Plumbotectonics of Japan: Some Evidence for a Rejuvenated Craton

Abstract

Lead isotopic data of high precision on some epigenetic hydrothermal deposits-recently shown to be in terrains containing Proterozoic cobbles-confirm previous studies that much of Japan is primarily a continental feature. Further, the low values of ²⁰⁶Pb/ ²⁰⁴Pb accompanying high values of ²⁰⁸Pb/ ²⁰⁴Pb in Tertiary (kuroko) deposits of the submarine volcanic exhalative type and epigenetic hydrothermal deposits of Japan are pointing towards the presence of a rejuvenated craton, perhaps as old as 1000 m.y. or greater in age. In contrast, previously published lead isotope evidence on pre-Cenozoic stratiform sulfide deposits of Japan (so-called Besshitype deposits) tend to show a more oceanic mantle character for a part of Japan. Japan, therefore, appears to have a full spectrum of plumbotectonic environments.