Contributions to Mineralogy and Petrology Mechanisms driving polymagmatic activity at a monogenetic volcano, Udo, Jeju Island, South Korea Marco Brenna 1 * Shane J. Cronin 1 Ian E. M. Smith 2 Young Kwan Sohn 3 Karoly Németh 1 1 Volcanic Risk Solutions, Massey University, Palmerston North, New Zealand 2 School of Geography, Geology and Environmental Science, The University of Auckland, Auckland, New Zealand 3 Department of Earth & Environmental Science, Gyeongsang National University, Jinju, South Korea Corresponding author: M.Brenna@massey.ac.nz, Tel: 0064 6 356 9099, Fax: 0064 6 350 5632