New data on the formation of the Verkhne-Aliinsky gold and Noyon-Tologoysky polymetallic deposits (Eastern Transbaikalia)

The paper presents new data on the formation of the Verkhne-Aliinsky gold and Noyon-Tologoysky polymetallic deposits in Eastern Transbaikalia. It established that in the Eastern Transbaikalia, the ore-magmatic systems of the Shakhtama intrusive complex (J2-3) are associated with the formation of gold and molybdenum deposits, with the ore-magmatic systems of the Akatuevsky complex (J2-3) -polymetallic deposits. The Verkhne-Aliinsky gold deposit is located 30 km east of the Baley city, within the Munginsky ore cluster of the Baleisky ore region of Eastern Transbaikalia. The formation of gold mineralization is associated with the formation of the Shakhtama complex, which together with the effusive structures of the Shadaron (J2-3) series forms a ring volcano-plutonic structure. The granitoids of the Shakh-tama complex developed in the center of this structure, and in the peripheral parts - effusives of the Shadaron series. The Noyon-Tologoysky polymetallic deposit is located in the northern part of the Klichkinsky ore region in the South-Eastern Transbaikalia. The formation of the deposit is associated with the formation of the Akatuevsky intrusive complex. The field contains volcanogenic-sedimentary deposits of the Zalgatui Suite of the Mulinsky series (J2-3), intrusions of the Akatuevsky complex (J2-3) and Middle-Late Jurassic sediments. It established that the isotopic age of granite Shakhtama complex is 161.7±1.4 Ma, monzonites Akatuevsky complex - 154±4 Ma. Intrusion Shakhtama complex (J_2-3) is represented by two- three-phase arrays. Rocks of the first phase are represented by quartz monzonites, diorites, gabbrodiorites; rocks of the second phase - granodiorites, granites, quartz syenites; rocks of the third phase - granodio-rites, coarse-grained porphyry granites. Akatuevsky intrusive complex forms two-phase arrays. Rocks of the first phase are composed of subalkaline gabbroids, olivine monzonites, rocks of the second phase-syenite-porphyry, quartz syenites. In geochemical features of intrusions Shakhtama and Akatuevsky complexes correspond to volcanic arc rocks, effusive formation of this deposits of calc-alkaline magmatic series. The syenite-porphyries of the Noyon-Tologoysky deposit corresponds to I-type granitoids, the Verkhne-Aliinsky granites correspond to S-type granitoids. These data indicate that the formation of the ore-magmatic system of the Verkhne-Aliinsky and Noyon-Tologoysky deposits is associated with collision processes. The initial ratio of strontium isotopes in the syenite-porphyries of the Noy-on-Tologoysky deposit is (⁸⁷Sr/⁸⁶ Sr)₀ = 0,70698±0,000. The magmatic source of these deposits was the adakite magma, formed as a result of the mantle-crust interaction, characterized by elevated concentrations of volatile components. The intrusions of these complexes correspond to the formations of volcanic arcs, the effusive formations to the calc-alkaline series. The presence of tetrad effects in the lanthanide spectra revealed in the magmatic formations of both deposits, indicating the enrichment of magmatic melts with volatile components. Analysis of the distribution of rare earth elements revealed the existence of tetrad effects in the spectra of the lanthanides in the intrusions Shakhtama complex (TE₁- 1,12-1,18), and in basalts Zalgatui Suite of the Mu-linsky series (TE₃ - 0,82-0,89).

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