Ore-Forming Fluids in Idrija Mercury Mine, Slovenia
2001
The Idrija mercury mine is situated 50 km west of Ljubljana, in the region which belongs to the Alpine promontary, transitional zone between Alps, Dinarides and Adriatic microplate. The ore deposit was formed by hydrothermal and exhalative processes within a Middle Triassic trough, deepened by extensional tectonics during the Tethyan rifting stage. Middle Triassic tectonics gave way to the upwelling hydrothermal solutions, which expelled their load onto the sea bottom through a thick pile of the Upper Paleozoic, Permian, Scythian, and Anisian clastics and carbonates, forming stratiform, synsedimentary mercury, pyrite rich ore in the black Sconca shales (Mlakar & Drovenik, 1971 ; Placer, 1976). On their way to the sea bottom, they mineralized fissures, pores, faults, breccia zones, and metasomatically replaced carbonates, and cement in clastics, assigning to the mineralization a clear epigenetic character. Mineral paragenesis of the deposit is almost monomineralic and consists of cinnabar, metacinnabar, native mercury, sporadic iron sulphides and gangue minerals, calcite and quartz. The objects of FIs study were colourless, transparent single quartz crystals, prepared as 0.2 mm thick wafers, and red, irregular cinnabar grains, prepared as 0.05-0.1 mm thick wafers. The most widespread FIs in Idrija ore deposit are low saline (1, 75-11, 50 wt.% equ. NaCl), L+V, CaCl2- NaCl-H2O with NaCl/CaCl2 ratio between 25 and 40%. Total homogenization into liquid phase was observed in the temperature interval between 175 and 215°C. Homogenization temperature could not be recorded into cinnabar samples due to decrepitation in temperature interval between 120 and 160°C. High saline CaCl2-NaCl-H2O FIs, with presence of isotropic daughter minerals, were observed only within one quartz crystal. NaCl/CaCl2 ratio and homogenization temperature are into the same range as in the low saline FIs. In the same sample the low saline (6, 75-8, 00 wt.% equ. NaCl), L+V, NaCl FIs were observed.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
0
References
0
Citations
NaN
KQI