The status of lead isotope studies of Japan

A brief review of lead isotope studies in Japan is made with particular reference to ''kuroko'' ore deposits. The lead isotopic evidence favors a continental crustal derivation for the lead in these deposits with possibly a component from subducted pelagic sediments. Supporting information is presented from the nature of the ''green tuff'' belt (abundant dacite and sparse basalt) and lead-rich nature of the ore. The question remains, however, whether the metals are derived from the immediate volcanics or the underlying volcanics or basement. A plan is briefly presented of lead isotope investigations to determine how important the ''green tuff'' is as a source of ore relative to the underlying volcanics or basement as accessed by deep penetration of ocean-water fluids along transverse fault and fracture zones. (auth.)