HR: 1340h
AN: V23A-1232    [Abstracts]
TI: The Aeolian Volcanic Arc: New Insights From Subduction Zone Thermal Models and Mineral Solubility Scaling Relationships
AU: * Creamer, J
EM: jcreamer@umail.ucsb.edu
AF: Department of Earth Sciences, UC Santa Barbara, 1006 Webb Hall, Santa Barbara, CA 93106, United States
AU: van Keken, P
EM: keken@umich.edu
AF: Department of Geological Sciences, University of Michigan, 2534 CC Little Building 1100 North University Avenue, Ann Arbor, CO 48109-1005, United States
AU: Engdahl, E R
EM: engdahl@colorado.edu
AF: University of Colorado, Campus Box 390, Boulder, CA 80309, United States
AU: Spera, F J
EM: spera@geol.ucsb.edu
AF: Department of Earth Sciences, UC Santa Barbara, 1006 Webb Hall, Santa Barbara, CA 93106, United States
AU: Bohrson, W A
EM: bohrson@geology.cwu.edu
AF: Central Washington University, Department of Geological Sciences, Central Washington University, Ellensburg, WA 98926-7418, United States
AB: The Calabrian subduction zone, situated southeast of the Italian ‘boot' in the Ionian Sea, is the latest manifestation of African-Eurasian plate interaction. This plate interaction has been remarkably dynamic since the Mesozoic, hosting episodes of mountain belt and volcanic arc formation including, for example, the Alpine, Carpathian and Apennine orogenic belts and Hellanic and, most recently, Aeolian volcanic arcs. Subduction of cold oceanic lithosphere beneath Europe initiated around 80 Ma, and the last 30 Ma have been characterized by alternating episodes of rapid back-arc rifting and back-arc spreading (up to 6-8 cm/yr) mediated by dip-parallel and/or trench-parallel tears in the descending slab resulting from differential trench rollback (Wortel and Spakman 2000). Backarc extension effectively moved the plate boundary from the European continental margin in the north to the African continental margin in the south, creating the modern Western Mediterranean basins. The Tyrrhenian oceanic basin was opened during the latest episode of trench rollback, from 5-2 Ma, followed by initiation of the subduction-related Aeolian volcanism by 1.3 Ma (Beccaluva et al. 1982) and complete cessation of extension of the overriding plate around 0.8-0.5 Ma (Goes et al. 2004). The seven subaerial volcanoes of the Aeolian volcanic arc sit atop thin (16-30 km) continental crust, and collectively tap a heterogeneous mantle source. Slab geometry in the depth range of 150 to 500 km has been refined using the hypocenter relocation procedure of Engdahl et al 1998 for teleseismic events beneath the Tyrrhenian Sea, in conjunction with recent tomographic results. The thermal state of the Calabrian subduction zone at depths relevant to dehydration and magma genesis has been investigated using a 2-dimensional time-dependent thermal model of the descending slab and convecting mantle wedge based on seismic, geologic and geodetic observational data. Modeling methodology follows van Keken et al. 2002 and includes power-law olivine rheology and shear-heating scaled to fit forearc heat flow. The computed thermal model is used with a thermodynamically-based mineral solubility scaling relationship between fluid solute content and the relative permittivity of the fluid to infer the solute content of a slab-derived aqueous fluid existing in equilibrium with slab and mantle wedge mineralogy. The relative abundances of different solutes in slab-derived fluids are critical in determining the trace element characteristics of subduction zone magmas. Among some of the Aeolian arc volcanic centers, the recent (<30 ky) evolution in magma composition from calc-alkaline to high-potassium has been variably attributed to melting of distinct source regions, or the increasing abundance of aqueous fluids in a source region associated with a young/incipient arc. Our approach of thermal-field and solute content modeling can contribute to the resolution of this and other petrogenesis questions for Aeolian arc lavas.
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8410 Geochemical modeling (1009, 3610)
DE: 8413 Subduction zone processes (1031, 3060, 3613, 8170)
DE: 9335 Europe
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting