Geologische Charakterisierung und 3D-Modellierung des Magnesitvorkommens Bürglkopf (Hochfilzen/Tirol; westliche Grauwackenzone)

Research output: ThesisMaster's ThesisResearch

Abstract

A geological 3D-model of the magnesite deposit Bürglkopf (Hochfilzen/Tyrol; western Graywacke zone) was generated after mapping of the accessible mining sites at the surface and underground. RFA-analyses of some qualitatively important chemical parameters (CaO, Fe2O3, SiO2, Al2O3, MnO) and microscopic investigations were performed of the sparry magnesite and Devonian carbonate host rock. The Bürglkopf magnesite displays a wide variety of colours. Black, brown, orange, reddish to violet magnesites are the most common types but there are many kinds of transitions in between. Magnesite occurs from massive, compact forms to weathered forms with earthy appearance. In the Rettenwand area brown, nodular magnesite (dm size) is enclosed mostly in greyish dolomite. Larger homogeneous magnesite bodies occur at the Bürgl open pit. A handicap of the 3D-modeling and detailed field mapping was the difficult field discrimination of dolomite and magnesite due to their similar colouration and the restricted accessibility of the galleries underground. The integration of the deposit into the regional tectonic structure is only tentative due to a lack of information outside the deposit. After a postulated pelagic calcareous sediment, six different generations of carbonate rocks/mineralizations were identified by microscopic analyses. Magnesite formed after the fine grained dolomite and was recognized as the second generation which was followed by three dolomite generations. Syngenetic formation can be excluded for the Bürglkopf magnesite due to field and thin section evidences, stratigraphy and sedimentary facies. Although favouring a metasomatic genetic model the origin and composition of the ore forming fluid, processes and age of mineralization are still uncertain. Different coloured types of carbonate rocks were analysed by RFA. The results indicate no significant variation of CaO, SiO2, Fe2O3, Al2O3 and MnO. The colouring is due to accessory minerals (limonite, pyrite, hematite, graphite). The basis for the 3D-modeling is a database with all available geological data (chemical analyses of channel samples underground, boreholes, geological cross sections, geological mapping). Contents of 6, 12 and 20 % CaO are the limiting values of the different qualities for the calculation of resources.

Details

Translated title of the contributionSparry magnesite deposit Bürglkopf (Hochfilzen/Tyrol; western Graywacke Zone): geological characterization and 3D-modeling
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
Award date25 Jun 2010
Publication statusPublished - 2010