FN Archimer Export Format
PT J
TI The Behavior of Rare Earth Elements during Green Clay Authigenesis on the Congo Continental Shelf
BT 
AF Bayon, Germain
   Giresse, Pierre
   Chen, Hongjin
   Rouget, Marie-Laure
   Gueguen, Bleuenn
   Moizinho, Gabriel Ribeiro
   Barrat, Jean-Alix
   Beaufort, Daniel
AS 1:1;2:2;3:3,8;4:8;5:8;6:4,5,8;7:6;8:7;
FF 1:PDG-REM-GEOOCEAN-ASTRE;2:;3:;4:;5:;6:;7:;8:;
C1 Univ Brest, CNRS, Ifremer, Geo-Ocean, F-29280 Plouzané, France
   Centre of Education and Research on Mediterranean Environments (CEFREM), UMR CNRS 5110, Perpignan Via Domitia University, F-66860 Perpignan, France
   Key Laboratory of Marine Mineral Resources, Ministry of Natural Resources, Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou 510760, China
   Géosciences-Environnement Toulouse, Université de Toulouse, UPS (SVT-OMP), CNRS, IRD, F-31400 Toulouse, France
   Instituto de Geociências, Universidade de Brasília, Campus Universitário Darcy Ribeiro, Ala Central, Brasília 70910-900, DF, Brazil
   Univ Brest, CNRS, LEMAR, Institut Universitaire Européen de la Mer (IUEM), F-29280 Plouzané, France
   Université de Poitiers, IC2MP-UMR 7285-CNRS, F-86073 Poitiers, France
   Univ Brest, CNRS, Ifremer, Geo-Ocean, F-29280 Plouzané, France
C2 IFREMER, FRANCE
   CEFREM, FRANCE
   CHINA GEOL SURVEY, CHINA
   UNIV TOULOUSE, FRANCE
   UNIV BRASILIA, BRAZIL
   UBO, FRANCE
   UNIV POITIERS, FRANCE
   UBO, FRANCE
SI BREST
SE PDG-REM-GEOOCEAN-ASTRE
UM LEMAR
   GEO-OCEAN
IN WOS Ifremer UMR
   WOS Cotutelle UMR
   DOAJ
   copubli-france
   copubli-univ-france
   copubli-int-hors-europe
   copubli-sud
IF 2.5
TC 2
UR https://archimer.ifremer.fr/doc/00850/96225/104386.pdf
   https://archimer.ifremer.fr/doc/00850/96225/104387.zip
LA English
DT Article
DE ;neodymium;hafnium;kaolinite;phosphate minerals;green marine clay authigenesis
AB Clay mineral authigenesis at continental margins plays an important role in global marine element cycles. However, despite being increasingly used as tracers for both modern and past oceanographic conditions, the behavior of the rare earth elements (REEs) and their isotopes during marine clay authigenesis still remains poorly known. In this study, we report on a detailed geochemical investigation of glauconite from the West African continental shelf, near the mouth of the Congo River. Elemental, neodymium, and hafnium isotope analyses were conducted on both acid leachate and separated clay-size fractions of glauconite pellets, in order to investigate the behavior of REE during the formation of authigenic clays. Our data indicate that kaolinite dissolution and subsequent Fe-bearing clay authigenesis act as a net source of REEs to seawater. We show that enhanced glauconitization, as inferred from increasing Fe and K contents, is accompanied by significant decoupling of the REE toward markedly LREE-enriched shale-normalized patterns in neoformed clay separates. Using both Nd and Hf isotopes and SEM observations, we rule out any seawater influence and argue that this shift primarily reflects the progressively overwhelming presence of insoluble nanocrystals of detrital LREE-rich phosphates, which are known to occur in close association with kaolinite in tropical soils. Due to their marked insolubility in surface environments, such nanocrystals can be preserved during kaolinite dissolution and subsequently incorporated into the aggregates of authigenic green clays forming the peloids. Most strikingly, we show that the combined influence of net REE loss (due to kaolinite dissolution) and decoupling (due to subsequent entrapment of inherited LREE-bearing accessory phases into neoformed clay minerals) is accompanied by preferential release of a dissolved REE fraction characterized by seawater-like distribution patterns. These findings reinforce the emerging view that clay mineral dissolution and authigenesis at continental margins possibly play a major role in marine REE cycling. 
PY 2023
PD AUG
SO Minerals
SN 2075-163X
PU MDPI AG
VL 13
IS 8
UT 001057121100001
DI 10.3390/min13081081
ID 96225
ER

EF