Abstract
Rare earth elements (REEs) and yttrium (Y), together known as REY, are extremely enriched in deep-sea pelagic sediments, attracting much attention as a promising new REY resource. To understand the influence of hydrothermal processes on the enrichment of REY in deep-sea sediments from the eastern South Pacific Ocean, we conducted detailed lithological, bulk sediment geochemical, and in situ mineral geochemical analyses on gravity core sample S021GC17 from the Yupanqui Basin of eastern South Pacific. The REY-rich muds of S021GC17 are dark-brown to black zeolitic clays with REY contents (ΣREY) ranging from 1057 to 1882 ppm (average 1329 ppm). The REY-rich muds display heavy rare earth elements (HREE) enriched patterns, with obvious depletions in Ce, and positive anomalies of Eu in Post-Archean Australian Shale (PAAS)-normalized REE diagrams. In contrast, the muds of S021GC17 show light rare earth elements (LREE) enriched patterns and positive anomalies of Ce and Eu in the seawater-normalized REE diagrams. Total REY abundances in the core show positive correlations with CaO, P2O5, Fe2O3, and MnO concentrations. In situ analyses of trace element contents by laser ablation-inductively coupled plasma–mass spectrometry (LA-ICP-MS) demonstrate that bioapatite fossils contain high REY concentrations (998 to 22,497 ppm, average 9123 ppm), indicating that they are the primary carriers of REY. The in situ Nd isotope values of bioapatites are higher than the average values of seawater in Pacific Ocean. Fe–Mn micronodules are divided into hydrogenetic and diagenetic types, which have average REY concentrations of 1586 and 567 ppm, respectively. The high contents of Fe-Mn-Ba-Co-Mo, the positive correlations between ΣREY and Fe-Mn, the ratios of Fe/Ti and Al/(Al + Fe + Mn), and the LREE-enriched patterns in the REY-rich muds, combined with high Nd isotope values shown by bioapatite fossils, strongly indicate that the hydrothermal fluids have played an important role in the formation of the REY-rich sediments in the eastern South Pacific Ocean.
Highlights
Rare earth elements and yttrium (REY) are critical materials in many present-day industrial products, including applications in the new energy, electronics, and medical fields.Recently, deep-sea sediments with high concentrations of REY, called “REY-rich mud”, have attracted attention as a promising new resource of REY [1,2,3].REY-rich mud is defined as a deep-sea sediment that contains more than 700 ppm of totalREY [4], which is higher than the grade of ion-adsorption-type ore deposits in southern China [5,6].REY-rich muds from the eastern South Pacific and the central North Pacific have been firstly reported as potential resources with significant amounts of REY [1]
In this paper we present the results of bulk sediment elemental analyses and data of in situ electron microprobe analysis (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) elemental analyses of bioapatite fossils, Fe–Mn micronodules, and phillipsite included in the REY-rich muds
Our results show that bioapatite is the main carrier of REY, even in the eastern South Pacific where significant REY accumulation is related to hydrothermal Fe–Mn oxides from the East Pacific Rise (EPR)
Summary
Rare earth elements and yttrium (REY) are critical materials in many present-day industrial products, including applications in the new energy, electronics, and medical fields.Recently, deep-sea sediments with high concentrations of REY, called “REY-rich mud”, have attracted attention as a promising new resource of REY [1,2,3].REY-rich mud is defined as a deep-sea sediment that contains more than 700 ppm of totalREY [4], which is higher than the grade of ion-adsorption-type ore deposits in southern China [5,6].REY-rich muds from the eastern South Pacific and the central North Pacific have been firstly reported as potential resources with significant amounts of REY [1]. Rare earth elements and yttrium (REY) are critical materials in many present-day industrial products, including applications in the new energy, electronics, and medical fields. Deep-sea sediments with high concentrations of REY, called “REY-rich mud”, have attracted attention as a promising new resource of REY [1,2,3]. REY-rich mud is defined as a deep-sea sediment that contains more than 700 ppm of total. REY-rich muds from the eastern South Pacific and the central North Pacific have been firstly reported as potential resources with significant amounts of REY [1]. Thick layers of REY-rich muds with comparable ΣREY contents have been found in the Indian Ocean, and they share similar geochemical and mineralogical features with those in the Pacific Ocean [7,8].
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