Orogenic Sb-Au deposits as archives of fractionation and hydrothermal activity in space and time

• Applicants: Dr. Marina Lazarov; Professor Dr. Juraj Majzlan, Ph.D.
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 521731442

Orogenic Sb-Au deposits are archives that record the processes that operated in orogenic belts in the middle and lower crust. The two elements antimony and gold, together with arsenic and sulfur, are typical constituents of the ores of these deposits. They formed already in the early history of Earth (Archean) but there are young examples (Phanerozoic), too. One of the objectives of this work is to find out the degree of fractionation of antimony from the mantle into the crust with the use of Sb isotopes (i.e., 123Sb values). Our working hypothesis is that the fractionation of antimony, and perhaps also the accompanying elements (Au, As, S) was complete early in the Earth’s history. This hypothesis can be tested because of distinct fractionation patterns of Sb, as this element fractionates both into silicate melts and metallic melts. Our previous work also showed that remobilization of Sb ores causes large changes in 123Sb. This work will be done on Archean and Proterozoic orogenic deposits in the Ukrainian shield. Another objective focuses on spatial variations of Sb-Au deposits which may be located at different crustal levels within a single camp of deposits. Our working hypothesis is that fluids that cause the formation of these deposits pass large volumes of crust and deposit the minerals sequentially, thus causing systematic pattern in 123Sb, as observed within single deposits in our previous work. For this work, we will use a camp of Sb-Au deposits in the Western Carpathians. In order to interpret the data correctly, fractionation factors for the Sb minerals are needed. The last objective of this work links the field and experimental work and will be used to calculate the fractionation factors  between Sb-bearing solids from the temperature dependence of the parameters of the Mössbauer spectra.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2238: Dynamics of Ore-Metals Enrichment - DOME