Trace element mapping of pyrite from Archean gold deposits - A comparison between PIXE and EPMA

A. Agangi, W. Przybyłowicz, A. Hofmann

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

Chemical zoning of pyrites can record the evolution of mineralising fluids at widely varying P-T conditions ranging from diagenesis to medium-grade metamorphism. If preserved, zoning can reveal growth textures, brecciation and veining, resorption and recrystallisation events, thus shedding light on the processes that contributed to ore formation. Chemical zoning of sulfides is invisible in optical microscopy, but can be studied by chemical etching, high-contrast back-scattering electron images, and elemental imaging. In this study we compared micro-PIXE and WDS-EPMA elemental maps on the chemically zoned pyrites in mineralised vein-bearing samples from the Sheba and Fairview gold mines in the Barberton Greenstone Belt, South Africa. Elemental images show complex distribution of trace elements, suggesting multiple events of pyrite crystallisation and gold deposition. EPMA maps show fine-scale variations reflecting growth and recrystallisation textures marked, in particular, by variations of As, Ni, and Co. In PIXE maps, gold occurs both as finely-distributed and discrete inclusions, suggesting incorporation in the pyrite structure as solid solution, and deposition as electrum inclusions, respectively. Micro-PIXE and EPMA provide complementary information, forming together a powerful tool to obtain information on chemical zoning of pyrites in ore deposits.

Original languageEnglish
Pages (from-to)302-306
Number of pages5
JournalNuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
Volume348
DOIs
Publication statusPublished - 2015

Keywords

  • Arsenopyrite
  • Barberton Greenstone Belt
  • Mesothermal gold
  • PIXE
  • Pyrite

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Instrumentation

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