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Rezumat articol ediţie STUDIA UNIVERSITATIS BABEŞ-BOLYAI
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Rezumat:
The Brad-Săcăr�mb basin is situated in the southwestern part of the Transylvanian Metaliferi Mountains and hosts several low-sulphidation type Au-base metal deposits. The host rocks of the mineralization are mainly Neogene andesites and dacites and subordinately Cretaceous to Neogene sandstones, shales and pelitic-psammitic sediments (Ianovici et al., 1969). The Neogene volcanic rocks were affected by two stages of hydrothermal alteration. The first stage is represented by propylitisation processes, the second stage is characterised by sericitisation, local adularitisation and argillitisation.
The main gangue minerals in the veins are quartz, Ca-Mn carbonates and barite. The predominant ore minerals are pyrite, galena, sphalerite, chalcopyrite, stibnite, alabandine, realgar, tetrahedrite, buornonite, boulangerite and Au, Ag, Pb, Sb and Hg tellurides. The gold and silver-bearing minerals formed in association with galena and sphalerite. In some places, an early stage of Au-Ag and a later stage of Pb-Zn (with only little amounts of Au and Ag) mineralizations can be distinguished. Sulphosalts and chalcopyrite, as well as carbonates are the latest minerals, following the earlier gold-bearing stages.
Quartz is a frequent hydrothermal mineral, which shows certain crystal forms under certain physico-chemical conditions (Moln�r 1986, 1993; Hurai & Stersko 1987). In addition, fluid inclusions trapped during the growth of the quartz crystal can also be used for the estimation of the P-T-X conditions. ... |
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