Time scales of storage and recycling of crystal mush at Krafla Volcano, Iceland Kari M. Cooper1, Kenneth W.W. Sims2, John M. Eiler3, Neil Banerjee4 1Department of Earth and Planetary Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616. Phone: +1 530-754-8826; fax: +1 530-752-0951.
[email protected] 2Department of Geology and Geophysics, University of Wyoming, Laramie, WY 82701 3Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 4Department of Earth Sciences, Western University, London, ON N6A 5B7, CANADA keywords: Iceland; crystal mush; uranium-series disequilibria; oxygen isotopes; magmatic time scales Abstract Processes in upper-crustal magma reservoirs such as recharge, magma mixing, recycling of previously-crystallized material, and eruption, affect both the physical state and the chemical composition of magmas. A growing body of evidence shows that crystals in intermediate to silicic volcanic rocks preserve records of these processes that may be obscured due to mixing in the liquid fraction of magmas. Fewer studies have focused on crystals in basaltic lavas, but these show evidence for a more subtle, but still rich record of magmatic processes. We present new 238U-230Th-226Ra data for plagioclase, combined with d18O and trace-element measurements of the same crystal populations, from basalts erupted at Krafla Volcanic Center, Iceland. These data document the presence of multiple crystal populations within each sample, with chemical and oxygen-isotope heterogeneity at a variety of scales: within individual crystals, between crystals in a given population, between crystal populations within the same sample, and between crystals in lavas erupted from different vents during the same eruption.