Potential for Porphyry Copper Mineralization Below the Kasuga Lithocap, Nansatsu District, Japan

Lithocaps consist of vuggy residual quartz and advanced argillic alteration formed at shallow depths and potentially related to porphyry copper‐bearing intrusions at depth, meaning that, conceptually, porphyry copper deposits may exist beneath the lithocap‐hosted Nansatsu‐type gold deposits. The Kasuga lithocap extends for about 5 km NE–SW by 2 km width; beyond the northeastern edge of this lithocap, there are contemporaneous epithermal gold‐quartz veins. A 1200‐m hole was drilled in 1999 beneath the main orebody at Kasuga but did not intersect porphyry copper mineralization. On the basis of detailed examination of the alteration pattern and paleothermal environment of the Kasuga area, a paleo high‐temperature zone appears to lie in a NE‐ward direction from the deep drilling site.