Age constraints for the Pre-Uralide-Timanide orogenic event inferred from the study of detrital zircons

Abstract

The PreUralide-Timanide orogeny is the oldest collision event, which is more or less reliably recorded in the presentday Arctic region (9, 10). This collision was determined by the convergence at the Vendian- Cambrian transition (or in the initial Cambrian) between the Timan-Waranger margin of the Baltica continent, an ancient framework of the East European Platform and the Bol'shezeml'skaya margin of Arc� tida. The PreUralide-Timanide orogeny was inferred from the study of PreUralide inliers among the Uralide complexes (2, 10, and references therein), the distribution of detrital zircons of corresponding ages in different Arctic areas (1, 2, 13, and references therein), and mostly the analysis of granitoid associa� tions in the northern areas of the Urals and basement of the Pechora basin (6, 8, 9, and references therein). It is known that northern segments of the western Urals and basement of the Pechora basin are intruded by Late Precambrian and Cambrian granites with ages from ~730 to 510 Ma (Fig. 1) (2, 6, 8, 9, and others). By their composition, these granites may be attributed to both subductionrelated and collisional types (6, 9). The ambiguous nature of these rocks hampers limiting the period when subductionrelated tectonic environ� ments gave way to continental collision settings. This means that granites that reflect convergence environ� ments cannot serve as a tool for an accurate age deter� mination for the onset of collision between Baltica and Arctida. This problem requires other independent tools. 1 We suggest to use erosional products of the Pre� Uralide-Timanide orogen that are represented by Upper Precambrian-Lower Paleozoic detrital rocks developed in the northern part of the East European Platform as one such tool. This approach is based on the concept that the composition of allothigenic min� erals constituting detrital rocks as well as their isotopic compositions and ages reflect the corresponding parameters of provenances, i.e., domains that yielded eroded material for detrital rocks. By analogy with recent collision orogens (Alps, Himalayas, and others), we assume that the Pre� Uralide-Timanide orogen represented a mountainous folded structure, which was subjected to intense ero�