Geodynamic Implications

Fractional crystallisation of hybrid silicic melts to produce high-silica aplites and pegmatites. 

The main steps of such a complex petrogenetic history are schematically shown in the Si02 vs. K20/Na20 diagram reported in Fig. 2.10 (Poli 2004). 

The conclusion that the trace element and isotopic characteristics of mafic Tuscan magmas require addition of crustal material to the upper mantle has led several authors to suggest a subduction-related origin for this mag-matism (Peccerillo et al. 1988 Conticelli and Peccerillo 1992 Serri et al. 1993). However, the age of the subduction event(s) is discussed. Such a problem applies to Italian potassic magmatism in general, and will be discussed further in the next chapters. 

It has been long established that there is a continuum of radiogenic isotope variation along the Italian peninsula, which requires a mixing between at least two end-members (e.g. Vollmer 1989). One end-member is represented by a relatively uncontaminated mantle reservoir best represented by 

According to several authors, Mesozoic to Oligocene convergence between Africa and Europe produced east-directed subduction of oceanic crust beneath the African continental margin until continent-continent collision generated the Alpine chain. There is evidence that upper crustal 

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There is a general agreement that the magmatism from the internal zones of Apennines has been generated in anomalous mantle sources, which have been affected by metasomatic enrichment in incompatible elements. However, the nature and timing of mantle metasomatic processes are still debated. This issue has paramount geodynamic implications and applies to all ultrapotassic magmatic provinces in Italy. 

The hypothesis for the occurrence of two distinct types of metasomatic events in a restricted area has important geodynamic implications. It has been suggested that the metasomatic modifications of the upper mantle beneath the Roman Province was produced by upper crustal material from the... 

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Tamburelli C, Babbucci D, Mantovani E (2001) Geodynamic implications of subduction related magmatism insight from the Tyrrhenian-Apennine region. J Volcanol Geotherm Res 104 3-43... 

Zhang M., Stephenson J., O Reilly S. Y., McCulloch M. T., and Norman M. (2001) Petrogenesis of Late Cenozoic basalts in North Queensland and its geodynamic implications trace element and Sr—Nd—Pb isotope evidence. J. Petrol. 42, 685-719. 

Matteini M., Mazzuoli R., Omarini R., Cas R., and Maas R. (2002) The geochemical variations of the upper cenozoic volcanism along the Calama-Olacapato-El Toro transversal fault system in central Andes ( 24°S) petrogenetic and geodynamic implications. Tectonophysics 345, 211-227. 

Bodinier J.-L., Guiraud M., Dupuy C., and Dostal J. (1986) Geochemistry of basic dykes in the Lanzo Massif (Western Alps) petrogenetic and geodynamic implications. Tectonophysics 128, 77-95. 

Marty, B. and Jambon, A. (1987) C/ He in volatile fluxes from the solid Earth Implications for carbon geodynamics. Earth Planet. Sci. Lett., 83, 16-26. 

Zindler A, Hart SR (1986) Chemical geodynamics. Aim Rev Earth Planet Sci 14 493-571 Zindler A, Standigel H, Batiza R (1984) Isotope and trace element geochemistry of young Pacific seamounts implications for the scale of upper mantle heterogeneity. Earth Planet Sci Lett 70 175-190... 

Huang L, Sturchio NC, Abrajano T, Heraty LJ, Holt BD (1999) Carbon and chlorine isotope fractionation of chlorinated aliphatic hydrocarbons by evaporation. Org Geochem 30(8A) 777-785 Jambon A, Deruelle B, Dreibus G, Pineau F (1995) Chlorine and bromine abundance in MORB the contrasting behavior of the Mid-Atlantic Ridge and East Pacific Rise and implications for chlorine geodynamic cycle. Chem Geol 126 101-117... 

Roperch P, Herail G, Fornari M (1999) Magnetostratigraphy of the Miocene Corque Basin, Bolivia implications for the geodynamic evolution of the Altiplano during the late Tertiary. J Geophys Res 104(9) 20415-... 

Beccaluva L, Rossi PL, Serri G (1982) Neogene to recent volcanism of the Southern Tyrrhenian-Sicilian area implications for the geodynamic evolution of the Calabrian Arc. Earth Evol Sci 3 222-238... 

Beccaluva L, Gabbianelli G, Lucchini F, Rossi PL, Savelli C (1985b) Petrology and K/Ar ages of volcanics dredged from the Eolian seamounts implications for geodynamic evolution of the southern Tyrrhenian basin. Earth Planet Sci Lett 74 187-208... 

De Astis G, Peccerillo A, Kempton PD, La Volpe L, Wu TW (2000) Transition from calc-alkaline to potassium-rich magmatism in subduction environments geochemical and Sr, Nd, Pb isotopic constraints from the island of Vulcano (Aeolian arc). Contrib Mineral Petrol 139 684-703 De Astis G, Kempton PD, Peccerillo A, Wu TW (2005) Geochemical and Sr-Nd-Pb isotope composition of Vulture and Campanian Province volcanics (southern Italy) implications for mantle evolution and geodynamics. Submitted for publication... 

Lombardo B. and Rolfo F. (2000) Two contrasting eclogite types in the Himalayas implications for the Himalayan orogeny. J. Geodynam. 30(1-2), 37-60. 

Jahn B. M. (1998) Geochemical and isotopic characteristics of UHP eclogites and ultramafic rocks of the Dabie orogen implications for continental subduction and collisional tectonics. In When Continents Collide Geodynamics and Geochemistry of Ultrahigh-pressure Rocks (eds. B. R. Hacker and J. G. Liou). Kluwer Academic, Dordrecht, pp. 203-239. 

Zheng Y.-F., Fu B., Gong B., and Li L. (2003) Stable isotope geochemistry of ultrahigh pressure metamorphic rocks from the Dabie-Su-Lu orogen in China implications for geodynamics and fluid regime. Earth Sci. Rev. 1276, 1 -57. 

Tardy M., Lapierre H., Struik L. C., Bosch D., and Brunet P. (2001) The influence of mantle plume in the genesis of the Cache Creek oceanic igneous rocks implications for the geodynamic evolution of the inner accreted terranes of the Canadian Cordillera. Can. J. Earth Sci. 38, 515-534. 

Allegre C. J. and Turcotte D. L. (1986) Implications of a two-component marble cake mantle. Nature 323, 123-127. Allegre C. J., Othman D. B., Polve M., and Richard P. (1979) The Nd-Sr isotopic correlation in mantle materials and geodynamic consequences. Phys. Earth Planet. Inter. 19, 293-306. 

Moyen, J.-F. and Stevens, G., 2005. Experimental constraints on TTG petrogenesis implications for Archaean geodynamics. In Benn, K., Mareschal, J.-C., and Condie, K. (eds) Archaean Geodynamics and Environments, AGU Monograph 164, Washington, Chapter 10, pp. 149-75. 

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