Shigen-Chishitsu
Online ISSN : 2185-4033
Print ISSN : 0918-2454
ISSN-L : 0918-2454
Volume 70, Issue 2
Displaying 1-5 of 5 articles from this issue
Preface
Original Articles
  • Shigenori OGIHARA
    Article type: Original Articles
    2020 Volume 70 Issue 2 Pages 89-99
    Published: December 21, 2020
    Released on J-STAGE: August 27, 2022
    JOURNAL FREE ACCESS

    Natural zeolites are produced in volcanic rocks and sedimentary rocks (pyroclastic rocks). Almost all zeolites in the volcanic rocks, which are in the primary occurrence, are secondary minerals due to alteration. The large zeolite crystals found in the veins and druses of volcanic rocks are formed by hydrothermal alteration or diagenesis. Zeolites in sedimentary rocks originate from highly reactive volcanic glass and are formed in high-alkaline environments or high-temperature environments. The formation of high-alkaline environment is classified into saline alkaline lakes, surface weathering of arid regions, and infiltration of rainwater. Zeolites formed by heat source are classified into hydrothermal alteration and diagenesis. In addition, there is a complex mixture cause of diagenesis and high-alkaline environment. An occurrence not classified in this category is zeolite in deep-sea sediments.

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Resource News
  • Eri SHIMIZU, Masanori SHIMOJO, Osamu TAKAHASHI
    2020 Volume 70 Issue 2 Pages 101-111
    Published: December 21, 2020
    Released on J-STAGE: August 27, 2022
    JOURNAL FREE ACCESS

    Japan Oil, Gas and Metals National Corporation (JOGMEC) and the State Committee of the Republic of Uzbekistan on Geology and Mineral Resources (GKG) started to jointly conduct an exploration on sandstone-type uranium deposits in the Meshetinskaya area, Navoi Region of the Republic of Uzbekistan in August 2016. The Meshetinskaya area northwardly straddles the Kyzylkum basin, where most of the sandstone-type deposits in the country are distributed, the Bukantau range and the Syr Darya basin. The area is approximately 2,057 km2. Although the potentiality of the sandstone-type uranium deposits had been suggested in this area, the detailed survey has not conducted before.

    JOGMEC and GKG have been carrying out a drilling campaign (35,780 m / 135 holes in total) up until now. As a result, favorable sandstone-type deposits with the redox front formation have been discovered in the Upper Cretaceous Maastrichtian, which are located less than 200m from the surface.

    The uranium deposits in the Meshetinskaya area are hosted in unconsolidated sand with good water permeability and sandstones in the Maastrichtian, laying between impermeable layers, such as marlstones, silty sandstones and siltstones. It turns out that this is the roll-front sandstone-type uranium deposits with the redox front formed through the infiltration of oxidized groundwater containing uranium from the east-northeastern project property. The reasons are that 1) uranium mineralization is recognized over the boundary between gray-colored reduced sand containing pyrite and carbonaceous material and light yellow-colored oxidized sand, 2) distribution of mineralization and the shape of deposits shown in the cross section, 3) distribution of the associated elements. The mineralization zone is continuously distributed along the extension of strike, running approximately 4.4 km long and a few to 300 m width. With resource estimation conducted in this targeted area, the scale of resource is confirmed approximately more than 2,000 tU, which is categorized as C2 in the resource classification of Uzbekistan.

    In terms of the development of uranium deposits in the Meshetinskaya area, the cost-competitive ISL (In-Situ Leaching) method is expected. The acquisition of various physical property values as applicable index and its evaluation were launched in 2019, and it is indicated that the ISL is an appropriate method as a preliminary result. In addition, it is confirmed that sulfuric acid leaching method is also suitable for the area due to the high recovery rate in the leaching test using sulfuric acid for the collected drilled cores.

    Since many of the areas along the extension of strike with the redox front have not yet explored, the further increase in the uranium resource will be expected. As a future plan, additional drilling campaigns to acquire and confirm the uranium resource, technical reviews, including Push-Pull tests and In-Situ tests, and economic evaluations toward the development will be conducted.

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  • Haruhisa MOROZUMI, Kazuo WATANABE, Hironobu SAKURAI, Hikari HINO, Yasu ...
    Article type: Resource News
    2020 Volume 70 Issue 2 Pages 113-119
    Published: December 21, 2020
    Released on J-STAGE: August 27, 2022
    JOURNAL FREE ACCESS

    Characteristics of ore deposits for marine mineral resources investigated by JOGMEC since 2014 was presented by Morozumi et al. (2020). Additional information for characteristics of seafloor hydrothermal deposits of the Gondou and Hakurei sites in the Okinawa area was obtained for three subjects.

    1) As to the footwall rocks of ore bodies of these sites, the multiple centers of the hydrothermal alteration are characterized by illite and kaolinite respectively. The footwall alteration is accompanied by chlorite, anhydrite and gypsum, whereas the centers of illite alteration lack anhydrite and gypsum.

    2) As to the footwall sediments of mound ore bodies of the Hakurei site, authigenic sulfides mineralization and exotic crystalline sulfides fragments are observed in these sediments.

    3) As to microscopic ore textures of the Gondou site, growth of chimneys with collapse and reworking are suggested for the formation of ore bodies, whereas some ore textures show the flow and feather structures about chalcopy rite and pyrite.

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  • Tetsuya SHOJI
    Article type: Resource News
    2020 Volume 70 Issue 2 Pages 121-155
    Published: December 21, 2020
    Released on J-STAGE: August 27, 2022
    JOURNAL FREE ACCESS

    COVID-19 is a topic taken up by everyone at every time in the latter half of this one year (from September 2019 to August 2020) when this annual review stands on. Many other topics, however, should be taken up for the exploration of mineral and energy resources in and by Japan as follows: 1) a Canadian exploration company drilled high-grade gold ore in Omu, Hokkaido, 2) a submarine hydrothermal deposit was discovered newly at sea floor near Amami-Oshima island, Kagoshima, 3) high grade Zn-Cu mineralization of the kuroko-type was fount in Fiji, 4) oil was also found at the Echino South structure in the Norwegian North Sea, and 5) commercial oil production was commenced from Yufutsu oil and gas field, Hokkaido, the Mariner gas field in UK North Sea, and the Layang oil and gas field offshore Sarawak, Malaysia.

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