|Title:||U‐series zircon age constraints on the plumbing system and magma residence times of the Changbai volcano, China/North Korea border|
|Authors:||H. Zou, Q. Fan, H. Zhang, and A. K. Schmitt|
|Publication:||Lithos, v. 200–201, p. 169‐180.|
|Publish Date:||July 2014|
The Changbai (or Baitoushan, Paektu) volcano on the China/Korea border is best known for its climactic caldera‐forming eruption of 100 km3 of comendite materials 1000 years (1 ka) ago. The polygenetic Changbai volcano also erupted moderate‐volume pre‐caldera comendite lava at 4 ka and small‐volume post‐caldera trachyte ignimbrite at 0.3 ka. Here we report 238U‐230Th disequilibrium ages of zircons from lavas and ignimbrites of the pre‐caldera ( 4 ka), syn‐caldera (1 ka), and post‐caldera ( 0.3 ka) events. The zircon isochron ages are 12.2 ± 1.1 ka (2σ) for the 4−ka comendite lava and 12.2 ± 1.7 ka for the 1 ‐ka comendite ignimbrite. Zircons from the 0.3‐ka 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 caldera‐forming eruption of comendite pumice and ignimbrite suggest that the 4‐ka lava provides an early sampling of a much larger magma body at depth and thus serves as a kind of petrologic early‐warning signal. In addition, 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 and indicate that Changbai’s magmatic plumbing system had changed after the 1‐ka caldera‐forming climactic eruption. Our results suggest 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).