Linking collisional and accretionary orogens during Rodinia assembly and breakup: Implications for models of supercontinent cycles

Periodic assembly and dispersal of continental fragments has been a characteristic of the solid Earth for much of its history. Geodynamic drivers of this cyclic activity are inferred to be either top-down processes related to near surface lithospheric stresses at plate boundaries or bottom-up processes related to mantle convection and, in particular, mantle plumes, or some combination of the two. Analysis of the geological history of Rodinian crustal blocks suggests that internal rifting and breakup of the supercontinent were linked to the initiation of subduction and development of accretionary orogens around its periphery. Thus, breakup was a top-down instigated process. The locus of convergence was initially around north-eastern and northern Laurentia in the early Neoproterozoic before extending to outboard of Amazonia and Africa, including Avalonia–Cadomia, and arcs outboard of Siberia and eastern to northern Baltica in the mid-Neoproterozoic (~760 Ma). The duration of subduction around the periphery of Rodinia coincides with the interval of lithospheric extension within the supercontinent, including the opening of the proto-Pacific at ca. 760 Ma and the commencement of rifting in east Laurentia. Final development of passive margin successions around Laurentia, Baltica and Siberia was not completed until the late Neoproterozoic to early Paleozoic (ca. 570–530 Ma), which corresponds with the termination of convergent plate interactions that gave rise to Gondwana and the consequent relocation of subduction zones to the periphery of this supercontinent. The temporal link between external subduction and internal extension suggests that breakup was initiated by a top-down process driven by accretionary tectonics along the periphery of the supercontinent. Plume-related magmatism may be present at specific times and in specific places during breakup but is not the prime driving force. Comparison of the Rodinia record of continental assembly and dispersal with that for Nuna, Gondwana and Pangea suggests grouping into two supercycles in which Nuna and Gondwana underwent only partial or no break-up phase prior to their incorporation into Rodinia and Pangea respectively. It was only after this final phase of assembly that the supercontinents then underwent full dispersal

Beiträge zum 28. Darmstädter Geotechnik-Kolloquium am 09. März 2022

Themenschwerpunkte: 1. Modell- und Feldversuche 2. Digitalisierung und künstliche Intelligenz in der Geotechnik 3. Nationale und internationale Großprojekte 4. Normung und Rechtliche

The Tectono-Magmatic Evolution of the Taimyr Peninsula: Further Constraints from New Ion-Microprobe Data

ern Connection of the Uralides Summary: We present the initial results of a V-Th-Pb zircon ion-microprobe investigation on samples frorn the Central Belt ofTaimyr, in order to constrain its tcctono-magmatic evolution. The zircon samples are from a defonned two-mica granite (Faddey Massif), deforrncd metarnorphosed gabbroic e1ike entraineel as pods anel lenses within metamorphoscd tholeiitic basalts of thc Kunar-Mod volcanic suite (Klyazrna River region), a metamorphoscd rhyolite ofthe samc volcanic suite overlying the basic metavolcanic rocks, as weil as an undefonned dolerite dike which intrudes the metamorphoscd Kunar-Mod basic volcanic rocks. Preliminary results on zircons from the two-mica granitc suggest a crystallization age of.-..630 Ma for this rock, with inheritance frorn assimilated crust 840 Ma to 1.1 Ga in age. In the Klyazrna River region, zircons from the meta-rhyolite yielel a concordant age of.-..630 Ma. Zircons frorn the entrained metagabbroic dikes have so far yielded an age of.-..615 Ma (1 grain), as weil as Archean age