Wolframvererzungen und Intrusionsgesteine am Lienzer Schlossberg, Osttirol

Research output: ThesisMaster's Thesis

Organisational units

Abstract

In this master thesis W-mineralisation in the polymetallic skarn district “Drauzug-Gurktal Deckensystem Lienz-Hochstein” and rocks of the Periadriatic intrusion Edenwald have been studied. It is part of the MRI project W Alps. Three types of scheelite mineralisations can be distinguished at Lienzer Schlossberg: (1) Stratabound disseminated scheelite in quartz veins or quartz-rich rocks in the Thurntal Complex. (2) Scheelite in a sulphide-dominated skarn-mineralisation. Massive pyrrhotite-rich massive sulphides are present in the former open pit Schlossberg. They are associated with thin marble layers and calcsilicate rocks in metapelitic hornfels in close proximity to a hydrothermally altered tonalite body. This mineralisation can be classified as a skarn mineralisation, consisting of a prograde anhydrous high temperature stage with grossular, vesuvianite, diopside-hedenbergite, wollastonite, plagioclase and minor scheelite and retrograde hydrous low temperature phases. In the latter actinolite, biotite, epidote, quartz and scheelite formed before pyrrhotite and chalcopyrite and a final calcite phase. This skarn mineralisation is similar to reduced, magmatic W-skarns. (3) Scheelite in quartz veins and joints in rocks of the Edenwald intrusion and in the open pit Schlossberg. The Edenwald intrusion consists of diorites, tonalites, granodiorites and granites. They formed during a polyphase subduction related post-collision magmatic phase in the Oligocene. They are magnesian, calc-alkalic, metaluminous to peraluminous rocks. Relics of orthopyroxene, clinopyroxene and plagioclase in mafic micro-enclaves indicate the crystallisation of mantle-derived melts at an early stage. During the main crystallisation stage diorite and tonalite formed. Due to higher water content of the melt, biotite and hornblende crystallised. Pyroxene in the mafic micro-enclaves was transformed into cummingtonite and actinolite/hornblende. In the third magmatic phase strongly fractioned, porphyritic granodioritic to granitic dykes and intrusions were emplaced. The Edenwald intrusion is of the same age and petrographically and chemically similar to other Periadriatic intrusions like the Rieserferner intrusion. However, due to (post-)magmatic hydrothermal processes it has been enriched in tungsten, what is a unique feature of this intrusion. A spatial and genetic connection between the Edenwald intrusion and the W-mineralisation is envisaged based on the geological situation, similar characteristics like the reduced character and chemical criteria such as low Ni, Zn and Mo in both the intrusives and the mineralisation.

Details

Translated title of the contributionTungstenmineralisation and Intrusive Rocks at Lienzer Schlossberg, East Tyrol
Original languageGerman
QualificationDipl.-Ing.
Awarding Institution
Supervisors/Advisors
Award date1 Jul 2022
Publication statusPublished - 2022