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Título
Caracterización de pizarras comerciales del NO de España a partir de DRX, microscopía electrónica (EMPA , SEM, TEM) y FRX
Autor
Facultad/Centro
Área de conocimiento
Título de la revista
Cadernos do Laboratorio Xeolóxico de Laxe: Revista de xeoloxía galega e do hercínico peninsular
Número de la revista
34
Cita Bibliográfica
Gómez Fernández, F., Ward, C. R., & Bauluz Lázaro, B. (2009). Caracterización de pizarras comerciales del NO de España a partir de DRX, microscopía electrónica (EMPA, SEM, TEM) y FRX. Cadernos do Laboratorio Xeolóxico de Laxe: Revista de xeoloxía galega e do hercínico peninsular, 34, 127-142.
Editorial
Instituto Universitario de Geología Isidro Parga Pondal
Fecha
2009
ISSN
0213-4497
Resumen
[EN] The aim of this paper is to characterize thoroughly the mineralogy and petrography of a set of
ten different types of commercial roofing slates from the NW of Spain. Representative samples of
each type have been studied by transmitted and reflected-light optical microscopy, scanning and
transmission electron microscopy, electron microprobe, X-ray fluorescence and X-ray diffraction
techniques. Quantitative analyses of the main mineral percentages in each slate sample were
made from XRD data using the Siroquant™ interpretation software system, based on Rietveld
principles. The microscopic textures of the slates vary depending on the samples, and lepidoblastic
to porphyroblastic textures have been described. Some slates with bands of sand layers display
grano-lepidoblastic textures. White mica, quartz, chlorite and feldspar (albite) are the main minerals.
The white micas and the chlorites have similar compositions in all the analyzed samples. Electron
microprobe analyses indicate that the micas are K-rich dioctahedral varieties, having a composition close to muscovite with a phengitic component. They show the following average formula: (Na0.16
K1.39 Ca0.01) (Al3.83 Ti0.03 Fe0.15 Mg0.14) (Si6.22 Al1.78) O20 (OH)4. The chlorites are magnesian chamosites
with an average formula of (Na0.02 K0.04 Ca0.01Al3.24 Ti0.01 Fe5.13 Mn0.03 Mg3.28) (Si5.23 Al2.77) O20 (OH)16.
Accessory minerals are ilmenite, rutile, sulphides, carbonates, graphite, monazite, apatite, zircon
and tourmaline. Two different associations of sulphide minerals are distinguished: 1) Type I with
pyrite, pyrrhotite, pentlandite, cobaltite, chalcopyrite, sphalerite, galena, ullmannite and gersdorffite
occurring as pre-kinematic porphydic aggregates; b) Type II mainly with post-kinematic pyrite and
sporadic chalcopyrite and galena. The main carbonate mineral is ankerite ((Mg0.26, Ca0.49, Mn0.05,
Fe0.19) CO3) with minor calcite and siderite also present.
Materia
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