Two stage of gold-bearing sulfide ores of early Proterozoic gabbroids in the north Ladoga area

In a study based on Pb isotopes, it has been shown that the formation of gold-sulfide mineralization in Early Proterozoic gabbros Northern Ladoga region is associated with different tectonic phases. This conclusion comparative isotopic data for feldspars and lead sulfides two intrusions; Velimäki Alattu-Päkylä. The investigated intrusions have similar geological settings at junction Svecofennian accretionary complex Karelian craton. Both massifs are characterized by manifestations noble metal sulfide zones local shear deformations. studied ore attributed to Caledonian stages. Feldspars intrusion parameters model age significantly older than U-Pb zircon (1.9 Ga), although they correspond time magmatic crystallization gabbro clinopyroxenites, while pyrite-pyrrhotite gold these rocks stage fluid-thermal processing mineral paracenteses. Alattu-Päkylä (~ 2 also somewhat zircon, but same indicating rock-forming associations during (Early Proterozoic) plutonic tectonic-thermal events. source massif upper crust high µ2 = 238U / 204Pb, parameter minerals slightly lower, which indicates participation mantle-lower crustal reservoir material magma.