HR: 0800h
AN: V21D-0633    [Abstracts]
TI: Structural Morphology and Backarc Tectonic Imprint on Submarine Volcano Construction and Destruction, Central Kermadec arc (35° - 30°S), SW Pacific.
AU: Campbell, M E
EM: ellecampbell@hotmail.com
AF: Department of Geology, University of Auckland, Private Bag 92019, Auckland, none New Zealand
AU: * Rowland, J V
EM: j.rowland@auckland.ac.nz
AF: Department of Geology, University of Auckland, Private Bag 92019, Auckland, none New Zealand
AU: Wright, I C
V21D-0633 AF: National Institute of Water & Atmospheric Research, Private Bag 14901, Wellington, none New Zealand
AU: Smith, I E
V21D-0633 AF: Department of Geology, University of Auckland, Private Bag 92019, Auckland, none New Zealand
AB: Recent investigations aimed at illuminating the interplay between magmatic and tectonic processes have focused largely on continental rifts and oceanic ridges. In comparison, such work for active arc systems, where rifting is proximal, is less advanced, certainly for the case of submarine arcs. We present a detailed structural and volcanic morphological analysis of high-resolution multibeam data of central Kermadec arc volcanoes that clearly demonstrate the control of backarc tectonism on the evolution of the arc front. Of the 11 areas investigated, Macauley, Kuiwai and Brothers illustrate the range in edifice types (caldera, stratovolcano, satellite cones) and the influence of oblique backarc rifting on edifice construction and destruction. Fabric-parallel volcanic lineaments (striking 030°-060°) include volcanic ridges ± cones and aligned cones ± faults. These features predominate outside areas of significant edifice construction, though they may also occur on the flanks of major volcanoes (e.g. Kuiwai). We infer control by dike intrusion parallel to the structural fabric of the rift. In contrast, major edifices are not clearly related to fabric-parallel structures, though they are in places intersected by them. Lineaments associated with major edifices have variable orientations, oblique and orthogonal to the predominant rift fabric. Magmatic intrusion associated with major volcanic centres may perturb the regional stress field, providing a plausible explanation for this structural variability. We suggest that the presence of major arc edifices provides, through thermal weakening, efficient transfer zones for the accommodation of extensional strain within the mechanically segmented upper crust. However, the lack of discrete transfer faults together with the prevalence of dike-controlled features indicates that this is achieved through magmatic rather than purely mechanical processes. Volcanic ridges, aligned cones and lineaments parallel to the rift fabric bound regions of sector collapse (vertical drops > 1500m); edifice destruction is in part controlled by faulting and dike intrusion.
DE: 3001 Back-arc basin processes
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 3075 Submarine tectonics and volcanism
DE: 8178 Tectonics and magmatism
DE: 8185 Volcanic arcs
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005