HR: 0800h
AN: V51C-1491    [Abstracts]
TI: Petrology of Newly Discovered Submarine Volcanoes From the Kermadec-Tonga arc: Initial Results
AU: * Graham, I J
EM: i.graham@gns.cri.nz
AF: GNS, PO Box 31-312 , Lower Hutt, 04 New Zealand
AU: Smith, I E
EM: ie.smith@auckland.zc.nz
AF: Auckland University, Private bag 92019, Auckland, 09 New Zealand
AU: Arculus, R J
EM: richard.arculus@anu.edu.au
AF: Australian National University, Dept Earth & Marine Sciences, Canberra, 0200 Australia
AU: McDonnell, S J
EM: s.j.mcdonnell@mars.ucc.ie
AF: UCC, Donovans Road, Cork, 01 Ireland
AU: de Ronde, C E
EM: cornel.deronde@gns.cri.nz
AF: GNS, PO Box 31-312 , Lower Hutt, 04 New Zealand
AU: Wright, I C
EM: i.wright@niwa.cri.nz
AF: NIWA, PO Box 14901, Wellington, 04 New Zealand
AB: The NZAPLUME III research cruise to the northern Kermadec - southern Tonga arc during September-October 2004 mapped and dredge-sampled eight newly discovered volcanic centres along the arc-front, including Monowai, now known to have a caldera complex immediately to the north of the previously mapped cone. These centres, which typically include one or more calderas with multiple associated volcanic cones, have an average spacing of 47 km, slightly greater than the average spacing of 41 km for the entire Kermadec arc (i.e., from Whakatane in the south to Monowai to the north). All of the newly discovered volcanic centres show evidence of hydrothermal venting and, in the case of Monowai, recent eruptive activity. The dredged lavas have calc-alkaline compositions ranging from high-alumina basalt to rhyolite, confirming the occurrence of evolved lava compositions associated with caldera structures along the entire Kermadec arc. Three of the volcanic centres exhibit the full compositional range from basalt to rhyolite, three are basalt-andesite, and the remaining two entirely rhyolitic. In contrast to published results for the southern Kermadec arc, there is no evidence for compositional bimodality, with the data set containing sub-equal proportions of basalt, basaltic andesite, andesite, dacite, rhyodacite and rhyolite. Despite the variety of volcanic edifices sampled, all of the volcanic centres yield tight geochemical correlations for major and trace elements, which are interpreted to indicate simple mixing or fractionation processes. There is a suggestion, yet to be fully established with trace element or isotopic modelling, that three of the four southern-most centres, spanning some 200 km of arc-front, are genetically related.
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 4832 Hydrothermal systems (0450, 1034, 3017, 3616, 8135, 8424)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005