O.V. PETROV (VSEGEI), E.A. KISELEV (Rosnedra), А.I. KHANCHUK, V.V. IVANOV (FEGI FEB RAS), V.V. SHATOV, A.A. ALENICHEVA, А.V. MOLCHANOV, А.V. TEREKHOV, V.I. LEONT’EV, N.V. RODIONOV, B.V. BELYATSKIY, S.А. SERGEEV (VSEGEI)

REE + Y, Hf, U, Th, and Pb distribution in zircon as an indicator for fertility of magmatic rocks of the Malmyzh and Pony Cu-­Au-­porphyry ore fields (Trans­-Amur Region, Russian Far East)

The results of studying distribution patterns of trace elements (REE + Y, Hf, U, Th, Pb) in zircons from magmatic rocks of the Malmyzh and Pony Cu­Au porphyry ore fields based on geochemical SIMS measurements of zircons are discussed in the paper. Trace elements contents in zircons were determined at the same spots in which isotopic age of crystallization was measured by SIMS U­Pb method (SHRIMP II). ∑REE content in zircons from the Malmyzh granitoids varies from 217 to 1158 ppm, Y – from 718 to 732 ppm, Hf – from 4524 to 4928 ppm, Pb – from 1.2 to 1.6 ppm, U – from 89 to 112 ppm, Th – from 58 to 76 ppm. Geochemical characteristics of zircons from the Pony monzodiorite­porphyry are strongly differing from the Malmyzh granitoid zircons. Concentrations of most trace elements in the Pony zircons, especially LREE and MREE, as well as Y, Pb, U and Th are of two­three times higher than in zircons from the Malmyzh granitoids. Assessment of magmatic rocks fertility from the Malmyzh and Pony ore fields based on geochemical characteristics of zircons was carried out using Eu/Eu* vs. Dy/Nd and Eu/Eu* vs. (Ce/Nd)/Y plots. Analysis of these plots shows that zircons from the Malmyzh granitoids fall into the field of fertile porphyry systems whereas zircons from the Pony monzodiorite­porphyry fall into the field of barren suites. This result can be utilized during prognostic and metallogenic considerations not only within the limits of Sikhote­Alin territory but also within the whole Russian Far East region.
Keywords: REE + Y, Hf, U, Th and Pb in zircons, ore potential of magmatic rocks, gold­-copper-­porphyry ore mineralization, Malmyzh and Pony ore fields, the Trans­Amur Territory, Russian Far East.