title: Arc-parallel flow in the mantle wedge beneath Costa Rica and Nicaragua.
abstract: Resolving flow geometry in the mantle wedge is central to understanding the thermal and chemical structure of subduction zones, subducting plate dehydration, and melting that leads to arc volcanism, which can threaten large populations and alter climate through gas and particle emission. Here we show that isotope geochemistry and seismic velocity anisotropy provide strong evidence for trench-parallel flow in the mantle wedge beneath Costa Rica and Nicaragua. This finding contradicts classical models, which predict trench-normal flow owing to the overlying wedge mantle being dragged downwards by the subducting plate. The isotopic signature of central Costa Rican volcanic rocks is not consistent with its derivation from the mantle wedge or eroded fore-arc complexes but instead from seamounts of the Galapagos hotspot track on the subducting Cocos plate. This isotopic signature decreases continuously from central Costa Rica to northwestern Nicaragua. As the age of the isotopic signature beneath Costa Rica can be constrained and its transport distance is known, minimum northwestward flow rates can be estimated (63-190 mm yr(-1)) and are comparable to the magnitude of subducting Cocos plate motion (approximately 85 mm yr(-1)). Trench-parallel flow needs to be taken into account in models evaluating thermal and chemical structure and melt generation in subduction zones.
authors.affiliation: SFB 574, University of Kiel, Wischhofstrasse 1-3, Kiel 24148, Germany. khoernle@ifm-geomar.de
authors.forename: Kaj
authors.initials: K
authors.lastname: Hoernle
authors.forename: David L
authors.initials: DL
authors.lastname: Abt
authors.forename: Karen M
authors.initials: KM
authors.lastname: Fischer
authors.forename: Holly
authors.initials: H
authors.lastname: Nichols
authors.forename: Folkmar
authors.initials: F
authors.lastname: Hauff
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Abers
authors.forename: Paul
authors.initials: P
authors.lastname: van den Bogaard
authors.forename: Ken
authors.initials: K
authors.lastname: Heydolph
authors.forename: Guillermo
authors.initials: G
authors.lastname: Alvarado
authors.forename: Marino
authors.initials: M
authors.lastname: Protti
authors.forename: Wilfried
authors.initials: W
authors.lastname: Strauch