The gold mineralization styles at the Harutomi Project are similar to those described within the near-by Fujimi and Onne Project areas, and are classified as rift-related, low-sulfidation epithermal. Mineralization is typically associated with quartz-chalcedony-adularia-sericite±calcite in silicified and veined- or brecciated-structures. The Harutomi veins comprise banded chalcedonic to microcrystalline quartz, which contain fine-grained sulfide mineral bands (‘ginguro’), pyrite, sphalerite, chalcopyrite, cinnabar, manganese oxide and free gold. Gangue minerals are quartz, calcite, kaolinite, chlorite, adularia and montmorillonite. Grey chalcedonic quartz with Ag-rich ginguro bands are common in the Shikami vein lodes that strike N80°E to N60°W and dip steeply towards the north and south. In contrast, calcite is dominant in the western lodes, which commonly strike northeasterly and dip steeply towards the northwest. Host rocks consist of Miocene andesitic tuff and a quartz diorite stock that are strongly silicified adjacent to the veins and chlorite-clay altered in more distal settings.

Historical mapping indicates there are at least ten known gold bearing quartz veins¹ and/or mineralized outcrops over a 900 m (north-south) by 600 m (east-west) zone with identified strike lengths that range from 90 to 500 m and vertical extents that range from 60 to 140 m (Table 1). The Shikami vein No. 5, one of the largest lodes, has a recorded average thickness of 2.1 m, with segments that reach up to 10 m wide. Ore-shoot lengths in the Shikami vein system range from 4 to 57m long, with average assay values reaching up to 15.8 g/t Au over a width of 0.95 m (note raw analytical data upon which published gold-silver values are based are not published) ¹.

Table 1.  Summary of the Harutomi veins.

*NDA    No data available

Quartz vein swarms within the central western portions of the Harutomi Project area.