Bias in measurement of fission-track length distributions

doi:10.1016/0735-245X(82)90031-X

Nuclear Tracks and Radiation Measurements (1982)

Volume 6, Issues 2–3, June–September 1982, Pages 79-85

https://doi.org/10.1016/0735-245X(82)90031-X Get rights and content

Abstract

Problems in the measurement of fission-track length distributions include biases in various methods of sampling and the amount of information about the true lenght distribution that can be recovered. It is concluded that all length measurements are biased and that this bias must be corrected before meaningful geological interpretations can be made. It is recommended that track-length measurements in minerals be restricted to horizontal confined fission tracks, because the length bias is then simple and easy to correct. Projected track-length measurements are not recommended because of complicated bias and insensitivity to important features of the true length distribution. These points are illustrated by length measurements on two Australian apatite samples.

References (17)

G. Bigazzi
Length of fission tracks and age of muscovite samples
Earth Planet. Sci. Lett.
(1967)
N. Bhandari et al.
Fission fragment lengths in apatite: recordable track length
Earth Planet. Sci. Lett.
(1971)
P.F. Green
On the cause of the shortening of spontaneous fission tracks in certain minerals
Nucl. Tracks
(1980)
P.F. Green
“Track-in-track” length measurements in annealed apatites
Nucl. Tracks
(1981)
D. Storzer
Fission track dating of volcanic glasses and the thermal history of rocks
Earth Planet. Sci. Lett.
(1970)
R.J. Cowan
Homogeneous line segment processes
Math. Proc. Camb. Phil. Soc.
(1980)
D.R. Cox
Some sampling problems in technology
M. Dakowski
Length distributions of fission tracks in thick crystals
Nucl. Track Detection
(1978)

There are more references available in the full text version of this article.

Cited by (231)

How many vs which: On confined track selection criteria for apatite fission track analysis
2023, Chemical Geology
Inter-laboratory and inter-analyst experiments on confined fission-track length measurements in apatite have reported considerable variation, which can be attributed primarily to differences in analyst decision-making. Here we explore how different etching sequences, track selection approaches, and analytical methods influence track length and density measurements. The first experiment focuses on analyst judgement across different track selection criteria and light sources, and variation in effective etching time, using moderately annealed induced tracks in Durango apatite. Tracks are selected either with the usual approach of only choosing well-etched tracks, which we term the sufficiently-etched criterion, or a more relaxed criterion of simply being measurable without judging how etched they are. For the sufficiently-etched criterion, we separately analyze tracks found using exclusively reflected or transmitted light. We then follow the evolution of all selected tracks through further etching steps, and compare results based on length, angle, and dip, and placed in the context of a variable along-track etching rate model. All step etches show evidence of along-track etching rate falling from core to tip, and tracks measured using the sufficiently-etched criterion are slightly under-etched compared to the full latent track zone with enhanced etching rate. Minimizing effective etch time variation, by only using tracks selected after 10 s of etching, produced tracks averaging ~0.3 μm longer after 20 s than tracks selected using the sufficiently-etched criterion. Ensuring a minimum track etching time by first selecting measurable tracks after 20 s and etching for 10 s more produced tracks ~0.4 μm longer, but correctable to the latent length. Utilizing exclusively transmitted light diminishes mean track dip, and likely reflects lower efficiency in finding dipping tracks. In the second experiment, we repeatedly measure dipping confined tracks at various stages of annealing with and without using a cross-sectional view of the track, finding that the latter avoids an increase in scatter with increasing dip. We propose a two-step etching procedure that may provide more plentiful and reproducible data by reducing the impact of human decision-making, while still being relatable to published annealing data sets.
Contrasting thermal histories in the Dom Feliciano Belt triggered by magmatism related to the Paraná-Etendeka LIP and fracture zone proximity
2023, Tectonophysics
The present-day southern Brazilian continental margin rests on top of the Dom Feliciano Belt (DFB) and adjacent cratons. This belt formed through the collision of the Rio de La Plata, Kalahari, Paranapanema, Congo and Luis Alves paleoplates in the Neoproterozoic. Several low-temperature thermochronology works were executed in the area, although none of them demonstrated how the basement temperature of the entire DFB evolved through time. To this end, this work aims to provide new Apatite Fission Track (AFT) and Apatite (UTh)/He (AHe) ages for samples collected in the Catarinense Shield, in the northern DFB, and to perform inverse modeling in those samples. Besides, the collection of the basement temperature of 128 locations across the entire belt and adjacent cratons provided thermal information to create inverse-distance weighted interpolation maps documenting the progression of the temperature from 360 to 30 Ma. New AFT ages range from 126.6 ± 24.1 to 60.3 ± 6.03 Ma, whereas AHe ages span from 153.0 ± 9.2 to 62.5 ± 3.7 Ma. Mean track lengths are short to medium, suggesting complete thermal annealing of apatite crystals. Apatite single-grain eU concentration range from 4.5 to 96 μg/g and display a sparse correlation with AHe ages. Interpolation maps evidence a contrasting temperature evolution of the northern DFB and bordering cratons relative to the southern segment and surrounding cratons. Near-surface exposure of the basement in the northern segment was possibly much earlier than in the south, followed by partial burial by the sedimentary successions of the Paraná Basin. The emplacement of volcanic rocks of the Paraná-Etendeka Large Igneous Province and associated dyke swarms and alkaline volcanic plugs related to the Florianópolis Fracture Zone raised and sustained higher basement temperatures until 30 Ma, resetting low-temperature thermochronometers in the northern DFB, which was minor to absent in the southern DFB.
Uplift-exhumation and preservation of the Yumugou Mo-W deposit, East Qinling, China: Insights from multiple apatite low-temperature thermochronology
2022, Ore Geology Reviews
As a result of the continued depletion of shallow ore resources, there has been renewed focus on the tectonic preservation of mineralized systems. Specifically, it is vital to constrain the post-mineralization exhumation and preservation history of existing economic deposits, in order to identify new regions suitable for mineral exploration. In this study, we present results from apatite U-Pb, fission-track and (U-Th-Sm)/He thermochronological and associated thermal history modeling studies on the Yumugou Mo-W deposit within the world-class East Qinling Mo polymetallic metallogenic belt, central China. Our major aim is to constrain the exhumation history and to evaluate preservation potential of the Yumugou Mo-W deposit, and provide related guidance for mineral exploration in the East Qinling Orogen. Apatite U-Pb dating yield Early Cretaceous lower intercept Terra-Wasserburg ages in the range of 153–141 Ma, interpreted as crystallization age of apatite, coeval with the formation of Yumugou deposit (ca. 145 Ma). Integrated apatite fission-track and apatite (U-Th-Sm)/He dating give ages varying from Late Cretaceous to Early Paleogene, representing the post-mineralization cooling ages. We also integrate these age data with confined fission-track length measurements and geological constraints from previous studies into the thermal history models, the resulting models suggest three cooling pulses: 1) a phase of Early Cretaceous (125–100 Ma) rapid cooling, followed by 2) a phase of Late Cretaceous (100–73 Ma) slow cooling, before finally, 3) a phase of Late Cretaceous to Paleogene (73–50 Ma) rapid cooling. The Early Cretaceous rapid cooling pulse correlates temporally with extension tectonic setting in the East Qinling Orogen, the magma emplacement and post-magmatic rapid cooling at ca. 160–130 Ma in the Luanchuan region might cause related exhumation at ca. 125–100 Ma to upper crustal temperatures. The Late Cretaceous slow cooling possibly corresponds to regionally slow extensive erosion in response to crustal shortening triggered by the westward subduction of the Paleo-Pacific Plate at this time. The Late Cretaceous-Paleogene rapid cooling likely result from the major far-field effects of the Pacific Plate subduction and the sinistral strike-slip motion of the Tan-Lu Fault Zone, as well as possible minor expansion effects derived by the Paleogene India-Eurasia collision. Moreover, we adopt thermal history modeling method to determine cooling rate, exhumation rate and depth of different cooling stages. In comparison with the calculated exhumation depth (∼5.6 km) and previously reported metallogenic depth (3–7 km) in the Luanchuan ore cluster, we infer that more than one kilometer metallogenic depth is theoretically preserved in the Yumugou Mo-W deposit. Combined the similar metallogenic setting and features with other giant Mo deposits in the East Qinling Orogen, we further suggest that the Mo deposits in this orogen possibly have underwent a similar degree of exhumation and show good prospecting potential.
The Mesozoic exhumation history of the Karatau-Talas range, western Tian Shan, Kazakhstan-Kyrgyzstan
2021, Tectonophysics
The Tian Shan mountain range maintains high topography across the Eurasian continent despite being distal to any modern plate boundary. Previous studies of the Tian Shan have revealed a history of mountain building in response to India-Asia collision which has overprinted much of its Mesozoic history. The Karatau and Talas ranges in the north-western Tian Shan represent a unique opportunity to investigate the erosional response to the Mesozoic tectonics of Central Asia. In this study, we present medium-to-low temperature thermochronology and thermal history modelling from a series of Neoproterozoic to Permian sedimentary and granitoid samples taken from the Karatau and Talas ranges. Our results identify three phases of late Paleozoic-Mesozoic deformation and exhumation: (1) a regional orogenic event in the Permian–Early Triassic (ca. 280–240 Ma) related to the final amalgamation of the Central Asian Orogenic Belt, (2) Late Triassic–Early Jurassic (ca. 230–190 Ma) reactivation in response to the collision of the Qiangtang block with the Eurasian margin, and a (3) phase of rapid basement cooling during the Late Jurassic–Early Cretaceous (ca. 160–140 Ma), associated with the closure of the Meso-Tethys Ocean. These results suggest that the Karatau and Talas ranges preserves extensive Mesozoic erosional signatures, which developed in response to Eurasian amalgamation of Central Asia and progressive closure of the Tethys Ocean.
Resolving mid- to upper-crustal exhumation through apatite petrochronology and thermochronology
2021, Chemical Geology
Double-dating using the apatite U-Pb and fission-track systems is becoming an increasingly popular method for resolving mid- to upper- crustal cooling. However, these thermochronometers constrain dates that are often difficult to link through geological time due to the large difference in temperature window between the two systems (typically >250 °C). In this study, we apply apatite U-Pb, fission-track, and apatite and whole rock geochemistry to fourteen samples from four tectonic domains common in Cordilleran orogenic systems: (1) basement-cored uplifts, (2) plutons intruded through a thick crustal column, (3) metamorphic core complexes and associated detachment faults, and (4) rapid, extrusive volcanic cooling, in order to provide a link between in situ geochemical signatures and cooling mechanisms. Comparisons of trace element partitioning between apatite and whole rock provide insights into initial apatite-forming processes and/or subsequent modification. Apatite trace element geochemistry and the Th/U and La/Lu_N ratios provide tools to determine if an apatite is primary and representative of its parent melt or if it has undergone geochemical perturbation(s) after crystallization. Further, we demonstrate that by using a combined apatite U-Pb, FT, trace element, and whole rock geochemistry approach it is possible to determine if a rock has undergone monotonic cooling since crystallization, protracted residence in the middle crust, and provide unique structural information such as the history of detachment faulting. Insights provided herein offer new applications for apatite thermochronology.
Thermal fluid activities along the Mozumi-Sukenobu fault, central Japan, identified via zircon fission-track thermochronometry
2019, Journal of Asian Earth Sciences: X
Citation Excerpt :
Spontaneous tracks were counted under an optical microscope (Nikon ECLIPSE E600; 100× dry objective lens and 10× ocular lens). Horizontal confined track (HCT; Laslett et al., 1982) lengths were measured using optical microscopy and image processing software (Image-Pro Plus). HCTs were used for length measurements when etched properly having widths of 1.0 ± 0.5 μm (Yamada et al, 1993).
This study uses zircon fission-track (ZFT) thermochronometry to investigate thermal anomalies along the Mozumi-Sukenobu fault, central Japan, and assesses the most plausible mechanisms by which reheating events occurred. In total, 14 samples were collected from Mesozoic sedimentary rocks along a research tunnel excavated across the fault. The mean ZFT ages range from 110.3 to 73.3 Ma, whereas the mean ZFT lengths are 7.1–9.0 μm. Thermal histories estimated by inverse modeling based on the ZFT data indicate two reheating episodes at ∼60 Ma and ∼30–15 Ma. The reheating episode at ∼60 Ma was detected from two samples collected from between the two major fracture zones. This episode can be attributed to thermal fluids sourced from the Kamioka Mine region in the south on the basis of the timing of the event and the presence of minerals produced via hydrothermal alteration. Reheating at ∼30–15 Ma is indicated in majority of the samples. This is thought to be related to magmatism associated with the opening of the Sea of Japan, but the source and mechanism of reheating cannot be clearly determined. Reheating is not attributable to simple thermal diffusion from volcanic products deposited at the surface. The spatial pattern of the thermal anomalies can be explained by the dextral slip along the two major fracture zones since the late Quaternary. Although the identified thermal episodes are background events potentially related to fluid activities, they are important for quantifying thermal history along the fault zone including the frictional heating.

View all citing articles on Scopus

View full text

Bias in measurement of fission-track length distributions

Abstract

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

Nucl. Tracks

Nucl. Tracks

Earth Planet. Sci. Lett.

Homogeneous line segment processes

Math. Proc. Camb. Phil. Soc.

Some sampling problems in technology

Length distributions of fission tracks in thick crystals

Nucl. Track Detection