Zircon U-Pb Ages of Ohno Volcanic Rocks in eastern Kyushu

Hironao Shinjoe, Yuji Orihashi
2017 Chishitsugaku zasshi  
The Ohno Volcanic Rocks in eastern Kyusyu occur at the western tip of the Setouchi Volcanic Rocks. Previously reported K-Ar ages of the Ohno Volcanic Rocks range from . to . Ma. Here we present the results of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) zircon U-Pb analyses of three felsic rocks from the Ohno Volcanic Rocks. We obtained mean U-Pb ages as follows: . . Ma ( σ) for the Shiraiwasan pyroclastic flow deposit at the lowermost horizon within the sequence, . .
more » ... Ma for the Koguraki Tuff, and . . Ma for the Miyakeyama pyroclastic flow deposit at the uppermost horizon within the sequence. Our results indicate that the Ohno Volcanic Rocks, except for the high-Mg andesite found only as dikes, were formed over a shorter period than previously considered (ca. m.y.).
doi:10.5575/geosoc.2017.0003 fatcat:vgbels3wdngahmpljnxadq7noa