Unique authigenic mineral assemblages reveal different diagenetic histories in two neighbouring cold‐water coral mounds on Pen Duick Escarpment,Gulf of Cadiz |
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Authors: | LAURA M WEHRMANN ANNELEEN FOUBERT BENJAMIN BRUNNER DOMINIQUE BLAMART LIES DE MOL DAVID VAN ROOIJ JAN DEWANCKELE VEERLE CNUDDE RUDY SWENNEN PHILIPPE DUYCK JEAN‐PIERRE HENRIET |
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Institution: | 1. Department of Biogeochemistry, Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, D‐28359 Bremen, Germany;2. Coral Reef Ecology Work Group, GeoBio‐Center, Ludwig‐Maximilians Universit?t, Richard‐Wagner‐Strasse 10, D‐80333 München, Germany;3. Department of Earth and Environmental Sciences, Geology, K.U. Leuven, Celestijnenlaan 200E, B‐3001 Heverlee, Belgium;4. Laboratoire des Sciences du Climat et de L’Environnement (LSCE), Unité Mixte CEA/CNRS/UVSQ, Bat 12, Avenue de la Terrasse, F‐ 91190 Gif‐sur‐Yvette, France;5. Renard Centre of Marine Geology, Department of Geology and Soil Science, Ghent University, Krijgslaan 281 s8, B‐9000 Gent, Belgium (E‐mail: hans.pirlet@vliz.be);6. Department of Geology and Soil Science – UGCT, Ghent University, Krijgslaan 281 s8, B‐9000 Gent, Belgium;7. Department of Radiology and Medical Imagery, Ghent University Hospital, De Pintelaan 185, B‐9000 Gent, Belgium Associate Editor – Bernhard Riegl |
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Abstract: | Alpha Mound and Beta Mound are two cold‐water coral mounds, located on the Pen Duick Escarpment in the Gulf of Cadiz amidst the El Arraiche mud volcano field where focused fluid seepage occurs. Despite the proximity of Alpha Mound and Beta Mound, both mounds differ in their assemblage of authigenic minerals. Alpha Mound features dolomite, framboidal pyrite and gypsum, whereas Beta Mound contains a barite layer and predominantly euhedral pyrite. The diagenetic alteration of the sedimentary record of both mounds is strongly influenced by biogeochemical processes occurring at shallow sulphate methane transition zones. The combined sedimentological, petrographic and isotopic analyses of early diagenetic features in gravity cores from Alpha Mound and Beta Mound indicate that the contrast in mineral assemblages between these mounds is caused by differences in fluid and methane fluxes. Alpha Mound appears to be affected by strong fluctuations in the fluid flow, causing shifts in redox boundaries, whereas Beta Mound seems to be a less dynamic system. To a large extent, the diagenetic regimes within cold‐water coral mounds on the Pen Duick Escarpment appear to be controlled by fluid and methane fluxes deriving from layers underlying the mounds and forcings like pressure gradients caused by bottom current. However, it also becomes evident that authigenic mineral assemblages are not only very sensitive recorders of the diagenetic history of specific cold‐water coral mounds, but also affect diagenetic processes in turn. Dissolution of aragonite, lithification by precipitation of authigenic minerals and subsequent brecciation of these lithified layers may also exert a control on the advective and diffusive fluid flow within these mounds, providing a feedback mechanism on subsequent diagenetic processes. |
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Keywords: | Barite calcite cold‐water coral mound dolomite gypsum pyrite sulphate methane transition zone |
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