Distribution of Rare Earth Elements plus Yttrium among Major Mineral Phases of Marine Fe–Mn Crusts from the South China Sea and Western Pacific Ocean: A Comparative Study

Abstract

Marine hydrogenetic Fe–Mn crusts on seamounts are known as potential mineral resources of rare earth elements plus yttrium (REY). In recent years, increasing numbers of deposits of Fe–Mn crusts and nodules were discovered in the South China Sea (SCS), yet the enrichment mechanism of REY is yet to be sufficiently addressed. In this study, hydrogenetic Fe–Mn crusts from the South China Sea (SCS) and the Western Pacific Ocean (WPO) were comparatively studied with mineralogy and geochemistry. In addition, we used an in situ REY distribution mapping method, implementing laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and a sequential leaching procedure to investigate the partitioning behavior of REY in the Fe–Mn crusts. The typical Fe–Mn crusts from SCS were mainly composed of quartz, calcite, vernadite (δ-MnO2), and amorphous Fe oxides/hydroxides (FeOOH). The Fe–Mn crusts from the Central SCS Basin and the WPO contained quartz, δ-MnO2, FeOOH, todorokite, and phillipsite. Furthermore, geochemical analysis indicated that the typical SCS crusts had a higher growth rate and lower REY concentrations. The LA-ICP-MS mapping results showed that the δ-MnO2 and FeOOH dominated the occurrence phases of REY in the SCS crusts. Four mineral phases (i.e., easily exchangeable and carbonate, Mn-oxide, amorphous FeOOH, and residual aluminosilicates) in these Fe–Mn crusts were separated by a sequential leaching procedure. In the SCS and WPO crusts, the majority of total REY (ΣREY) was distributed in the Mn-oxide and amorphous FeOOH phases. The post-Archean Australian shale-normalized REY patterns showed that light REY (LREY) and heavy REY (HREY) were preferentially adsorbed onto δ-MnO2 and FeOOH, respectively. It is noteworthy that ~27% of ΣREY was associated with the residual aluminosilicates phase of the WPO crusts. The La/Al ratios in the aluminosilicates phase of the typical SCS crusts were the values of the upper crust. We conclude that large amounts of terrigenous materials dilute the abundance of REY in the SCS crusts. In addition, the growth rates of Fe–Mn crusts have a negative correlation with the FeOOH-bound and aluminosilicate-bound REY. As a result of the fast growth rates, the SCS crusts contain relatively low concentrations of REY.

Compositional Variations and Genesis of Sandy-Gravel Ferromanganese Deposits from the Yōmei Guyot (Holes 431, 431A DSDP), Emperor Ridge

“…The study of REY distribution in the mineral phases is the most useful method for studying the samples' geneses. For example, the REY distribution in the Mn phase of hydrothermal crusts differs significantly from those of the hydrogenous and diagenetic geneses and from the Fe phases of all genetic types [6,7,48,49].…”

“…In addition, Pliocene (6-3 Myr) volcanic activity in the Pacific Ocean might have influenced the destruction of Fe-Mn deposits [56]. Growth of the brown-coal upper layer on Detroit Guyot initiated since 3.21 Myr [48,49], broadly corresponding to global events such as the initiation of northern hemisphere glaciation, the final closing of the Isthmus of Panama, decreasing activity of AABW, and an increase in eolian dust flux [54,[57][58][59]. Thus, the destruction of Fe-Mn crusts and the post-deposition of its fragments on the Yōmei Guyot top occurred in the Late Pliocene.…”

Enrichment Characteristics and Mechanisms of Critical Metals in Marine Fe-Mn Crusts and Nodules: A Review

“…(3) Partitions between δ-MnO 2 and amorphous FeOOH for REY, Cd, Mo, W and V [24,33,63,[129][130][131][132][133]. REY (except for Ce) possess both negative and positive species in seawater, generally showing complex preferences of LREE-CO 3 + and HREE-CO 3 2− and exhibiting sorption preferences to both the Mn oxides and Fe oxyhydroxides, causing a partitioned distribution between Mn and Fe phases.…”

“…Generally, they exist as LREE-CO 3 + and HREE-CO 3 2− , which direct their sorption preferences onto δ-MnO 2 and amorphous FeOOH. Upon REY adsorption on the surface of the Fe-Mn oxides, the ligand exchanges between the carbonate and the hydroxyl are induced [129,161,164,167]. Hydrogenetic REY distribution generally shows an increasing proportion in Fe phase and a decreasing proportion in Mn phase from La to Yb, which suggests that Mn phase and Fe phase show preferences to REE adsorptions, each relatively adsorbing more LREE and HREE [24,46,91,165,167].…”

Separation of Rare Earth Elements In Geological Samples with High Concentrations of Barium Using RE Resin

“…Rare earth elements (REE) are one of the main geochemical tools that play an important role in the genesis of rocks, the origin of ore-forming materials, and the redox environments of paleooceans. [1][2][3][4][5] The determination of REEs in geological samples is usually performed after acid digestion by inductively coupled plasma mass spectrometry (ICP-MS). 6 However, for samples with high matrix elements, such as carbonates, siliceous rocks, seawater and sulfides, and low REE concentrations, the determination of their REE concentrations has always been problematic.…”