Post-Archean Granitic Rocks: Petrogenetic Processes and Tectonic Environments
CONTAINS OPEN ACCESS
Granites (sensu lato) represent the dominant rock-type forming the upper–middle continental crust but their origin remains a matter of long-standing controversy. The granites may result from fractionation of mantle-derived basaltic magmas, or partial melting of different crustal protoliths at contrasting P–T conditions, either water-fluxed or fluid-absent. Consequently, many different mechanisms have been proposed to explain the compositional variability of granites ranging from whole igneous suites down to mineral scale. This book presents an overview of the state of the art, and envisages future avenues towards a better understanding of granite petrogenesis. The volume focuses on the following topics:
compositional variability of granitic rocks generated in contrasting geodynamic settings during the Proterozoic to Phanerozoic Periods;
main permissible mechanisms producing subduction-related granites;
crustal anatexis of different protoliths and the role of water in granite petrogenesis; and
new theoretical and analytical tools available for modelling whole-rock geochemistry in order to decipher the sources and evolution of granitic suites.
Peter I. Nabelek, 2020. "Petrogenesis of leucogranites in collisional orogens", Post-Archean Granitic Rocks: Petrogenetic Processes and Tectonic Environments, V. Janoušek, B. Bonin, W. J. Collins, F. Farina, P. Bowden
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Leucogranites are a characteristic feature of collisional orogens. Their generation is intimately related to crustal thickening and the active deformation and metamorphism of metapelites. Data from Proterozoic to present day orogenic belts show that collisional leucogranites (CLGs) are peraluminous, with muscovite, biotite and tourmaline as characteristic minerals. Isotopic ratios uniquely identify the metapelitic sequences in which CLGs occur as sources. Organic material in pelitic sources results in fO2 in CLGs that is usually below the fayalite–magnetite–quartz buffer. Most CLGs form under vapour-poor conditions with melting involving a peritectic breakdown of muscovite. The low concentrations of Mg, Fe...