Polyphase scheelite and stanniferous silicates in a W-(Sn) skarn close to Felbertal tungsten mine, Eastern Alps

Alexander Ordosch, Johann G. Raith, Steffen Schmidt, Karsten Aupers

Research output: Contribution to journalArticleResearchpeer-review

3 Citations (Scopus)

Abstract

The scheelite exploration target Messelingscharte (Eastern Tyrol, Austria) is located in vicinity of the world-class Felbertal tungsten deposit. W-(Sn) mineralisation occurs in Early Palaeozoic amphibolites (Basal Amphibolite unit) in the Tauern Window of the Eastern Alps. The most important mineralisation type is a Sn-bearing clinozoisite-scheelite skarn of pre-Alpine (Variscan?) age. It occurs as metre-sized irregular pods within amphibolites and amphibole schists. It is composed of major clinozoisite, quartz, plagioclase and scheelite with minor and accessory titanite, calcite and chlorite. Bulk chemical analyses reveal high concentrations of the granitophile elements W (≤7.74 wt% WO3), Sn (≤1254 ppm SnO2), Be (≤41 ppm) and base metals (Cu, Pb, Zn; ∑ ≤ 2500 ppm) in the skarn rock. Three scheelite types are distinguished based on micro-textures, zoning, Mo-content and UV- fluorescence. They show intriguing similarities to scheelite from the Felbertal tungsten deposit where pre-Alpine Mo-bearing scheelite was apparently overprinted by two stages of metamorphism. The unique feature of the investigated W-(Sn) skarn is the association of scheelite with Sn-bearing silicates. Stanniferous clinozoisite and stanniferous titanite were identified as the main Sn carriers (clinozoisite ≤3.00 wt% SnO2; titanite ≤6.48 wt% SnO2); both minerals evidence metamorphic re-crystallisation. Substitution of (Al, Fe)3+ by (Sn, Ti)4+ in clinozoisite is coupled with incorporation of Fe2+. The skarn formed by interaction of fluids of likely magmatic-hydrothermal origin with metabasites. The clinozoisite-dominated calc-silicate rocks are interpreted as a metamorphosed distal W-(Sn) skarn.
Original languageEnglish
Pages (from-to)703-725
Number of pages23
JournalMineralogy and Petrology
Volume113.2019
Issue number5
DOIs
Publication statusPublished - 6 Jul 2019

Keywords

  • Eastern Alps
  • Scheelite
  • Stanniferous clinozoisite
  • Tauern Window
  • Tungsten-tin skarn

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