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TitrePossible mechanism of mud volcanism at the prism-backstop contact in the western Mediterranean Ridge Accretionary Complex
AuteurKioka, A; Ashi, J; Sakaguchi, A; Sato, T; Muraoka, S; Yamaguchi, A; Hamamoto, H; Wang, K; Tokuyama, H
SourceMarine Geology vol. 363, 2015 p. 52-64, https://doi.org/10.1016/j.margeo.2015.01.014
Année2015
Séries alt.Secteur des sciences de la Terre, Contribution externe 20140139
ÉditeurElsevier
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1016/j.margeo.2015.01.014
Mediapapier; en ligne; numérique
Formatspdf
Lat/Long OENS 15.0000 35.0000 40.0000 30.0000
Sujetsvulcanologie; volcans de boue; pression; réflectance de la vitrinite; migration des fluides; caractéristiques sous-marines
Illustrationslocation maps; bathymetric profiles; 3-D models; photographs; histograms; graphs; diagrams
ProgrammeOuest du Canada, risque géoscience, Géoscience pour la sécurité publique
Résumé(disponible en anglais seulement)
The EasternMediterranean seafloor has numerousmud volcanoes,most ofwhich formawell-defined beltwithin the Mediterranean Ridge (MedRidge) accretionary complex. However, mud volcano fields in the western MedRidge are less well known as those in the central and eastern MedRidge. This study investigates material cycling and fluid migration within the westernMedRidge. We propose a possible ascent style of the ejecta forming the Médée-Hakuho Mud Volcano (MHMV) in the western MedRidge by applying the vitrinite reflectance technique to ejecta samples. First, we model the 2-D thermal structure in the western MedRidge, taking into account frictional heating on the plate interface, to help estimate the source depth of the MHMV ejecta. The result suggests an effective coefficient of friction of around 0.01, and a temperature of about 160 ± 15 °C along the plate interface at a distance of ~180 kmfromthe deformation front, the location of the seaward toe of the Aegean backstop. Second,we evaluate the source depth of theMHMV ejecta using vitrinite reflectance in conjunctionwith the modeled thermal structure. The results suggest that the ejecta matrix showing vitrinite reflectance values of ~0.6% was subjected to a temperature of around 85 °C, corresponding to a depth of approximately 5 km below the seafloor (kmbsf), whereas older clasts of Aptian or earlier age, with vitrinite reflectance values of ~0.6-1.0%, are derived from much deeper depths. Most of the clasts are considered to have been lifted to the depth of 5 kmbsf as a result of underplating at the toe of a rigid backstop that had developed below MHMV after underthrusting related to plate subduction. At that depth, fluid pressures that are dramatically increased because of underplating promote the ascent of fluid-rich sediments and entrain clasts along an existing fault in the accretionary wedge.
Résumé(Résumé en langage clair et simple, non publié)
La pression interstitielle le long des méga-chevauchements d¿une zone de subduction est l¿un des principaux paramètres susceptibles d¿influer sur l¿occurrence de séismes. Il est difficile d¿étudier sur place le niveau de la pression interstitielle. Cependant, les volcans de boue, résultant d¿une pression interstitielle élevée par endroits, offrent des occasions rares de le faire. Nos travaux sont axés sur une étude de cas d¿un site comportant des volcans de boue, dans la zone de subduction hellénique. Les résultats de cette étude nous aident à comprendre des processus similaires dans d¿autres zones de subduction, y compris celles où les volcans de boue sont rares, voire absents, comme la zone de subduction de Cascadia.
GEOSCAN ID294897