Promising Geothermal Resources in the Neogene Volcanitectonic Depressions Along the Volcanic Front of Northern Honshu, Japan

Abstract

In Japan, the Quaternary volcanic areas have been the main target of prospecting for geothermal reservoir, because of appearance of meny geothermal ·manifestations on surface. The late Miocene to Pliocene sedimentary basins in a specific terrane are also candidated as deep and large geothermal reservoirs. Really the Sanzugawa basin, Akita Prefecture, is very promising as a result of prospecting by the Agent of Japan and a private company. The prospecting for geothermal reservoirs in these Neogene basins, however, is more difficult than those in Quaternary volcanic areas, as the former may be deeply seated and bring few geothermal manifestations on surface. In this paper, the writers describe the outline of surveyed volcanotectonic depressions( VTD) of Neogene age which are distributed along the volcanic front of northern Honshu, Japan. They also evaluate the possibility of each VTD as a geothermal reservoir in comparison with active geothermal areas in Quaternary calderas.