Abstract The bonanza-grade, low-sulfidation epithermal Hishikari gold deposit is located in the Plio-Pleistocene volcanic area of southern Kyushu, Japan. The concealed veins were discovered in 1981 and the mine has since produced 5.462 million metric tons (Mt) of ore averaging 44.3 g/t Au (242 t Au) from 1985 to the end of 2018, at which time reserves were 7.98 Mt at 20.9 g/t Au. The Hishikari deposit consists of the Honko, Sanjin, and Yamada ore zones, which occur in a NE-trending area 2.8 km long and 1.0 km wide. The veins are hosted by basement sedimentary rocks of the Cretaceous Shimanto Supergroup and by overlying Hishikari Lower Andesites of Pleistocene age. Sinter occurs about 100 m above the Yamada ore zone. Temperature-controlled hydrothermal alteration zones occupy an area of >5 km long and 2 km wide. The Honko and Sanjin veins occur within a chlorite-illite alteration zone (paleotemperature >230°C), whereas the Yamada veins occur within an interstratified clay mineral zone (150°–230°C). The marginal alteration comprises quartz-smectite (100°–150°C) and cristobalite-smectite (<100°C) zones. Ore-grade veins are located between –60- and 120-m elev, with the paleowater table over the Honko-Sanjim veins at ~300-m elev. Overall, the Ag/Au wt ratio is about 0.6. Vein-forming minerals consist of quartz, adularia, and clay minerals plus truscottite, with electrum and minor pyrite, chalcopyrite, naumannite, galena, and sphalerite. The major veins formed from repeated episodes of boiling and strong fluid flow inferred from bands of quartz, adularia, and smectite with bladed quartz, columnar adularia, and truscottite.

Abstract Epithermal gold deposits are the principal source of gold in Japan, and mesothermal vein gold or by-product gold from skarn deposits, VMS (the Kuroko type and the Besshi type), and polymetallic veins contribute historically only 10 percent of domestic gold production. Gold production from epithermal gold deposits of Kyushu amounts to 284 tonnes and comprises about 40 percent of total Japanese gold production, 576 tonnes, from the Meiji Restoration (1868) to present (1999). The silver/gold ratio of ores in Kyushu is less than three and differs from the value that exceeds 10 in other areas ( Fig. 1 ). The Yamagano mine in the Edo era and later the Taio and Kushikino mines were the largest gold-silver mines in Kyushu before the discovery of the Hishikari deposit. At present the Hishikari underground operation and three opencut mines of the Nansatsu-type gold deposits at Kasuga, Iwato, and Akeshi are producing gold. The major gold deposits in Kyushu, typically of the low- sulfidation vein type and locally the high-sulfidation Nansatsu type, occur in extinct or waning geothermal systems of the Pliocene and Pleistocene volcanic areas. The young formation ages relate to the well-preserved shallow bonanza zones and overlying thick argillic alteration zones, and in places surface expression of hydrothermal activity, such as sinters and nearby acid alteration related to steam- heated acid hot springs. This contribution aims to present supplementary data to a previous review paper ( Izawa and Urashima, 1989 ), which described the relationship

Abstract The Hishikari high-grade low-sulfidation epithermal gold deposit is located in the Hokusatsu district, about 30 km north of the Kagoshima International Airport, Kagoshima Prefecture ( Fig. 1 ). In early 1981, a narrow (15 cm) but high-grade (290 g/t Au) vein was discovered 200 m below the surface by the Metal Mining Agency of Japan ( MITI, 1982 ), and subsequent development has proved Hishikari to have substantial reserves of high-grade ore. Production from July 1985 to March 2000 totaled 105 tonnes (t) of gold and 58 t of silver from 1.87 Mt of ore. The production plus total reserves are estimated to be 5.5 Mt, including 3.5 Mt at an average grade of 60 to 70 g/t Au in the Honko-Sanjin ore zone and 2 Mt at 20 to 25 g/t Au in the Yamada ore zone, for a total of approximately 260 t of contained gold. The Hishikari deposit, especially the Honko-Sanjin zone, is characterized by high gold contents in almost all veins and by a very high aluminum content in the veins due to abundant adularia and common smectite. This article presents a summary of the gold deposit at Hishikari and the detailed mineralogical description of a high-grade vein, the Hosen no. 1 vein, hosted by basement sedimentary rocks.

Abstract The Kushikino gold mine (Gold Park) is located 30 km northwest of Kagoshima city (Fig. 1) and historically has been the fourth largest gold mine in Japan. The mine was opened in 1660 by a lord of the Satsuma Province (a province in southern Kyushu during the Edo era) and development took place mainly on the Serigano vein group (Fig. 2) in the south central part of the area (Miyahisa and Wakabayashi, 1972). In the late Meiji era, 1905, Mitsui Mining and Smelting Co., Ltd. acquired the central part of the Kushikino area including the Kushikino no. 1 vein. In 1913, an all-slime cyanidation plant, the first of its kind in Japan at that time, began treating ore at a rate of 150 (t) per day. Since 1660 the mine has produced 55 t of gold and 497 t of silver, of which more than 80 percent was produced from the Kushikino no. 1 vein. Approximate average Au and Ag grades have been reported as 6.7 g/t and 61 g/t, respectively (MITI, 1979). In 1988, the Kushikino Gold Park was opened adjacent to the operating gold mine. In the park, the western part of the champion vein (Kushikino no. 1 vein) around the “New” inclined shaft (Shin-shako) can be seen in the adit (mine level 2L, 60 m above sea level), though the mining operation is no longer active. This article compiles previous studies and revises our understanding of the epithermal gold mineralization at the Kushikino deposit.

Abstract Siliceous sinter forms around geysers and hot springs by the deposition of amorphous silica and is well preserved in fossil systems. Except for geyserite, siliceous sinter has biogenic structures principally derived from thermophilic bacteria, which live in the hot water of pools, outflow channels, and sinter terraces. The species of bacterium process unique temperature ranges, and much work on thermophilic bacteria at Yellowstone National Park has been undertaken by a number of biologists (e.g., Castenholz, 1969 ; Brock, 1978 ). Structural studies on present-day siliceous sinter forming in Yellowstone National Park have been well documented by Walter (1976) .