FN Archimer Export Format PT J TI Early diagenesis in the sediments of the Congo deep-sea fan dominated by massive terrigenous deposits: Part II – Iron–sulfur coupling BT AF TAILLEFERT, Martial BECKLER, Jordon S. CATHALOT, Cecile MICHALOPOULOS, Panagiotis CORVAISIER, Rudolph KIRIAZIS, Nicole CAPRAIS, Jean-Claude PASTOR, Lucie RABOUILLE, Christophe AS 1:1;2:1,2;3:3;4:4;5:5;6:1;7:6;8:6;9:7; FF 1:;2:;3:PDG-REM-GM-LCG;4:;5:;6:;7:PDG-REM-EEP-LEP;8:PDG-REM-EEP-LEP;9:; C1 Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. Mote Marine Lab, Ocean Technol Res Program, Sarasota, FL 34236 USA. IFREMER, Ctr Bretagne, REM GM Lab Cycles Geochim & Ressources, F-29280 Plouzane, France. Hellen Ctr Marine Res, Inst Oceanog, Anavyssos Attiki, Greece. Inst Univ Europeen Mer, CNRS, UBO, Lab Sci Environm Marin, F-29280 Plouzane, France. IFREMER, Ctr Bretagne, REM EEP Lab Environm Profond, F-29280 Plouzane, France. CEA, CNRS, UVSQ, Lab Sci Climat & Environm, F-91198 Gif Sur Yvette, France. C2 GEORGIA INST TECHNOL, USA MOTE MARINE LAB, USA IFREMER, FRANCE HELLEN CTR MARINE RES, GREECE UBO, FRANCE IFREMER, FRANCE CEA, FRANCE SI BREST SE PDG-REM-GM-LCG PDG-REM-EEP-LEP UM LEMAR IN WOS Ifremer jusqu'en 2018 copubli-france copubli-europe copubli-univ-france copubli-int-hors-europe IF 2.451 TC 17 UR https://archimer.ifremer.fr/doc/00389/50068/52254.pdf LA English DT Article CR CONGOLOBE BO Pourquoi pas ? DE ;Sediment diagenesis;Iron reduction;Sulfate reduction;Deep-sea fans AB Deep-sea fans are well known depot centers for organic carbon that should promote sulfate reduction. At the same time, the high rates of deposition of unconsolidated metal oxides from terrigenous origin may also promote metal-reducing microbial activity. To investigate the eventual coupling between the iron and sulfur cycles in these environments, shallow sediment cores (< 50 cm) across various channels and levees in the Congo River deep-sea fan (~5000 m) were profiled using a combination of geochemical methods. Interestingly, metal reduction dominated suboxic carbon remineralization processes in most of these sediments, while dissolved sulfide was absent. In some ‘hotspot’ patches, however, sulfate reduction produced large sulfide concentrations which supported chemosynthetic-based benthic megafauna. These environments were characterized by sharp geochemical boundaries compared to the iron-rich background environment, suggesting that FeS precipitation efficiently titrated iron and sulfide from the pore waters. A companion study demonstrated that methanogenesis was active in the deep sediment layers of these patchy ecosystems, suggesting that sulfate reduction was promoted by alternative anaerobic processes. These highly reduced habitats could be fueled by discrete, excess inputs of highly labile natural organic matter from Congo River turbidites or by exhumation of buried sulfide during channel flank erosion and slumping. Sulfidic conditions may be maintained by the mineralization of decomposition products from local benthic macrofauna or bacterial symbionts or by the production of more crystalline Fe(III) oxide phases that are less thermodynamically favorable than sulfate reduction in these bioturbated sediments. Overall, the iron and sulfur biogeochemical cycling in this environment is unique and much more similar to a coastal ecosystem than a deep-sea environment. PY 2017 PD AUG SO Deep-sea Research Part Ii-topical Studies In Oceanography SN 0967-0645 PU Pergamon-elsevier Science Ltd VL 142 UT 000408783500011 BP 151 EP 166 DI 10.1016/j.dsr2.2017.06.009 ID 50068 ER EF