The Lower Proterozoic Metasandstones of the Sakukan Formation of the Udokan Complex of the South of the Siberian Craton—A Unique Object for the Early Precambrian Paleomagnetism?

This work presents results of the paleomagnetic analysis of metasandstones of the middle and upper parts of the Sakukan Formation of the Udokan complex Kodar-Udokan trough of the western part of the Aldan Shield. The rocks of the Sakukan Formation were deposited in a relatively narrow time interval of 1.90–1.88 Ga, during which the folding and metamorphism of greenschist facies occurred. According to high-temperature components of remanent magnetization and remagnetization circles of eight sites, the average direction is: D = 192.7°, I = 21.5°, k = 18.0, α95 = 13.4°, fold and reversal tests are positive. The pole, calculated by averaging virtual geomagnetic poles of eight sites (Plat = –21.0° Plong = 104.8° A95 = 11.4°), coincided with the poles of the Early Proterozoic granites of the Kodar Complex and gabbroids of the Chinei Series of the Udokan, the age of which is 1867–1876 Ma. According to our data, 1.90–1.88 Ga ago, the Chara–Olekma block was located in near-equatorial (11°) latitudes. The Sakukan Formation of the Kemen Group of the Udokan Complex is probably the most ancient geological object, which makes it possible to obtain a reliable paleomagnetic determination for the Siberian Craton.