| Summary: | Research Doctorate - Doctor of Philosophy (PhD) Along the western and northern margins of the Siberian Craton the Proterozoic sedimentary formations form pre-orogenic and post-orogenic sedimentary cycles, separated by a major unconformity. In various uplifts of Meso-to Neoproterozoic sedimentary rocks of Siberian cratonic margin, such as the Taimyr, the Yenisey Ridge and the Prisayan, detrital zircon signatures below the unconformity are compared with those of immature post-accretionary sedimentary rocks occurring above the unconformity. The data are further used to characterize the age of Early Precambrian basement and Neoproterozoic crust along the northern and western Siberian cratonic margins and to assist with identifying the tectonic setting of Neoproterozoic magmatic belts, their cratonic affinity and the overall geological evolution of these margins. It has been confirmed that Siberian cratonic basement is heterogenous in its age. Along the southwestern cratonic margin (Prisayan Uplift) the basins accumulated predominantly 3.4-2.7 Ga and 1.9-1.85 Ga detritus; along the western cratonic margin (Turukhansk Uplift, northern Yenisey Ridge), the basins accumulated predominantly 2.6–2.5 Ga and 1.9–1.85 Ga erosional products, while the main sources for the fill of intracratonic basin to the northeast near the Anabar Shield (East Anabar basin) were 2.9–2.7 Ga and 2.1–1.95 Ga old igneous rocks. The studied pre-orogenic rocks were mostly deposited during the Meso – to Early Neproterozoic rift-related or passive margin settings. Along with magmatic components of the Neoproterozoic crustal fringe, these rocks underwent major craton-wide recycling to produce late Ediacaran post-orogenic siliciclastic successions. Results of Hf in zircon study allow to identification of four distinct magmatic systems belt, associated with development of continental arcs at ca. 970-800 Ma and 720-600 Ma, and an oceanic arc at ca. 800-720 Ma in the Taimyr orogenic belt, and development of a long term continental arc during 950-600 Ma in the Yenisey Ridge and the north-western East Sayan. In addition to isotopic data, a geological evidence is discussed to support that Neoproterozoic crustal growth occurred near the northern and western Siberian margins and resulted in forming siginifcant portion of Arctic crust.
|
|---|