岐阜県神岡鉱山茂住鉱床の鉱化プロセス-鉱物化学と流体包有物による研究- Ore Formation Processes of the Mozumi Skarn-type Pb-Zn-Ag Deposit in the Kamioka Mine, Gifu Prefecture, Central Japan -A Mineral Chemistry and Fluid Inclusion Study-

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著者

    • 鞠子 正 MARIKO Tadashi
    • Institute of Earth Science, School of Education, Waseda University Institute of Earth Science, School of Education, Waseda University
    • 河田 真伸 KAWADA Masanobu
    • Department of Mineral Resources, School of Science and Engineering, Waseda University Department of Mineral Resources, School of Science and Engineering, Waseda University
    • 三浦 充 [他] MIURA Mitsuru
    • Department of Mineral Resources, School of Science and Engineering, Waseda University Department of Mineral Resources, School of Science and Engineering, Waseda University
    • 小野 周平 ONO Shuhei
    • Department of Mineral Resources, School of Science and Engineering, Waseda University Department of Mineral Resources, School of Science and Engineering, Waseda University

抄録

神岡鉱山茂住スカルン型Zn-Pb-Ag鉱床は飛騨片麻岩類の結晶質石灰岩中に産する,その鉱化プロセスは5期に分けることができる.最初の単斜輝石―亜鉛―鉛鉱化期は第1ステージ(400-330℃)での大量の単斜輝石(Di<SUB>10-35</SUB>Hd<SUB>43-75</SUB>Jo<SUB>11-35</SUB>)の生成に始まる.これに伴って少量のグランダイト系ざくろ石(Ad<SUB>16-78</SUB>),方解石,石英,含銀・蒼鉛方鉛鉱,自然蒼鉛,輝蒼鉛鉱, Ag-Pb-Bi-S系鉱物および鉄に乏しい閃亜鉛鉱(3-8 FeS mole%)が晶出する.この期の第2ステージ(320-240℃)は,第1ステージに晶出が始まった硫化鉱物生成の最盛期となる.第2ステージ末期には鉱化流体の鉄濃度が上がり早期生成の単斜輝石および閃亜鉛鉱の一部を交代して,それぞれヘデンベルグ輝石質輝石(Hd<SUB>59-88</SUB>)と鉄に富む閃亜鉛鉱(9-14FeS mole%)を生成している.数の方解石―石英―鉛―亜鉛鉱化期の第1ステージ(400-300℃)には早期方解石,早期石英および鉄に乏しい閃亜鉛鉱(3-7 FeS mole%)が含銀・蒼鉛方鉛鉱,自然蒼鉛,輝蒼鉛鉱, Ag-Pb-Bi-S系鉱物を伴い石灰岩あるいは一部の単斜輝石―亜鉛―鉛鉱を交代して生成した.第2ステージ(300-230℃)には,浸透してきた鉄に富む鉱化流体が早期の閃亜鉛鉱を一部鉄閃亜鉛鉱(7-21 FeS mole%)に置換し,少量の黄銅鉱,黄鉄鉱磁硫鉄鉱,硫砒鉄鉱磁鉄鉱を生成した.また含銀・蒼鉛方鉛鉱,自然蒼鉛,輝蒼鉛鉱, Ag-Pb-Bi-S系鉱物の晶出もひき続いた.第3ステージ(230-150℃)にはいると,鉄に富む閃亜鉛鉱(10-14 FeS mole%),含銀四面銅鉱とともに後期方鉛鉱(銀に乏しい)が生成された.このステージの末期には少量の赤鉄鉱が,後期方解石,後期石英,緑廉石とともに生じている.第3のアクチノ閃石―銅鉱化期は早期に形成された単斜輝石不毛スカルンおよび単斜輝石―亜鉛―鉛鉱に対する加水分解および鉄・銅付加作用により特徴づけられる.すなわち,鉱床下部で単斜輝石はアクチノ閃石により広く交代され,これに伴い石英,硫石比鉄鉱,磁鉄鉱,黄鉄鉱,磁硫鉄鉱,黄銅鉱,鉄閃亜鉛鉱などが晶出した.第4の石英―方解石―銅鉱化期および第5の石英―銀鉱化期の鉱化作用は局部的である.以上の各鉱化期の鉱化作用は,熱源としての火成岩は共通しているが,それぞれ独自の通路を持った循環熱水系により行われたと考えられる.

The Mozumi skarn-type Zn-Pb-Ag deposit of the Kamioka mine occurs in crystalline limestone of the Hida gneisses. The ore formation processes are divided into five periods: clinopyroxene-Zn-Pb, calcite-quartz-Pb-Zn, actinolite-Cu, quartze-calcite-Cu and quartz-Ag periods, in order of formation. The clinopyroxene-Zn-Pb period began with the formation of huge amounts of clinopyroxene (Di<SUB>10-35</SUB>Hd<SUB>43-75</SUB>Jo<SUB>11-35</SUB>) at 400-330°C, associated with minor amounts of grandite garnet (Ad<SUB>16-78</SUB>), calcite, quartz, Ag-and Bi-bearing galena, native bismuth, bismuthinite, Ag-Pb-Bi-S minerals and Fe-poor sphalerite(3-8 FeS mole%). The second stage (240-12°C) of the first period was the main sulfidation stage. The sulfide minerals, which had already begun to crystallize during the first stage, vigorously formed in this second stage and replaced earlier-formed pyroxene and garnet. During the late second stage, the ore fluid increased in Fe content and produced hedenbergetic pyroxene (Hd<SUB>53-88</SUB>) and Fe-rich sphalerite (9-14 FeS mole%), which replaced portions of earlier-formed pyroxene and sphalerite, respectively. During the first stage of the calcite-quartz-Pb-Zn period, early calcite(400-270°C), quartz (360-310°C) and Fe-poor sphalerite (400-270°C; 3-7 FeS mole%) associated with Ag-and Bi-bearing galena, native bismuth, bismuthinite and Ag-Pb-Bi-S minerals were formed by replacing limestone and a part of the clinopyroxene-Zn-Pb ore. In the second stage (300-230°C), infiltrated Fe-rich ore fluid produced Fe-rich sphalerite (7-21 FeS mole%) which replaced early sphalerite and minor amounts of chalcopyrite, pyrite, pyrrhotite, arsenopyrite and magnetite. Ag-and Bi-bearing galena, native bismuth, bismuthinite and Ag-Pb-Bi-S minerals continued to precipitate at this stage. During the succeeding third stage (230-150°C), late galena (Ag-poor), freibergite and Fe-rich sphalerite (10-14 FeS mole%) were formed. At the end of this stage, a minor amount of hematite crystallized in association with late calcite, quartz and epidote. The actinolite-Cu period was characterized by hydration and Fe and Cu metasomatism of the early-formed barren clinopyroxene skarn and clinopyroxene-Zn-Pb ore. During this period, clinopyroxene was extensively replaced by actinolite in the lower levels of the deposit, associated with quartz, arsenopyrite, magnetite, pyrite, pyrrhotite, chalcopyrite, Fe-rich sphalerite and other sulfide minerals. Ore formation during the quartz-calcite-Cu and quartz-Ag periods was local. Ores produced during these five periods are thought to have been formed by different hydrothermal circulation systems that were controlled by a common igneous heat source.

収録刊行物

  • 資源地質  

    資源地質 46(6), 337-354, 1996-12-01 

    The Society of Resource Geology

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各種コード

  • NII論文ID(NAID)
    10002859167
  • NII書誌ID(NCID)
    AN10379890
  • 本文言語コード
    ENG
  • 資料種別
    ART
  • ISSN
    09182454
  • NDL 記事登録ID
    4127416
  • NDL 雑誌分類
    ZM49(科学技術--地球科学--地質) // ZM46(科学技術--地球科学--岩石・鉱物・鉱床)
  • NDL 請求記号
    Z15-123
  • データ提供元
    CJP書誌  CJP引用  NDL  J-STAGE 
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