Open AccessAxial high topography and partial melt in the crust and mantle beneath the western Galápagos Spreading Center
Author(s) -
Blacic Tanya M.,
Ito Garrett,
Shah Anjana K.,
Canales Juan Pablo,
Lin Jian
Publication year - 2008
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2008gc002100
Subject(s) - geology , mantle (geology) , crust , partial melting , lithosphere , upwelling , seafloor spreading , buoyancy , oceanic crust , petrology , mid ocean ridge , hydrothermal circulation , geophysics , volcano , asthenosphere , mantle wedge , volcanism , seismology , subduction , tectonics , oceanography , physics , quantum mechanics
The hot spot‐influenced western Galápagos Spreading Center (GSC) has an axial topographic high that reaches heights of ∼700 m relative to seafloor depth ∼25 km from the axis. We investigate the cause of the unusual size of the axial high using a model that determines the flexural response to loads resulting from the thermal and magmatic structure of the lithosphere. The thermal structure simulated is appropriate for large amounts of cooling by hydrothermal circulation, which tends to minimize the amount of partial melt needed to explain the axial topography. Nonetheless, results reveal that the large axial high near 92°W requires that either the crust below the magma lens contains >35% partial melt or that 20% melt is present in the lower crust and at least 3% in the mantle within a narrow column (<∼10 km wide) extending to depths of 45–65 km. Because melt fractions >35% in the crust are considered unreasonable, it is likely that much of the axial high region of the GSC is underlain by a narrow region of partially molten mantle of widths approaching those imaged seismically beneath the East Pacific Rise. A narrow zone of mantle upwelling and melting, driven largely by melt buoyancy, is a plausible explanation.