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.

First, we show that a compact object C in a triangulated category, which satisfies suitable conditions, induces a t-structure. Second, in an abelian category we show that a complex P of small projective objects of term length two, which satisfies suitable conditions, induces a torsion theory. In the case of module categories, using a torsion theory, we give equivalent conditions for P to be a tilting complex. Finally, in the case of artin algebras, we give one to one correspondence between tilting complexes of term length two and torsion theories with certain conditions.

Studies of Mesozoic granites associated with rare earth element (REE)-rich weathered crust deposits in southernmost Jiangxi Province indicate that they have high-K to shoshonite compositions and belong to ilmenite-series I-type granites. Of the studied rocks at 59 -292 ppm of bulk REE content, the highest are seen in the biotite granites of Dingnan (358, 429 ppm) and mafi c biotite granite of the Wuliting Granite (344 ppm) near the Dajishan tungsten mine, both areas where weathered-crust REE deposits occur. REE-bearing accessory minerals in these granites are mainly zircon, apatite and allanite, and REE-fl uorocarbonates are common. REE enrichment occurs in the rims of apatite crystals, and in fl uorocarbonates that occur along grain boundaries of and cracks in major silicate minerals, and in fl uorocarbonates that replaced altered biotite. It is therefore thought that a major part of the REE content of these granites was concentrated during deuteric activity, rather than during magmatic crystallization. The crack-fi lling REE-fl uorocarbonates could subsequently have been easily leached out and deposited in weathered crust developed during a long period of exposure.