Caledonian formation of gold-bearing sulfide depositions in Early Proterozoic gabbroids in the northern Ladoga region


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We have studied Pb isotopic systems of K-feldspar, pyrite, and pyrrhotine from gabbroids and ore of the Velimyaki Early Proterozoic massif in the northern Ladoga region in the southeastern part of the Fennoscandian Shield. The isochronous Pb–Pb age of sulfides has been determined as ∼450 Ma, which corresponds to intersection of the regression line with the lead accumulation curve with μ = 10.4–10.8; the model Pb age of sulfides is close to isochronous under the condition that the composition of lead evolved from a geochemical reservoir with an age of 1.9 Ga. The isotopic parameters of the lead in sulfides and K-feldspar indicate their formation in upper crust conditions (μ = 238U/204Pb > 10). From the obtained data, it follows that the isotopic composition of lead in K-feldspar corresponds to a Proterozoic age (1890 Ma) of magmatic crystallization of the rocks in the massif, and strongly radiogenic lead sulfides testify, with the greatest probability, to the later (Caledonian) formation of sulfide ores.

Sobre autores

Sh. Baltybaev

Institute of Precambrian Geology and Geochronology

Autor responsável pela correspondência
Email: sb@ipgg.ru
Rússia, St. Petersburg, 199034

G. Ovchinnikova

Institute of Precambrian Geology and Geochronology

Email: sb@ipgg.ru
Rússia, St. Petersburg, 199034

V. Glebovitskii

Institute of Precambrian Geology and Geochronology; St. Petersburg State University

Email: sb@ipgg.ru
Rússia, St. Petersburg, 199034; St. Petersburg

I. Alekseev

St. Petersburg State University

Email: sb@ipgg.ru
Rússia, St. Petersburg

I. Vasil’eva

Institute of Precambrian Geology and Geochronology

Email: sb@ipgg.ru
Rússia, St. Petersburg, 199034

N. Risvanova

St. Petersburg State University

Email: sb@ipgg.ru
Rússia, St. Petersburg

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