Structure Of Continental Lithosphere Research Articles

Continental lithospheric structure from the East European Craton to the Pannonian Basin based on integrated geophysical modelling

Due to uncertainty of single-method interpretation we applied 2-D integrated lithospheric modelling along three CELEBRATION 2000 profiles CEL01, CEL04 and CEL05. Modelling of the lithospheric thermal structure is based on the joint interpretation of gravity, geoid, topography and surface heat flow data with temperature-dependent density. The models for each profile were constrained by seismic modelling results of the large-scale international project CELEBRATION 2000. The results indicate large variations of the lithosphere thickness from the old and cold East European Craton (~200 km) and the Trans European suture zone via the Western Carpathian orogeny to the young and hot Pannonian Basin (~90 km). Important differences in the lithospheric thickness were also found along-strike of the Western Carpathian orogeny and the Trans-European Suture Zone. The western part of the Western Carpathians is characterized by weak thickening of the lithosphere (only about 145 km), while their eastern segment presents strong lithospheric thickening (~190 km). The Małopolska unit in southern Poland has a lithospheric thickness of about 130 km. Thickest lithosphere (220 km) is observed around the junction of the Carpathian Foredeep and the East-European Craton. The crustal thickness follows generally the course of the lithosphere-asthenosphere boundary. The results suggest different geodynamic evolution of the collision of the ALCAPA microplate with the European platform on the one hand and the East-European Craton on the other hand. It is suggested that the tectonic evolution of this very complex area consisting of different tectonic units has changed in time and space.

Evolution of pantellerite-trachyte-phonolite volcanoes by fractional crystallization of basanite magma in a continental rift setting, Marie Byrd Land, Antarctica

The Marie Byrd Land province includes 18 large (up to 1,800 km3) central volcanoes distributed across an active volcano-tectonic dome. The typical volcano structure consists of a basal 1,000–5,000 m of basanite surmounted by trachyte and subordinate intermediate rocks, plus phonolite, or pantellerite, or comendite. The volumes of felsic sections are large (~30–700 km3), but these rocks probably make up <10% of volcanic rock in the province. This paper describes pantellerite volcanoes in the Ames and Flood Ranges, which include a large and varied suite of these iron-rich, silica-poor rhyolites. Isotopic and trace element data, maintenance of isotopic equilibrium throughout the basalt-felsic range, and the results of modeling, all exclude significant crustal contamination and point to fractional crystallization as the process that controls magmatic evolution. The most unusual feature of these volcanoes is the apparent need to derive pantellerites from basanite, the long interval of fractionation at the base of the lithosphere and crust, involving kaersutite as the key phase in developing pantellerite, and a plumbing system that permitted coeval eruption of pantellerite and phonolite from the same edifice. Peralkalinity most likely developed in upper crustal reservoirs during the final 4–5% of magmatic history, by fractionating a high proportion of plagioclase under low pH2O. Mantle plume activity appears to drive doming and volcanism. This, a stationary plate, and continental lithospheric structure seem to provide an optimal environment for the evolution of a diverse, large volume suite of felsic rocks by fractional crystallization.