Ring Structures, Resurgent Cauldron, and Ore Deposits in the Hokuroku Volcanic Field, Northern Akita, Japan*

Abstract

Ring dikes, normal faults, central uplift, and slumping structure are considered to be the key factors of the submarine resurgent cauldron. In the east Odate area, there occurs a ring distribution of post-Kuroko dacites and epithermal ore deposits around the central Otaki quartz diorite. Vein-type and Kuroko deposits are distributed almost along the half of the ring. There also occur submarine slumping structures. The estimated sub- surface structure indicates the central uplifting and marginal depression in the inside of ring dacites. Those phe- nomena are interpreted as the fossil submarine resurgent cauldron in the Miocene age with the intermediate scale of about 8 kilometers in horizontal diameter, associated with the genesis of Kuroko deposits and epithermal veins. A structural model of the relationship between the processes of a cauldron formation and ore genesis is proposed.