The Ohra-Takamine Project
|Target:||Low Sulphidation Epithermal Gold|
|Location:||Southern Kyushu, Japan|
- The Ohra-Takamine project lies within the Hokusatsu-Kushikino mining district, 7.5 kilometres to the southwest of the historic Yamagano mine which produced 910,000 ounces of gold at a grade of 17.4 g/t. Within the property historical production included the Ohra (27K oz gold), Takamine-Urushi (13K oz gold) and Takamine (1.6K oz gold) mines. Vein number 2 of the Takamine-Urushi mine was reported to carry gold grades between 50-100 g/t1,2.
- Other notable gold producers within the district include: Hishikari mine with 7.4 million ounces produced to date at average grades of 30-40 g/t7; Kushikino mine, 1.8 million ounces at 6.7 g/t; Yamagano mine, 910,000 ounces at 17.4 g/t; and the Ohkuchi mine with 714,000 ounces at 13.6 g/t4,8.
- The presence of sinter at several localities indicates the fossil geothermal system is well preserved and with known surface/near surface mineralization, represents a significant exploration target for shallow-level epithermal gold-silver deposits.
- Like all of the major gold mines in the Hokusatsu-Kushikino mining district, the Ohra-Takamine project straddles the margin of a gravity-high feature inferred to indicate upward doming of the basement which produced suitable fracture pathways for mineralised hydrothermal fluid flow.
The Takamine-Urushi Project comprises five (5) contiguous Prospecting Rights blocks (1,681 Ha) near the coastal town of Kirishima in southern Kuyshu. The project area contains an intact mineralized low sulfidation epithermal vein system part of which was historically mined up to 1943. Regional metallogenic surveys and later prospect evaluation work (including scout diamond) by the Metal Mining Agency of Japan (‘MMAJ’) in the 1980’s has further enhanced the level of geological understanding on this property.
Initially discovered in 1885 and mined periodically to 1943 the Ohra mine produced in the order of 27,000 ounces of gold at grades reported between 3.5 to 20 g/t. The northeast striking vein is reported as 1,200m long with an average width of 0.9 meter1,2.
The Takamine and Takamine-Urushi mines were discovered in latter part of the nineteenth century and mined periodically up to 1943. Takamine mine produced 9,654 tonnes of ore with average grades of 5.1g/t gold and 28.3 g/t silver. The vein strikes northeast, has a length of 450 meters, and average width of 1 meter.
Takamine-Urushi mine was estimated to have produced 13,000 ounces of gold between 1896 and 1916. Three northeast striking gold-bearing quartz veins, with lengths up to 350m were mined, the so-called number 2 vein was reported to carry gold grades between 50 to 100 g/t1,2.
The Metal Mining Agency of Japan (MMAJ) (Metal Mining Agency of Japan) conducted regional and more detailed studies over the Ohra-Takamine area between 1982 and 1989, eight drill holes were completed as part of this work. Drill hole 60MAH-2 located to the east of the Takamine-Urushi mine intersected two 10-centimetre wide quartz veins with respective gold grades of 12.3 and 13.3 g/t, 100 meters below the deepest mine workings, and approximately 245 meters vertically below surface3.
Four other historic Au mines (Yamada, Kohwa, Kizushi and Maruyama) are reported from outside the application area, located 1 to 3 km to the east and south-east.
Yamada mine was mined by Kagoshima Mining Co. from 1916 to 1930 after which the mining rights were transferred to local people. 7000t of ore was produced with average grades of 4 to 5 g/t Au (~1000 ounces). Kohwa mine was operated from 1946 to 1963 by Takara Mining Co. Kizushi mine was operated by local people from 1910 to 1926. Maruyama mine (also known as Oh-shika mine) was opened in 1925 and operated until 1928 with approximately 100 kg (14,100 ounces) of gold produced (METI, 19893).
More recent MMAJ exploration undertaken between 1979 and 1993 as part of a regional metallogenic study included regional geophysical surveys and prospect-scale surface sampling and drilling.
- 1979: Regional gravity survey completed which concluded that known gold deposits were associated with gravity high anomalies.
- 1982: Geochemical survey undertaken with 415 soil samples and 145 rock chip samples collected. One hundred and five (105) of the samples were analysed via X-ray diffraction to determine alteration mineral type.
- 1985-1989: Eight drill holes were completed within the property area (59MAHT-2,3; 60MAHT-2; 61MAHT-2,3,4,5; and 63MAHT-5). Drill hole 61MAH-2 located to the east of the Takamine-Urushi mine intersected two 10-centimetre wide quartz veins which assayed 12.3 g/t Au and 13.3 g/t Au respectively. These intercepts were 100 meters below the deepest mine workings, and approximately 245 meters vertically below surface.
- 1991: Two drillholes (63MAHT -1/2, drilled to 300.1m and 400m respectively) tested a resitivity anomaly along strike and down dip of the Yamada mine. Intercepts of 0.6m @ 0.18 g/t Au from 203m (3MAHT – 1) and 0.6m @ 0.14 g/t Au from 227.35m (3MAHT – 2) were returned.
- 1992: Geochemical rock chip sampling was undertaken to the east of the property with samples also analysed for alteration minerals.
- 1993: Sixty-four quartz vein and sinter samples were taken from around the Aira mines (Maruyama, Kizushi, Kowa) with six samples returning assays >10 g/t Au (mostly proximal to Maruyama) to a maximum of 154 g/t Au. Based on these high grades a drillhole (65MAHT-1, depth 502.4m) targeted along trend to the north-east of Maruyama mine and was mostly unmineralized with a single interval reporting an intercept of 0.15m @ 0.17 g/t Au from 324.5m.
Geology and Mineralisation
Geology of the Ohra-Takamine Property comprises a sequence of predominately Pleistocene aged volcanics underlain by Pliocene sediments and volcanic rocks (Kagoshima Block, 1997).
The Hokusatsu andesite is the primary host rock to known gold deposits, reported to be Middle Pleistocene in age (1.8 Ma 4Watanabe, 2005). The formation comprises andesitic to dacitic intrusives and volcanics of the same composition.
Small areas younger post-mineralisation Ito Formation volcanics cover the other units in the southeast of the project.
The seven Au mine deposits found within and in proximity to the Ohra-Takamine property are classified as rift low-sulphidation epithermal. Details of the mineralization at the deposits are described below.
The Takamine-Urushi mine was developed over three northeast (N45° E) striking gold-bearing quartz veins, with lengths up to 350m. The No. 2 vein was reported to carry gold grades between 50 to 100 g/t. Quartz-calcite-adularia veins were notable for massive zones consisting of black bands and transparent quartz. Native gold, pyrite, chalcopyrite and sphalerite are recorded. Fluid inclusions temperatures of 213 to 227 degrees have been reported (6METI, 2000).
Takamine mine vein strikes northeast, has a length of 450 meters, average width of 1 metre and was exploited over a vertical height of 120m (METI, 1989). Veins are composed of quartz with lesser amounts of calcite, carrying native-gold, pyrite, galena and manganese-bearing minerals. Fluid inclusion temperatures of 233 to 252 degrees are recorded (6METI, 2000).
The Ohra northeast striking vein is reported as 1,200m long with an average width of 0.9 meter (1Michitoshi, 1967). Three veins are recorded striking N60°E dipping 60°N. Average widths of the quartz-calcite veins are 0.9m. Veins are divided into many small parallel veinlets carrying native gold, argentite, chalcopyrite, pyrite and galena. A fluid inclusion temperature of 221 degrees is recorded (6METI, 2000).
The Company to date has conducted preliminary traverses, literature reviews and data searches on the property. The results of these efforts have been compiled to a GIS database.
More detailed reconnaissance work program is scheduled to commence in early Q2 2018.
The Ohra-Takamine project is located within the highly gold endowed Hokusatsu-Kushikino
mining district, in the northern part of the Southern Kyushu Epithermal Gold Province. In excess of 10 million ounces of gold has been produced from high grade epithermal deposits of the district. Notable gold producers within the district include: the Hishikari mine with 7.4 million ounces produced to date at average grades of 30-40 g/t7; Kushikino mine, 1.8 million ounces at 6.7 g/t; Yamagano mine, 910,000 ounces at 17.4 g/t; and the Ohkuchi mine with 714,000 ounces at 13.6 g/t4,8.
Due to the high prospectivity of the district, known auriferous low sulfidation epithermal vein mineralization both within and peripheral to the property and basically intact fossil geothermal systems, the company believes this area is worthy of more detailed exploration. The Company will seek to define the limits of the alteration around these vein systems by building on the existing data with detailed surface mapping, geochemical-sampling and geophysics to target new zones and extensions to known veins for scout drill testing.
1 Michitoshi Miyahisa, 1967: Report of gold deposits survey in Takamine/Ohra district, Kagoshima prefecture, Association of Kagoshima Prefecture mineral resources development promotion.
2 Gold Mines of Japan, 1989. The Mining & Materials Processing Institute of Japan.
3 MITI (1984- 1989): Report on the regional survey of the Hokusatsu-Kushikino region, Showa 58 (FY) to 63(FY). Ministry of International Trade and Industry.
4 Watanabe, 2005. Late Cenozoic evolution of epithermal gold metallogenic provinces in Kyushu, Japan. Mineralium Deposita (2005) 40: pp 307-323.
5 Ota, R., Koriyama, S., and Wakimoto, Y., Geological classification of Shirasu, Planning Department of Kagoshima Prefecture, 1967. pp. 7-19 (in Japanese).
6 METI, 2000. Report on the regional geological structure survey in the Hokusatsu-Kushikino area in the fiscal year Heisei 11. The Agency of Natural Resources and Energy of MITI.
7Sumitomo Metal Mining Co., LTD. website.
8 Garwin et al. 2005. Tectonic setting, Geology, and gold and copper mineralization in the Cenozoic magmatic arcs of Southeast Asia and the West Pacific. Economic Geology 100th Anniversary Vol. pp 891-930