Geochemical characteristics of mercurian tetrahedrite, barite and fl uorite from the Duboki Vagan, Glumac and Dubrave-Dugi Dol barite deposits, south of Kresevo,Mid-Bosnian Schist Mts.

摘要

The geochemical characteristics of tetrahedrite and barite of the Duboki Vagan barite deposit near the town of Kresevo in the MBSM (Mid-Bosnian Schist Mountains) have been determinated and correlated with the results of previously studied barite, from the adjacent Glumac deposit, and fl uorite, from the Dubrave-Dugi Dol barite deposits. The studied tetrahedrite is characterized by a high content of Au (39 ppm) and Ag (>300 ppm), the presence of Co (63.5 ppm),Ni (266.2 ppm) and Cd (313,6 ppm) in the crystal lattice and negative δ~(34)S_(CDT) values (–11.80‰). On the plot of its C1 chondrite-normalized REE abundances, a slightly expressed positive Eu anomaly and high HREE concentrations are observed. The high content of SrSO_4 (2.33 to 3.42 wt.%) in the barite crystal lattice indicates hydrothermal parent solutions. The δδ~(18)O_(SMOW) values of the studied barite are +10.40‰, which is typical for Permian seawater and its δ~(18)O_(SMOW) values range between 15.6 and 17.7‰. A distinct positive Eu anomaly is shown on the plot of the C1 chondrite-normalized REE abundances in barite. Geochemical characteristics of the studied tetrahedrite and barite of Duboki Vagan are very similar to those of previously investigated Glumac and Dubrave-Dugi Dol barite deposits.The fl uorite from the Dubrave-Dugi Dol deposits displays a negative Eu anomaly and its Tb/La and Tb/Ca ratios indicate a quite different origin in relation to barite formation. This is all in the accordance with the possible existence of two different paragenetic types of barite deposits in the MBSM and SEB (Southeastern Bosnia), which signifi -cantly differ in the δ18OSMOW ranges of their barites and δ~(34)S_(CDT) values of their sulphides. The fi rst type of barite deposits originated in the Late Variscan phase (Lower Permian). It is characterized by numerous Cu, Fe, Zn, Sb, As, Pb sulphides and Cu-Sb-tetrahedrite without mercury, all having positive δ~(34)S_(CDT) values (0 to +5 ‰). Early intercontinental rifting took place between the uppermost Permian and Lower Triassic and enabled, in a great number of ba rite deposits, (especially in the MBSM), remobilization and partial fl uidization of their Fe, Cu, Zn, Sb and Pb sulphides which reacted with ascended mercury, sulphur and fl uorine rich mantle fl uids and resulted in the formation of Hgtetrahedrite and octahedral fl uorite. These processes caused the occurrence of the second paragenetic type of barite deposit with Hg-tetrahedrite as the main ore mineral, but characterized by strongly negative δ~(34)S_(CDT) values.