Copper - Gold - Arsenic - (Bismuth) deposits of the orogenic type in Flatschach, Styria

Structurally controlled Cu-Au mineralisations were mined in the historic Flatschach mining area (Styria, Austria). The mineralisations are bound to steep NE-SW to NNE-WSW vein-like structures with calcite-(dolomite)-quartz as vein type, which intersect amphibolite-facies metamorphic rocks (banded biotite gneisses/amphibolites, orthogneiss, metagranitoid). The secondary rocks are attributed to the polymetamorphic eastern alpine Silvretta-Seckau cover system. The formation of the veins occurred after the ductile deformation phases and after the peak of the eoalpid metamorphism in the Upper Cretaceous, but before the deposition of the coal-bearing early to middle Miocene sediments of the Fohnsdorf Pull-Apart Basin.

Three gold-bearing stages of mineralisation can be distinguished. Stage 1 is the primary hydrohermal (mesothermal?) mineral assemblage dominated by chalcopyrite, pyrite and arsenopyrite. Associated minerals are alloclasite, enargite, bornite, sphalerite, galenite, bismuth and matildite. Gold occurs in inclusions, healed microcracks and at the grain boundaries of the sulphides. Sericite-carbonate alteration accompanies this stage. Stage 2 ore minerals are formed by displacement of the older sulphides and include digenite, anilite, "covelline" (spy-copite, yarrowite), dignified bismuth, and the rare copper arsenides domeykite and koutekite. Stage 2 gold occurs preferentially with carbonates (calcite, Fe dolomite) and less frequently with digenite, domeykite/ koutekite and bismuth. Stage 3 comprises the strongly oxidised mineral association with haematite, cuprite and other secondary Cu and Fe hydroxides and carbonates. It is formed in the course of supergene weathering processes. Stage 1 and 2 gold is mainly electrum (gold fineness 640-860), rarely pure gold (fineness 930-940). Stage 3 gold is silver-rich electrum (fineness 350-490), and also has a high mercury content (up to 11 mass % Hg).

The Cu-Au mineralisation in the Flatschach area shows similarities to meso- to epizonal orogenic vein-type gold deposits in terms of geology, structural control of mineralisation, style of alteration, mineral assemblage of early stage mineralisation and composition of gold.  Unusually, the overprinting of this earlier mineralisation stage at lower temperatures resulted in the formation of the arsenides domeykite and koutekite and the copper sulphides djurleit, yarrowite and spionkopite. Based on the stability relationships of these phases, the formation temperature for stage 2 is narrowed down between 70 °C and 160 °C. Gold was found very locally during this low-temperature phase. Gold was mobilised very locally during this low-temperature hydrothermal phase and by supergene oxidation and cementation processes (stage 3).

Mineralogical studies on carbonation

As part of the GreenRef third-party funded project with a company in the raw materials industry, various possibilities for CO2 reduction in the production and processing of raw materials are being investigated in an interdisciplinary manner at the University of Leoben, with a focus on the carbonation of geogenic and technogenic materials. A sub-project carried out at the Chair of Geology and Deposit Science and Chair of Resource Material Mineralogy investigates the availability and suitability of rocks for carbonation and CO2 fixation. Third-party funded projects on similar topics are being carried out with the oil and gas industry.

The methodological approach of these externally funded projects is based on the most complete mineralogical-petrographical and chemical characterisation possible using optical microscopy, electron microscopy, X-ray diffraction and chemical analysis (XRF). These projects are supervised by Dr. Monika Feichter.

Formation of sparry magnesite from the Hochfilzen mining district (European Eastern Alps, Austria)

Magnesite is an essential raw material for the refractory industry and therefore of cardinal importance for Europe as an industrial location. Austria has always played a leading role in the research of sparry magnesite. However, despite the long history of research, there is still no consensus on the formation of this type of magnesite and the number of modern publications on Austrian magnesite occurrences is low.

As part of the Horizon Europe project MultiMiner and the project MRI_Magnesit in cooperation with the GeoSphere Austria and RHI Magnesita AG, the magnesite mining district of Hochfilzen (Weißenstein, Bürgl) is being scientifically reprocessed by using modern methods. This district is part of the Tirolic-Noric Nappe System and the magnesite deposits are largely associated with Silurian-Devonian dolostones of the Hochhörndler Complex. The formation of the Hochfilzen magnesite has been controversially discussed in the past. 

In order to understand the formation of magnesite and to establish a formation model, (1) the age of the magnesite must be determined and (2) the mineralizing fluid must be characterized. A number of analytical methods are used for this purpose: The geochemical information of the main minerals is determined by electron microprobe analyses (major elements) and LA-ICP-MS (trace elements). In addition, the element distribution in hand specimens is mapped (µ-XRF), stable isotopes are measured and carbon-rich material is analyzed by Raman spectroscopy. In order to define the mineralizing fluid, fluid inclusion studies will be carried out and Sm-Nd age dating of carbonates will help to place the magnesite formation in a geodynamic context.

Hydrogen storage - In-situ hydrogen storage in depleted gas fields - Investigations on the interactions of hydrogen with well cements and on well integrity

In order to be able to use hydrogen safely and efficiently as a sustainable energy carrier in the future, there is still a considerable need for research, especially on the topic of hydrogen storage. Due to their size, natural geological reservoirs (e.g. depleted natural gas or oil fields) in particular promise great potential for underground hydrogen storage (UHS).

A significant knowledge gap still exists regarding the integrity of borehole materials, in particular the resistance of borehole cements with regard to the interaction with hydrogen or hydrogen-containing gas mixtures. The aim of this research project is therefore to evaluate fundamental questions regarding the mechanical and chemical integrity of downhole cements with respect to hydrogen, as well as possible qualitative and quantitative mineralogical changes in the composition of various downhole cements used in practice and their influence on physical parameters such as porosity or permeability. Thomas Sammer is working on these questions in the course of a doctoral thesis. This doctoral project is a cooperation between the Chairs of Resource Mineralogy and Drilling Engineering. It is financed by the doctoral initiative "Hydrogen Storage" of the University of Leoben.

W Alps - Studies on the genesis of deposits and the assessment of the prospectivity of tungsten deposits in the Eastern Alps

Tungsten is one of the raw materials classified as critical by the EU Commission and is extracted in Austria in the Felbertal deposit.

Within the framework of the W Alps project (W for tungsten), various tungsten deposits and occurrences in the Eastern Alps are being scientifically re-examined, which occur in different geological-tectonic units of the Eastern Alps and were found in the course of prospecting activities in the past decades. The most important tungsten mineral in the Eastern Alps is the Calcium Tungstate Scheelite (Ca[WO4]), which fluoresces under short-wave UV light.

One focus of the "W Alps" project is the chemical analysis (LA-ICP-MS) of the trace elements in scheelite with the central question to what extent there is a deposit-specific "fingerprint" that can be used for tungsten prospecting. This project is carried out within the framework of the "Mineral Resources Research Partnerships (MRI) - a strategic research focus of the Federal Geological Survey" and is a cooperation of the University of Leoben with the Federal Geological Survey (GBA) and Wolfram Bergbau und Hütten AG (WBH). The TU Bergakademie Freiberg and the University of Münster are also involved. Florian Altenberger, a doctoral student in the department, has been working on this project since 2019 as part of his doctoral thesis.

MRI Project Magnesit

Austria is an important producer of Magnesite, which is largely used in the refractory industry. Of the different types of Magnesite deposits, spar Magnesite is of greatest economic importance in Austria (e.g. Breitenau). They occur in different eastern alpine geological-tectonic units and their genesis has been controversially discussed for decades. In the MRI-Magnesite project, open scientific questions on the formation of Magnesite deposits occurring in different geological units of the Eastern Alps will be addressed. Application-relevant aspects of the project investigate, in cooperation with RHI Magnesita, the spatial-vertical distribution and composition of the Magnesite accessory minerals within the Breitenau deposit and their possible influence on the raw material quality. In addition to the Geological Survey and the University of Leoben, the Graz University of Technology is a scientific cooperation partner. On the industry side, this project is supported by RHI Magnesita AG.