HR: 11:05h
AN: V22C-04 INVITED    [Abstracts]
TI: Sources and Rates of Fluid Flow at Mud Volcanoes - Examples from the Gulf of Cadiz
AU: * Haeckel, M
EM: mhaeckel@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Liebetrau, V
EM: vliebetrau@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Linke, P
EM: plinke@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Reitz, A
EM: areitz@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Schneider v. Deimling, J
EM: jschneider@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Schönfeld, J
EM: jschoenfeld@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Vanneste, H
EM: hlaev105@soton.ac.uk
AF: NOC, European Way, Southampton, SO14 3ZH, United Kingdom
AB: Mud volcanism is a widespread phenomenon in the Gulf of Cadiz (GoC) and provides a window into deep structural and diagenetic processes. Pore fluids from the Mercator mud volcano (MMV), located in the El Arraiche mud volcano field offshore Morocco, are highly enriched in Cl (5.3 M). Na/Cl ratios are close to 1 indicating halite dissolution by the rising fluid. This is corroborated by 3D seismic data that shows ongoing localized uplift creating an anticline below the eastern flank of the MMV, which can only be explained by a rising salt diapir. Triassic evaporites are known on the Moroccan margin 500 km further south as well as on land in Spain.
In addition, the fluids are highly enriched in Li (5.3 mM) and B (12 mM) indicating a deep fluid source from mineral dewatering at T>150° C. The porewater d18O vs dD relation shows a negative correlation typical for clay mineral dehydration (smectite-illite transformation). A deep fluid source is also supported by a radiogenic 87Sr/86Sr porewater signal of 0.7106. The emitted gas contains mainly methane of thermogenic origin (d13C = -30 to -40 ‰ vPDB). The morphology of quartz crystals found in the mud suggests transport from large depths. In contrast, gypsum crystals also found in the mud, exhibit the same radiogenic Sr signature as the porewater suggesting secondary precipitation.
Applying a 1-D transport-reaction model using conservative porewater compounds constrains the fluid advection rates to be 6 cm/a at the summit, decreasing to 0.3 cm/a towards the rim. The advection rates correlate well with T and S data recorded with a CTD mounted to a video sled system. Combining the CTD track data across the MMV and the model results allows to calculate spatial budgets for water and methane release as well as the heat flow of the MMV.
DE: 0400 BIOGEOSCIENCES
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 1009 Geochemical modeling (3610, 8410)
DE: 1039 Alteration and weathering processes (3617)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting