HR: 17:15h
AN: V52G-06    [PDF]
TI: Structural Control of the Ubinas-Huaynaputina-Ticsani System: A Large, Young Silicic Magmatic System in Southern Peru
AU: * Lavallee, Y
EM: yanlavallee@hotmail.com
AF: Department of Space Studies, University of North Dakota, 4149 Campus Road Clifford Hall, Grand Forks, ND 58202 United States
AU: de Silva, S L
EM: desilva@space.edu
AF: Department of Space Studies, University of North Dakota, 4149 Campus Road Clifford Hall, Grand Forks, ND 58202 United States
AU: Salas, G
EM: guidovolcan@yahoo.com
AF: Department of Space Studies, University of North Dakota, 4149 Campus Road Clifford Hall, Grand Forks, ND 58202 United States
AU: Byrnes, J
EM: byrnes@space.edu
AF: Department of Space Studies, University of North Dakota, 4149 Campus Road Clifford Hall, Grand Forks, ND 58202 United States
AB: The location of magma reservoirs and volcanic centers are commonly controlled by tectonic structures (e.g., Hutton, 1989; Gibbons and Moreno, 2002). In the Central Volcanic Zone, southern Peru, volcanism is mainly associated with the major NNW-SSE sinistral strike slip fault systems underlying the main volcanic arc. However, a group of related silicic volcanoes was recently discovered which crop out beyond the arc; the Ubinas-Huaynaputina-Ticsani system (UHTS). Characterizing its dimension and tectonic influences are crucial in order to evaluate corresponding volcanic hazards. Potentially active fault systems as well as major tectonic features in and around the UHTS were mapped and the structural framework was elucidated. The UHTS is located within a north to south extensional domain housing three fault systems: (1) the arc related NNW-SSE fault system, intersected by (2) a unique N-S en echelon strike slip fault system, and (3) a minor W-E fault system. Identification of confined Cretaceous volcanics known as the Matalaque formation indicated the presence of a narrow graben that developed on the western side of the N-S fault system. Interestingly all volcanic centers are positioned at the intersection of the NNW-SSE faults with the N-S faults. Seismic records revealed the concentration of seismicity around depths ranging between 20 and 33 km. The position of the UHTS is dictated by the intersection of the NNW-SSE and N-S major en echelon strike slip fault systems. We propose the role of the NNW-SSE fault as a deep pathway for magma ascent whereas the N-S strike-slip motion allowed the release of stress and deviation of magma, which scattered and ponded between adjacent NNW-SSE faults at ~30 km depths. Based on the vent distribution, we estimated the size of the silicic magma reservoir as approximately 40 x 60 km; this is a reasonable estimate since the withdrawal of a volume larger than 10 km$^{3}$ was not significant enough to produce an equivalent caldera collapse. We finally propose that the occurrence of five 33-km deep earthquakes about 45 km to the SSE of Ubinas, in the last 40 years, may indicate the progression of the next regional eruption. References: Gibbons, W., Moreno, T., 2002, Tectonomagmatism in continental arcs; evidence from the Sark arc complex. Tectonophysics 352, 185-201. Hutton, D.H.W., 1989, The role of regional tectonics in the emplacement mechanism of granites (Abstr.). 28th International Geological Congress, 2, 2.88-2.89.
DE: 8015 Local crustal structure
DE: 8035 Pluton emplacement
DE: 8499 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting