Age of provenance for the Palaeoproterozoic Kemen Group, Udokan Complex: Newly recognised Palaeoproterozoic crust-forming event in the western Aldan Shield, Siberian Craton

Abstract

In this study, new geological, geochronological, and Hf isotopic data are presented for the metaterrigenous deposits of the Kemen Group of the Udokan Complex in the Chara-Olekma terrane of the Aldan Shield, Siberian Craton. Their age of deposition and possible provenances are discussed, along with crust-forming events in the Aldan Shield. The Palaeoproterozoic carbonate-terrigenous deposits of the Udokan Complex in the Kodar-Udokan basin are the hypostratotype of the Lower Proterozoic deposits of the Eastern Siberia and the Far East, and host one of the largest and oldest sediment-hosted copper deposits. Concordia ages of detrital zircons demonstrate age peaks of ca. 2.02, 2.15, 2.38, 2.54, 2.73, 2.82, 2.93, 2.96, 3.00, 3.04 and 3.14 Ga on the probability plot. The morphology, internal texture, and Hf isotopic composition of the Meso- and Neoarchean detrital zircons indicate reworked Paleo- to Mesoarchean crustal sources in provenance areas. No rocks with the ages of ca. 2.02 Ga have been previously recognised in the Chara-Olekma terrane. Characteristics of the ca. 2.02 detrital zircons indicate their primary magmatic origin and proximal sedimentary transport. Hf isotopic data imply that the Palaeoproterozoic rocks in provenance area originated mainly from juvenile sources in a subduction-related setting. The Palaeoproterozoic island arc or an active continental margin probably existed within the western Aldan Shield or its framing and were later completely eroded or partially overlain by younger sediments. Erosion of the Palaeoproterozoic orogen led to deposition of the Chinei and Kemen groups of the Udokan Complex over a short time interval of ca. 1.90–1.88 Ga. Detrital zircons from the Kemen Group deposits reveal for previously unrecognised and lost from geological record Palaeoproterozoic crust-forming event on the western Aldan Shield. Available data show that significant part of the Siberian Craton was formed during ca. 2.07–1.98 Ga crust-forming events that indicate the discrete episodic nature of the continental crust formation and must be considered in models of its growth. The differences in isotope structure and geological history of the Siberia and the Laurentia are in agreement with palaeogeographic reconstructions suggesting that Siberia and Laurentia were not joined together in the Columbia/Nuna supercontinent.