Microgranular enclaves as evidence of rapid cooling in granitoid rocks; the case of the Los Pedroches Granodiorite, Iberian Massif, Spain

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doi: 10.1007/s00410-005-0652-0
Authors:Donaire, Teodosio; Pascual, Emilio; Pin, Christian; Duthou, Jean-Louis
Author Affiliations:Primary:
Universidad de Huelva, Departamento de Geología, Huelva, Spain
Université Blaise Pascal, France
Volume Title:Contributions to Mineralogy and Petrology
Source:Contributions to Mineralogy and Petrology, 149(3), p.247-265. Publisher: Springer International, Heidelberg-New York, International. ISSN: 0010-7999
Publication Date:2005
Note:In English. 62 refs.; illus., incl. 4 tables, geol. sketch map
Summary:Microgranular enclaves from the Los Pedroches granodiorite have Sr-Nd isotopic and mineral chemical compositions close to those of their host. This similarity is not related to restite unmixing, as indicated by the igneous textures of the enclaves. A number of other geological and geochemical lines of evidence, including the high REE and HFSE contents of the microgranular enclaves relative to the host granitic, strongly suggest that this similarity cannot be explained by magma mixing. Alternatively, a crystallization process by rapid cooling within the host granitic magma could explain the geochemical and textural characteristics of the microgranular enclaves, including shape, grain size, mineralogy, texture, chemistry and Sr-Nd isotopic composition. Such crystallization occurred at the walls of the magma conduits through which the granitic magmas were emplaced in the upper crust. This process should be considered as an alternative hypothesis to magma mixing for the generation of some microgranular enclaves, especially where no direct evidence exists for the presence of basic magmas coeval with granitic rocks, and where there is a lack of isotopic contrast between hosts and enclaves. As the process is favoured by feeder-dyke related emplacement, it is suggested that abundance of microgranular enclaves can be related to the mechanism of emplacement of granitic bodies. [G.L.B.]
Sections:Geochemistry; Petrology
Subsections:Igneous rocks
Subjects:Alkaline earth metals; Chemical composition; Cooling; Crust; Crystallization; Dikes; Emplacement; Fractional crystallization; Geochemistry; Granodiorites; ICP mass spectra; Igneous rocks; Intrusions; Isotope ratios; Isotopes; Magma contamination; Magmas; Magmatic differentiation; Major elements; Mass spectra; Mesozoic; Metals; Mineral assemblages; Mineral composition; Mixing; Nd-144/Nd-143; Neodymium; Orogeny; P-T conditions; Paleozoic; Permian; Petrography; Plutonic rocks; Rare earths; Restites; Sedimentary rocks; Spectra; Sr-87/Sr-86; Stable isotopes; Strontium; Textures; Trace elements; Triassic; Upper crust; Variscan Orogeny; X-ray fluorescence spectra; Europe; Iberian Massif; Iberian Peninsula; Los Pedroches Batholith; Southern Europe; Spain; Los Pedroches Granodiorite
Coordinates:N380000 N390000 W0040000 W0050000
Abstract Numbers:05M/2089
Record ID:2006034271
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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