A Monte-Carlo calculation of the size distribution of latent alpha-recoil tracks in phlogopite: Implications for the recoil-track dating method

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

“…As they grow-for example, during the eight successive alpha-recoil events during the complete radioactive decay chain of 238 U to 206 Pb-alpharecoil tracks typically "zigzag" through their host material (Figure 4(a)), ∼30-50 nm in new random directions with each successive alpha-recoil event (e.g., Figure 3 in Jonckheere and Gögen [131]; Table 1 in Stübner and Jonckheere [132]), resulting in a final composite cluster of radiation damage measuring about 120 nm across (e.g., estimates for the mean diameter of alpha-recoil tracks derived from the complete decay of 238 U to stable 206 Pb in micas range from ∼110 nm [132] to ∼120 nm [129] and to ∼125 nm [131]). In this theoretical modelling study of the distribution of alpharecoil tracks in DSDP 418A basaltic glass, we consider each alpha-recoil track to be the end result of complete U-or Thseries decay.…”

“…In this theoretical modelling study of the distribution of alpharecoil tracks in DSDP 418A basaltic glass, we consider each alpha-recoil track to be the end result of complete U-or Thseries decay. For example, even though a total of eight alpharecoil events take place during the complete radioactive decay of 238 U to 206 Pb, because they are all interconnected they are considered as a "single" composite ∼120 nm wide alpharecoil track (Figure 4(a) [129,131,132]). In addition, for simplicity in this high spatial resolution theoretical modelling study (Figures 10(i) and 15(c)) each alpha-recoil track is modelled as a ∼120 nm diameter sphere (instead of as myriad different geometric varieties of zigzagging structures) and this is in keeping with the observation that when fully etched, alpha-recoil tracks tend to form relatively equant etch-pits (e.g., see Figure 4(b); Figure 1 in Stübner et al [133]); that is, the theoretical nanoscopic "zigzagging" threedimensional structure of alpha-recoil tracks is effectively destroyed upon etching.…”

“…carried out in the laboratory during fission track dating studies ( Figure 3), in which the polished surfaces of volcanic glass samples etch preferentially along elongate (typically ∼6-8 m long) latent damage trails in the glass caused by the spontaneous fission of 238 U during aging of the sample (or the induced fission of 235 U) [125][126][127][128]. Similarly, experimental chemical etching of alpha-recoil tracks ( Figure 4) caused by the radioactive decay of U and Th (e.g., in alpha-recoil track dating studies of micas [129][130][131][132][133][134]) represents another style of etch-tunnelling of geological samples that could potentially be relevant to understanding the origin of naturally formed etch-tunnels in minerals and glasses. Furthermore, radiation damage in synthetic borosilicate nuclear waste glasses (for which basaltic glass is an ideal natural analog: [135,136]), including fission tracks and simulated alpha-recoil damage, also leads to preferential etching of glass in a matter of hours, even at low temperatures (20-100 ∘ C) and using very weak etchants including deionized water or seawater (Figure 3(d)) [137,138].…”

“…Glasses. As with fission tracks, the areal density of alpharecoil tracks in geological samples can be exploited as a geochronometer, when the tracks are revealed by chemical etching in the laboratory and then counted-although this geochronological technique has so far only been applied to very young volcanic micas (i.e., <1 Ma phlogopites) due to the relatively rapid accumulation of alpha-recoil tracks and the simplicity of etching those which intersect the exposed cleavage surfaces of micas (Figure 4(b)) [129][130][131][132][133][134]. Therefore, the discovery of naturally etched alpha-recoil tracks in ∼120.60 Ma basaltic glass in this study opens up for the first time, the possibility of carrying out geochronological studies of volcanic/impact glasses and obsidian archaeological artefacts using alpha-recoil tracks-originally suggested as being worthy of pursuit if alpha-recoil tracks were ever found in volcanic glass [130].…”

Alpha-recoil track densities in mica and radiometric age determination

“…Because the directions in which the alpha particles are emitted and the daughter nuclides recoil are random, tracks resulting from a number of successive disintegrations will be more or less equidimensional in all directions. The size distribution of recoil tracks depends on the time of track accumulation and is in general bimodal with maxima at ∼ 30 and ∼ 125 nm (Jonckheere and Gögen, 2001;Stübner and Jonckheere, 2005).…”