Paleomagnetic and Geochronological Study of Post-Collisional Early Proterozoic Granitoids in the Southern Siberian Platform: Methodological and Geodynamic Aspects

摘要

Paleomagnetic and geochronological constraints are obtained for post-collisional Early Proterozoic granitoids of the Sharyzhalgai inlier of the Siberian craton basement. The formation age of granitoids was determined by the U/Pb method from zircons (1844 ± 15 and 1855 ± 5 Ma) and by the Ar/Ar method from amphiboles (1854 ± 4 Ma) and biotites (1741 ± 12 Ma). A high temperature component of the natural remanent magnetization of the granitoids is shown to have thermal origin. Its average direction from samples of two sites is (D = 353.0°, I = -26.0°; K = 9.4; α_(95) = 5.9°), and the paleomagnetic pole has the coordinates (Plat = 23.9°, Plong = 290.0°, d_p = 3.4°, d_m = 6.4°). The results are compared with paleomagnetic data for Laurentia of this age interval, and a reconstruction of the mutual position of the poles at 1850 Ma is proposed.