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.
Antonio Castro, 2020. "The dual origin of I-type granites: the contribution from experiments", Post-Archean Granitic Rocks: Petrogenetic Processes and Tectonic Environments, V. Janoušek, B. Bonin, W. J. Collins, F. Farina, P. Bowden
Download citation file:
New laboratory experiments using granulite xenoliths support a dual origin for I-type granites as primary and secondary. Primary I-type granites represent fractionated liquids from intermediate magma systems of broadly andesitic composition. Fluid-fluxed melting of igneous rocks that resided in the continental crust generates secondary I-type granites. The former are directly related to subduction, with Cordilleran batholiths as the most characteristic examples. Experiments with lower crust granulite sources, in the presence of water, show that amphibole is formed by a water-fluxed peritectic rehydration melting reaction. Entrainment of only 10% of restites composed of amphibole, pyroxene, plagioclase and magnetite, is...