The First Evidence for Late Devonian Granitoid Magmatism in the Northeastern Flank of the South Mongolia–Khingan Orogenic Belt

This paper reports the geochemical, U–Pb geochronological, and Sm-Nd isotopic–geochemical data on granites of the Medvedka Massif in the northern part of the Nora–Sukhotino terrane. It has been found that these granites have an age of 378 ± 3 Ma. They contain ferruginous silicates, have high iron index (FeO*/(FeO*+MgO)), low concentrations of Al2O3, CaO, MgO, high contents of Nb, Ga, Y, a deficiency of Sr and Eu, positive values of eNd(t) (+3.0…+4.1), and a high Y/Nb ratio. All these data indicate that the granites of the Medvedka massif are A2-type granites. The Late Devonian hastingsite–biotite granites of the Medvedka massif most likely reflect a transform continental margin setting in the evolution of the South Mongolian–Khingan orogenic belt.