Annealing effects in muscovite and their influence on dating by fission track method

Xe- and U-tracks in apatite and muscovite near the etching threshold

“…The value for muscovite agrees well with the measured length deficits of Fe, Br and I tracks in mica [21], in particular that of I (1.2 lm), the next lighter element from Xe. It also agrees with estimates based on the difference between the etchable lengths of confined fission tracks [22,23] and the range of the 235 U fission fragments (1.1 lm [12]), and on the relative registration efficiencies of induced fission tracks in muscovite and diallyl-phthalate (1.1 lm [24]). However, these estimates are at odds with the much higher values reported for 197 Au and 58 Ni tracks in muscovite (10-21 lm [25]).…”

Fission Track Ages of some Indian Muscovites

“…Fossil tracks were found to be shorter than the induced tracks and the decrease ranged from 13 to 19 (Table 1). However, as Bigazzi (1967) suggested, the age correction is not linearly related to shortening of track length, and a tion of +3 % (Mehta and Rama 1969). In the present study, corrections to the ages are negligible as compared to other experimental errors.…”

“…A number of minerals, such as muscovite, biotite, apatite, zircon, sphene, and epidote, have been considered suitable for dating rocks. Mehta and Rama (1969) and Mehta and Nagpaul (1971) used muscovite for dating Precambrian igneous and metamorphic rocks. In the present study seven samples of muscovite of pegmatitic origin, collected from different mica mines of India, have been dated by following an experimental technique similar to that of Mehta and Rama (1969) and Mehta and Nagpaul(l971).…”

Discovery of Naturally Etched Fission Tracks and Alpha-Recoil Tracks in Submarine Glasses: Reevaluation of a Putative Biosignature for Earth and Mars

“…Exposing a polished or cleavage surface to an etchant preferentially dissolves the damaged regions in the mineral or glass that result from the spontaneous fission of 238 U (Figure 3) or by the induced fission of 235 U caused by irradiating the sample with thermal neutrons from a nuclear reactor (Figure 3(b)-right) [202,223,224] (note: strong etchants such as HF, HNO 3 , HCl, or NaOH solutions are typically used in fission track dating studies, although weak etchants-such as deionized water-have also been used to reveal fission tracks in silicate glasses (e.g., Figure 3(d)) [138]). Fission fragments cause linear damage tracks (Figure 3(a)) that range in etchable length depending on numerous factors including host mineralogy and composition [225,226], fission fragment mass [225,227], crystallographic orientation [228], etching time and efficiency [222], and the degree of thermal annealing which may have occurred [229]. For example, the mean etchable length of pristine fission tracks (e.g., unannealed or induced tracks) is ∼8-9 m in volcanic glass (Figure 3(b); Figure 1 in Sandhu et al [198]; Figure 8(b) in Westgate and Naeser [199]; Arias et al [126]; Sandhu and Westgate [128]) and tektites ( Figures 1 and 2 in Storzer and Wagner [218], ∼11 m in zircon [212,230], ∼16 m in apatite [213], and ∼20 m in micas [207,229], although experimentally etched "fossil" (i.e., spontaneous) fission tracks may be substantially shorter in each case, especially due to annealing and track fading [126,128,207,212,…”

“…Fission fragments cause linear damage tracks (Figure 3(a)) that range in etchable length depending on numerous factors including host mineralogy and composition [225,226], fission fragment mass [225,227], crystallographic orientation [228], etching time and efficiency [222], and the degree of thermal annealing which may have occurred [229]. For example, the mean etchable length of pristine fission tracks (e.g., unannealed or induced tracks) is ∼8-9 m in volcanic glass (Figure 3(b); Figure 1 in Sandhu et al [198]; Figure 8(b) in Westgate and Naeser [199]; Arias et al [126]; Sandhu and Westgate [128]) and tektites ( Figures 1 and 2 in Storzer and Wagner [218], ∼11 m in zircon [212,230], ∼16 m in apatite [213], and ∼20 m in micas [207,229], although experimentally etched "fossil" (i.e., spontaneous) fission tracks may be substantially shorter in each case, especially due to annealing and track fading [126,128,207,212,213,229,230]. For natural (and synthetic) silicate glasses exhibiting a wide range of chemical compositions, the lengths of fully revealed (i.e., etched) fission tracks are consistently reported as being ∼6-9 m long (e.g., Figures 3(b), 3(d), and 3(e))-including those in hydrated silicic volcanic glass shards [128], tektites (including: australite [216,231], bediasite [218], indochinite [216], and moldavite [128,…”