Ra/Th ages of sanidine in young trachytes erupted at Changbaishan Volcano, China
Abstract
Accurately dating Holocene volcanic rocks poses many challenges but is critical to assessing the magmatic evolution and hazard risks of highly active volcanoes. Here, Ra/Th isotopes are used to determine crystallization ages of sanidine from trachytes recently erupted at Changbaishan volcano, best known for its destructive "Millennium Eruption" at 946 CE. To determine Ra/Th crystallization ages, the partition coefficient of radium (DRa) in sanidine has to be known or accurately estimated. We employ the lattice strain model (Blundy and Wood, 1994) to predict DRa and DRa/DBa that yields ages that are consistent with historical eruption dates at Changbaishan and that allow for 100-500 years of crystal residence prior to eruption. Deduced 226Ra/230Th sanidine ages are progressively younger in trachytes erupted at 946, 1668, and 1903 CE. These ages confirm young sanidine-hosting eruptions that post-date Millennium Eruption activity at 946 CE and indicate the likely continued presence of explosive trachytic magma residing under the edifice.
- Publication:
-
Journal of Volcanology and Geothermal Research
- Pub Date:
- April 2019
- DOI:
- 10.1016/j.jvolgeores.2019.02.006
- Bibcode:
- 2019JVGR..374..226R
- Keywords:
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- Ra/Th dating;
- Holocene geochronology;
- Holocene volcanism;
- Crystal residence;
- Changbaishan