Megacrystic phengite-bearing quartz veins associated with retrogressed eclogites occur along terrane boundary zone in the northern Ross orogen, Antarctica. The vein zircons crystallized from metamorphic fluid under high-pressure (P) conditions rather than captured as xenocrysts from the host eclogites, on the basis of: (1) weak oscillatory- and fir tree-zoned cathodoluminescence textures and extremely low Th/U ratios of zircon, (2) highly steep patterns of heavy rare earth elements and weak negative to positive Eu anomaly of zircons, suggesting their growth not in equilibrium with garnet and plagioclase, respectively; and (3) the high celadonite contents of phengite megacrysts (up to 3.33 a.p.f.u. Si for O = 11). Zircon U-Pb ages dated the high-P quartz vein formation at 501 ± 7 Ma (2σ), which overlaps with time of peak metamorphism of the eclogites at c. 500–498 Ma. The zircon crystallization age and marginal breakdown of phengite megacrysts into biotite–oligoclase symplectites suggest that the high-P quartz vein formation was at near-peak to early-exhumation stages of the eclogite facies metamorphism. The similarity in depths of the vein formation and major dehydration of subducting metamafic rocks further suggests that this fluid activity would be one of possible agents responsible for arc-related magmatism in northern Victoria Land of the Ross orogen.
The mineralogy and geochemistry of the weathered intercumulate-type anorthosite complex in the Hadong district of South Korea were investigated as a prospective area for rare earth resource exploration. In this area, gabbroic anorthosite was intruded by rare-earth elements and yttrium (REE)-bearing dioritic pegmatites (av. 242 ppm), which caused REE-enriched Fe–Ti orebody accumulation (av. 857 ppm) near the dioritic pegmatites. REE-bearing minerals, such as allanite, cerite, and xenotime, were identified from the pegmatite and orebody, which had undergone various degrees of weathering. The total REE (∑REE) in kaolin minerals-bearing clay fractions increased compared to those of the whole rocks. When treated with ammonium-salt solvents of different pH values, that is, 4.6 (NH4Cl(aq)), 5.0 ((NH4)2SO4(aq)), and 7.8 (NH4CO3(aq)), 81%, 73%, and 70% of the exchangeable REE of the kaolin minerals-bearing clay fractions were recovered in the dioritic pegmatites. respectively. In contrast, in kaolin minerals-deficient clay fractions separated from the Fe–Ti ores, exchangeable REE were recovered less than 10% after treatment, regardless of the ammonium-salt solvent species. Therefore, the occurrence of REE-bearing primary minerals in the parent rock, the formation of kaolin minerals-bearing clay fractions, and the extraction rate of exchangeable REE with ammonium-salt solvents seem to be crucial to securing the ion-adsorption type REE resources.
Observations in Oshino Village, Yamanashi Prefecture, Japan were conducted in January and August, 2017, and the water quality characteristics of the shallow and deep groundwater and spring water were elucidated. The water quality of the area’s shallow groundwater indicated the presence of relatively high levels of Ca-HCO3, Mg2+, and SO42– at some sites, and the deep groundwater contained Ca-HCO3, (Ca+Na)-HCO3, (Ca+Mg)-HCO3, and Na-HCO3. In August, the shallow groundwater at some sites was mixed with irrigation and paddy water affected by evaporation and fertilization. In deep groundwater, δ18O and δ2H levels were lower than those in shallow groundwater; therefore, the recharge area of deep groundwater probably increased as a result of elevation. The dissolved matter contents and isotope ratios of Deguchi-ike, which is one of the Oshino-Hakkai springs, were different from those of other Oshino-Hakkai springs, which may have been caused by differences in the recharge elevation. The vanadium and phosphorus concentrations of deep groundwater were relatively higher than those of the shallow groundwater and spring water, which may be ascribed to the influence of the basaltic rock of Mt. Fuji. Additionally, the observation of the groundwater level revealed two regional groundwater flow systems in Oshino Village: one flowed from south to north in the western part of the village, and the other flowed from east to west in the central to eastern part of the village. The former corresponded to a flow from Mt. Fuji to Oshino-Hakkai, and the latter to that from the Doshi Mountains to near Oshino-Hakkai.