COMPOSITION OF SOLUTIONS FORMING MOLYBDENUM MINERALIZATION OF PERVOMAISKOE DEPOSIT (DZHIDA ORE FIELD, SOUTH-WESTERN TRANSBAIKALIA)

The purpose of this study is determination of the composition of ore-forming solutions and physico-chemical formation conditions of molybdenum mineralization in the Pervomaiskoe stockwork deposit within the Dzhida ore field (South-Western Transbaikalia). A set of mineralogical, petrographic and geochemical studies allowed to identify the material composition of ore quartz-molybdenum veins and near-veinlet zones. The methods of cryometry and thermometry, as well as modern instrumental microprobe methods of matter study (Raman- spectroscopy and LA-ICP-MS) were used to examine fluid inclusions in quartz of bonanza and lean quartz-molybdenite veinlets. The composition of a gas phase and metal concentrations in the solutions forming quartz-molybdenite veinlets were determined. Conducted studies show that the quartz-molybdenite veins of the Pervomaiskoe deposit were formed in the temperature range of 314-186 °C under the participation of homogeneous fluids with solution heterogenization periods. Total salt concentrations are 6.3-11.7 wt.% eq. NaCl. The gas phase contains CO₂, СH4 and N₂. Using LA-ICP-MS method the concentrations of a wide range of elements including Li, Be, B, F, Na, Mg, Al, Cl, K, Ca, Mn, Fe, Cu, Zn, Nb, Mo, Ag, Sn, La, Ce, Ta, W, Au, Pb, Th, U were determined. The content of the main ore element Mo in bonanza quartz-molybdenite veinlets reaches up to 559 g/t, whereas the average value is 182 g/t. The content of Mo in lean veinlets does not exceed 85 g/t, whereas the average value is 13 g/t. Richer veinlets were formed by near-neutral solutions with a high content of Mo, S and F, while relatively poor veinlets were precipitated from high alkaline solutions. All these enable us to consider the pH of solutions as one of the factors of ore content.

LA-ICP-MS, Pervomaiskoe deposit, molybdenum, fluid inclusions, ore-forming solutions, LA-ICP-MS, metal content

1. Reif F.G., Bazheev E.D. Magmaticheskii protsess i vol'framovoe orudenenie [Magmatic process and tungsten mineralization]. Novosibirsk: Nauka Publ., 1982, 158 р. (In Russian).

2. Reif F.G. Usloviya i mekhanizmy formirovaniya granitnykh rudno-magmaticheskikh sistem (po termobarogeokhimicheskim dannym) [Conditions and formation mechanisms of granite ore-magmatic systems (according to thermobaric geochemical data)]. Moscow: Institute of Mineralogy, Geochemistry and Crystallochemistry of Rare Elements Publ., 2009, 498 р. (In Russian).

3. Bodnar R.J., Vityk M.O. Interpretation of microthermometric data for H2O-NaCl fluid inclusions. Fluid inclusions in minerals: methods and application / ed. by B. De Vivo, M.L. Frezzotti. Pontignano, 1994, рр. 117–130.

4. Borisenko A.S. Study of salt composition of gas-liquid inclusions in minerals by the method of cryometry. Geologiya i geofizika [Russian Geology and Geophysics], 1977, vol. 18, no. 8, рр. 16–27. (In Russian).

5. Borovikov A.A., Goverdovskii V.A., Borisenko A.S., Bryanskii N.V., Shabalin S.I. Composition and metal contents of oreforming fluids of the Kalguty Mo-W(Be) deposit (Gorny Altai). Geologiya i geofizika [Russian Geology and Geophysics], 2016, vol. 57, no. 4, рр. 647–662. (In Russian).

6. Bayanov V.D. Late Mesozoic shashanite-latite series of the Dzhida ore district (South-Western Transbaikalia). Doklady Akademii nauk [Doklady Earth Sciences], 1994, vol. 339, no. 3, рр. 374–377. (In Russian).

7. Gordienko I.V., Gorokhovskii D.V., Smirnova O.K., Lantseva V.S., Badmatsyrenova R.A., Orsoev D.A. Dzhida Ore District: Geology, Structural and Metallogenic Regionalization, Genetic Types of Ore Deposits, Geodynamic Conditions of Their Formation, Forecast, and Outlook for Development. Geologiya rudnykh mestorozhdenii [Geology of Ore Deposits], 2018, vol. 60, no. 1, рр. 3–37. https://doi.org/10.7868/S001677701801001X. (In Russian).

8. Ignatovich V.I. Daiki i molibdenvol'framovaya mineralizatsiya Pervomaiskoi intruzii granit-porfirov (Dzhidinskoe mestorozhdenie) [Dykes and molybdenum-tungsten mineralization of the Pervomaiskaya intrusion of granite-porphyry (Dzhida deposit)]. Ulan-Ude: Buryatskoe knizhnoe izdatel'stvo Publ., 1959, рр. 29–47. (In Russian).

9. Malinovskii E.P. Opredelenie prostranstvennogo polozheniya istochnikov rudoobrazuyushchikh flyuidov Dzhidinskikh mestorozhdenii po dannym strukturnogo analiza [Spatial localization of ore-forming fluid sources of Dzhida deposits by structural analysis data]. Dzhidinskii rudnyi raion (problemy razvitiya i osvoeniya mineral'nykh resursov) [Dzhida ore district (problems of mineral resources development and mining)]. Novosibirsk: Nauka Publ., 1984, рр. 116–126. (In Russian).

10. Ontoev D.O. Stadiinost' mineralizatsii i zonal'nost' mestorozhdenii Zabaikal'ya [Mineralization staging and zoning of Transbaikalian deposits]. Moscow: Nauka Publ., 1974, 241 р. (In Russian).

11. Povilaitis M.M. Osnovnye cherty mineralogii Dzhidinskogo molibdenvol'framovogo mestorozhdeniya [Main features of the Dzhida molybdenum-tungsten deposit mineralogy]. Moscow: USSR Academy of Sciences Publ., 1960, 165 р. (In Russian).

12. Povilaitis M.M., Mozgova N.N., Senderova V.M. Bismuth minerals in the Dzhida molybdenum-tungsten deposit (Western Transbaikalia). Zapiski Vsesoyuznogo mineralogicheskogo obshchestva [Proceedings of the All-Union Mineralogical Society], 1969, part 98, issue 6, pp. 655–664. (In Russian).

13. Stel'machonok K.Z. On formation synchronicity of ore-hosting faults and molybdenum mineralization formation in the Pervomaisky stockwork field (Transbaikalia) and the causes of faulting. Doklady Akademii nauk [Doklady Earth Sciences], 1994, vol. 337, no. 3, рр. 382–385. (In Russian).

14. Stel'machonok K.Z. On the simultaneous formation of single-system veinlets in the molybdenite stockwork ore body of the Dzhida deposit (Transbaikalia). Doklady Akademii nauk [Doklady Earth Sciences], 1995, vol. 341, no. 3, рр. 399–402. (In Russian).

15. Khodanovich P.Yu., Smirnova O.K. Vol'framonosnye berezity i lokal'nyi prognoz orudeneniya [Tungsten beresites and local forecast of mineralization]. Novosibirsk: Nauka Publ., 1991, 208 р. (In Russian).

16. Khodanovich P.Yu. Molibdenovol'framovye mestorozhdeniya Dzhidinskogo rudnogo polya [Molybdenum-tungsten deposits of the Dzhida ore field]. Mestorozhdeniya Zabaikal'ya [Deposits of Transbaikalia]. Vol. I. Book 1. Chita – Moscow: Geoinformmark Publ., 1995, рр. 149–163. (In Russian).

17. Chernyshev I.V., Gol'tsman Yu.V., Bairova E.D., Ivanova G.F. Rb-Sr-geochronometry of sequential formation of granites, greysening and hydrothermal mineralization: Dzhida W-Mo deposit, Western Transbaikalia. Doklady Akademii nauk [Doklady Earth Sciences], 1998, vol. 360, no. 4, рр. 537–540. (In Russian).