Geochemical Characteristics of Apatite in HeavyREE‐rich Deep‐Sea Mud fromMinami‐Torishima Area, SoutheasternJapan

Abstract

We have conducted geochemical and mineralogical investigations of the rare earth and yttrium (REY)-rich mud from the Minami-Torishima area in the Pacific in order to clarify the concentration of REY and their host-phase in the mud. X-ray diffraction analysis shows that the mud is mainly composed of phillipsite, fluorapatite, quartz, albite, illite and montmorillonite. Whole-rock CaO, P2O5 and total REY contents of the mud are positively correlated. Relative abundance of apatite is also positively correlated to P2O5 and total REY contents. These correlations suggest that apatite is the main host of the P2O5 and REY in the mud. We make in situ compositional analyses of constituent minerals in the REY mud. The results show that the apatite is abundant in REY (9300-32,000 ppm) and is characterized by a negative Ce anomaly and enrichment in heavy rare-earth elements. This abundance and composition of REY of the mud is similar those of fish debris apatites. In contrast, phillipsite is less abundant in REY (60-170 ppm). Therefore we conclude that the main REY host phase of the mud is apatite.

Major and trace element compositions and resource potential of ferromanganese crust at Takuyo Daigo Seamount, northwestern Pacific Ocean

“…Based on the mole fractions of Ca and P, the regression-line slope is 0.48. This value is smaller than the ideal stoichiometry of Ca and P fractions in the Ca-phosphate phase (apatite) (5:3 = 0.6), but is similar to that in the REE-rich deep-sea mud near the Minami-Torishima Island (Kon et al, 2014). Moreover, the Ca-and P-rich parts of the crusts sometimes appear white or pale brownish color, indicating that the amount of apatite increases with depth in the crust.…”

“…8b). A laser ablation ICP-MS analysis of apatite in the REE-rich deep-sea mud near Minami-Torishima Island has shown that apatite has a HREE-enriched pattern with a conspicuous negative Ce anomaly, similar to modern seawater (Kon et al, 2014). Thus, the slightly HREE-enriched patterns in samples with more than 0.5 wt% P can be produced by a mixture of non-phosphatized Fe-Mn crust and apatite.…”

Transfer of rare earth elements (REE) from manganese oxides to phosphates during early diagenesis in pelagic sediments inferred from REE patterns, X-ray absorption spectroscopy, and chemical leaching method

“…We identified the host phase of REEs based on chemical leaching technique previously employed by Toyoda and Masuda (1991) and Takebe (2005). In addition, we have obtained the REE patterns of Mn 4+ oxides and apatite by measuring REE contents of each phase directly using laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) as reported by Kon et al (2014). As for chemical species that can be effected by the early diagenesis, the oxidation state of Ce related to the appearance of Ce anomaly in sediments was determined by X-ray absorption near-edge structure (XANES) at the Ce L III -edge (Takahashi et al, 2000a), coupled with the speciation of Mn and Fe by K-edge XANES (Fukukawa et al, 2004;Takahashi et al, 2011).…”

Challenges for the Production of Heavy Rare Earth Elements from Hard Rocks

“…The apatite in the deep-sea mud around Minami-Torishima Island is enriched in REE, especially HREE (Table 5), and has characteristics similar to those of fish debris [16]. Thus, the origin of the deep-sea mud apatite is completely different from those in IOA deposits, and is characterized by relatively low contents of radioactive elements (Th: 140 ppm, U : 21 ppm) [16].…”