Electromagnetic constraints on a melt region beneath the central Mariana back-arc spreading ridge
Evans, Rob L.
Chave, Alan D.
MetadataShow full item record
KeywordBack-arc spreading ridge; Central Mariana Trough; Electrical resistivity structure; Upper mantle melting
An electrical resistivity profile across the central Mariana subduction system shows high resistivity in the upper mantle beneath the back-arc spreading ridge where melt might be expected to exist. Although seismic data are equivocal on the extent of a possible melt region, the question arises as to why a 2-D magnetotelluric (MT) survey apparently failed to image any melt. We have run forward models and inversions that test possible 3-D melt geometries that are consistent with the MT data and results of other studies from the region, and that we use to place upper bounds on the possible extent of 3-D melt region beneath the spreading center. Our study suggests that the largest melt region that was not directly imaged by the 2-D MT data, but that is compatible with the observations as well as the likely effects of melt focusing, has a 3-D shape on a ridge-segment scale focused toward the spreading center and a resistivity of 100 Ω-m that corresponds to ∼0.1–∼1% interconnected silicate melt embedded in a background resistivity of ∼500 Ω-m. In contrast to the superfast spreading southern East Pacific Rise, the 3-D melt region suggests that buoyant mantle upwelling on a ridge-segment scale is the dominant process beneath the slow-spreading central Mariana back-arc. A final test considers whether the inability to image a 3-D melt region was a result of the 2-D survey geometry. The result reveals that the 2-D transect completed is useful to elucidate a broad range of 3-D melt bodies.
Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 13 (2012): Q10017, doi:10.1029/2012GC004326.
Suggested CitationArticle: Matsuno, Tetsuo, Evans, Rob L., Seama, Nobukazu, Chave, Alan D., "Electromagnetic constraints on a melt region beneath the central Mariana back-arc spreading ridge", Geochemistry Geophysics Geosystems 13 (2012): Q10017, DOI:10.1029/2012GC004326, https://hdl.handle.net/1912/5604
Showing items related by title, author, creator and subject.
Composition of hydrothermal fluids and mineralogy of associated chimney material on the East Scotia Ridge back-arc spreading centre James, Rachael H.; Green, Darryl R. H.; Stock, Michael J.; Alker, Belinda J.; Banerjee, Neil R.; Cole, Catherine; German, Christopher R.; Huvenne, Veerle A. I.; Powell, Alexandra M.; Connelly, Douglas P. (Elsevier, 2014-05-06)The East Scotia Ridge is an active back-arc spreading centre located to the west of the South Sandwich island arc in the Southern Ocean. Initial exploration of the ridge by deep-tow surveys provided the first evidence for ...
Submarine back-arc lava with arc signature : Fonualei Spreading Center, northeast Lau Basin, Tonga Keller, Nicole S.; Arculus, Richard J.; Hermann, Jörg; Richards, Simon (American Geophysical Union, 2008-08-30)We present major, volatile, and trace elements for quenched glasses from the Fonualei Spreading Center, a nascent spreading system situated very close to the Tofua Volcanic Arc (20 km at the closest), in the northeast Lau ...
Faulting and volcanism in the axial valley of the slow-spreading center of the Mariana back arc basin from Wadatsumi side-scan sonar images Deschamps, Anne; Fujiwara, Toshiya; Asada, Miho; Montesi, Laurent G. J.; Gente, Pascal (American Geophysical Union, 2005-05-13)We analyzed in detail the geology of the median valley floor of the Mariana Basin slow-spreading ridge using sea surface geophysical data and a high-resolution deep-tow side-scan sonar survey over one spreading segment. ...