Petrochemical features of the dike complex of the Vorontsovskoye gold-ore deposit (Northern Urals)

Abstract

Relevance of the work. The Vorontsovskoye deposit has some peculiarities of the Carlin-type deposit and is one of the largest gold fields in the Urals. However, nowadays, it is almost worked out; similar objects in the region have not been identified. The dike complex of the stockwork type was not previously studied at the deposit. The undertaken research can help clarify both the model of formation of ore mineralization and the predictive model. Purpose of the work. Study of the composition and petrochemical features of the dike complex of the Vorontsovskoye deposit as one of the possible factors for the formation of gold-ore mineralization. Methods of research. The measurements of the occurrence of dikes within the current open-pit with the results on the azimuth grid were carried out. A silicate dike sample assay was performed, and available past data was also used. The lithologic study of dikes was accompanied by the study of samples using the JSM-6390LV scanning electron microscope (JEOL) with the IncaEnergy-450 energy-dispersive spectrometer and the CamecaSX100 electron probe microanalyzer. Results of the work. At the first stage of the research, the structural position of dikes was specified; results of lithologic and petrochemical studies and data obtained by microanalyzers were summarized. A significant prevalence of the main dikes with various compositions from picrobasalt to gabbrodiorite (andesibasalt) has been identified. A group of dikes with increased and high alkalinity (including lamprophyres) with compositions from moderately alkaline and alkaline picrobasalt to monzodiorite (trachyandesibasalt) has been identified as well. Occurrences of kalifeldspath metasomatism with the mineral association of chlorite-quartzpotassium feldspar-pyrite (±galena) were recorded in dikes of complete line. Earlier, areas of kalifeldsparization were observed in tuff siltstones. Conclusions. Availability of dike stockwork can be considered as a positive structural factor in the formation of the deposit. Its role as a magmatic factor is unclear; however, it can be assumed that occurrences of kalifeldsparization are allied to dykes of increased alkalinity.