Evidence of magmatic hybridization related with feeding zones: the synkinematic Guitiriz granitoid, NW Iberian Massif
Published:January 01, 1999
M. Menéndez, L. A. Ortega, 1999. "Evidence of magmatic hybridization related with feeding zones: the synkinematic Guitiriz granitoid, NW Iberian Massif", Understanding Granites: Integrating New and Classical Techniques, Antonio Castro, Carlos Fernández, Jean Louis Vigneresse
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The hybridization zone of Guitiriz (NW Iberian Massif) displays numerous features resulted from the interaction of two contemporaneously emplaced felsic and intermediate magmas. A combined study, including field geology, petrography, chemistry and Sr isotopic data, reveals a simple two-component mixing between a mantle-derived magma with an initial 87Sr/86Sr isotopic ratio <0.7042 and a crustal-derived component with an initial Sr isotopic ratio > 0.7104. Both magmas rose through a common feeding zone developed in an extensional regime in which favourable conditions for magma mixing occurred. Calculated emplacement temperature and pressure for the Guitiriz hybridization zone are 700 °C and 2.5 kbar, respectively, and are comparable with those estimated from regional metamorphism. Magmatic epidote occurrence, exhibiting textural and compositional characteristics suggestive of magmatic origin, does not require high-pressure granite solidification. Its presence may be related to a rapid magma transport through the feeding zone that favoured the preservation of epidote.
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Understanding Granites: Integrating New and Classical Techniques
Granite magmatism represents a major contribution to crustal growth and recycling and, consequently, is one of the most important mechanisms to have contributed to the geochemical differentiation of the Earth’s crust since Archaean time. Granites are also often associated with ore bodies, and their study therefore has direct commercial relevance.
The modern view of the granite problems requires the application of many different theoretical, experimental and empirical resources provided by geophysics, geochemistry, experimental petrology, structural geology, scale modelling and field geology. Because of the complexity of the granite problem, it is necessary to integrate a variety of techniques and corroborate the findings with field observations.This is the philosophy of this book.
Many chapters are review papers dealing with the development and achievements of a particular technique, whilst other chapters deal with the application of a number of techniques to a specific problem. This volume brings together papers that would otherwise be dispersed in different publications.
The book will be of interest to igneous petrologists, geophysicists, structural geologists and geochemists.