engleski

Structural control and three-dimensional geological modelling of the epithermal Au-Ag deposit of Banská Hodruša (Štiavnica Stratovolcano, Slovakia)

Neogene volcanism and back-arc related extension is the main area of epithermal deposits of low to intermediate sulphidation types in the Carpathian arc. The study mineralization occurs within the Štiavnica-Hodruša ore district in the central zone of the Štiavnica Stratovolcano of Miocene age. The intermediate-sulphidation Au-Ag-Pb-Zn-Cu Banská Hodruša deposit is located in the middle of the central zone of the stratovolcano. This deposit at the Rozália mine represents a subhorizontal multi-stage vein system. A low angle normal fault zone (LANF) with the dip azimuth of 125° and generally flat, less than 30°, inclination hosts the mineralisation. LANF was newly identified during our research and it is the unusual structural setting of the deposit resulted in several unique characteristics, such as fluid properties of the hydrothermal system, distribution of ores and alteration patterns. LANF is related to processes of exhumation of subvolcanic granodiorite pluton. The mineralization is located in intensively altered pyroxene andesite of pre-caldera age. The thickness of the mineralized zone is typically tens of metres up to one hundred and has a tabular shape and gently dipping south eastward. LANF is characterised by normal faulting with the NE–SW strike of fault planes and complex structures among the fault damage zone. The Krištof type veins fill tension gashes, predominantly oriented in the NNE–SSW direction with moderate dip to the ESE. The Agnesa type veins occurs in a gentle dipping releasing bends predominantly at the roof of LANF, having the same age as the Krištof type veins. These veins are typically shallow dipping (less than 30°) with the dip direction south eastward. Most probably, the slightly older kinematics is responsible for the formation of the Central Stockwork controlled by a NNW–SSE oriented σ3 with the general strike in the WNW–ESE direction. This zone represents the initial phase of precious metal mineralisation in LANF and can be interpreted as a damage zone along the ramp fault. Continuous mining, exploration and associated geological research provided large amount of data that is needed for construction of 3D geological model of the Banská Hodruša deposit. Input data for this model are provided by three datasets. First dataset consists of a database of lithological and geochemical data from drillholes. Second dataset is composed of adit data, which contains structural, lithological, and geochemical data. Third dataset is represented by the geological adit maps and sections. Given the above described dataset, 3D geological model of Banská Hodruša deposit was constructed by data and knowledge-driven explicit method. There are: i) Rozália vein system model ; ii) andesite and porphyry intrusion models ; iii) Base and top of LANF models ; iv) Svetozár vein model ; and v) Agnesa and Krištof vein system models (Fig. 1). The modeling area is subdivided on the western part (W of Bakali vein) and the eastern part (between Bakali and Terézia veins) based on input data type. General conclusions from the modeling are i) General gentle increasing in the dip angle of Rozália vein type towards Terézia ; ii) Thickness of the vein-host andesites are greater in the W of the deposit than in the E, which reflects on vein size, thickness amount, and spatial distribution ; iii) Vein sets defined by structural data are collative with vein sets defined by mineralogical features ; iv) Based on structural settings it is possible to define multiple generations of porphyry intrusions ; v) 3D geological model represents a solid base for further planning of research and mining activities as well as geological prospection of poorly investigated or uninvestigated areas.

3D geological modeling ; Banská Hodruša ; Štiavnica Stratovolcano ; Gold deposit

nije evidentirano