Isotopic (δ34s, δ13c, δ18o) properties of the disseminated mineralization of plutonic rocks in the Dukat ore field (Northeast of Russia)

Abstract

The variations in the δ34S, δ13C, and δ18O values of the disseminated sulfides and carbonate phase, which occurred in trace amounts in the plutonic rocks controlling the position of the unique Dukat Au-Ag field (Northeast of Russia), were examined. These properties were compared with similar isotopic parameters of the ore associations in the field. The δ34S values of sulfides and jarosite obtained from plutonic rocks were in a relatively narrow range (from -3.4 to +3.6‰) when compared with the range of variation of the δ34S values of sulfides obtained from the ore bodies (from 4.5 to +2.0 ‰). Pyrite sulfur obtained from the early mineralization of K-Na-leucogranite and pyrite obtained from the ore bodies were observed to have the same source. Pyrite formed during the later magmatic stages is characterized by a small amount of lighting based on the sulfur isotopic signature. The carbonate phases of the plutonic ore in the Dukat ore field are characterized by the δ13С values (from 12.8 to 8.8‰). The carbonates are split into groups according to the oxygen isotopic signature: carbonate balanced with the rock silicate matrix at high temperatures and carbonate with abnormally low δ18О values (from -0.8 to +0.9 ‰). The obtained data can be described using the model that assumes that the formation of the isotopic parameters of sulfide sulfur and carbonate carbon occurs during the process of sulfate recovery using organic carbon oxidation (TSR). Further, the calculations revealed that the observed δ34S and δ13С values in the rocks and ore associations in the Dukat field can be obtained during the abiogenic recovery of marine sulfate in a temperature range of 300 °C–450 °C. The comparison of the isotopic parameters of the rock carbonate with those of the ore association carbonate demonstrated that the surrounding/base rocks and fluid that separated during the cooling of the K-Na-leucogranite intrusion bodies, which resulted in a loss of approximately 80% CO2, could serve as the source of the carbonates of the ore bodies.