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History of Volcanic Activity, Magma Evolution and Eruptive Mechanisms of the Changbai Volcanic Province

FAN Qi-cheng1, SUI Jian-li2, WANG Tuan-hua1, LI Ni1, SUN Qian1   

  1. 1. Institute of Geology, China Seismological Bureau, Beijing 100029, China;2. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
  • Received:2007-06-20 Revised:2007-06-20 Online:2007-06-20 Published:2007-06-20

Abstract: Volcanic rocks cover large area of the Changbai Mountain Range, Northeast China. As the largest Quaternary volcanic province in China, the Changbaishan volcanic province can be divided into four parts, including the Tianchi volcanic province (TVP), the Wangtian,e volcanic province (WVP), the Longang volcanic provicne (LVP) and the Tumen River volcanic province (TRVP). Volcanic activity in TRVP and WVP began in Pliocene, dominated in Pliocene-Mid-Pleistocene (5.5 ~0.19 Ma) and Pliocene-Early-Pleistocene (4.77 ~2.12 Ma), respectively. TVP and LVP activated in Quaternary, from Early-Pleistocene to Holocene. The volcanic activities and products in these four volcanic provinces are different. In TRPV, it is tholeiite from flood eruption; while in TVP, WVP and LVP, the volcanic eruptions formed lava shields of potassic trachybasalt in the early stage, and then different magma evolution paths occurred. In TVP and WVP, potassic trachyebasalt emplaced into the crustal chamber, stored and experienced strong fractional crystallization. The evolved magma was mainly alkaline rhyolitic and pantelleritic, highly enriched in silicon, alkalies and volatiles. Its eruptions formed two huge stratovolcanoes. Activity of the potassic trachybasalt beneath the TVP controlled two kinds of eruptions: the millennium eruption of Tiachi Volcano, which was triggered by refluxing of the mantle trachybasalt magma to the crustal chamber and subsequent magma mixing; and the centric eruption of the potassic trachybasalt, which formed the big cone of Tianchi Volcano and many other small cones in the vicinity. In the LVP, on the lava shield occurred over 160 volcanic cones, The rock type of these eruptions was unique potassic trachybasalt. Geochemical data of trace elements and Sr-Nd-Pb isotopes indicate that the mantle sources were mixtures of asthenosphere and enriched lithospheric mantle. As to the LVP, the volcanics were dominated by depleted mantle of asthenosphere, and with less entertainment of enriched lithosphere. After the late Pliocene, geodynamics of the Changbai Mountain Range was controlled by the subduction of the western Pacific Plate and the extension of the Northeastern Asian back arc. In this special active continental margin, large scale of potassic trachybasalt activity occurred again.