Reconstruction of Icelanditic dacite submarine volcanic edifices distributed along the Tanakura Fault

Abstract

Miocene syn-rift sediments in strike-slip basins along the Tanakura Fault were deposited during major strike-slip movement coeval with the opening of the Japan Sea. Interstratified with these sediments is the Nantaisan Volcanic Breccia, an Icelandic-type volcanic rock related to the opening of the Japan Sea. In this study, the genesis and development of a submarine volcano, termed the Nantaisan volcano, has been reconstructed using facies analyses of submarine volcanic rocks of the Nantaisan Volcanic Breccia. The Nantaisan volcano is a composite volcano that consists mainly of the products of effusive eruptions. The orientations of quartz veins in the breccia record NW-SE to NNW-SSE transtension related to strike-slip movement on the Tanakura Fault. The Nantaisan submarine volcano most likely formed due to rapid upwelling of Icelandic-type magma that formed by partial melting of lower crust due to transtension along the Tanakura Fault.