orebody is an open

pit mine which is composed of graphic granite. It has a height of 25 and width of 24 m.

The third orebody is composed of granite, graphic granite, and pegmatite, which were

extracted through both underground and open pit mining (Fig. 6c, d). There are big

crystals of quartz, feldspar, biotite, tourmaline, and garnet. At the fourth orebody, there

are innumerable tourmaline and mica on the ceiling of the orebody (Fig. 6e, f, g).

2.6. Museum of History and Folklore in Ishikawa town, Fukushima

To understand history and precious minerals in Japan, we visited the Museum of History

and Folkore in Ishikawa town, Fukushima that was established in 1981. It is located close

to Ishikawa pegmatite mines. The town had not only pegmatite mines but also a secret

uranium mine for the Japanese atomic bomb project during World War II. About 160

beautiful minerals are exhibited here including tourmaline, garnet, beryl, and REE

minerals.

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Figure 6. a) Entrance of the first orebody of the Ishikawa pegmatite mine. b) The inside of the

first orebody. c) Outcrop of the third orebody. d) Graphic granite with garnet and mica (black

color). e) Outcrop of the fourth orebody. f, g) Big tourmaline crystals distributed on the ceiling of

pegmatite in the fourth orebody.

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2.0. Financial Statement

The SEG-Akita University Student Chapter’s field trip conducted between August 5th and

7th, 2019 was funded by the Steward R. Wallace funding and complimented by Akita

University and self-funding from members. A lump sum of 158,674JPYen (US$1,500.00)

was received from the Steward R. Wallace funding and was used to pay for part of the

accommodation fee and dinners for the sixteen (16) participants. Two (2) minibuses

equivalent to 40,000JPYen were provided by Akita University to be used for the entire

trip, while the self-funding from fieldtrip participants summed up to 80,000JPYen. Self-

funds were used to pay for part of the accommodation fee. From these funds, the total

amount at our disposal was 238,674JPYen which slightly fell short resulting to an

outstanding balance of -8,766JPYen. The outstanding balance is attributed to the large

turnout of participants in this year’s field trip, which we regard as a great achievement.

For the mobilization during the fieldtrip, 2 minibuses were provided by Akita University

upon which the gas fee and toll gate fees were taken care of. 8,740JPYen from the Student

Chapter monthly contribution savings was used to cover for the outstanding balance. The

details of the expenses are tabulated below with the receipts attached;

Table 3. Estimated field trip budget.

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Table 4. Details of field trip expenses

Table 5. Source of funds

FUNDING JYPEN US$

Steward R. Wallace (SEG) 158,674.00 1,500.00

Akita University ~48,000.00 428.86

Akita SEG Student Chapter

Monthly contributions

8,740.00 80.20

Self-fund 80,000.00 714.77

TOTAL 295,414.00 2,723.83

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Receipts

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3.0. Conclusion

In conclusion, Akita University SEG Student Chapter field trip to southern Tohoku region

was a great success. It was an incredible experience appreciating and learning about

metallic and non-metallic deposits, hydrothermal alterations, and history of deposits in

Japan. We give deepest gratitude to Society of Economic Geologists (SEG) and Akita

University for the financial support.

Figure 7. Last group photo at the end of a successful field excursion.

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4.0. References

1. Urabe, T., 1977. Partition of cadmium and manganese between coexisting sphalerite

and galena from some Japanese epithermal deposits. Mineralium Deposita, 12 (3),

319-330.

2. Yamamoto, T. and Sakaguchi, K., 2000. Eruptive history of Adatara volcano, NE

Japan during last 250,000 years based on tephra stratigraphy. Journal of the

Geological Society of Japan, 106, 865-882.

3. https://www.japan-guide.com/e/e5001.html