Palaeomagnetism and U-Pb dates of the Palaeoproterozoic Akitkan Group (South Siberia) and implications for pre-Neoproterozoic tectonics

Abstract

We present new geochronological and palaeomagnetic results from the late Palaeoproterozoic Akitkan Group in South Siberia. The zircon U–Pb conventional age of the rhyodacite from the upper part of the group is 1863±9 Ma and the age of the dacite from the lower part of the group is 1878±4 Ma. Palaeomagnetic study of sedimentary and some igneous rocks from the upper part of the group isolated a high-temperature characteristic component (D=193°, I=19°, k=51, α95=7°) which is supported by two of three applied conglomerate tests. However, the third intra-formational conglomerate test demonstrates a contaminating overprint of uncertain nature for a part of our collection. The analysis of data suggests that this overprint occurred at time when the geomagnetic field's direction was similar to that at the time of the deposition. Therefore the corresponding palaeomagnetic pole (22.5 °S, 97.4 °E, dp=1.5°, dm=2.8°) may be considered as representative for the deposition time. Palaeomagnetic study of the sediments in the lower part of the Akitkan Group isolated a stable primary remanence (D=189°, I=8°, k=111, α95=5°) supported by positive intra-formational conglomerate and fold tests. The palaeomagnetic pole (30.8 °S, 98.7 °E, dp =2.5°, dm=5.0°) is nearly coeval with the 1879 Ma Molson B pole from the Superior craton. We used these two poles to compare the relative position of Siberia and the Superior craton in the late Palaeoproterozoic. It is different from their reconstruction around 1000 Ma. This demonstrates their relative movements in the Mesoproterozoic.

Paleomagnetism of Mesoproterozoic margins of the Anabar Shield: A hypothesized billion-year partnership of Siberia and northern Laurentia

“…The volcanosedimentary pole from the Elgetey Formation, dated at 1732±4 Ma, passes both fold and intraformational conglomerate tests, but it is highly discordant to other poles from the Siberian craton and is thus interpreted by the authors as having been deflected by local rotations during graben development. The granitoid pole, with an estimated age of 1719 Ma (Didenko et al, 2015) is more consistent with other granitoidderived poles from southern Siberia (Didenko et al, 2009), but none of those granitoid-based data have reliable estimates of paleohorizontal. Due to this lack of structural control, neither Ulkan result can be considered as a robust estimate of Siberia's paleogeography at ca.…”

“…In the past 15 years, paleomagnetic data have strongly supported a mid-Proterozoic location of Siberia near Laurentia's northern margin, such that southern Siberia faced northern Laurentia (Gallet et al, 2000;Ernst et al, 2000;Pavlov et al, 2002;Metelkin et al, 2007;Wingate et al, 2009;Didenko et al, 2009). An unresolved issue is whether such a fit is loose, in which the two cratons were separated by several thousand km (Pisarevsky and Natapov, 2003;Pisarevsky et al, 2008) or tight (Pavlov et al, 2002;Metelkin et al, 2007;Evans and Mitchell, 2011).…”

Radiating rifts and dyke swarms of the middle Paleozoic Yakutsk plume of eastern Siberian craton

“…Specifically, in the Late Paleoproterozoic the Akitkan belt (boundary structure between the Aldan and Anabar superterranes) was located along the Vilyui rift ( Fig. 1) (Rosen et al, 1994(Rosen et al, , 2006Donskaya et al, 2009;Didenko et al, 2009). The Akitkan belt was later reused in the Mesopoterozoic for Nyurba rifting (Smelov et al, 2003).…”

Petrogenesis and Structural Position of the Early Proterozoic Charnockites of the Tatarnikovsky Massif in the South Siberian Post-Collisional Magmatic Belt of the Siberian Craton

“…1) [Larin et al, 2003]. В настоящее время установлено, что породы Южно-Сибирского пояса фиксируют окончательную стадию становления структуры Сибирского кратона и, возможно, отражают процесс его вхождения в палеопротерозойский суперконтинент Колумбия [Didenko et al, 2009;Donskaya et al, 2013a]. Гранитоиды и вулканиты данного пояса характеризуются большим разнообразием составов, при этом среди них преобладают разности с геохимическими характеристиками гранитов А-типа [Donskaya et al, 2002[Donskaya et al, , 2003[Donskaya et al, , 2005[Donskaya et al, , 2008[Donskaya et al, , 2014Larin et al, 2000Larin et al, , 2003Larin et al, , 2006Larin et al, , 2009Levitskii et al, 2002;Nozhkin et al, 2003;Turkina, 2005;Turkina, Kapitonov, 2017;Turkina et al, 2003Turkina et al, , 2006.…”