Naslov
Ore-forming fluids in the Grübler orebody, Idrija mercury deposit, Slovenia

Autori
Palinkaš, Ladislav ; Strmić, Sabina ; Spangenberg, J.E. ; Prochaska, W. ; Herlec, U.

Izvornik
Schweizerische mineralogische und petrographische Mitteilungen (0036-7699) 84 (2004), 1-2; 173-188

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Idrija mercury deposit; fluid inclusions; S-isotopes; hydraulic fracturing; rifting

Sažetak
The Idrija mono-mineral mercury deposit is located in NW Dinarides, Slovenia, within a fault trough developed during Scythian-Ladinian aborted rifting. A paleo-geothermal system, a product of the Middle Triassic volcanism, created epigenetic and stratiform mercury mineralizations. Ascending chloride and hydrocarbon-rich fluid deposited cinnabar along sub-vertical normal faults and in pervasive host rocks, issuing its load in shallow water, euxinic environment. The subject of the research are fluid inclusions (FIs) in minerals, cinnabar, barite and quartz, and S-isotopes of cinnabar and barite, from the Grübler ore body, placed at the lower part of the geothermal system. The minerals in open-void fillings, cavities and dolomitic breccia were deposited during hydraulic fracturing and stained with hydrothermal petroleum. The ore-forming fluid was studied by micro-thermometry, laser Raman spectrometry, bulk ion crush-leach method with use of ion chromatography and atomic absorption spectrometry. The fluid has following characteristics: temperature of homogenization, Th, is between +160 and +180 °C, and salinity between 2.6 - 12.8 wt% NaCl equ. Low eutectic temperature, Te, (average -52 °C) indicates presence of bivalent cations, Mg, Ca, Na, K &plusmn ; ; ; ; ; ; ; Li, as confirmed by the bulk ion crush-leach method. Independent geothermometers attested formation temperature ; Na/K (206-265 °C), Na/Li (183 °C), Na/K/Ca (172-220 °C). Laser Raman spectroscopy determined no other liquids beside water, and confirmed dolomite as solid inclusions and daughter minerals in FIs. Cinnabar solid inclusions in the paragenetic quartz and barite point to their coeval origin. The δ 34S in cinnabar is between -0.7 and +1.5‰ (CDT), and in barite is between +45.6 and +56.3‰ . High values were attributed to disequilibrium during hydraulic fracturing. The data on FIs and S-isotopes obtained in the Idrija resemble in many respects to those in the Almaden deposit. The paper presents fluid inclusion data directly on the major ore mineral cinnabar, and introduces idea of hydraulic fracturing as an important event, which predestined evolution of the ore-forming fluids in a paleo-geothermal system of the Idrija deposit.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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