Mineralogy, geochemistry, and evolution of the Mn-Fe phosphate minerals within the pegmatite in Cheolwon, Gyeonggi Massif

Gyoo Bo Kim, Seon-Gyu Choi, Jieun Seo, Chang Seong Kim, Jiwon Kim, Minho Koo

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Abstract

Mn-Fe phosphate mineral complexes included within the pegmatite are observed at Jurassic Cheolwon two-mica granite in Gyeonggi Massif, South Korea. The genetic evolution between the Cheolwon two-mica granite and pegmatite, and various trend of Mn-Fe phosphate minerals is made by later magmatic, hydrothermal, and weathering process based on mineralogical, geochemical analysis. The Cheolwon two-mica granite is identified as S-type granite, considering its chemical composition (metaluminous ∼ peraluminous), post-collisional environment, low magnetic susceptibility, and existence of biotite and muscovite. The K-Ar age (ca. 153 Ma) of pegmatite is well coincident with age of the Cheolwon two-mica granite (151±4 Ma). It indicates that these two rocks are originated from the same magma. Pegmatite indicates the LCT geochemical signature, and was classified as muscovite-rare element class / Li subclass / beryl type / beryl-columbite-phosphate subtype pegmatite. The triplite {(Fe0.4 2+,Mn1.6)(PO4)(F0.9)} is dominant phosphates in later magmatic stage which partly altered to leucophosphite {KFe3+ 2(PO4)2OH·2H2O} and jahnsite {(Fe3+ 0.7,Mn2.3)(PO4)2OH·4H2O} by hydrothermal alteration. In particular, near fractures, the triplite has been separatelty replaced by the phosphosiderite (Fe3+PO4·2H2O) and Mn-oxide minerals during weathering stage.

Original languageEnglish
Pages (from-to)181-193
Number of pages13
JournalEconomic and Environmental Geology
Volume50
Issue number3
DOIs
Publication statusPublished - 2017 Jun 1

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Keywords

  • Jahnsite
  • Leucophosphite
  • Pegmatite
  • Phosphate mineral
  • Phosphosiderite
  • Triplite

ASJC Scopus subject areas

  • Geology
  • Economic Geology
  • Environmental Science (miscellaneous)

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