Differentiation und Lagerstättenpotential ausgewählter Pegmatite in Defereggen (Osttirol)

Translated title of the contribution: Differentiation and mineral potential of selected pegmatites in Defereggen (Eastern Tyrol)

Christian Horvat

Research output: ThesisMaster's Thesis

172 Downloads (Pure)

Abstract

In the eastern part of the Defereggen valley (Eastern Tyrol, Austria) pegmatites of Permian age occur in the Petzeck-Rotenkogel Complex and the Michelbach Complex of the Koralpe-Wölz and Drauzug-Gurktal Nappe System, respectively. Most of the pegmatites intruded concordantly into mica schists and gneisses. The pegmatites form dykes with a few centimeters up to some tens of meters in thickness. In some outcrops, faults can be observed. In addition to simple pegmatites, spodumene pegmatites occur in the area of Poling, Ratzell, Glanzalm and a newly discovered one at Großer Zunig mountain. The Li-pegmatites are mainly composed of quartz, K-feldspar, plagioclase, muscovite, spodumene, tourmaline and garnet. The contact to the host rock is often characterized by tourmalinisation. Accessory minerals detected in heavy mineral concentrates and thin sections include apatite, cassiterite, columbite group minerals, monazite group minerals, microlite group minerals, rutile, strüverite, uraninite, native bismuth, an undefined bismuth phosphate mineral, xenotime group minerals and zircon. Zircon and the columbite group minerals follow a general fractionation trend where Hf and Ta are enriched with respect to Zr and Nb, respectively. Columbite-(Fe) is the main columbite group mineral. Whole rock analyses of 5 simple pegmatite samples and 8 spodumene pegmatite samples are consistent with other pegmatites from the Eastern Alps. They yield up to 2,28 % Li2O, 99 ppm Nb and 249 ppm, respectively. LA-ICP-MS and SEM-EDS measurements were performed on 112 muscovites from 74 pegmatite occurrences. Maximum trace element contents are 1204 ppm Li, 6992 ppm Rb, 396 ppm Nb, 1181 ppm Sn, 1953 ppm Cs, 188 ppm Ta and 61 ppm Tl. The muscovites show low to high differentiation, with the highest ones exhibiting a K/Rb ratio of 11.5. Except of Li the trace element contents do not correlate with the occurrence of heavy minerals in the pegmatites. The spatial distribution of the degree of differentiation in mica shows east-west trending areas of a few hundred meters thickness where low degrees of differentiation alternate with high degrees. This distribution can be associated with regional folds. Certain zones of spodumene pegmatites contain up to 50 vol% of spodumene. Whole rock analyses of 8 spodumene pegmatite samples yield an average Li2O content of 1.12 %. Economically important heavy minerals were found in trace amounts. Further exploration is necessary for an economic assessment.
Translated title of the contributionDifferentiation and mineral potential of selected pegmatites in Defereggen (Eastern Tyrol)
Original languageGerman
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Mali, Heinrich, Co-Supervisor (internal)
  • Melcher, Frank, Supervisor (internal)
Publication statusPublished - 2021

Bibliographical note

embargoed until null

Keywords

  • Eastern Tyrol
  • Defereggen
  • Defereggen valley
  • pegmatites
  • spdoumene : differentiation
  • deposit

Cite this