Hishikari deposit

S S value of sedimentary rocks of the Shimanto Supergroup which hosts the Hishikari deposits, southern Kyushu is — 12%o (Ishihara et al., 1986) which is considerably lower than those of the Hishikari deposits (+l%o to - -2%c) (Shikazono, unpublished. This suggests that sedimentary sulfide sulfur is one of the sources of the sulfides and probably igneous sulfide sulfur is the dominant source. 

Hishikari deposit an example of Japanese epithermal Au-Ag vein-type deposits... 

Much research on the Hishikari deposits has been carried out since the discovery of gold veins in 1981. Urashima and Izawa (1983) reported fluid inclusion studies using core samples. Abe et al. (1986) made a detailed description of the veins. The regional geology of this district is described in MMAJ and SMM (1987) and Urashima et al. (1987). 

The Special Issue of Resource Geology on the Hishikari deposits (Shikazono et al., 1993) includes various aspects of the Hishikari deposits (oxygen isotopes of gangue minerals, hydrothermal alteration, precipitation sequence, fluid inclusions, vertical electric profiling and electric sounding surveys, structural geological analysis, opaque minerals. 

Nagayama, T. (1993a) Precipitation sequence of veins at the Hishikari deposits, Kyushu Japan. Resource Geology Special Issue, 14, 13-28. 

Shikazono, N., Yonekawa, N. and Karakizawa, T. (2002) Mass transfer, oxygen isotope, and gold precipitation in epithermal gold system A case study of the Hishikari deposit, southern Kyushu Japan. Resource Geology, 52, 211-222. 

Urashima, Y. and Izawa, E. (1983) Ore of the Hishikari deposit from the boring core. Mining Geology, 33, 50 (in Japanese). 

Figure 1.8. Schematic northwest-trending section across the Main and the Sanjin deposits of Hishikari mine (Ibaraki and Suzuki, 1993).

Hydrated calcium silicate minerals such as xonotlite, truscottite, and gyrolite are rare but have been reported from several Au-Ag deposits. They do not coexist with Au-Ag minerals but instead are found with quartz, carbonates, and johannsenite. However, in the Keisen No. 3-2 vein in the Hishikari Au-Ag deposits, a close association of electrum with truscottite, smectite and calcite is observed (Imai and Uto, 2001). 

Advanced arigillic alteration is found at the upper horizon than the sites of potassic and intermediate argillic alterations where the Au-Ag mineralization occurs (e.g., Seigoshi, Yatani, Kushikino, Hishikari). This type of alteration takes blanket-form in upper part and vein-form in lower part (Iwao, 1962 Shikazono, 1985a). The conspicuous zonation from upper to lower horizon is known at the Ugusu silica deposit, namely, silica zone, alunite zone, kaolinite zone and montmorillonite zone (Iwao, 1949, 1958, 1962). 

Figure 1.103. 8D and 8 0 of ore fluids responsible for epithermal Au-Ag vein-type deposits in Japan (Hattori and Sakai, 1979 Imai et al., 1998). S.W. seawater, M.W. line meteoric water line, KK Kushikino, SG Seigoshi, YUG Yugashima, TK Takatama, FUK Fuke, YN Yatani, KN Kanisawa (Yatani), HK Hishikari. 

Sedimentary rocks often occur as host rocks, footwall rocks and basement rocks in the Non-Green tuff mine area. For example, in southern Kyushu, the Shimanto Supergroup shale is dominant as basement and a host rock for epithermal Au-Ag vein-type deposits (e.g., Hishikari). 

Host rocks for the Se-type and Te-type epithermal An—Ag deposits are summarized in Table 1.17. In general, the dominant host rocks for both deposits types are intermediate and felsic volcanic rocks. Sedimentary rocks (usually shale) sometimes host the Se-type (e.g., Sanru, Kohryu, Takadama, Ohmidani, Hishikari), but never host the Te-type deposits. 

Shikazono et al. (2002) considered the depositional mechanism of quartz and cristobalite and the change in silica concentration of fluid migrating through the altered rocks in the Hishikari mine district based on kinetics-fluid flow mixing model. Their discussion is summarized below. 

Reed and Spycher (1985) made a computation on the gold deposition from the mixed fluids. Their results support that gold deposition occurred in the Hishikari veins... 

Etoh, J., Taguchi, S. and Izawa, E. (2001) Gas compositions in fluid inclusions from the Hishikari epithermal gold deposit, southern Kyushu, Japan. Proceedings of International Symposium on Gold and Hydrothermal Systems, pp. 99-104. 

Ibaraki, K. and Suzuki, R. (1993) Gold-silver quartz-adularia veins of the Main, Yamada and Sanjin deposits, Hishikari gold mine a comparative study of their geology and ore deposits. Resource Geology Special Issue, 14, 1-11. 

Imai, A., Shimazaki, H. and Nishizawa, T. (1998) Hydrogen isotope study of fluid inclusions in vein quartz of the Hishikari gold deposits, Japan. Resource Geology, 48, 159-170. 

Ishihara, S., Sakamaki, Y., Sasaki, A., Teraoka, Y. and Terashima, S. (1986) Role of the basement in the genesis of the Hishikari gold-quartz vein deposit, southern Kyushu. Japan. Mining Geology, 36, 495-510. 

Izawa, E., Urashima, Y, Ibaraki, K., Suzuki, R., Yokoyama, T., Kawasaki, K., Koga, A. and Taguchi, S. (1990) The Hishikari gold deposit high-grade epithermal veins in Quaternary volcanics, southern Kyushu,... 

Nagayama, T. (1992) The precipitation sequence of the Hishikari vein deposits, Kyushu, Japan. Unpub. Masters Thesis, U. Tokyo. 

Fig. 2.36. Tectonic setting of Kyushu, Japan, showing location of (north) Hishikari and Nansatsu (south) deposits in Kirishima arc. Triangle volcanoes younger than Middle Pleistocene stipple accretionary prism of Cretaceous and Tertiary age W-B zone isobath of deep Wadati-Benioff seismic zone MTL Median Tectonic Line BTL Butsuzo Tectonic Line K-P Ridge Kyushu-Palau Ridge (Mitchell and Leach, 1991).

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