BACSÓ, Z., 2023: The Brehov volcanogenic and stratabound base metal and gold deposit (Eastern Slovakia): Position and genetic relations in the Internal Carpathian–Alpine Cenozoic metallogenetic belt. Mineralia Slovaca, 55, 1, 27 – 52.
DOI: https://doi.org/10.56623/ms.2023.55.1.3
Abstract: The Brehov ore deposit, near the village of Brehov, is located in the East Slovakian Basin 15 km south-east of the Trebišov town. A progressive development of Middle Badenian to Middle Sarmatian sedimentation and volcanism in the Brehov hydrothermally mineralized area is manifested in the article. The volcanogenic, stratabound, polymetallic (Zn, Pb, Cu) and gold sulphide deposit within the Brehov–Sirník interpreted resurgent caldera occurs in the volcanosedimentary sequence. Mineralization in the deposit, consisting of the fine-grained aggregate of sulphides, is interpreted to be of shallow water origin. It is placed mostly in the rhyodacite volcaniclastics and partly in calcareous claystone, altered and brecciated. Three types of ores – the stringer (keiko), yellow and black ore – were distinguished near the Brehov village on the basis of ore composition, being formed by successive mineralization stages. The stringer ore, consisting of the sulphide minerals, dominates in the quartz-dioritic (siliceous) rocks. The yellow ore is represented primarily by pyrite, but contains also minor chalcopyrite and quartz. The black ore is an intimate mixture of sphalerite, galena, sometimes barite and minor pyrite and chalcopyrite. Tetrahedrite and marcasite occur sporadically. The ore in all cases is fine-grained. The ore bodies are almost everywhere enclosed by clay, composed of montmorillonite, sericite and chlorite. The ore bearing fluids were probably colloids of hydrothermal origin. Textures are considered to indicate that the colloids replaced the country rocks, rather than merely filled open spaces in the rhyodacite pyroclastics and epiclastics. Despite the precious metals (mostly gold) are economically important commodity in many Kuroko type deposits, in the Brehov ore deposit they occur in volumetrically minor amounts. Visible gold is present as inclusions of native gold in major sulphide minerals, whereas silver occurs in Ag-sulphides and sulphosalts, e.g. tetrahedrite and ferberite.
The location of important Neogene magmatic, as well as metallogenetic structures in the “Boundary Zone” between the Western and Eastern Carpathians, in the Brehov–Zemplín area, is controlled by the orthogonal deep penetrative regional faults – lineaments. They are interpreted as the surface expression of deep-crustal and mantle rooted trans-lithospheric structures, which have been periodically reactivated as pure-shear regional faults during individual orogenic cycles, forming discontinuities long several tens, hundreds, or even thousands of kilometers.
In regions of subduction-related magmatism, the Kuroko type volcanogenic stratabound sulphide and gold ore deposits, like Brehov in Eastern Slovakia, may be generated along these lineaments, because the discontinuities allow the ascent of relatively evolved magmas and fluids from the deep-crustal magma reservoirs. However, the lineament intersections can focus this activity under appropriate lithospheric stress conditions only where a magma supplies exist – as was demonstrated in the case of the Brehov ore deposit, represented by an extended quartz diorite-porphyry stock body related sills and dikes (like in Cenozoic rifted back arc basin between Western and Eastern Carpathians).
The Brehov ore deposit occurs in the crossing of the Ondava submeridional lineament zone with the Komárovce–Brehov subequatorial lineament, which developed in weakened zone of Mesozoic Meliata suture zone after Neo-Tethys Ocean. The resurgent elevation of the Brehov–Sirník caldera is developed on this crossing.