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Diagenetic formation of gypsum and dolomite in a cold-water coral mound in the Porcupine Seabight, off Ireland

(2010) SEDIMENTOLOGY. 57(3). p.786-805
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Abstract
Authigenic gypsum was found in a gravity core, retrieved from the top of Mound Perseverance, a giant cold-water coral mound in the Porcupine Basin, off Ireland. The occurrence of gypsum in such an environment is intriguing, because gypsum, a classic evaporitic mineral, is undersaturated with respect to sea water. Sedimentological, petrographic and isotopic evidence point to diagenetic formation of the gypsum, tied to oxidation of sedimentary sulphide minerals (i.e. pyrite). This oxidation is attributed to a phase of increased bottom currents which caused erosion and enhanced inflow of oxidizing fluids into the mound sediments. The oxidation of pyrite produced acidity, causing carbonate dissolution and subsequently leading to pore-water oversaturation with respect to gypsum and dolomite. Calculations based on the isotopic compositions of gypsum and pyrite reveal that between 21·6% and 28·6% of the sulphate incorporated into the gypsum derived from pyrite oxidation. The dissolution of carbonate increased the porosity in the affected sediment layer but promoted lithification of the sediments at the sediment-water interface. Thus, authigenic gypsum can serve as a signature for diagenetic oxidation events in carbonate-rich sediments. These observations demonstrate that fluid flow, steered by environmental factors, has an important effect on the diagenesis of coral mounds.
Keywords
dolomite, Cold-water coral, early diagenesis, gypsum, Lophelia, Porcupine Seabight, sulphur isotopes, NORTHEAST ATLANTIC, AUTHIGENIC GYPSUM, CARBONATE MOUNDS, SULFIDE OXIDATION, MEDITERRANEAN-SEA, DEEP, SEDIMENTS, SULFATE, PYRITE, ISOTOPE

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Chicago
Pirlet, Hans, Laura Wehrmann, Benjamin Brunner, Norbert Frank, Jan Dewanckele, David Van Rooij, Anneleen Foubert, et al. 2010. “Diagenetic Formation of Gypsum and Dolomite in a Cold-water Coral Mound in the Porcupine Seabight, Off Ireland.” Sedimentology 57 (3): 786–805.
APA
Pirlet, H., Wehrmann, L., Brunner, B., Frank, N., Dewanckele, J., Van Rooij, D., Foubert, A., et al. (2010). Diagenetic formation of gypsum and dolomite in a cold-water coral mound in the Porcupine Seabight, off Ireland. SEDIMENTOLOGY, 57(3), 786–805.
Vancouver
1.
Pirlet H, Wehrmann L, Brunner B, Frank N, Dewanckele J, Van Rooij D, et al. Diagenetic formation of gypsum and dolomite in a cold-water coral mound in the Porcupine Seabight, off Ireland. SEDIMENTOLOGY. 2010;57(3):786–805.
MLA
Pirlet, Hans, Laura Wehrmann, Benjamin Brunner, et al. “Diagenetic Formation of Gypsum and Dolomite in a Cold-water Coral Mound in the Porcupine Seabight, Off Ireland.” SEDIMENTOLOGY 57.3 (2010): 786–805. Print.
@article{978200,
  abstract     = {Authigenic gypsum was found in a gravity core, retrieved from the top of Mound Perseverance, a giant cold-water coral mound in the Porcupine Basin, off Ireland. The occurrence of gypsum in such an environment is intriguing, because gypsum, a classic evaporitic mineral, is undersaturated with respect to sea water. Sedimentological, petrographic and isotopic evidence point to diagenetic formation of the gypsum, tied to oxidation of sedimentary sulphide minerals (i.e. pyrite). This oxidation is attributed to a phase of increased bottom currents which caused erosion and enhanced inflow of oxidizing fluids into the mound sediments. The oxidation of pyrite produced acidity, causing carbonate dissolution and subsequently leading to pore-water oversaturation with respect to gypsum and dolomite. Calculations based on the isotopic compositions of gypsum and pyrite reveal that between 21{\textperiodcentered}6\% and 28{\textperiodcentered}6\% of the sulphate incorporated into the gypsum derived from pyrite oxidation. The dissolution of carbonate increased the porosity in the affected sediment layer but promoted lithification of the sediments at the sediment-water interface. Thus, authigenic gypsum can serve as a signature for diagenetic oxidation events in carbonate-rich sediments. These observations demonstrate that fluid flow, steered by environmental factors, has an important effect on the diagenesis of coral mounds.},
  author       = {Pirlet, Hans and Wehrmann, Laura and Brunner, Benjamin and Frank, Norbert and Dewanckele, Jan and Van Rooij, David and Foubert, Anneleen and Swennen, Rudy and Naudts, Lieven and Boone, Matthieu and Cnudde, Veerle and Henriet, Jean},
  issn         = {0037-0746},
  journal      = {SEDIMENTOLOGY},
  keyword      = {dolomite,Cold-water coral,early diagenesis,gypsum,Lophelia,Porcupine Seabight,sulphur isotopes,NORTHEAST ATLANTIC,AUTHIGENIC GYPSUM,CARBONATE MOUNDS,SULFIDE OXIDATION,MEDITERRANEAN-SEA,DEEP,SEDIMENTS,SULFATE,PYRITE,ISOTOPE},
  language     = {eng},
  number       = {3},
  pages        = {786--805},
  title        = {Diagenetic formation of gypsum and dolomite in a cold-water coral mound in the Porcupine Seabight, off Ireland},
  url          = {http://dx.doi.org/10.1111/j.1365-3091.2009.01119.x},
  volume       = {57},
  year         = {2010},
}

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