78. Kusano, Y. Hayashi, M., Adachi, Y., Umino, S. and Miyashita, S, 2014. Evolution of volcanism and magmatism during initial arc stage: constraints on the tectonic setting of the Oman Ophiolite. In Rollinson, H.R., Searle, M.P., Abbasi, I.A., Al-Lazki, A. and Al Kindi, M.H. (eds.), Tectonic Evolution of the Oman Mountains. Geological Society, London, Special Publications, 392, 177-193, http://dx.doi.org/10.1144/SP392.9

Based on the detailed stratigraphy, petrology and geochemistry, an initial arc magmatism of the Oman Ophiolite consisting of tholeiitic lavas followed by boninite flows and tephras is comprehended atin Wadi Bidi area, northernin the Oman Mountainsophiolite. An 1110 m thick V2 sequence is divided into the lower 970 m (LV2) and upper 140 m (UV2) thick subsequences by a 1.0 m thick sedimentary layer. Pahoehoe flows dominate in the lower part of the LV2, while the upper part consists mainly of sheet flows with intervened few pelagic sediments and a cylindrical plug. In addition to the presence of feeder conduit, the flow-dominant lithofacies with a few thin sedimentary interbeds in the LV2 indicates that the study area was the center of a volcano grown in a short period. The UV2 is composed of boninite sheet flows overlain by a 2.0 m thick pyroclastic fall deposit. A small amount of boninite lavas at the end of the V2 sequence overlain by thick pelagic sediments suggests that the subduction related arc volcanism was short lived and terminated long before the ophiolite obduction.

Keyword: Oman Ophiolite, boninite, V2, arc tholeiite, subduction initiation
キーワード: オマーンオフィオライト，無人岩，V2，島弧ソレアイト，沈み込み帯発生