Recent, deep-sourced methane/mud discharge at the most active mud volcano in the western Mediterranean

Active mud volcanism in the West Alboran Basin (WAB) is closely associated with tectonically mobilized, overpressurized shales and shale-diapirism. This appears to control mud expulsion at Carmen mud volcano, a cone-shaped structure 65 m high and 1 km in basal diameter. The presence of gas-rich mud...

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Authors: López-Rodríguez, Carmina, De Lange, G. J., Comas, M. C., Martínez Ruíz, Francisca C., Nieto, F., Sapart, C. J., Mogollón, J. M.
Format: article
Status:Versión aceptada para publicación
Publication Date:2019
Country:España
Institution:Consejo Superior de Investigaciones Científicas (CSIC)
Repository:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/205877
Online Access:http://hdl.handle.net/10261/205877
Access Level:Open access
Keyword:Alboran Sea
Clay minerals
Isotopes
Deep fluids
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spelling Recent, deep-sourced methane/mud discharge at the most active mud volcano in the western MediterraneanLópez-Rodríguez, CarminaDe Lange, G. J.Comas, M. C.Martínez Ruíz, Francisca C.Nieto, F.Sapart, C. J.Mogollón, J. M.Alboran SeaClay mineralsIsotopesDeep fluidsActive mud volcanism in the West Alboran Basin (WAB) is closely associated with tectonically mobilized, overpressurized shales and shale-diapirism. This appears to control mud expulsion at Carmen mud volcano, a cone-shaped structure 65 m high and 1 km in basal diameter. The presence of gas-rich mud breccia, living chemosynthetic fauna, the absence of hemipelagic draping and the abrupt transition that occurs between high dissolved sulfate in the uppermost interval and low sulfate together with high methane concentrations in the lowermost sediment interval all point to a recent expulsion of mud breccia at the summit of Carmen MV. For the lowermost interval, the depletion of major elements (i.e., Ca and Mg) and the enrichment of trace species (i.e., Li and B) in the pore water all indicate a deep fluid source. The δO (5.7‰ VSMOW) and δD (−10‰ VSMOW) of pore water in the lowermost interval correspond with smectite dehydration as the main pore-water freshening mechanism. Water-formation temperatures calculated with empirical geo-thermometers (K-Na, K-Mg; δO, δD, and dissolved B) reveal that fluids were generated at temperatures of ~140 ± 20 °C. Taking a regional geothermal gradient for the WAB of 25–27 °C/km, this points to a fluid source from ~5 ± 1 km sediment depth. This is not only consistent with the depth of overpressurized shales and megabreccia of Lower to Middle Miocene age, but it also fits nicely with the Upper/Middle-Miocene seawater value for the porewater Sr/Sr derived from dissolving carbonates. The stable carbon and hydrogen isotopic composition of methane (δC ~ −59.4‰ VPDB and δD −184‰ VSMOW) for the deepest samples of summit-core GP05PC is consistent with the mentioned deep origin. Mud breccia expulsion of overpressurized deep sedimentary units would be accompanied by rigorous degassing, leading to rapid, ‘instantaneous’ replacement of pore fluid by bottom water in the upper sediments. The absence of oxidized sediment draping, the seawater-like pore-water composition in the uppermost part of the mud breccia interval, and the abrupt methane to sulfate transition all provide evidence for a very recent mud expulsion. The distinctively kink-shaped pore-water Cl profile in core GP05PC has been used in a numerical transport-reaction model to derive the timing for this event. This eruptive event appears to have taken place very recently, namely 12 ± 5 yrs prior to the 2012 coring, thus in the year 2000 CE.This work was supported by MINECO Spanish Projects [CTM2009-07715, CGL2011-1441, CGL2012-32659 and CGL2015-66830-R]; and the Andalusian Government Research Group [RNM-179 and RNM-215]. C. F. López-Rodríguez was funded by a JAE-PhD fellowship from the CSIC (Spain); she acknowledges subsequent funding from the STSM in the framework of COST action ES1301.Elsevier BVMinisterio de Economía y Competitividad (España)Junta de AndalucíaEuropean CommissionConsejo Superior de Investigaciones Científicas (España)Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]2020202020192020info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_6501Postprintinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/10261/205877reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)Inglés#PLACEHOLDER_PARENT_METADATA_VALUE#info:eu-repo/grantAgreement/MINECO/Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016/CGL2015-66830-Rhttp://dx.doi.org/10.1016/j.margeo.2018.11.013Síinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/2058772026-05-22T06:33:51Z
dc.title.none.fl_str_mv Recent, deep-sourced methane/mud discharge at the most active mud volcano in the western Mediterranean
title Recent, deep-sourced methane/mud discharge at the most active mud volcano in the western Mediterranean
spellingShingle Recent, deep-sourced methane/mud discharge at the most active mud volcano in the western Mediterranean
López-Rodríguez, Carmina
Alboran Sea
Clay minerals
Isotopes
Deep fluids
title_short Recent, deep-sourced methane/mud discharge at the most active mud volcano in the western Mediterranean
title_full Recent, deep-sourced methane/mud discharge at the most active mud volcano in the western Mediterranean
title_fullStr Recent, deep-sourced methane/mud discharge at the most active mud volcano in the western Mediterranean
title_full_unstemmed Recent, deep-sourced methane/mud discharge at the most active mud volcano in the western Mediterranean
title_sort Recent, deep-sourced methane/mud discharge at the most active mud volcano in the western Mediterranean
dc.creator.none.fl_str_mv López-Rodríguez, Carmina
De Lange, G. J.
Comas, M. C.
Martínez Ruíz, Francisca C.
Nieto, F.
Sapart, C. J.
Mogollón, J. M.
author López-Rodríguez, Carmina
author_facet López-Rodríguez, Carmina
De Lange, G. J.
Comas, M. C.
Martínez Ruíz, Francisca C.
Nieto, F.
Sapart, C. J.
Mogollón, J. M.
author_role author
author2 De Lange, G. J.
Comas, M. C.
Martínez Ruíz, Francisca C.
Nieto, F.
Sapart, C. J.
Mogollón, J. M.
author2_role author
author
author
author
author
author
dc.contributor.none.fl_str_mv Ministerio de Economía y Competitividad (España)
Junta de Andalucía
European Commission
Consejo Superior de Investigaciones Científicas (España)
Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]
dc.subject.none.fl_str_mv Alboran Sea
Clay minerals
Isotopes
Deep fluids
topic Alboran Sea
Clay minerals
Isotopes
Deep fluids
description Active mud volcanism in the West Alboran Basin (WAB) is closely associated with tectonically mobilized, overpressurized shales and shale-diapirism. This appears to control mud expulsion at Carmen mud volcano, a cone-shaped structure 65 m high and 1 km in basal diameter. The presence of gas-rich mud breccia, living chemosynthetic fauna, the absence of hemipelagic draping and the abrupt transition that occurs between high dissolved sulfate in the uppermost interval and low sulfate together with high methane concentrations in the lowermost sediment interval all point to a recent expulsion of mud breccia at the summit of Carmen MV. For the lowermost interval, the depletion of major elements (i.e., Ca and Mg) and the enrichment of trace species (i.e., Li and B) in the pore water all indicate a deep fluid source. The δO (5.7‰ VSMOW) and δD (−10‰ VSMOW) of pore water in the lowermost interval correspond with smectite dehydration as the main pore-water freshening mechanism. Water-formation temperatures calculated with empirical geo-thermometers (K-Na, K-Mg; δO, δD, and dissolved B) reveal that fluids were generated at temperatures of ~140 ± 20 °C. Taking a regional geothermal gradient for the WAB of 25–27 °C/km, this points to a fluid source from ~5 ± 1 km sediment depth. This is not only consistent with the depth of overpressurized shales and megabreccia of Lower to Middle Miocene age, but it also fits nicely with the Upper/Middle-Miocene seawater value for the porewater Sr/Sr derived from dissolving carbonates. The stable carbon and hydrogen isotopic composition of methane (δC ~ −59.4‰ VPDB and δD −184‰ VSMOW) for the deepest samples of summit-core GP05PC is consistent with the mentioned deep origin. Mud breccia expulsion of overpressurized deep sedimentary units would be accompanied by rigorous degassing, leading to rapid, ‘instantaneous’ replacement of pore fluid by bottom water in the upper sediments. The absence of oxidized sediment draping, the seawater-like pore-water composition in the uppermost part of the mud breccia interval, and the abrupt methane to sulfate transition all provide evidence for a very recent mud expulsion. The distinctively kink-shaped pore-water Cl profile in core GP05PC has been used in a numerical transport-reaction model to derive the timing for this event. This eruptive event appears to have taken place very recently, namely 12 ± 5 yrs prior to the 2012 coring, thus in the year 2000 CE.
publishDate 2019
dc.date.none.fl_str_mv 2019
2020
2020
2020
dc.type.none.fl_str_mv info:eu-repo/semantics/article
http://purl.org/coar/resource_type/c_6501
Postprint
info:eu-repo/semantics/acceptedVersion
format article
status_str acceptedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/205877
url http://hdl.handle.net/10261/205877
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv #PLACEHOLDER_PARENT_METADATA_VALUE#
info:eu-repo/grantAgreement/MINECO/Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016/CGL2015-66830-R
http://dx.doi.org/10.1016/j.margeo.2018.11.013
Sí
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.publisher.none.fl_str_mv Elsevier BV
publisher.none.fl_str_mv Elsevier BV
dc.source.none.fl_str_mv reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
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