R6: Plutonic rocks, volcanic rocks and subduction factory

[R6-01] Shoshonitic-Mugearitic Plateau Lava from Harguit/Us-Tolgoi volcano, Khangai Mountains, Central Mongolia

*Tsukasa Ohba¹, Takashi Hoshide¹, Takumi Imura¹, MunkhErdene Natsagdorj¹ (1. Akita Univ. IRS.)

Keywords:Mongolian Quaternary volcano, Continental Alkaline Lava Plateau

Geology and petrology of Harguit-Us Tolgoi volcano, Mongolia, were studied. The northern lava was derived from UsTolgoi small shield and the southern lava from Harguit cone. Northern lava and UsTolgoi are composed of mugerite, whereas the rock of southern lava is shoshonite. The pyroclasts of Harguit cone broadly range from olivine basanite/K trachybasalt to cpx shoshonite. The variation of southern lava and Harguit cone can be accounted for by crystallization from the least differentiated basanite whereas the mugearitic northern lava was derived from an independent magma system.