Shigen-Chishitsu
Online ISSN : 2185-4033
Print ISSN : 0918-2454
ISSN-L : 0918-2454
Volume 64, Issue 3
Displaying 1-3 of 3 articles from this issue
Review Articles
  • Kyoko YAMAOKA
    2014Volume 64Issue 3 Pages 117-125
    Published: 2014
    Released on J-STAGE: January 14, 2016
    JOURNAL FREE ACCESS
    Evaporite borates are the largest industrial source of boron in the world. The major productions come from the Neogene lacustrine borate deposits in western Turkey and California, USA. The formation of large borate deposits is closely related to 1) magmatic processes to form volcanic rocks enriched in boron, 2) leaching of boron from rocks by hydrothermal activity, and 3) evaporation of playa lakes in a dry climate. Boron isotope could be a useful tool to identify the origin of boron and to constrain the physicochemical conditions (e.g., pH) during borate precipitation. This article reviews the studies on boron isotope geochemistry of borate deposits. The future possibility of lithium production from borate deposits is also presented.
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  • Shunso ISHIHARA
    2014Volume 64Issue 3 Pages 127-132
    Published: 2014
    Released on J-STAGE: January 14, 2016
    JOURNAL FREE ACCESS
    Zr contents of granitic rocks of the major intrusive bodies in Japan were evaluated on the Harker diagrams. The contents show three patterns as (i) increasing type, (ii) decreasing type, and (iii) decreasing after increasing type. The first type is best shown in the M-type magnetite-series of Tanzawa tonalites, which was generated in Zr-poor mafic igneous source rocks at depth, then never saturated with Zr in magmas; thus the contents increase with the crystallization. The second type is common in the ilmenite series originated in crust materials, which was saturated with Zr at the beginning of crystallization; thus the content decreases as the silica increases. In the third-type magma, Zr increases with the increasing silica content, then around 66% SiO2 starting to decease after saturation of Zr. This is most commonly seen in the magnetite-series granitoids. Thus, variation of the Zr contents in granitoids is essentially controlled by the original Zr contents of the granitic magmas in Japan.
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