Occurrence of halogen-rich phlogopite in Late Cenozoic volcanic rocks in the Japanese arcs

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Abstract

Halogen-rich phlogopite occurs in the groundmass of andesite and dacite lavas from Late Tertiary to Quaternary volcanoes associated with native sulfur and limonite deposits (Shiretoko-Iwozan, Hachimantai, Adatara, Omeshidake, Masaki) and hydrothermal ore deposits (Harukayama, Muineyama, Hishikari) in Japan. The F contents of the halogen-rich phlogopite range from 3.6 to 5.7 wt%, corresponding to atomic F/(F+Cl+OH) ratios ranging from 0.45 to 0.69. On the other hand, the Cl contents of the halogen-rich phlogopite are around 0.2 wt%. The atomic Mg/(Mg+Fe) ratios range from 0.69 to 0.83. The fluorine intercept value [IV(F)] defined by Munoz (1984) of the phlogopites ranges from 0.79 to 3.17, and the chlorine intercept value [IV(Cl)] ranges from -7.11 to -7.77. The observed IV(F) of the phlogopites broadly overlap the range of the IV (F) for biotites from porphyry copper deposits. On the other hand, the observed IV(Cl) are significantly lower than the IV(Cl) for biotites from porphyry copper deposits. Whereas the F contents of the phlogopite appear more prominent compared to the Cl contents, the calculation of halogen intercept values revealed that the phlogopites are enriched in Cl with respect to the element distribution effect of Mg-Fe substitution. Since the degree of Cl enrichment of the phlogopite is more significant compared to that of biotite in porphyry copper deposits, the phlogopites are considered to have formed under the condition of significantly high activity of halogens. Hydrothermal ore deposits may be formed in magmatic hydrothermal system associated with volcanoes where halogen-rich phlogopite is formed by hypersaline fluid.

Original languageEnglish
Pages (from-to)153-166
Number of pages14
JournalResource Geology
Volume54
Issue number2
DOIs
Publication statusPublished - Jun 1 2004

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Volcanic rocks
Halogens
phlogopite
halogen
volcanic rock
Copper deposits
porphyry
Ore deposits
Volcanoes
copper
ore deposit
volcano
Fluorine
Chlorine
fluorine
dacite
hydrothermal system
Sulfur
andesite
chlorine

All Science Journal Classification (ASJC) codes

  • Geology
  • Geochemistry and Petrology

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Occurrence of halogen-rich phlogopite in Late Cenozoic volcanic rocks in the Japanese arcs. / Imai, Akira.

In: Resource Geology, Vol. 54, No. 2, 01.06.2004, p. 153-166.

Research output: Contribution to journalArticle

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title = "Occurrence of halogen-rich phlogopite in Late Cenozoic volcanic rocks in the Japanese arcs",
abstract = "Halogen-rich phlogopite occurs in the groundmass of andesite and dacite lavas from Late Tertiary to Quaternary volcanoes associated with native sulfur and limonite deposits (Shiretoko-Iwozan, Hachimantai, Adatara, Omeshidake, Masaki) and hydrothermal ore deposits (Harukayama, Muineyama, Hishikari) in Japan. The F contents of the halogen-rich phlogopite range from 3.6 to 5.7 wt{\%}, corresponding to atomic F/(F+Cl+OH) ratios ranging from 0.45 to 0.69. On the other hand, the Cl contents of the halogen-rich phlogopite are around 0.2 wt{\%}. The atomic Mg/(Mg+Fe) ratios range from 0.69 to 0.83. The fluorine intercept value [IV(F)] defined by Munoz (1984) of the phlogopites ranges from 0.79 to 3.17, and the chlorine intercept value [IV(Cl)] ranges from -7.11 to -7.77. The observed IV(F) of the phlogopites broadly overlap the range of the IV (F) for biotites from porphyry copper deposits. On the other hand, the observed IV(Cl) are significantly lower than the IV(Cl) for biotites from porphyry copper deposits. Whereas the F contents of the phlogopite appear more prominent compared to the Cl contents, the calculation of halogen intercept values revealed that the phlogopites are enriched in Cl with respect to the element distribution effect of Mg-Fe substitution. Since the degree of Cl enrichment of the phlogopite is more significant compared to that of biotite in porphyry copper deposits, the phlogopites are considered to have formed under the condition of significantly high activity of halogens. Hydrothermal ore deposits may be formed in magmatic hydrothermal system associated with volcanoes where halogen-rich phlogopite is formed by hypersaline fluid.",
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