K-Ar age and chemistry of volcanic rocks dredged from Jingu Seamount, Emperor Seamount chain.

Abstract

40Ar/39Ar incremental heating experiments on three samples dredged from Jingu Seamount indicate that Jingu is 55.4 +- 0.9 m.y. old - older than the Hawaiian-Emperor bend and younger than the two dated Emperor Seamounts to the north. Major-oxide chemistry and petrography show that the samples are similar to hawaiite and mugearites from the Hawaiian Island. By analogy with Hawaiian alkalic volcanic rocks, groundmass plagioclase compositions (An40-47) indicate that the three Jingu samples are probably mugearites. These results suggest that Jingu is a Hawaiian-type volcano and that the Emperor volcanoes become progressively older from south to north, as predicted by the hot-spot hypthesis. -Authors