Structural state of K-feldspar in some Hercynian granites from Iberia; a review of data and controlling factors

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Authors:Neves, L. J. P. F.; Godinho, M. M.
Author Affiliations:Primary:
Universidade de Coimbra, Dipartamento de Ciencias da Terra, Portugal
Volume Title:Canadian Mineralogist
Source:The Canadian Mineralogist, Vol.37(Part 3), p.691-700. Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada. ISSN: 0008-4476
Publication Date:1999
Note:In English with French summary. 38 refs.; illus.
Summary:Several hundred concentrates of K-feldspar from the Hercynian granites and associated aplites and pegmatites of central Portugal were studied by XRD to assess their structural state and to make inferences about their petrogenesis. Their structural state was indicated by the diffraction pattern in the 2θ region 29-31° using CuKα radiation, the ordering index ΔSM and Al-Si distribution derived from cell parameters; a range of values were obtained, though aplites and pegmatites showed less variability. In the great majority of samples from the granites, > 80% of Al is in the T1 site of the K-feldspar. It is concluded that the cooling rate of the granite was the factor controlling the ordering process of these K-feldspars; rapid unroofing of the older granites enhanced the cooling rate, retarding ordering. [R.A.H.]
Sections:Crystal structure
Subsections:Specific structures: silicates
Subjects:Alkali feldspar; Feldspar group; Framework silicates; Granites; Igneous rocks; K-feldspar; Mineral composition; Orogeny; Paragenesis; Pegmatite; Plutonic rocks; Silicates; Thermal history; Variscan Orogeny; X-ray diffraction data; Europe; Iberian Massif; Iberian Peninsula; Portugal; Southern Europe
Abstract Numbers:00M/2461
Record ID:2000018381
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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040 |a ViAlAGI  |c ViAlAGI 
041 |a eng  |b fre 
072 7 |a 05A  |2 georeft 
100 1 |a Neves, L. J. P. F.  |e analytic author  |u Universidade de Coimbra, Dipartamento de Ciencias da Terra, @PRT 
245 1 0 |a Structural state of K-feldspar in some Hercynian granites from Iberia; a review of data and controlling factors 
300 |a p. 691-700 
500 |a In English with French summary. 38 refs. 
500 |a Abstract number: 00M/2461 
500 |a Abstractor: R.A.H. 
500 |a Category Section: Crystal structure 
500 |a Category Subsection: Specific structures: silicates 
500 |a Affiliation: Universidade de Coimbra, Dipartamento de Ciencias da Terra; ; PRT; Portugal 
500 |a Key title: The=Canadian Mineralogist 
500 |a Source note: The Canadian Mineralogist, Vol.37(Part 3), p.691-700. Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada. ISSN: 0008-4476 
500 |a Publication type: journal article 
504 |b 38 refs. 
510 3 |a GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom 
520 |a Several hundred concentrates of K-feldspar from the Hercynian granites and associated aplites and pegmatites of central Portugal were studied by XRD to assess their structural state and to make inferences about their petrogenesis. Their structural state was indicated by the diffraction pattern in the 2θ region 29-31° using CuKα radiation, the ordering index Δ<SM` and Al-Si distribution derived from cell parameters; a range of values were obtained, though aplites and pegmatites showed less variability. In the great majority of samples from the granites, #GT 80% of Al is in the T1 site of the K-feldspar. It is concluded that the cooling rate of the granite was the factor controlling the ordering process of these K-feldspars; rapid unroofing of the older granites enhanced the cooling rate, retarding ordering. 
650 7 |a Alkali feldspar  |2 georeft 
650 7 |a Feldspar group  |2 georeft 
650 7 |a Framework silicates  |2 georeft 
650 7 |a Granites  |2 georeft 
650 7 |a Igneous rocks  |2 georeft 
650 7 |a K-feldspar  |2 georeft 
650 7 |a Mineral composition  |2 georeft 
650 7 |a Orogeny  |2 georeft 
650 7 |a Paragenesis  |2 georeft 
650 7 |a Pegmatite  |2 georeft 
650 7 |a Plutonic rocks  |2 georeft 
650 7 |a Silicates  |2 georeft 
650 7 |a Thermal history  |2 georeft 
650 7 |a Variscan Orogeny  |2 georeft 
650 7 |a X-ray diffraction data  |2 georeft 
651 7 |a Europe  |2 georeft 
651 7 |a Iberian Massif  |2 georeft 
651 7 |a Iberian Peninsula  |2 georeft 
651 7 |a Portugal  |2 georeft 
651 7 |a Southern Europe  |2 georeft 
700 1 |a Godinho, M. M.,  |e analytic author 
773 0 |t Canadian Mineralogist  |d Ottawa, ON : Mineralogical Association of Canada, Jun. 1999  |x 0008-4476  |y CAMIA6  |n The Canadian Mineralogist, Vol.37(Part 3), p.691-700. Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada. ISSN: 0008-4476 Publication type: journal article  |g Vol. 37, Part 3  |h illus.