An Isotope Study of the Dzhida Mo–W Ore Field (Western Transbaikalia, Russia)

The Dzhida ore field includes Pervomaika (Mo), Inkur (W) and Kholtoson (W) deposits. This article presents stable and radiogenic isotopic data (O, C, D, S, Sr and Nd) in an attempt to better understand the petrogenetic processes and the problem concerning the sources of ore-forming fluids. Granites from the Pervomaika deposit, which includes Mo-ores, as well as the syenite dikes that precede W-mineralization, have low delta O-18 values (about 5 parts per thousand and 4 parts per thousand respectively), and low initial ratios Sr-87/Sr-86 (0.704-0.705). The epsilon Nd (T) values (+0.9--1.1) in granites and syenites are close to the evolution trend of the mantle-derived source. It was determined that a mantle-derived source was involved in ore-forming processes. It was also confirmed that delta S-34 values in sulfide minerals (molybdenite, pyrite, sphalerite, galena, and chalcopyrite) were close to the meteoric standard (from -2 parts per thousand to +2 parts per thousand). The delta C-13 and delta O-18 values in carbonate minerals (rhodochrosite and ankerite) of the Kholtoson deposit are located within the primary igneous carbonatite (PIC)-square, as a possible juvenile source of CO2. This was also confirmed by the delta O-18 and delta D values in muscovite from greisens (4.2 parts per thousand-6.5 parts per thousand delta O-18,-78.8 parts per thousand ... -84.0 parts per thousand delta D). The delta O-18 values calculated in a fluid equilibrated with hydrothermal minerals indicated a meteoric origin.