On the Mode of Acidic Volcanism in the Miocene in the Region of Hanaoka-Kuroko Belt

Abstract

The Hanaoka area, which is one of the most prosperous "Kuroko" field in Japan, is widely covered by acidic volcanic rocks of the Miocene.
The authors summarized the nature and occurrences of all stratigraphical units of the volcanic rocks and discussed the modes of eruption and emplacement under subaqueous conditions infferred by many paleogeographical analyses.
Generally, two cycles of the volcanism are recognised (as for the Hanaoka formation). They are shown in Figure 9. If the exhalative sedimentary hypothesis was adopted for the origin of "Kuroko" deposits, it appears that the mineralization occurred at the last stage of the second cycle.