GSA Annual Meeting in Seattle, Washington, USA - 2017

Paper No. 47-6
Presentation Time: 4:00 PM


ZOU, Haibo, Department of Geosciences, Auburn University, Auburn, AL 36849, FAN, Qi-Cheng, Institute of Geology, Chinese Earthquake Administration, Beijing, 100029, China, ZHANG, Hongfu, State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China and SCHMITT, Axel K., Earth and Space Sciences, University of California, Los Angeles, CA 90095,

Recently, the Changbai (or Baitoushan, Paektu) volcano located on the border of China and North Korea has drawn much attention as a result of its large climactic caldera-forming eruption 1000 years (1 ka) ago and the recent detection of swarms of small tremors at the volcano between 2002 and 2006. In addition to the 1-ka eruption of 100 km3 of comendite ignimbrite and pumice, the Changbai volcano also erupted moderate–volume pre-caldera comendite lava at ~4 ka and small-volume post-caldera trachyte ignimbrite at ~0.3 ka. We report uranium-series ages of zircons from these 3 eruptions, in order to investigate potential genetic relationships of these eruptions and their magma residence time scales. Zircon isochron ages are 12.2±1.1 ka (2σ) for the 4-ka pre-caldera comendite lava and 12.2±1.7 ka for the 1 -ka syn-caldera comendite materials. In contrast, zircons from the 0.3-ka post-caldera trachyte ignimbrite exhibit 3 respective peaks at 2.6±1.8 ka, 130±10 ka and >230 ka. The indistinguishable zircon ages for the 4-ka pre-caldera eruption of comendite lava and the 1-ka syn-caldera explosive eruption suggest that the 4-ka lava provides an early sampling of a much larger magma body at depth and thus serves as a petrologic early-warning signal. Calculated magma temperatures indicate that the 4-ka lava may represent the lowest-temperature magma in the roof zone of a thermally zoned magma chamber that usually escapes first. The distinctive multi-modal zircon age distributions of the 0.3-ka trachytic eruption, however, reveal that this post-caldera eruption tapped a different magma body. Our results also indicate very short zircon and magma residence times for the Changbai volcano (8 kyr for the 4-ka eruption, 11-12 kyr for the 1-ka eruption and 2.3 kyr for the 0.3-ka eruption).