HR: 14:25h
AN: V12G-04    [PDF]
TI: Diffuse Rift Zones: Subaerial and Submarine Satellite Vents at Wolf Volcano, Galapagos
AU: * Geist, D
EM: dgeist@uidaho.edu
AF: University of Idaho, Geology, Moscow, ID 83843 United States
AU: Naumann, T
EM: aftrn@uaa.alaska.edu
AF: University of Alaska, Geology, Anchorage, AK 99508 United States
AU: Standish, J
EM: jstandish@whoi.edu
AF: WHOI, Woods Hole Rd., Woods Hole, MA 02543 United States
AU: Harpp, K
EM: kharpp@mail.colgate.edu
AF: Colgate University, Geology, Hamilton, NY 13346 United States
AU: Kurz, M
EM: mkurz@whoi.edu
AF: WHOI, Woods Hole Rd., Woods Hole, MA 02543 United States
AU: Fornari, D
EM: dfornari@whoi.edu
AF: WHOI, Woods Hole Rd., Woods Hole, MA 02543 United States
AB: Wolf Volcano is one of the type-locality Galapagos shields, characterized by steep upper slopes, circumferential fissures near the summit, and a large and deep caldera. Fissures on the flanks of the volcano are radially distributed. Although the radial vents are concentrated in the northwest, northeast, and southern sectors of the volcano, the individual fissures are not aligned in sharp rift zones. Our preferred interpretation is that instead of being classic volcanic rifts, sectors of the volcano are absent vents, owing to gravitational stresses exerted by the caldera walls, neighboring volcanoes, and unusually steep slopes. The lack of vents in these areas concentrates vents in other sectors of the volcano. In contrast, bathymetry and sidescan sonar reveal that submarine Wolf has two volcanic rifts, one to the northwest and another that extends to Roca Redonda volcano. These submarine rifts are marked by linear alignments of vents and fissures and have produced young unsedimented lava. The submarine lavas are compositionally identical to those erupted from the subaerial part of the volcano, indicating that they intrude laterally from the subcaldera magma chamber. All of the lavas erupted from the volcano are similar in composition, indicating thermal and chemical buffering of the magma in a well-mixed, steady-state system. Wolf lavas are unusual in that their isotopic composition is indistinguishable from that of depleted MORB erupted from the nearby Galapagos Spreading Center. Their trace element concentrations, however, are nearly that of E-MORB. Thus, we believe that Wolf magmas are produced by low degrees of melting of nearly pure asthenosphere, either from the margins of or entrained within the Galapagos plume.
DE: 1025 Composition of the mantle
DE: 3640 Igneous petrology
DE: 8434 Magma migration
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting