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Claire Ansberque - One of the best experts on this subject based on the ideXlab platform.
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apatite Fission Track Dating by la q icp ms imaging
Chemical Geology, 2021Co-Authors: Claire Ansberque, David Chew, Kerstin DrostAbstract:Obtaining accurate and precise apatite Fission-Track (AFT) ages is dependent on producing plentiful high-quality apatite grains from a sample, ideally with high spontaneous Fission-Track densities (c. >105 Tracks.cm-2). Many natural samples, such as bedrock samples from young orogenic belts or low-grade metamorphic samples with low U contents yield low spontaneous Fission-Track densities. Such apatites must be counted to avoid biasing the resultant FT age. AFT Dating employing LA-Q-ICP-MS spot ablation works very well for grains with high spontaneous Fission-Track densities which enable potential U-zoning to be detected, while also removing the need for an irradiation step and facilitating simultaneous acquisition of U-Pb and trace element data. The LA-Q-ICP-MS spot ablation thus offers several advantages compared to the External Detector Method (EDM). However, for grains with low spontaneous Fission-Track densities where U zoning cannot be observed, the LA-Q-ICP-MS spot ablation approach requires the counted area to mimic exactly the site of the laser spot, with the downside that this smaller counted area limits the precision of the resultant AFT age. Here we present an alternative approach to LA-Q-ICP-MS analysis of low Fission-Tracks density grains by generating a U distribution (238U/43Ca) map of the entire apatite surface by LA-Q-ICP-MS elemental mapping which enables characterization of U zonation. The Monocle plugin for the Iolite LA-ICP-MS data reduction software package is used to display elemental maps and extract mean 238U/43Ca values of the same area counted for the Fission Tracks. A typical grain-mapping session takes < 5 hours to map 80 grains. The method was employed on the Durango and Fish Canyon Tuff apatite reference materials, and on apatite from six bedrock samples with low Fission-Track densities (≤ 1.105 Track.cm-2). Most apatite samples investigated here were previously dated by the EDM or the LA-Q-ICP-MS ablation spot method. The AFT grain-mapping ages agree with previously published EDM or LA-Q-ICP-MS spot ablation ages at the 2σ level. For each apatite sample, we simultaneously acquired U-Pb age and trace element data (Mn, Sr, La, Ce, Sm, Eu, Gd, Lu); here again the data agree with literature constraints (when available) within uncertainties. The mapping approach is therefore a practical solution to low-temperature thermochronology studies employing apatite grains with low spontaneous Fission-Track densities, while also facilitating investigation of the spatial relationships between thermo- and geochronometric ages and grain chemistry.
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LA-ICP-MS apatite Fission Track Dating: A practical zeta-based approach
Chemical Geology, 2020Co-Authors: Nathan Cogné, David Chew, Raymond Donelick, Claire AnsberqueAbstract:The LA-ICP-MS method is becoming increasingly popular for uranium determinations in Fission Track Dating of apatite, zircon or titanite. This is because the approach has several advantages over the classical external detector method (EDM), including faster sample throughput, simultaneous acquisition of additional data (such as UPb age information and trace element abundances), while removing the need for neutron irradiation. Two different approaches are used to determine U contents in LA-ICP-MS Fission Track Dating: an absolute Dating approach, or a zeta-based determination analogous to the classical EDM. Absolute age Dating by LA-ICP-MS potentially suffers from small but systematic deviations in apatite U contents, which in turn propagate through to minor systematic deviations in the accuracy of absolute Fission Track age determinations. A zeta-based approach typically requires time-consuming counting of large numbers of zeta-standard grains (usually Durango apatite) so as to yield a precise zeta factor for every LA-ICP-MS session containing unknowns. The modification of the zeta-based approach proposed here has two major advantages. Firstly, it employs just one large primary LA-ICP-MS session to determine a precise primary zeta factor on a large number of counted Durango primary zeta grains. During subsequent secondary LA-ICP-MS sessions with unknowns, no further Fission Track counting of the primary zeta standard is required. This is because we reanalyse a subset of the primary zeta grains to calculate a session-specific zeta fractionation factor, which is related to variations in the instrumental operating conditions (primarily plasma tuning) between primary and secondary LA-ICP-MS sessions. This enables us to ‘reuse’ the primary zeta factor, and thus avail of its precision derived from the large spontaneous Track count. The second advantage is that reusing the primary zeta grains by applying a session-specific zeta fractionation factor allows us to verify that background and drift corrections applied during the secondary LA-ICP-MS session were fully appropriate. This method has been successfully tested by Dating samples of known apatite Fission Track age, by comparing EDM and LA-ICP-MS data from the same sample and by participating in a round robin test between international Fission Track laboratories where ‘blind’ Fission Track Dating of two unknown samples was undertaken. Our LA-ICP-MS apatite Fission Track Dating approach is also easily modifiable for Fission Track Dating of zircon or titanite if suitable age standards are employed.
Peter Van Den Haute - One of the best experts on this subject based on the ideXlab platform.
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standardless Fission Track Dating of the durango apatite age standard
Chemical Geology, 2015Co-Authors: Peter Van Den Haute, Raymond Jonckheere, Lothar RatschbacherAbstract:Abstract Five Dating strategies were used for determining the standardless Fission-Track age of the Durango apatite. These use the same fossil-Track densities but differ in the manner in which the induced-Track densities are determined. A conventional age calculation, without correction for experimental factors, gives inconsistent ages with method-related differences > 15%. Correcting for these factors brings the ages in line with each other and with the reference age but leaves no room for a partial-annealing correction based on the confined-Track lengths. Three further reasons suggest that a length correction is not appropriate. (1) The evidence for length-based corrections is inconclusive. (2) The plateau age of the Durango apatite is consistent with its apparent Fission-Track age to within 1%. (3) The calculated effective etchable length of the fossil Tracks agrees within error with that of the induced Tracks; both are further consistent with the measured mean length of confined induced Tracks. The circumstance that the (U,Th)/He ages of the accepted and proposed apatite age standards are consistent with their reference ages leaves no margin for a lowered Fission-Track age resulting from partial annealing, although the case of the Durango apatite itself is inconclusive because of its exceptional crystal size. It is conjectured that the shortening of the fossil tacks in the Durango apatite is due to a lowering of the Track etch rate over time. In this case, annealing equations fitted to induced-Track data underestimate the extent of confined-Track-length reduction in geological samples.
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distant effects of india eurasia convergence and mesozoic intracontinental deformation in central asia constraints from apatite Fission Track thermochronology
Journal of Asian Earth Sciences, 2007Co-Authors: M M Buslov, Johan De Grave, Peter Van Den HauteAbstract:Abstract During the Mesozoic, the active southern margin of Eurasia was the site of several accretion and collision events that fit into a framework of convergence between Eurasia and advancing (peri-) Gondwanan units. Far-field effects of the Mesozoic Mongol–Okhotsk and Cimmerian orogenies have been recorded deep within the interior of Eurasia. Convergence finally culminated in the massive India–Eurasia continent–continent collision in the Early Cenozoic. This collision, continued convergence between both continents, and resulting ongoing indentation of India into Eurasia have dominated the geological, tectonic and geodynamic evolution of Eurasia. Amongst others, distant effects of these events have reactivated an array of mobile belts in Central Asia. Apatite Fission-Track Dating and thermal history modeling performed on samples from the Kyrgyz Tien Shan and Siberian Altai Mountains record both Mesozoic deformation and Cenozoic reactivation of intracontinental Eurasia. The onset of the building and growth of the modern Tien Shan and Altai orogens is constrained to the Late Miocene and Pliocene, with a likely trend of activity younger towards the north. This would underscore the general model that deformation related to India–Eurasia convergence was progressively propagated northwards through Central Asia via the inherited structural fabric of the Eurasian crust.
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a new u doped glass certified by the european commission for the calibration of Fission Track Dating
Advances in Fission-Track Geochronology (1998) 67-78 (Proc.Int.FT-Dating Workshop Gent 1996) Ed. by P.Van den haute F.De Corte; Kluwer Aca' demic Publ, 1998Co-Authors: F De Corte, Peter Van Den Haute, F Bellemans, C Ingelbrecht, C NichollAbstract:In this paper we present a new series of unirradiated and pre-irradiated uranium doped glass discs that were manufactured and characterized for use in Fission-Track analysis. They are issued as Nuclear Reference Material IRMM-540. The certified quantities are the uranium mass fraction [=13.9 mgxkg−1], the n(235U)/n(238U) amount ratio [=0.007277] and the thermal Maxwellian neutron fluence [=1.070x1019 m−2]. Additional information is given related to the nominal composition of the glass and its content of thorium and neutron absorbing elements, the uranium homogeneity between and within discs, the neutron fluence monitors, the parameters of the neutron spectrum in the irradiation facility, the thermal stability of the Fission Tracks in the glass and the properties of the mica that has been used as external detector in contact with the irradiated discs.
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Fission Track Dating of the western border of the bohemian massif thermochronology and tectonic implications
IJEaS, 1997Co-Authors: Ewald Hejl, Peter Van Den Haute, D A Coyle, Nand Lal, G A WagnerAbstract:Since 1985, apatite Fission-Track analysis was applied to more than 70 samples from surface outcrops and shallow boreholes at the western margin of the Bohemian massif. Apatite ages were determined by the grain-population method. Additional information from the frequency distributions of fully confined spontaneous Tracks was used for modelling of t–T paths in the low-temperature range (<120 °C). Seven zircon samples were dated by the external detector method. Zircon ages between 283 and 215 Ma indicate unroofing during the Permian molasse stage and the Triassic. Tectonic quiescence and slow subsidence prevailed from the Jurassic until the middle Cretaceous. In the basement area south of Weiden, a Mesozoic partial annealing zone (for apatite Fission Tracks) is now exposed at the surface. Farther north, the basement was affected by stronger Cretaceous and Palaeogene erosion, which yielded cooling ages between 110 and 49 Ma. This second period of post-Variscan denudation was correlated to reverse faulting along the Franconian Line.
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composition of srm and cn u doped glasses significance for their use as thermal neutron fluence monitors in Fission Track Dating
Radiation Measurements, 1995Co-Authors: F Bellemans, F De Corte, Peter Van Den HauteAbstract:Abstract The I mm thick (NIST) SRM glasses 611, 613, 615 and 617, and the (Corning) CN glasses 1, 2, 5 and 6 have been investigated for their U and Th content and for their concentration of neutron absorbing elements (B, Cd, Sm, Eu, Gd, Dy, It and Hg). The analyses of these elements were performed with reactor neutron activation analysis and, for boron, with charged-particle activation analysis. The significance of the results is discussed in relation to the use of the glasses as thermal neutron fluence monitors in Fission Track Dating.
Thomas Zack - One of the best experts on this subject based on the ideXlab platform.
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characterisation of apatites as potential uranium reference materials for Fission Track Dating by la icp ms
Geostandards and Geoanalytical Research, 2015Co-Authors: S Guedes, C J Soares, Regina Mertzkraus, Daniel F Stockli, Thomas ZackAbstract:We report homogeneity tests on large natural apatite crystals to evaluate their potential as U reference materials for apatite Fission-Track (AFT) thermochronology by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The homogeneity tests include the measurements of major element concentrations by electron probe microanalysis (EPMA), whereas for U concentration, isotope dilution (ID) ICP-MS and laser ablation (LA) ICP-MS were employed. Two apatite crystals are potential reference materials for LA-ICP-MS analysis: a 1 cm3 fraction of a Durango crystal (7.5 μg g−1 U) and a 1 cm3 Mud Tank crystal (6.9 μg g−1 U). The relative standard deviation (1 RSD) of the U concentration determined by ID-ICP-MS of both apatite crystals was ≤ 1.5%, whereas 1 RSD for the LA-ICP-MS results was better than 4%, providing sufficient homogeneity for Fission-Track Dating. The results on the U homogeneity for two different apatite samples are an important step towards establishing in situ Dating routines for AFT analysis by LA-ICP-MS. Nous restituons des tests d'homogeneite sur des grands cristaux d'apatite naturelle afin d’evaluer leur potentiel en tant que materiaux de reference pour l'U en vue d'une application dans le domaine de la thermochronologie par traces de Fission sur apatite (AFT) par spectrometrie de masse a plasma induit couplee a l'ablation laser (LA-ICP-MS). Les tests d'homogeneite incluent des mesures des concentrations en elements majeurs par microsonde electronique (EPMA), alors que pour la concentration en U, la dilution isotopique (ID) ainsi que l'ablation laser (LA) ICP-MS ont ete employees. Deux cristaux d'apatite sont des materiaux de reference possibles pour les analyses LA-ICP-MS: une fraction d'1 cm3 d'un cristal de Durango (7,5 µg g−1 U) et un cristal d'1 cm3 de Mud Tank (6,9 µg g−1 U). L’ecart type relatif (1 RSD) de la concentration en U determinee par ID-ICP-MS des deux cristaux d'apatite est ≤ 1,5%, tandis que celui pour les resultats LA-ICP-MS est inferieur a 4%, offrant ainsi une homogeneite suffisante pour les datations par la methode des traces de Fission sur apatite. Les resultats concernant l'homogeneite de l'U pour deux echantillons differents d'apatite sont une etape importante vers la possibilite d'envisager des datations AFT in situ en routine par LA-ICP-MS.
Nathan Cogné - One of the best experts on this subject based on the ideXlab platform.
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Some comments on the effect of uranium zonation on Fission Track Dating by LA-ICP-MS
Chemical Geology, 2021Co-Authors: Nathan Cogné, Kerry GallagherAbstract:The use of LA-ICP-MS for uranium determination in the Fission Track Dating technique is becoming increasingly popular because of several advantages over the classical external detector method and a variety of analytical and statistical protocols have been developed. However, two important issues remain unresolved in the context of the LA-ICP-MS approach (i) how to best deal with low Track density (ρs) samples, and (ii) does a correlation between age and uranium content (or eU) reflect an annealing dependence or not? To assess the impact of the analytical methodology on these issues, we compare the multi-spot and more classical single spot methods on samples of known ages, variably zoned and/or with low Track densities. To make the comparison we use an approach, implemented in a Python script, that randomly samples our multi-spot ICP-MS data to choose a single U measurement per grain, simulating the single spot approach. We then calculate the central age, p(χ2) and dispersion of the simulated single spot analysis and repeat this 2000 times. Our results show that the multi-spot approach is robust for low ρs and zoned samples, yielding both accurate and precise results without over-dispersion. Additionally, our random sampling approach shows that a single spot measurement can induce an overdispersion coupled to a relationship between single grain age and U content. This is at least partly attributable to zonation that creates a mismatch between the U in the counted area and the spot-measured U. Therefore, we recommend that if over-dispersion is observed for basement samples, when one typically expects a single age population, then multiple spot analysis should be carried out to assess if the excess dispersion is linked to undetected zoning and/or laser spot misplacement rather than to U dependent annealing behaviour.
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LA-ICP-MS apatite Fission Track Dating: A practical zeta-based approach
Chemical Geology, 2020Co-Authors: Nathan Cogné, David Chew, Raymond Donelick, Claire AnsberqueAbstract:The LA-ICP-MS method is becoming increasingly popular for uranium determinations in Fission Track Dating of apatite, zircon or titanite. This is because the approach has several advantages over the classical external detector method (EDM), including faster sample throughput, simultaneous acquisition of additional data (such as UPb age information and trace element abundances), while removing the need for neutron irradiation. Two different approaches are used to determine U contents in LA-ICP-MS Fission Track Dating: an absolute Dating approach, or a zeta-based determination analogous to the classical EDM. Absolute age Dating by LA-ICP-MS potentially suffers from small but systematic deviations in apatite U contents, which in turn propagate through to minor systematic deviations in the accuracy of absolute Fission Track age determinations. A zeta-based approach typically requires time-consuming counting of large numbers of zeta-standard grains (usually Durango apatite) so as to yield a precise zeta factor for every LA-ICP-MS session containing unknowns. The modification of the zeta-based approach proposed here has two major advantages. Firstly, it employs just one large primary LA-ICP-MS session to determine a precise primary zeta factor on a large number of counted Durango primary zeta grains. During subsequent secondary LA-ICP-MS sessions with unknowns, no further Fission Track counting of the primary zeta standard is required. This is because we reanalyse a subset of the primary zeta grains to calculate a session-specific zeta fractionation factor, which is related to variations in the instrumental operating conditions (primarily plasma tuning) between primary and secondary LA-ICP-MS sessions. This enables us to ‘reuse’ the primary zeta factor, and thus avail of its precision derived from the large spontaneous Track count. The second advantage is that reusing the primary zeta grains by applying a session-specific zeta fractionation factor allows us to verify that background and drift corrections applied during the secondary LA-ICP-MS session were fully appropriate. This method has been successfully tested by Dating samples of known apatite Fission Track age, by comparing EDM and LA-ICP-MS data from the same sample and by participating in a round robin test between international Fission Track laboratories where ‘blind’ Fission Track Dating of two unknown samples was undertaken. Our LA-ICP-MS apatite Fission Track Dating approach is also easily modifiable for Fission Track Dating of zircon or titanite if suitable age standards are employed.
David Chew - One of the best experts on this subject based on the ideXlab platform.
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apatite Fission Track Dating by la q icp ms imaging
Chemical Geology, 2021Co-Authors: Claire Ansberque, David Chew, Kerstin DrostAbstract:Obtaining accurate and precise apatite Fission-Track (AFT) ages is dependent on producing plentiful high-quality apatite grains from a sample, ideally with high spontaneous Fission-Track densities (c. >105 Tracks.cm-2). Many natural samples, such as bedrock samples from young orogenic belts or low-grade metamorphic samples with low U contents yield low spontaneous Fission-Track densities. Such apatites must be counted to avoid biasing the resultant FT age. AFT Dating employing LA-Q-ICP-MS spot ablation works very well for grains with high spontaneous Fission-Track densities which enable potential U-zoning to be detected, while also removing the need for an irradiation step and facilitating simultaneous acquisition of U-Pb and trace element data. The LA-Q-ICP-MS spot ablation thus offers several advantages compared to the External Detector Method (EDM). However, for grains with low spontaneous Fission-Track densities where U zoning cannot be observed, the LA-Q-ICP-MS spot ablation approach requires the counted area to mimic exactly the site of the laser spot, with the downside that this smaller counted area limits the precision of the resultant AFT age. Here we present an alternative approach to LA-Q-ICP-MS analysis of low Fission-Tracks density grains by generating a U distribution (238U/43Ca) map of the entire apatite surface by LA-Q-ICP-MS elemental mapping which enables characterization of U zonation. The Monocle plugin for the Iolite LA-ICP-MS data reduction software package is used to display elemental maps and extract mean 238U/43Ca values of the same area counted for the Fission Tracks. A typical grain-mapping session takes < 5 hours to map 80 grains. The method was employed on the Durango and Fish Canyon Tuff apatite reference materials, and on apatite from six bedrock samples with low Fission-Track densities (≤ 1.105 Track.cm-2). Most apatite samples investigated here were previously dated by the EDM or the LA-Q-ICP-MS ablation spot method. The AFT grain-mapping ages agree with previously published EDM or LA-Q-ICP-MS spot ablation ages at the 2σ level. For each apatite sample, we simultaneously acquired U-Pb age and trace element data (Mn, Sr, La, Ce, Sm, Eu, Gd, Lu); here again the data agree with literature constraints (when available) within uncertainties. The mapping approach is therefore a practical solution to low-temperature thermochronology studies employing apatite grains with low spontaneous Fission-Track densities, while also facilitating investigation of the spatial relationships between thermo- and geochronometric ages and grain chemistry.
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LA-ICP-MS apatite Fission Track Dating: A practical zeta-based approach
Chemical Geology, 2020Co-Authors: Nathan Cogné, David Chew, Raymond Donelick, Claire AnsberqueAbstract:The LA-ICP-MS method is becoming increasingly popular for uranium determinations in Fission Track Dating of apatite, zircon or titanite. This is because the approach has several advantages over the classical external detector method (EDM), including faster sample throughput, simultaneous acquisition of additional data (such as UPb age information and trace element abundances), while removing the need for neutron irradiation. Two different approaches are used to determine U contents in LA-ICP-MS Fission Track Dating: an absolute Dating approach, or a zeta-based determination analogous to the classical EDM. Absolute age Dating by LA-ICP-MS potentially suffers from small but systematic deviations in apatite U contents, which in turn propagate through to minor systematic deviations in the accuracy of absolute Fission Track age determinations. A zeta-based approach typically requires time-consuming counting of large numbers of zeta-standard grains (usually Durango apatite) so as to yield a precise zeta factor for every LA-ICP-MS session containing unknowns. The modification of the zeta-based approach proposed here has two major advantages. Firstly, it employs just one large primary LA-ICP-MS session to determine a precise primary zeta factor on a large number of counted Durango primary zeta grains. During subsequent secondary LA-ICP-MS sessions with unknowns, no further Fission Track counting of the primary zeta standard is required. This is because we reanalyse a subset of the primary zeta grains to calculate a session-specific zeta fractionation factor, which is related to variations in the instrumental operating conditions (primarily plasma tuning) between primary and secondary LA-ICP-MS sessions. This enables us to ‘reuse’ the primary zeta factor, and thus avail of its precision derived from the large spontaneous Track count. The second advantage is that reusing the primary zeta grains by applying a session-specific zeta fractionation factor allows us to verify that background and drift corrections applied during the secondary LA-ICP-MS session were fully appropriate. This method has been successfully tested by Dating samples of known apatite Fission Track age, by comparing EDM and LA-ICP-MS data from the same sample and by participating in a round robin test between international Fission Track laboratories where ‘blind’ Fission Track Dating of two unknown samples was undertaken. Our LA-ICP-MS apatite Fission Track Dating approach is also easily modifiable for Fission Track Dating of zircon or titanite if suitable age standards are employed.