Some New Concepts in the Plate Tectonics Paradigm Fifty Years after Its Inception

We have gained significant insights into the dynamic evolution of the earth, causes of geohazards, processes of continental growth, feedback mechanisms between tectonics, topography and climate, and rates of deformation and uplift in collision zones since the initial formulation of the plate tectonics theory 50 years ago. The articles in this special issue present some new concepts, data, and interpretations on various aspects of the plate tectonics paradigm. The onset of plate tectonics may have occurred in a major transition period (2.5–2.0 Ga) in Earth history during which short-lived, geographically limited subduction events resulted in a regime switch from stagnant-lid to plate tectonics. The 1.90–1.87 Ga granulites in the continental lower crust of the Siberian craton contain significant amount of water in the form of structural OH in nominally anhydrous minerals, indicating that the water content of the Precambrian granulites might have been considerably higher than that of the Phanerozoic granulites and the lower crust. The major mountain-building episode (vertical thickening, topographic buildup, and normal faulting) in the evolution of the continental collision zone of the Alps was driven by buoyant, solid-state emplacement of subducted oceanic and crustal material in a subduction return flow from depths more than 100 km. Chaotic rock deposits and mass transport deposits in the sedimentary covers of some ophiolites may represent synextensional and syncontractional submarine slides during the opening and closure stages of ancient ocean basins, respectively. The Lower Jurassic (201–190 Ma) mafic rock assemblages in the Rif orogenic belt of NW Morocco are part of the Central Atlantic Magmatic Province (CAMP), a major Phanerozoic large igneous province (LIP). The mantle melt source of the CAMP was a subduction-metasomatized mantle lithosphere of supercontinent Pangea and was not associated with mantle-plume activities, as was the case for the development of many other LIPs in Earth history. The Pleistocene seismicity and earthquake event (i.e., August 2011 Mineral earthquake in Virginia, Mw=5.7) in the eastern North American intraplate setting resulted from the release of accumulated strain associated with the state of regional compression. Based on the combined river terrace paleogeodetic data and modeled coseismic deformation of the 2011 Mineral earthquake, the estimated recurrence interval for similar-sized earthquakes in the region is 5.5 ky, significant information regarding the potential seismic hazard for an intraplate tectonic setting, where there is no historical record of seismic activity.