From migmatites to crustal granites: Pb–Pb isotopic system of feldspars of partial melting products, Northern Ladoga region, Fennoscandinavian Shield

Abstract

The isotopic–geochemical features of late and postorogenic granites of the S type and ambient migmatites are studied within the Russian part of the Svecofennian orogen of the Fennoscandinavian Shield. The spatial association of leucosomes of migmatites and granites of the S type and their similar petro- and geochemistry and distribution of Pb isotopes are evidence of the genetic similarity of their parental melts. The Borodinskoe pluton has a more primitive ²⁰⁶Pb/²⁰⁷Pb ratio, which indicates the presence of upper and U-poor lower crustal material in the source of granitic magmas. This conclusion is supported by the ɛ_Nt(t) lower value of granites of this pluton relative to those of other plutons of the region.