HR: 1340h
AN: V33A-1155    [Abstracts]
TI: A broad Galápagos hotspot melting anomaly and disturbance of the underlying core- mantle boundary: A natural laboratory for studying interaction between the core-mantle boundary and overlying lithosphere?
AU: * O'Connor, J M
EM: John.O.Connor@falw.vu.nl
AF: Department of Isotope Geochemistry, Vrije University Amsterdam, Amsterdam, 1081 HV, Netherlands
AU: Stoffers, P
EM: pst@gpi.uni-kiel.de
AF: Institute for Geosciences, Christian-Albrechts-University, Kiel, D-24118, Germany
AU: Wijbrans, J R
EM: Jan.Wijbrans@falw.vu.nl
AF: Department of Isotope Geochemistry, Vrije University Amsterdam, Amsterdam, 1081 HV, Netherlands
AU: Worthington, T J
EM: tw@gpi.uni-kiel.de
AF: Institute for Geosciences, Christian-Albrechts-University, Kiel, D-24118, Germany
AB: New evidence from direct isotopic dating of the oceanic hotspot record is suggesting that hotspot melting anomalies might be much broader than commonly inferred from the dimensions of individual seamount chains and aseismic ridges and their associated active `volcanic` hotspots. Such an inference is supported by recent thermo-chemical numerical modelling exploring scenarios where upwelling structures are more irregular in shape and behaviour compared to a classic thermal plume `head-tail` (e.g., Farnetani and Samuel, 2006). New age data from the Galápagos Volcanic Province suggest that it developed via the progression of broad regions of widespread, long-lived and possibly concurrent volcanism resulting from tectonic plate motion over a broad Galápagos hotspot melting anomaly (O'Connor et al., 2007). Seismic imaging of the core-mantle boundary under the Cocos plate shows a 100-km vertical step occurring in an otherwise flat D" shear velocity discontinuity (Thomas et al., 2004, Hutko et al., 2006, Kito et al., 2007). One possible explanation is that folding and piling of a cold subducted slab on reaching the core-mantle boundary might account for this lateral variation in terms of a post-perovskite phase change (Thomas et al., 2004, Hutko et al., 2006, Kito et al., 2007). Low velocities inferred at the edge of this proposed slab material may result from the lateral displacement of a thin hot thermal boundary layer leading to upwelling at the tip of the slab, (Thomas et al., 2004, Hutko et al., 2006, Kito et al., 2007), which in turn might possible be connected to our inferred broad hotspot melting anomaly. The combination of the recent imaging of an anomaly at the D"-discontinuity and the inference of a broad overlying Galápagos hotspot melting anomaly suggest that the Galápagos region is an ideal natural-laboratory for studying the possibility of interaction between the core-mantle boundary and overlying lithosphere.
DE: 1033 Intra-plate processes (3615, 8415)
DE: 1213 Earth's interior: dynamics (1507, 7207, 7208, 8115, 8120)
DE: 1821 Floods
DE: 3037 Oceanic hotspots and intraplate volcanism
DE: 8137 Hotspots, large igneous provinces, and flood basalt volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting