S.I. TURCHENKO, B.M. GOROKHOVSKY (IPGG RAS)

Polygenic nature of the May gold deposit (Northern Karelia): geological and isotope evidences

]In the article is considered Pb isotope data for galenites of May gold ore deposit and its importance in age determination also exploration role. Ore bearing quarts veins in deposit belong to system meridian faults layering within mafic vulcanite Palaeproterozoic apajarvi suite. This suite is subjected to be­stage metasomatic transformations: 1 – regional propilitisation and 2 – local magnesium metasomatic alternation (gumbeitization). With second stage was connected also rock shistousing and forming of gold­sulfide­quarts veins. The age of propilite change mafic volcanites by Rb­Sr isochron determination in interval 1.70–1.61 Ga and ore bearing gumbeit metasomatic rocks near 1.4 Ga. The gold associate with chalcopyrite, pyrrhotite, pyrite and galenite, which is characterized primitive Pb isotope composition: average composition for 9 samples are ²⁰⁶Pb/²⁰⁴Pb=14.001 ± 0.013, ²⁰⁷Pb/²⁰⁴Pb=14.832 ± 0.008, ²⁰⁸Pb/²⁰⁴Pb=33.781 ± 0.019 . These signs meet modal age 2530 Ma by model Stasy­Kramers and signs of µ2 = 9.67 и К2 = 3.91 reply mantle­crust character regional sources.
Keywords: Palaeproterozoic, propilites, gumbeites volcanites, Pb­isotope, gold mineralization, stages ore forming.