We report bulk-sediment compositions of rare-earth elements and yttrium (REY), major and trace elements for “REY-rich mud” from 6 drill cores obtained by Ocean Drilling Program (Site 1215A, 1216A, 1217A, 1218A, 1220A and 1222A) off the southeastern coast of Hawaiian Islands. The REY-rich mud in study area has high REY contents, 400-1,178 ppm total REY (ΣREY), which are comparable to those of ion-absorption-type REY deposits in southern China. The core profiles indicate that the REY-rich mud has accumulated to thicknesses of 25-70 m. Some portions of REY-rich mud are typically enriched in Fe₂O₃, and their post-Archean average Australian shale (PAAS)-normalized REE patterns show strikingly negative Ce anomalies with the same magnitude of seawater. These geochemical characteristics are similar to those of modern hydrothermal Fe-rich sediments near the East Pacific Rise. This indicates that one of the main hosts for REY in the mud is a Fe-oxyhydroxide precipitate from hydrothermal plumes that has taken up REY from ambient seawater. On the other hand, the correlation diagram between ΣREY and Fe₂O₃ shows another ΣREY enrichment trend characterized by relatively low Fe contents, which infers an existence of the second REY-rich component. As the REY-rich samples on this trend contain significant amounts of phillipsite, the second REY-rich component is considered to be phillipsite. Here we estimate that a volume of 1 km² × Maximum Cumulated Concentration Depth (MCCD; in metric unit), which represents an appropriate mining depth, at Site 1222A holds nearly 12,200 t (14,000 tREO), which could provide one-tenth of the current annual world consumption of REY. We conclude that deep-sea REY-rich mud off the southeastern coast of Hawaiian Islands has a potential as a new mineral resource for REY.

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Based on the newly determined double-beta-decay half life of ¹³⁰Te ((7.0 ± 0.9_stat ± 1.1_syst) ×10²⁰ yr: Arnold et al., 2011), we have measured the direct mineralization ages on tellurium-bearing minerals from some hydrothermal gold deposits by the ¹³⁰Te-¹³⁰Xe* method. The results are as follows: Calaverite (21.9±2.3 Ma) from the epithermal Au-Te vein, Cripple Creek mining district, USA; Hessite-petzite (34.9±5.4 Ma) from the epithermal Au-Te vein, Cash mine, Boulder County, Colorado, USA; Altaite (1,040±80 Ma) from the Au-Te quartz-carbonate vein of the Mattagami Lake mine, Matagami, Quebec, Canada; Tellurobismuthite-tetradymite (9.4±1.2 Ma) from Bi-Te quartz vein, Tsushima Island, Nagasaki Prefecture, Japan; Tellurobismuthite (81.4±2.6 Ma) from hydrothermal Au-Te vein, Oya mine, Miyagi Prefecture, Japan;　Tellurobismuthite (85±18 Ma ) from the Au-Te quartz vein, Suwa mine, Ibaraki Prefecture, Japan. These ages are obviously younger than previously reported mineralization ages by K-Ar, Ar-Ar or Pb-Pb methods.

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Heavy minerals are examined in uranium ores and the associated rocks of the Tsukiyoshi orebody, Tono sandstone-type uranium deposit, central Japan. The samples used are uranium ores hosted in the Toki Lignite-bearing Formation, sandstones taken from a series of a stratigraphic succession, i.e., Toki Lignite-bearing, Hongo and Akeyo Formations in the Miocene Mizunami Group, in ascending order, and late Cretaceous to Paleogene basement granitic rocks. Amounts of heavy minerals are counted under a microscope for non-magnetic fractions with the specific gravity of >2.85 and the diameter from 0.0625 to 0.125 millimeter.
Heavy minerals in the uranium ores are composed mainly of biotite, green hornblende and opaque minerals, with minor clinopyroxene, epidote, zircon and brown hornblende. One ore sample contains topaz, cassiterite, garnet and allanite. Heavy minerals in the non-mineralized sandstone from the Toki Lignite-bearing Formation consist mainly of green hornblende and opaque minerals, with some clinopyroxene and orthopyroxene and minor brown hornblende, apatite, epidote and anatase. The sandstones from Hongo and Akeyo Formations contain clinopyroxene, orthopyroxene and opaque minerals. Heavy minerals in basement granitic rocks are composed mainly of biotite with some opaque mineral, zircon, fluorite, epidote and anatase.
On the basis of comparison of heavy mineral composition of rocks around the Tsukiyoshi orebody, three sources of detritus are estimated, i.e., (1) granitic source composed mainly of biotite, zircon and fluorite, (2) volcanic ash source of hornblendes and pyroxenes and (3) pegmatitic and hydrothermal sources of topaz and cassiterite. Uranium ores are proved to be embedded in the detritus mainly of granitic source, whereas the other sandstones in the Mizunami Group are mainly from volcanic source. Topaz and cassiterite in the ores are estimated to be derived from the pegmatitic and hydrothermal deposits with the Naegi granite developed at the northeastern side of the Tsukiyoshi orebody.

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Some technical notes on methodology of high quality in-situ deep groundwater sampling in drill holes are described. It is essential to know deep groundwater chemistry to make safety assessment of geological isolation of high level radioactive wastes. Chemistry of sampled groundwater can be changed by artificial disturbances such as drilling water contamination, mix with groundwater in different aquifers, reaction with atmosphere, and degassing by pressure leak. Because of low permeability of hard rocks in deeper formation, it is necessary to find water paths like open-space fractures to obtain groundwater in situ in realistic time periods. Water seepage records in drilling log, well loggings such as precise flowmeter log and flowing electric conductivity log, and drilled core observation are effective to recognize water paths. Attention should be paid for sampling immediately after drilling (if possible), removal of contaminated water from wells and adjacent formation, suppression of hydrogeochemical disturbance in and around wells, and maintenance of physicochemical conditions during sampling, withdrawal and transportation.

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It is one of the most important topics in not only geosciences but also mineral and energy resources world in Japan that the “Recommendations of the Commission on the Limits of the Continental Shelf regard to the submission made by Japan on 12 November 2008” was adopted by consensus on April 19, 2012. It is one of sensational topics, on the other hand, that gold prices recorded the highest values 1917.9 $/oz = 67.66 $/g on August 22, 2011 (NYMEX), and 4749 \/g on September 7, 2011 (TOCOM). Japanese mining, petroleum and trading companies and JOGMEC (Japan Oil, Gas and Metals National Corporation) continue their activities steadily, and get many fruitful results in exploration and development of mineral and energy resources, which have been carried out in these several years and decades. For example, Sumitomo Metal Mining Co., Ltd and Sumitomo Corporation have discovered a new gold deposit near the Pogo gold mine, Alaska. Idemitsu Kosan Co., Ltd has been awarded several exploration licences located in Norwegian North Sea. Mitsui Oil Exploration Co., Ltd has successfully commenced its first oil production from the Block L11/43, onshore Thailand on June 29, 2012. On January 13, 2011, INPEX Corp. and TOTAL S.A. confirmed the Final Investment Decision on the US$34 billion Ichthys LNG Project.

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The 13th Chilean Geological Congress was held in August 5th to 9th at Antofagasta. The author participated in the congress as an organizing committee member of economic geology areas. A short report on the congress and field trips is presented here for Resource Geology members.

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