Zircon morphology and isotope U-Pb and Sm-Nd dating the rocks of the Kanozero alkaline granite massif (the Kola region)

Abstract

The U-Pb dating zircon and Sm-Nd dating the whole rock and secondary minerals from the Kanozero massif of alkaline granites of the Kola region (the Fennoscandian shield) have been carried out. The age of alkaline granites of the Kanozero massif by zircon is 2667 ± 36 Ma, aplite-like alkaline granites - 2301 ± 13 Ma and blastomylonites - 2264 ± 12 Ma. The crystallization temperature of zircon has been estimated from the crystal habit. According to the zircon morphology of alkaline granites and blastomylonites the conditions during the crystallization process of the Kanozero massif have been established as long-term cooling high-temperature volatile- and alkali-rich crustal-mantle melts. The mineral Sm-Nd isochron by whole rock and by secondary minerals - biotite and titanite - has an age of 1921 ± 53 Ma interpreted as the time of regional Svecofene metamorphism. Based on the obtained isotopic data it can be noted that the rocks of the Kanozero massif of alkaline granites have similar features of formation and transformation with alkaline granites of the Keivsky terrane.