Stable isotope geothermometry applied to selected vein type ore deposits of the Eastern Alps

Research output: ThesisDoctoral ThesisResearch

Abstract

Quartz and various carbonate minerals often form gangue minerals within hydrothermal ore deposits. This thesis deals with the applicability of carbonate-quartz gangue as geothermometer. The results are comparable with “classical” geothermometers like microthermometry and cation exchange geothermometers. The temperature range is crosschecked with results of arsenopyrite and solid solution geothermometry. The applicability of stable isotope geothermometry is limited by the grade of isotopic equilibrium between quartz and carbonate and possible younger alteration by migrating fluids. Vein deposits with great vertical extent within the Austroalpine and Sub-Penninic parts of the Eastern Alps were the objects of study. The individual deposits of Erzwies-Siglitz (Pb-Zn), Mitterberg-Buchberg (Cu), Radmer (Cu), Zinkwand (Ni-Co-Bi), Tösens (Pb-Zn) and Kraubath (magnesite) are discussed in detail. The reconstruction of the mineralising fluids results in similar mineralising processes during Eo-Alpine and Neogene times. The main motor of metallogenesis within the worked deposits are metamorphic waters driven by orogenic induced fluid flow. The formation of the Erzwies-Siglitz, Mitterberg-Buchberg, Radmer, Tösens and Zinkwand deposits is related to such metamorphogenous _uids. Although formation ages, mineralogy and host rocks are different the mineralising fluids are dominated by fluids enriched in δ18O (7 to 18 ‰ VSMOW) and depleted in δ13C (-6 to -14 ‰ VPDB). Metasediments and metacarbonates represent the main source rocks for this kind of metamorphogenic fluids. The investigated metamorphogenous deposits are the product of a multiphase genesis. Primary fine dispersed metals or transition metals or enrichments thereof were mobilised by metamorphogenous fluids during Variscan and Alpine orogenesis. The declining orogenesis with subsequent extensional tectonics lead to the formation of vein type deposits. Another important mineralisation process is represented by the formation of magnesite close to the palaeosurface. The cryptocrystalline magnesite deposit of Kraubath is bound to shallow extensional tectonic structures in form of veins. Subsidiary sedimentary magnesite occurs within hangingwall Miocene sediments. In this case, the mineralising low tempered hydrothermal fluid system is strongly influenced by meteoric waters. Suggestions for the application of quartz-carbonate mineral pairs as geothermometer and for the reconstruction of mineralising fluid systems at a regional scale conclude this work.

Details

Translated title of the contributionStabile Isotopengeothermometer angewendet an ausgewählten gangförmigen Erzvorkommen der Ostalpen
Original languageEnglish
QualificationDr.mont.
Supervisors/Advisors
Publication statusPublished - 2013