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Alkali feldspars in syenite from the Cerro Balmaceda pluton in the Patagonian Andes, Chile, show various petrographic microtextures formed during the magmatic to high-and low-temperature hydrothermal stages in which cathodoluminescence (CL) shows a wide range of blue, violet, and pink to red colors with variable brightness. Their CL spectra exhibit two emission bands: one at 405-420 nm in the blue region and the other at 700-760 nm in the red-infrared (IR) region. Asymmetrically shaped spectral peaks in energy units suggest overlapping of each individual emission, which corresponds to various luminescence centers. Blue emission bands were separated into two spectral peaks fitted by Gaussian curves centered at 3.055-3.076 and 2.815-2.845 eV. A positive correlation is found between emission intensities at 3.055-3.076 eV and Ti[O.sub.2] contents, suggesting the activation of a [Ti.sup.4+] impurity as an emission center. The intensities at 2.815-2.845 eV, where clear and featureless feldspar (CF; not affected by hydrothermal metasomatism) is shown under optical microscopy, which have intensities appreciably higher than those showing patched microperthite (PMP), formed during low-temperature hydrothermal reactions, correlate reciprocally with the intensities of red-IR emission caused by a [Fe.sup.3+] impurity center. The peak at 2.815-2.845 eV can be attributed to oxygen defects associated with Al-O-Al and Al-O-Ti bridges. Most of the areas show CL emissions at 700-760 nm in the red-IR region, in which intensities increase with an increase in Fe203 contents as impurities. The [Fe.sup.3+] ion acts as an activator for the red-IR emission. The Ab-rich and Or-rich phases of PMP have emission components at 1.644 eV (754 nm) and 1.727 eV (717 nm), respectively. The red-IR emission from CF consists of emission components at 1.677 eV (739 nm) and 1.557 eV (796 nm), according to an [Fe.sup.3+] impurity center in the Or-rich phase and in the Ab-rich phase as cryptoperthite, respectively. Both components are centered at a wavelength longer than the emission band of Ab-rich and Or-rich phases of PMP, suggesting a change in configurational state around the [Fe.sup.3+] ion from the T2 to the T1 site by low-temperature hydrothermal metasomatic reactions. Accordingly, the peak positions of the red-IR emission are controlled by the ordering state of [Fe.sup.3+] ion into the T I site, the existence of multiphase perthite and chemical composition. Keywords: Cathodoluminescence, alkali feldspar, [Ti.sup.4+] center, Al-[O.sup.-]-A1 center, oxygen defects associated with Al-O-Al and A1-O-Ti bridges, [Fe.sup.3+] center, hydrothermal metasomatic reaction, cathodoluminescence spectral deconvolution DOI: 10.2138/am.2010.3427

Cathodoluminescence (CL) spectra of tridymite and cristobalite have broad peaks around 430 and 400 nm, respectively, both of which can be assigned to the [[Al[O.sub.4]/[M.sup.+]].sup.0] defect. The CL intensities of these spectral peaks in the blue region decrease with prolonged exposure to electron irradiation, similar to the short-lived luminescence observed in quartz, although quartz shows a lower decrease in CL intensity compared to these minerals. Cristobalite has a higher CL intensity reduction rate during irradiation than does tridymite. Irradiation of these minerals at low temperatures results in a more rapid decay of CL emission, whereas that of quartz shows no apparent change in the rate of CL emission at similar temperatures. Confocal micro-Raman spectroscopy of the electron irradiated surface of these minerals reveals the amorphization caused by the interaction of the electron beam with the surface layer to a depth of several micrometers. This suggests that such structural destruction diminishes the activity of CL emission centers related to the [[Al[O.sub.4]/[M.sup.+]].sup.0] defects by migration of monovalent cations associated with exchanged Al in the tetrahedral sites. Both samples present a considerable reduction of their CL intensities at higher temperature, suggesting a temperature quenching phenomenon. The activation energy in the quenching process was evaluated by a least-squares fitting of the Arrhenius plots, assuming the Mott-Seitz model. The result implies that the energy of non-radiative transition in this process might be transferred to lattice vibrations as phonons in two different manners. This might be related to different irradiation responses of the CL with a change in sample temperature. Keywords: Tridymite, cristobalite, cathodoluminescence, electron irradiation, temperature quenching, Raman spectroscopy

He+ ion implantation on albite (Minas Gerais, Brazil) at 4.0 MeV, corresponding to the energy of a particle from 238U fission, has been conducted to clarify the radiation effects of α particles from radioactive minerals on cathodoluminescence (CL) of albite. CL of albite results in various emission bands at ~380, ~560, and ~740 nm, and in the UV range. Red emission at 700-750 nm is detected in the CL spectra of the implanted samples. Total CL intensities of these UV, blue, yellow, red, and IR emissions vary among the samples. High-resolution CL imaging of the cross-section samples shows a CL halo on the implanted surface of approximately 14 µm thickness, which is consistent with a theoretical range of α particles of 4.0 MeV. It was first confirmed experimentally that the CL halo is created by α particles. The deconvolution of CL spectra in the red emission range by Gaussian fitting provides the component at 1.861 eV that is attributed to a radiation-induced defect center produced by He+ ion implantation. The intensity of the component at 1.861 eV linearly correlates with the dose density of He+ implantation on albite as a function of the population of the radiation-induced defect center, regardless of other factors such as concentration and distribution of other emission centers, existence of microstructures and textures, and crystallographic orientation. The CL spectral deconvolution has a high potential for quantitative evaluation of the radiation dose of α particles from natural radionuclides on albite for a geodosimetry. [ABSTRACT FROM AUTHOR]