Zircon U-Pb Ages of Ohno Volcanic Rocks in eastern Kyushu
九州東部大野火山岩類のジルコンU-Pb年代

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