Palaeoarchaean TTGs and metapelites as protoliths of the Neoarchaean A-type rhyolites from the Kursk block, Sarmatia: the dehydrating melting experimental results

Abstract

Introduction: The 2.61 Ga intraplate A-type magmatism in the Kursk block of the Eastern Sarmatia is represented by volcano-plutonic association of potassium high-silica rhyolites and granites. Isotopic data suggests that the crustal source of these rocks was heterogeneous. According to the modeling data parental melts could have been formed due to metapelite+TTG mixture 20% dehydrating melting at pressure no more than 4 kbar. Methodology: The experimental melting of possible protoliths was carried out to verify the results of geo-chemical data modeling. The composition of melt and restite minerals was analyzed in the experimental samples. Results and discussion: The concentrations of major oxides are close in the experimental melt obtained at 950°С, and in the Neoarchaean rhyolites. Average rare earth elements distribution in the experimental melt is also close to the Neoarchaean rhyolites. Conclusion: The experimental study indicated that the Neoarchaean rhyolite A-type magmas could have been formed at high temperatures and shallow depths as a result of partial melting of the Palaeoarchaean crust consisting of TTGs and metasediements in the Kursk block of Sarmatia.