Chemical variation and significance of micas from the Fregeneda-Almendra pegmatitic field (Central-Iberian Zone, Spain and Portugal)
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Romeu Vieira
,
Encarnación Roda-Robles
Abstract
Field, textural, paragenetic, and chemical data for micas from pegmatites of the Fregeneda-Almendra pegmatitic field (Central-Iberian Zone) are used to characterize and evaluate their petrogenesis. These pegmatites show a zonal distribution from barren to evolved, with an increase in degree of evolution with increasing distance from the Mêda-Penedono-Lumbrales leucogranite. Five types of evolved pegmatites have been recognized: (1) petalite-rich, (2) spodumene-rich, (3) Li-mica + spodumenerich, (4) Li-mica-rich, and (5) cassiterite-rich pegmatites, plus six types of barren and intermediate pegmatites. Representative micas from the different pegmatite types and from the leucogranite were analyzed for major and trace elements. All micas belong to the muscovite-lepidolite series. Lithium is incorporated into Li-micas via the Li3Al-1□-2 and Si2LiAl-3 substitutions, where □ represents vacancies. The Al4Si-3□-1 and Al2□1R2+-3 substitutions, where R2+ = (Fe + Mg + Mn), account for the compositional variability of micas from the Li-mica-free pegmatites. The Li, Rb, Cs, Be, Ta, and Nb contents of micas increase in the order: leucogranites and barren pegmatites < intermediate pegmatites < spodumene-bearing and petalite-bearing dikes < Li-mica-bearing pegmatites. The Ba content decreases in the same order, and Sn and Zn are relatively abundant in the intermediate pegmatites. These variations are consistent with rare-element enrichment via fractionation processes combined with partitioning of rare elements from the pegmatite melt into the minerals and volatile phases. However, some pegmatite types occurring in this area, such as the cassiterite-rich dikes, do not seem to form part of the same evolutionary trend.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- Roebling Medal Lecture. The three partners of metamorphic petrology
- Relationship between structure, morphology, and carbon isotopic composition of graphite in marbles: Implications for calcite-graphite carbon isotope thermometry
- Crystal structure, mosaicity, and strain analysis of Hawaiian olivines using in situ X-ray diffraction
- Characterization of deep weathering and nanoporosity development in shale—A neutron study
- Structural water in ferrihydrite and constraints this provides on possible structure models
- Critical evaluation of the revised akdalaite model for ferrihydrite
- Neutron diffraction study of hydrogen in birnessite structures
- Pressless split-sphere apparatus equipped with scaled-up Kawai-cell for mineralogical studies at 10–20 GPa
- Dislocation microstructures in majorite garnet experimentally deformed in the multi-anvil apparatus
- Density of carbonated peridotite magma at high pressure using an X-ray absorption method
- Stability and bulk modulus of Ni3S, a new nickel sulfur compound, and the melting relations of the system Ni-NiS up to 10 GPa
- Far-infrared spectra of synthetic [4][(Al2-xGax)(Si2–yGey)](OH,OD,F)2-kinoshitalite: Characterization and assignment of interlayer Ba-Oinner and Ba-Oouter stretching bands
- High-temperature elasticity of polycrystalline orthoenstatite (MgSiO3)
- Anatomy of a metabentonite: Nucleation and growth of illite crystals and their coalescence into mixed-layer illite/smectite
- Zn-O tetrahedral bond length variations in normal spinel oxides
- A new thermodynamic analysis of the intergrowth of hedenbergite and magnetite with Ca-Fe-rich olivine
- Raman spectroscopic investigations of some Tl-sulfosalt minerals containing pyramidal (As,Sb)S3 groups
- A first record of strong structural relaxation of TO4 tetrahedra in a spinel solid solution
- The high-pressure behavior of orthorhombic amphiboles
- XAS determination of the Fe local environment and oxidation state in phonolite glasses
- Chemical variation and significance of micas from the Fregeneda-Almendra pegmatitic field (Central-Iberian Zone, Spain and Portugal)
- Light-induced molecular change in HgI2·As4S4: Evidence by single-crystal X-ray diffraction and Raman spectroscopy
- Low-temperature electron paramagnetic resonance studies on natural calumetite from Khetri copper mine, Rajasthan, India
- Chromatite and its Cr3+- and Cr6+-bearing precursor minerals from the Nabi Musa Mottled Zone complex, Judean Desert
- Hazenite, KNaMg2(PO4)2⋅14H2O, a new biologically related phosphate mineral, from Mono Lake, California, U.S.A.
- The fractional latent heat of crystallizing magmas
Articles in the same Issue
- Roebling Medal Lecture. The three partners of metamorphic petrology
- Relationship between structure, morphology, and carbon isotopic composition of graphite in marbles: Implications for calcite-graphite carbon isotope thermometry
- Crystal structure, mosaicity, and strain analysis of Hawaiian olivines using in situ X-ray diffraction
- Characterization of deep weathering and nanoporosity development in shale—A neutron study
- Structural water in ferrihydrite and constraints this provides on possible structure models
- Critical evaluation of the revised akdalaite model for ferrihydrite
- Neutron diffraction study of hydrogen in birnessite structures
- Pressless split-sphere apparatus equipped with scaled-up Kawai-cell for mineralogical studies at 10–20 GPa
- Dislocation microstructures in majorite garnet experimentally deformed in the multi-anvil apparatus
- Density of carbonated peridotite magma at high pressure using an X-ray absorption method
- Stability and bulk modulus of Ni3S, a new nickel sulfur compound, and the melting relations of the system Ni-NiS up to 10 GPa
- Far-infrared spectra of synthetic [4][(Al2-xGax)(Si2–yGey)](OH,OD,F)2-kinoshitalite: Characterization and assignment of interlayer Ba-Oinner and Ba-Oouter stretching bands
- High-temperature elasticity of polycrystalline orthoenstatite (MgSiO3)
- Anatomy of a metabentonite: Nucleation and growth of illite crystals and their coalescence into mixed-layer illite/smectite
- Zn-O tetrahedral bond length variations in normal spinel oxides
- A new thermodynamic analysis of the intergrowth of hedenbergite and magnetite with Ca-Fe-rich olivine
- Raman spectroscopic investigations of some Tl-sulfosalt minerals containing pyramidal (As,Sb)S3 groups
- A first record of strong structural relaxation of TO4 tetrahedra in a spinel solid solution
- The high-pressure behavior of orthorhombic amphiboles
- XAS determination of the Fe local environment and oxidation state in phonolite glasses
- Chemical variation and significance of micas from the Fregeneda-Almendra pegmatitic field (Central-Iberian Zone, Spain and Portugal)
- Light-induced molecular change in HgI2·As4S4: Evidence by single-crystal X-ray diffraction and Raman spectroscopy
- Low-temperature electron paramagnetic resonance studies on natural calumetite from Khetri copper mine, Rajasthan, India
- Chromatite and its Cr3+- and Cr6+-bearing precursor minerals from the Nabi Musa Mottled Zone complex, Judean Desert
- Hazenite, KNaMg2(PO4)2⋅14H2O, a new biologically related phosphate mineral, from Mono Lake, California, U.S.A.
- The fractional latent heat of crystallizing magmas
