Supergene vermiculitization of phlogopite and biotite in ultramafic and mafic rocks, central Korea

Hi Soo Moon, Yungoo Song, S. Y. Lee

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

An X-ray diffraction study of vermiculitized micas in ultramafic and mafic intrusive rocks from Cheongyang, Korea, shows the following weathering sequence: mica → ordered mica/vermiculite interstratification → vermiculite. Electron microprobe analyses show the general trends of K leaching and Ca enrichment with increased weathering. The vermiculitization of phlogopite from ultramafic rocks proceeds by means of a continuous decrease in Al-for-Si tetrahedral substitutions and a progressive increase in Al-for-(Fe2+ + Mg) octahedral substitutions in the early stage of weathering. These substitutions occur to compensate for the excess of negative charge in the mica-like layer, in agreement with currently accepted vermiculitization mechanisms. They change to a slight increase of Al-for-Si tetrahedral substitutions in the late stage of the vermiculitization of phlogopite, owing to the oxidation of Fe despite its low content. However, the behavior of Fe in the late stage of the transformation of biotite into vermiculite is significantly different; that is, Fe increases substantially. The reason for this Fe increase in the late stage remains unresolved. Recalculations of the structural formulas on the basis of several assumptions indicate that the oxidation of Fe is necessary for the vermiculite derived from biotite to form the reasonable structural formulas.

Original languageEnglish
Pages (from-to)259-268
Number of pages10
JournalClays and Clay Minerals
Volume42
Issue number3
DOIs
Publication statusPublished - 1994 Jun

Fingerprint

biotite
vermiculite
phlogopite
ultramafic rock
mafic rock
mica
Korean Peninsula
substitution
Substitution reactions
Weathering
rocks
Rocks
weathering
weathering sequences
ultramafic rocks
oxidation
Oxidation
X-ray diffraction
electron probe analysis
Leaching

All Science Journal Classification (ASJC) codes

  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)

Cite this

@article{0677590fc00143448cde7605d3ce487f,
title = "Supergene vermiculitization of phlogopite and biotite in ultramafic and mafic rocks, central Korea",
abstract = "An X-ray diffraction study of vermiculitized micas in ultramafic and mafic intrusive rocks from Cheongyang, Korea, shows the following weathering sequence: mica → ordered mica/vermiculite interstratification → vermiculite. Electron microprobe analyses show the general trends of K leaching and Ca enrichment with increased weathering. The vermiculitization of phlogopite from ultramafic rocks proceeds by means of a continuous decrease in Al-for-Si tetrahedral substitutions and a progressive increase in Al-for-(Fe2+ + Mg) octahedral substitutions in the early stage of weathering. These substitutions occur to compensate for the excess of negative charge in the mica-like layer, in agreement with currently accepted vermiculitization mechanisms. They change to a slight increase of Al-for-Si tetrahedral substitutions in the late stage of the vermiculitization of phlogopite, owing to the oxidation of Fe despite its low content. However, the behavior of Fe in the late stage of the transformation of biotite into vermiculite is significantly different; that is, Fe increases substantially. The reason for this Fe increase in the late stage remains unresolved. Recalculations of the structural formulas on the basis of several assumptions indicate that the oxidation of Fe is necessary for the vermiculite derived from biotite to form the reasonable structural formulas.",
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Supergene vermiculitization of phlogopite and biotite in ultramafic and mafic rocks, central Korea. / Moon, Hi Soo; Song, Yungoo; Lee, S. Y.

In: Clays and Clay Minerals, Vol. 42, No. 3, 06.1994, p. 259-268.

Research output: Contribution to journalArticle

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AB - An X-ray diffraction study of vermiculitized micas in ultramafic and mafic intrusive rocks from Cheongyang, Korea, shows the following weathering sequence: mica → ordered mica/vermiculite interstratification → vermiculite. Electron microprobe analyses show the general trends of K leaching and Ca enrichment with increased weathering. The vermiculitization of phlogopite from ultramafic rocks proceeds by means of a continuous decrease in Al-for-Si tetrahedral substitutions and a progressive increase in Al-for-(Fe2+ + Mg) octahedral substitutions in the early stage of weathering. These substitutions occur to compensate for the excess of negative charge in the mica-like layer, in agreement with currently accepted vermiculitization mechanisms. They change to a slight increase of Al-for-Si tetrahedral substitutions in the late stage of the vermiculitization of phlogopite, owing to the oxidation of Fe despite its low content. However, the behavior of Fe in the late stage of the transformation of biotite into vermiculite is significantly different; that is, Fe increases substantially. The reason for this Fe increase in the late stage remains unresolved. Recalculations of the structural formulas on the basis of several assumptions indicate that the oxidation of Fe is necessary for the vermiculite derived from biotite to form the reasonable structural formulas.

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