Evaluation of radiation-damage halos in quartz by cathodoluminescence as a geochronological tool

Response of cathodoluminescence of alkali feldspar to He+ ion implantation and electron irradiation

“…These facts imply that He + ion implantation causes a drastic change in CL properties of adularia, anorthoclase and amazonite, but the behavior varies between alkali feldspars. The distance of the CL halos from the implanted surface is consistent with the maximum of electronic energy loss of 4.0 MeV He + ion in alkali feldspars (Bragg and Kleeman, 1905;Nogami and Hurley, 1948;Faul, 1954;Owen, 1988;Komuro et al, 2002;Okumura et al, 2008). CL line analysis, acquired through the cross-sections of the implanted alkali feldspars from the implanted surface to a depth of 20 μm including the CL halo at 12 to 15 μm, shows exponential increase for the adularia and decreases for the anorthoclase and amazonite in intensities along the depth direction down to 15 μm, and exhibits subsequently decrease and increase over this point, respectively.…”

“…The cross section is denoted by "C" after the sample identifier, e.g., Adu00C for unimplanted adularia and Adu10C for the implanted adularia at highest radiation dose. The details of the He + ion implantation experiments and sample preparation are described by Okumura et al (2008) and Kayama et al (2011a).…”

“…CL analysis allow us to estimate their radiation effects on the mineral grains with high spatial resolution. Recently, CL measurements on ion-implanted and electron irradiated quartz and albite have enabled interpretation of radiation effects, including observation of micrometer-sized radiation halos produced by α particles and estimation of the α and β radiation doses as geodosimetry (Owen, 1988;Komuro et al, 2002;Okumura et al, 2008;Krickl et al, 2008;Kayama et al, 2011a;Kayama et al, 2011b;King et al, 2011). Although great scientific interest exists concerning CL of radiation-induced quartz and albite, very few such investigations have been carried out for alkali feldspars up to now.…”

Cathodoluminescence of synthetic zircon implanted by He⁺ ion

“…In this case, the dose of 2.5×10 -5 C/cm 2 corresponds to the exposed dose estimated from the radiation of uranium of 1000 ppm in natural zircon for 1.0×10 6 y. Detailed information on the He + ion implantation experiment and sample preparation has been reported in Okumura et al (2008) and Kayama et al (2011).…”

“…Therefore, CL emissions in zircon are attributable to two-types of radiation-induced and intrinsic defects in addition to impurity centers. Recently, luminescent features of radiation damages by simulating the α and β particles in natural and/or synthetic minerals such as quartz, feldspar and zircon have been characterized by a spectroscopic method to assign individual emission centers (e.g., Finch et al, 2004;Okumura et al, 2008;Kayama et al, 2011;Tsuchiya et al, 2014), which suggests an evaluation of dose dependence on luminescence intensity related to radiation-induced defects (King et al, 2011;Kayama et al, 2014). Furthermore, a process of metamictization in radioactive minerals (e.g., zircon) has been estimated by luminescence methods for ionimplanted samples as a simulation of radiation-induced damage on minerals (e.g., Weber et al, 1994;Lian et al, 2003;Ewing et al, 2003;Finch et al, 2004;Nasdala et al, 2011).…”