1,721,010 research outputs found
Mantle Expansion Driving Lithosphere Tectonics: The Mediterranean Case
No full textWe propose a geodynamic model for the Mediterranean area that put in mantle expansion growing eastward, above a relatively cold, chemical plume trapped in the Transition Zone (410-670 km) after that core/mantle perturbations released H, C, N, K, S long trapped within the D??? layer. Lithosphere above the expanded asthenosphere undergone stretching and thinning and subordinate peripheral compression. Low-degree melting of the metasomatised asthenosphere produced ultra-alkaline magmas with a distinctive radiogenicity derived by the long term Rb/87Sr and U/Th decay leading to a unique isotopic end-member (ITEM, i.e. Italian Enriched Mantle)
Tettonica e magmatismo nell’Appennino settentrionale lungo la geotraversa Isola del Giglio- M.ti Sibillini.
No full textIn this paper a geologic cross-section extending from Isola del Giglio to the Sibillini Mountains has been studied. This section provides a good exemple of the relationship between tectonics and magmatism during the Neogene to Quaternary evolution of the Northern Apennines (Italy). Its structural setting supports the hypothesis of crustal deformations by simple shear progressively migrating eastward towards the Adriatic foreland, resulting in thinning and stretching of the Tyrrhenian hinterland. the geochemistry of the igneous rocks, whose major elements have been investigated on the basis of statistical criteria, appears to be consistent with a continental extensional tectonic environment and with the possibility of a small number of different parental magmas located at well defined structural levels (crust, mantle lithosphere, mantle astenosphere). The tectonic setting of the igneous centers testifies that their emplacement post-dates the main low-angle extensional deformations, being allowed by a late vertical tectonics, possibly related to rebound processes. The kinematic and volcanotectonic evolution of the studied area appear to be closely linked together and explainable in terms of a coherent geologic model concerning the evolution of the Tyrrhenian "rift" zone
Un plume mantellico pulsante nel Mediterraneo e nella Tetide Alpina.
No full textWe interpret the Oligocene to Recent geodynamic evolution of the western and central Mediterranean asins and surrounding mountain chains in the frame of a plume model. A wide plume head would have progressively grown eastward within the transition zone (410 to 670 km depth), determining asthenospheric asymmetric expansion and consequent stretching of the overlying lithosphere. Rift push forces would have generated compression at the outer border of the thinned lithospheric zone, leading to the nucleation of the
Apennine-Maghrebian fold-and-thrust belt system. The development of the Plio-Quaternary Tyrrhenian and peri-Tyrrhenian volcanism was also strictly controlled by the lithospheric extension and asthenospheric unloading, but the very aged isotopic signatures of the parental melt source, characterised by C-H-O and K metasomatic enrichments, reflects a contribution from deep mantle fluids and materials possibly carried by the plume. This contribute is very different from any typical asthenospheric or lithospheric reservoir, being consistently marked by two isotopic end-members, named ITEM and FOZO (for their definitions see BELL et alii, 2004). Basing on the recognition of these geochemical signals also in Late Cretaceous-Eocene Italian igneous products, we deduce that the plume rise must date back to the Alpine Tethys extensional phase. Possibly, during the early Cenozoic, the plume was relatively quiescent allowing the Alpine orogen to form, but still sending tiny fingers of low viscosity ultramafic magmas towards the surface, thus generating a number of isolated lamprophyric occurrences. Starting with early Oligocene times, there was a new pulse of
material from the deep mantle into the plume which initiated its growth within the transition zone giving birth to the Mediterranean rift basins and associated magmatism. Two discrete plume pulses would have lead to the opening of the Ligurian and Balearic basins between 30 and15 Ma ago and of the Tyrrhenian Sea between 13 My and recent
The Tyrrhenian large-scale detachment system: distinctive tectonic features and magmatogenetic implications.
No full textSeismicity and related extensional stress field: the case of the Norcia seismic zone (Central italy).
No full text
Contractional and extensional tectonics along the transect Lake Trasimeno-Pesaro (Central Italy). In: Boriani et al.(EDS), Italian Mid-Term Conference on the Lithosphere Program. Rome, 5-6 May 1987. ATTI CONV. LINCEI, 80,177-194.
No full text- …
