Geochemistry of granitic rocks and their micas from the west border of the Alvão Plateau, northern Portugal

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Authors:Neiva, A. M. R.
Author Affiliations:Primary:
Univ. Oporto, Dept. Mineral. Geol., Oporto 4000, Portugal
Volume Title:Chemie der Erde
Source:Chemie der Erde, 42(1), p.31-44. Publisher: Gustav Fischer Verlag, Jena, Federal Republic of Germany. ISSN: 0009-2819
Publication Date:1983
Note:In English with German summary. 24 refs.; illus. incl. 100 anal., 6 tables, 6 plates, geol. sketch map
Summary:Within this area, outcrops occur of an older fine-grained muscovite-biotite granite and of a younger medium-grained porphyritic muscovite-biotite granite. Both granites are of Hercynian age, but their geochemistries and those of the micas suggest that they correspond with different pulses of magma. REE contents indicate that the granitic magmas may be derived by partial melting of greywackes and pelites. The major- and trace-element chemistries of the porphyritic granite and associated aplites and pegmatites, as well as those of their contained micas, indicate that these rocks result from some degree of magmatic fractionation. The porphyritic granite magma had a lower fH2O, PH2O and fHF and a higher fH2O/fHF than the magma from which the non-porphyritic fine-grained granite formed: fH2O, PH2O are higher, and fO2, fH2O/fHF are lower in the aplitic and pegmatitic liquors than in the magma from which the porphyritic granite crystallized. Chemical analyses and norms of five granitic rocks, with trace-element analyses, are presented. Chemical analyses, structural formulae and trace-element analyses of biotites (2) and muscovites (5) from the granitic rocks are also given. [P.Br.]
Subjects:Geochemistry; Granite porphyry; Granites; Igneous rocks; Magmas; Major elements; Metals; Mica group; Partial melting; Petrology; Plutonic rocks; Rare earths; Sheet silicates; Silicates; Trace elements; Europe; Iberian Peninsula; Portugal; Southern Europe; Alvao Plateau
Abstract Numbers:83M/3194
Record ID:1985060149
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique
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