Affiliation:
1. St. Petersburg State University
2. AO “Polymetal UK”
3. LLC “Polar Forwarding Company”
4. A.N. Zavaritsky Institute of Geology and Geochemistry, UB RAS
Abstract
Research subject. The Tessemsky granite massif is located in the North Taimyr tectonic zone, surrounded by Cambrian rocks. The Pekinsky granite massif is located within the Central Taimyr zone, surrounded by metamorphosed Proterozoic rocks. Aim. To develop a methodology for using the composition of accessory granitoid minerals when prospecting Cu-Mo-Au-porphyry mineralization on the example of the Pekinsky and Tessemsky granitoid massifs of the Taimyr Peninsula. Materials and methods. Accessory zircon and apatite contained in two granitoid samples from the Pekinsky massif (P1, P2) and two granitoid samples from the Tessemsky massif (T2, T3) were studied. Their mineral composition was examined using an EPMA Cameca SX100 instrument. The element content in minerals was determined by LA-ICPMS using an NexION 300S instrument equipped with an NWR 213 attachment. Results. Most of the zircons from the Pekinsky and Tessemsky massifs were formed at T < 738°C in oxidized magma with ΔFMQ of 0.6–2.6, which is a favorable sign for the identification of Cu-Mo-Au-porphyry mineralization. Zircons are characterized by elevated (Eu/Eu*)Y and (Ce/Nd)n/Y ratios, which is also a favorable, though not a strongly reliable, sign for identifying porphyry mineralization. The Eu/Eu* and Sr/Y ratios in the apatites from the Tessemsky massif are higher than those in the apatites from the Pekinsky massif. The rock compositions of both massifs fall within the fields of adakites on the classification diagrams. The estimates of oxygen fugacity (logfO2) calculated from Mn in apatites for four samples agree well within the error limits. Conclusion. Specific features of using the composition of accessory minerals (zircon and apatite) for prospecting the Cu-Mo-Au-porphyry mineralization associated with granitoids were considered. Accessory indicator minerals can be used to rank granitoid massifs in order to assess their ore content. The example of two granite intrusions of the Taimyr Peninsula made it was possible to show that the Tessemsky massif is more promising for the discovery of associated Cu-Mo-Auporphyry mineralization than the Pekinsky massif.