Geology and Mineralisation
The gold mineralization style at Tenryu is classified as rift-related, low-sulfidation epithermal. Mineralization is typically associated with quartz-chalcedony-adularia-sericite±calcite fill in silicified and veined- or brecciated-structures, including dark sulfidic material, termed ginguro bands. Veins display crustiform-colloform banding, cockade, lattice blades (quartz pseudomorphs after calcite, indicative of fluid boiling zones) and other quartz textures typical of high-level epithermal systems. Wall-rock alteration comprises a silicified core and peripheral mixed quartz-illite-smectite (argillic) assemblages.
Tenryu is hosted in similar volcanic stratigraphy to the historic mine workings located within Japan Gold’s Aibetsu Project, the most prominent of which, Tokusei, produced 38,580 ounces of gold and 472,620 ounces of silver between 1930-1942¹.
Mapping on the 1:50,000 scale Japanese government geological map shows three parallel northeast trending altered / mineralized zones at Tenryu, over a 2.5 by 2 km area centred on the historic Tenryu mine workings.