TY - JOUR
T1 - Impacts of nepheloid layers and mineralogical compositions of oceanic margin sediments on REE concentrations and Nd isotopic compositions of seawater
AU - Huang, Yi
AU - Colin, Christophe
AU - Liu, Zhifei
AU - Douville, Eric
AU - Dapoigny, Arnaud
AU - Haurine, Frederic
AU - Wu, Qiong
AU - Tien-Shun Lin, Andrew
N1 - Publisher Copyright:
© 2023 Elsevier Ltd
PY - 2023/10/15
Y1 - 2023/10/15
N2 - Nepheloid layers and turbidity currents transport large quantities of detrital sediments to deep-sea basins. Locally they may control seawater – detrital particle interactions and modify dissolved REE concentrations and εNd distributions of the oceanic margin. However, to date, such processes have been poorly documented, especially in oceanic margins characterized by contrasted mineralogical compositions. Dissolved REEs and εNd from three water stations collected in the northern South China Sea (SCS) close to the Taiwanese deep-sea canyons have been analyzed, with the aim of determining the influence of nepheloid layers and mineralogical composition of lithogenic inputs on dissolved REE and εNd distributions in the ocean. Results indicate that the most radiogenic εNd value (−2.5 ± 0.2), observed at about 400 m, corresponds to the inflow of North Pacific Intermediate Water (NPIW) into the SCS. When compared with previously published Nd isotope, our current study suggests that the εNd value of NPIW which enters the SCS (from 300 to 800 m water depth) is not modified by unradiogenic sediments off the southern margin of Taiwan Island, whereas they become less radiogenic along the margin of eastern China due to Nd exchange with unradiogenic sediments (between −10.2 and −12.6) from the tropical soils of Chinese rivers basins. We have proposed that pedogenetic minerals from Chinese tropical soils modify the Nd isotopic compositions of seawater more efficiently than fresh detrital minerals resulting from very high rates of physical erosion on Taiwan Island. The MREE/MREE*, La/Sm and La/Yb ratios in nepheloid layers indicate that lateral transportation of lithogenic material within the water column can preferentially adsorb LREE compared to MREE and HREE through the scavenging process. However, this process has a negligible impact on seawater εNd of the northern SCS. At the bottom of several water stations, a negative excursion of εNd values, associated with an increase in MREE/MREE* ratios and a decrease in La/Sm ratios, suggests a remineralization flux resulting from the dissolution of Mn oxides during early diagenesis of deep-sea sediments.
AB - Nepheloid layers and turbidity currents transport large quantities of detrital sediments to deep-sea basins. Locally they may control seawater – detrital particle interactions and modify dissolved REE concentrations and εNd distributions of the oceanic margin. However, to date, such processes have been poorly documented, especially in oceanic margins characterized by contrasted mineralogical compositions. Dissolved REEs and εNd from three water stations collected in the northern South China Sea (SCS) close to the Taiwanese deep-sea canyons have been analyzed, with the aim of determining the influence of nepheloid layers and mineralogical composition of lithogenic inputs on dissolved REE and εNd distributions in the ocean. Results indicate that the most radiogenic εNd value (−2.5 ± 0.2), observed at about 400 m, corresponds to the inflow of North Pacific Intermediate Water (NPIW) into the SCS. When compared with previously published Nd isotope, our current study suggests that the εNd value of NPIW which enters the SCS (from 300 to 800 m water depth) is not modified by unradiogenic sediments off the southern margin of Taiwan Island, whereas they become less radiogenic along the margin of eastern China due to Nd exchange with unradiogenic sediments (between −10.2 and −12.6) from the tropical soils of Chinese rivers basins. We have proposed that pedogenetic minerals from Chinese tropical soils modify the Nd isotopic compositions of seawater more efficiently than fresh detrital minerals resulting from very high rates of physical erosion on Taiwan Island. The MREE/MREE*, La/Sm and La/Yb ratios in nepheloid layers indicate that lateral transportation of lithogenic material within the water column can preferentially adsorb LREE compared to MREE and HREE through the scavenging process. However, this process has a negligible impact on seawater εNd of the northern SCS. At the bottom of several water stations, a negative excursion of εNd values, associated with an increase in MREE/MREE* ratios and a decrease in La/Sm ratios, suggests a remineralization flux resulting from the dissolution of Mn oxides during early diagenesis of deep-sea sediments.
KW - Boundary exchange
KW - Nd isotope composition
KW - Nepheloid layers
KW - REE contents
KW - Seawater
UR - http://www.scopus.com/inward/record.url?scp=85170559017&partnerID=8YFLogxK
U2 - 10.1016/j.gca.2023.08.026
DO - 10.1016/j.gca.2023.08.026
M3 - 期刊論文
AN - SCOPUS:85170559017
SN - 0016-7037
VL - 359
SP - 57
EP - 70
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
ER -