Scheelitvererzungen im Thurntaler Quarzphyllitkomplex, Osttirol: Petrographische und chemische Untersuchungen an Nebengesteinen und Bachsedimenten

Translated title of the contribution: Scheelite occurrences in the Thurntaler Quartzphyllite Complex, Eastern Tyrol: petrographic and chemical investigations of host rocks and stream sediments

Tamara Portugaller

Research output: ThesisMaster's Thesis

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Abstract

This master thesis is part of an exploration project of Wolfram Bergbau und Hütten AG and was supervised by Prof. Johann G. Raith. Scheelite occurrences were studied in the Thurntaler Quartzphyllite Complex in Eastern Tyrol (communities of Innervillgraten, Ausservillgraten, Sillian; Marchginggele-Gumriaul). The complex consists of Early Palaeozoic quartzphyllites, (quartzitic) phyllites, greenstones (chlorite- and actinolite-rich varieties, amphibolites) and porphyroids (felsic metavolcanics). The protoliths of the metabasites were transitional subalkaline to alkaline tholeiites formed in an intra-plate geotectonic setting. Compared to MORB the rare earth elements (REE) patterns are enriched in light REE, do not show pronounced Eu anomalies and have flat heavy REE distribution. The stratabound scheelite mineralisation is hosted by greenschist facies carbonate-bearing metabasites. It mainly occurs in quartz-carbonate-(albite) veinlets, which are interpreted as pre- to synmetamorphic. The tungsten mineralisation and the host rocks were affected by several deformation phases and are metamorphically overprinted. The host rocks and stream sediments were petrographically and chemically characterised. The whole rock major and trace element composition of host rocks and the fine fraction of the stream sediments were analysed using ICP-ES and ICP-MS techniques. Mineral chemical compositions of scheelite, heavy minerals and rock-forming silicates were determined by electron microprobe techniques. Scheelite is Mo-poor, does not exhibit zoning and is sometimes associated with arsenopyrite and pyrite. This paragenetic association is also reflected in the stream sediment data and has been confirmed by multivariate statistics (factor analysis); W together with As defines one factor. Scheelite is the main W carrier although concentrations of up to 0.69 wt.% WO3 were detected in the Ti oxides ilmenite and rutile. The genesis of this mineralisation - a syngenetic ore formation was postulated in the past - and its possible profitability remain unclear.
Translated title of the contributionScheelite occurrences in the Thurntaler Quartzphyllite Complex, Eastern Tyrol: petrographic and chemical investigations of host rocks and stream sediments
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Raith, Johann, Supervisor (internal)
Award date25 Jun 2010
Publication statusPublished - 2010

Bibliographical note

embargoed until null

Keywords

  • Thurntaler Quartzphyllite Eastern Tyrol stratabound tungsten mineralisation scheelite stream sediment and whole rock geochemistry

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