Articles | Volume 2, issue 1
https://doi.org/10.5194/gchron-2-119-2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/gchron-2-119-2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
11 May 2020
Research article |
| 11 May 2020
| 11 May 2020
Unifying the U–Pb and Th–Pb methods: joint isochron regression and common Pb correction
London Geochronology Centre, Department of Earth Sciences, University College London, London, UK
Related authors
Pieter Vermeesch
Geochronology Discuss., https://doi.org/10.5194/gchron-2024-5, https://doi.org/10.5194/gchron-2024-5, 2024
Preprint under review for GChron
Short summary
Short summary
The age of some geological materials can be estimated from the ratio of certain radiogenic 'daughter' isotopes to their radioactive 'parent'. However, in many cases, the age estimation process is complicated by the presence of an inherited component of nonradiogenic daughter isotopes. This paper presents an improved algorithm to estimate the radiogenic and non-radiogenic components, either separately or jointly.
Pieter Vermeesch, Yuntao Tian, Jae Schwanethal, and Yannick Buret
Geochronology, 5, 323–332, https://doi.org/10.5194/gchron-5-323-2023, https://doi.org/10.5194/gchron-5-323-2023, 2023
Short summary
Short summary
The U–Th–He method is a technique to determine the cooling history of minerals. Traditional approaches to U–Th–He dating are time-consuming and require handling strong acids and radioactive solutions. This paper presents an alternative approach in which samples are irradiated with protons and subsequently analysed by laser ablation mass spectrometry. Unlike previous in situ U–Th–He dating attempts, the new method does not require any absolute concentration measurements of U, Th, or He.
Alex Lipp and Pieter Vermeesch
Geochronology, 5, 263–270, https://doi.org/10.5194/gchron-5-263-2023, https://doi.org/10.5194/gchron-5-263-2023, 2023
Short summary
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We propose using the Wasserstein-2 distance (W2) as an alternative to the widely used Kolmogorov–Smirnov (KS) statistic for analysing distributional data in geochronology. W2 measures the horizontal distance between observations, while KS measures vertical differences in cumulative distributions. Using case studies, we find that W2 is preferable in scenarios where the absolute age differences in observations provide important geological information. W2 has been added to the R package IsoplotR.
Matthew Fox, Adam G. G. Smith, Pieter Vermeesch, Kerry Gallagher, and Andrew Carter
Geochronology Discuss., https://doi.org/10.5194/gchron-2022-23, https://doi.org/10.5194/gchron-2022-23, 2022
Publication in GChron not foreseen
Short summary
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The Great Unconformity represents an enormous amount of time lost from the sedimentary record. Its origin is debated, in part, due to different approaches used to interpret zircon (U–Th)/He ages. This thermochronometric system is ideal for this problem because the temperature sensitivity varies according to radiation damage. Here we explore the uncertainty associated with the radiation damage model and show how this limits our ability to resolve the origin of the Great Unconformity.
Pieter Vermeesch
Geochronology, 4, 561–576, https://doi.org/10.5194/gchron-4-561-2022, https://doi.org/10.5194/gchron-4-561-2022, 2022
Short summary
Short summary
Secondary ion mass spectrometry (SIMS) is the oldest and most sensitive analytical technique for in situ U–Pb geochronology. This paper introduces a new algorithm for SIMS data reduction that treats data as
compositional data, which means that the relative abundances of 204Pb, 206Pb, 207Pb, and 238Pb are processed within a tetrahedral data space or
simplex. The new method is implemented in an eponymous computer programme that is compatible with the two dominant types of SIMS instruments.
Yang Li and Pieter Vermeesch
Geochronology, 3, 415–420, https://doi.org/10.5194/gchron-3-415-2021, https://doi.org/10.5194/gchron-3-415-2021, 2021
Short summary
Short summary
A conventional isochron is a straight-line fit to two sets of isotopic ratios, D/d and P/d, where P is the radioactive parent, D is the radiogenic daughter, and d is a second isotope of the daughter element. The slope of this line is proportional to the age of the system. An inverse isochron is a linear fit through d/D and P/D. The horizontal intercept of this line is inversely proportional to the age. The latter approach is preferred when d<D, which is the case in Re–Os and K–Ca geochronology.
Pieter Vermeesch
Geochronology, 3, 247–257, https://doi.org/10.5194/gchron-3-247-2021, https://doi.org/10.5194/gchron-3-247-2021, 2021
Short summary
Short summary
This paper shows that the current practice of filtering discordant U–Pb data based on the relative difference between the 206Pb/238U and 207Pb/206Pb ages is just one of several possible approaches to the problem and demonstrably not the best one. An alternative approach is to define discordance in terms of isotopic composition, as a log ratio distance between the measurement and the concordia line. Application to real data indicates that this reduces the positive bias of filtered age spectra.
Pieter Vermeesch
Geochronology Discuss., https://doi.org/10.5194/gchron-2024-5, https://doi.org/10.5194/gchron-2024-5, 2024
Preprint under review for GChron
Short summary
Short summary
The age of some geological materials can be estimated from the ratio of certain radiogenic 'daughter' isotopes to their radioactive 'parent'. However, in many cases, the age estimation process is complicated by the presence of an inherited component of nonradiogenic daughter isotopes. This paper presents an improved algorithm to estimate the radiogenic and non-radiogenic components, either separately or jointly.
Pieter Vermeesch, Yuntao Tian, Jae Schwanethal, and Yannick Buret
Geochronology, 5, 323–332, https://doi.org/10.5194/gchron-5-323-2023, https://doi.org/10.5194/gchron-5-323-2023, 2023
Short summary
Short summary
The U–Th–He method is a technique to determine the cooling history of minerals. Traditional approaches to U–Th–He dating are time-consuming and require handling strong acids and radioactive solutions. This paper presents an alternative approach in which samples are irradiated with protons and subsequently analysed by laser ablation mass spectrometry. Unlike previous in situ U–Th–He dating attempts, the new method does not require any absolute concentration measurements of U, Th, or He.
Alex Lipp and Pieter Vermeesch
Geochronology, 5, 263–270, https://doi.org/10.5194/gchron-5-263-2023, https://doi.org/10.5194/gchron-5-263-2023, 2023
Short summary
Short summary
We propose using the Wasserstein-2 distance (W2) as an alternative to the widely used Kolmogorov–Smirnov (KS) statistic for analysing distributional data in geochronology. W2 measures the horizontal distance between observations, while KS measures vertical differences in cumulative distributions. Using case studies, we find that W2 is preferable in scenarios where the absolute age differences in observations provide important geological information. W2 has been added to the R package IsoplotR.
Matthew Fox, Adam G. G. Smith, Pieter Vermeesch, Kerry Gallagher, and Andrew Carter
Geochronology Discuss., https://doi.org/10.5194/gchron-2022-23, https://doi.org/10.5194/gchron-2022-23, 2022
Publication in GChron not foreseen
Short summary
Short summary
The Great Unconformity represents an enormous amount of time lost from the sedimentary record. Its origin is debated, in part, due to different approaches used to interpret zircon (U–Th)/He ages. This thermochronometric system is ideal for this problem because the temperature sensitivity varies according to radiation damage. Here we explore the uncertainty associated with the radiation damage model and show how this limits our ability to resolve the origin of the Great Unconformity.
Pieter Vermeesch
Geochronology, 4, 561–576, https://doi.org/10.5194/gchron-4-561-2022, https://doi.org/10.5194/gchron-4-561-2022, 2022
Short summary
Short summary
Secondary ion mass spectrometry (SIMS) is the oldest and most sensitive analytical technique for in situ U–Pb geochronology. This paper introduces a new algorithm for SIMS data reduction that treats data as
compositional data, which means that the relative abundances of 204Pb, 206Pb, 207Pb, and 238Pb are processed within a tetrahedral data space or
simplex. The new method is implemented in an eponymous computer programme that is compatible with the two dominant types of SIMS instruments.
Yang Li and Pieter Vermeesch
Geochronology, 3, 415–420, https://doi.org/10.5194/gchron-3-415-2021, https://doi.org/10.5194/gchron-3-415-2021, 2021
Short summary
Short summary
A conventional isochron is a straight-line fit to two sets of isotopic ratios, D/d and P/d, where P is the radioactive parent, D is the radiogenic daughter, and d is a second isotope of the daughter element. The slope of this line is proportional to the age of the system. An inverse isochron is a linear fit through d/D and P/D. The horizontal intercept of this line is inversely proportional to the age. The latter approach is preferred when d<D, which is the case in Re–Os and K–Ca geochronology.
Pieter Vermeesch
Geochronology, 3, 247–257, https://doi.org/10.5194/gchron-3-247-2021, https://doi.org/10.5194/gchron-3-247-2021, 2021
Short summary
Short summary
This paper shows that the current practice of filtering discordant U–Pb data based on the relative difference between the 206Pb/238U and 207Pb/206Pb ages is just one of several possible approaches to the problem and demonstrably not the best one. An alternative approach is to define discordance in terms of isotopic composition, as a log ratio distance between the measurement and the concordia line. Application to real data indicates that this reduces the positive bias of filtered age spectra.
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This study is focused on the accurate measurement of U and Th by wet chemistry and laser ablation methods to improve (U–Th)/He dating of magnetite and spinel. The low U–Th content and the lack of specific U–Th standards significantly limit the accuracy of (U–Th)/He dating. Obtained U–Th results on natural and synthetic magnetite and aluminous spinel samples analyzed by wet chemistry methods and LA-ICP-MS sampling have important implications for the (U–Th)/He method and dates interpretation.
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U–Pb dating by the in situ laser ablation mass spectrometry (LA-ICPMS) technique requires reference materials of the same nature as the samples to be analysed. Here, we have explored the suitability of using carbonate materials as a reference for sulfates, since there is no sulfate reference material. The results we obtained are satisfactory, and thus, from now on, the sulfates can also be analysed.
Pieter Vermeesch
Geochronology, 4, 561–576, https://doi.org/10.5194/gchron-4-561-2022, https://doi.org/10.5194/gchron-4-561-2022, 2022
Short summary
Short summary
Secondary ion mass spectrometry (SIMS) is the oldest and most sensitive analytical technique for in situ U–Pb geochronology. This paper introduces a new algorithm for SIMS data reduction that treats data as
compositional data, which means that the relative abundances of 204Pb, 206Pb, 207Pb, and 238Pb are processed within a tetrahedral data space or
simplex. The new method is implemented in an eponymous computer programme that is compatible with the two dominant types of SIMS instruments.
Emily H. G. Cooperdock, Florian Hofmann, Ryley M. C. Tibbetts, Anahi Carrera, Aya Takase, and Aaron J. Celestian
Geochronology, 4, 501–515, https://doi.org/10.5194/gchron-4-501-2022, https://doi.org/10.5194/gchron-4-501-2022, 2022
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Apatite and zircon are the most widely used minerals for dating rocks, but they can be difficult to identify in some crushed rock samples. Incorrect mineral identification results in wasted analytical resources and inaccurate data. We show how X-ray computed tomography can be used to efficiently and accurately distinguish apatite from zircon based on density variations, and provide non-destructive 3D grain-specific size, shape, and inclusion information for improved data quality.
Dale R. Issler, Kalin T. McDannell, Paul B. O'Sullivan, and Larry S. Lane
Geochronology, 4, 373–397, https://doi.org/10.5194/gchron-4-373-2022, https://doi.org/10.5194/gchron-4-373-2022, 2022
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Phanerozoic sedimentary rocks of northern Canada have compositionally heterogeneous detrital apatite with high age dispersion caused by differential thermal annealing. Discrete apatite fission track kinetic populations with variable annealing temperatures are defined using elemental data but are poorly resolved using conventional parameters. Inverse thermal modelling of samples from northern Yukon reveals a record of multiple heating–cooling cycles consistent with geological constraints.
Michael Dietze, Sebastian Kreutzer, Margret C. Fuchs, and Sascha Meszner
Geochronology, 4, 323–338, https://doi.org/10.5194/gchron-4-323-2022, https://doi.org/10.5194/gchron-4-323-2022, 2022
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The R package sandbox is a collection of functions that allow the creation, sampling and analysis of fully virtual sediment sections, like having a virtual twin of real-world deposits. This article introduces the concept, features, and workflows required to use sandbox. It shows how a real-world sediment section can be mapped into the model and subsequently addresses a series of theoretical and practical questions, exploiting the flexibility of the model framework.
Gregor Pfalz, Bernhard Diekmann, Johann-Christoph Freytag, Liudmila Syrykh, Dmitry A. Subetto, and Boris K. Biskaborn
Geochronology, 4, 269–295, https://doi.org/10.5194/gchron-4-269-2022, https://doi.org/10.5194/gchron-4-269-2022, 2022
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We use age–depth modeling systems to understand the relationship between age and depth in lake sediment cores. However, depending on which modeling system we use, the model results may vary. We provide a tool to link different modeling systems in an interactive computational environment and make their results comparable. We demonstrate the power of our tool by highlighting three case studies in which we test our application for single-sediment cores and a collection of multiple sediment cores.
Andrea Madella, Christoph Glotzbach, and Todd A. Ehlers
Geochronology, 4, 177–190, https://doi.org/10.5194/gchron-4-177-2022, https://doi.org/10.5194/gchron-4-177-2022, 2022
Short summary
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Cooling ages date the time at which minerals cross a certain isotherm on the way up to Earth's surface. Such ages can be measured from bedrock material and river sand. If spatial variations in bedrock ages are known in a river catchment, the spatial distribution of erosion can be inferred from the distribution of the ages measured from the river sand grains. Here we develop a new tool to help such analyses, with particular emphasis on quantifying uncertainties due to sample size.
Yang Li and Pieter Vermeesch
Geochronology, 3, 415–420, https://doi.org/10.5194/gchron-3-415-2021, https://doi.org/10.5194/gchron-3-415-2021, 2021
Short summary
Short summary
A conventional isochron is a straight-line fit to two sets of isotopic ratios, D/d and P/d, where P is the radioactive parent, D is the radiogenic daughter, and d is a second isotope of the daughter element. The slope of this line is proportional to the age of the system. An inverse isochron is a linear fit through d/D and P/D. The horizontal intercept of this line is inversely proportional to the age. The latter approach is preferred when d<D, which is the case in Re–Os and K–Ca geochronology.
Cécile Gautheron, Rosella Pinna-Jamme, Alexis Derycke, Floriane Ahadi, Caroline Sanchez, Frédéric Haurine, Gael Monvoisin, Damien Barbosa, Guillaume Delpech, Joseph Maltese, Philippe Sarda, and Laurent Tassan-Got
Geochronology, 3, 351–370, https://doi.org/10.5194/gchron-3-351-2021, https://doi.org/10.5194/gchron-3-351-2021, 2021
Short summary
Short summary
Apatite and zircon (U–Th) / He thermochronology is now a mainstream tool to reconstruct Earth's evolution through the history of cooling and exhumation over the first dozen kilometers. The geological implications of these data rely on the precision of measurements of He, U, Th, and Sm contents in crystals. This technical note documents the methods for He thermochronology developed at the GEOPS laboratory, Paris-Saclay University, that allow (U–Th) / He data to be obtained with precision.
Kalin T. McDannell and Dale R. Issler
Geochronology, 3, 321–335, https://doi.org/10.5194/gchron-3-321-2021, https://doi.org/10.5194/gchron-3-321-2021, 2021
Short summary
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We generated a synthetic dataset applying published kinetic models and distinct annealing kinetics for the apatite fission track and (U–Th)/He methods using a predetermined thermal history. We then tested how well the true thermal history could be recovered under different data interpretation schemes and geologic constraint assumptions using the Bayesian QTQt software. Our results demonstrate that multikinetic data increase time–temperature resolution and can constrain complex thermal histories.
Birk Härtel, Raymond Jonckheere, Bastian Wauschkuhn, and Lothar Ratschbacher
Geochronology, 3, 259–272, https://doi.org/10.5194/gchron-3-259-2021, https://doi.org/10.5194/gchron-3-259-2021, 2021
Short summary
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We carried out thermal annealing experiments between 500 and 1000 °C to determine the closure temperature of radiation-damage annealing in zircon (ZrSiO4). Our results show that the different Raman bands of zircon respond differently to annealing. The repair is highest for the external rotation Raman band near 356.6 cm−1. The closure temperature estimates range from 250 to 370 °C for different bands. The differences in closure temperatures offer the prospect of multi-T zircon Raman dating.
Pieter Vermeesch
Geochronology, 3, 247–257, https://doi.org/10.5194/gchron-3-247-2021, https://doi.org/10.5194/gchron-3-247-2021, 2021
Short summary
Short summary
This paper shows that the current practice of filtering discordant U–Pb data based on the relative difference between the 206Pb/238U and 207Pb/206Pb ages is just one of several possible approaches to the problem and demonstrably not the best one. An alternative approach is to define discordance in terms of isotopic composition, as a log ratio distance between the measurement and the concordia line. Application to real data indicates that this reduces the positive bias of filtered age spectra.
Blair Schoene, Michael P. Eddy, C. Brenhin Keller, and Kyle M. Samperton
Geochronology, 3, 181–198, https://doi.org/10.5194/gchron-3-181-2021, https://doi.org/10.5194/gchron-3-181-2021, 2021
Short summary
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We compare two published U–Pb and 40Ar / 39Ar geochronologic datasets to produce eruption rate models for the Deccan Traps large igneous province. Applying the same approach to each dataset, the resulting models agree well, but the higher-precision U–Pb dataset results in a more detailed eruption model than the lower-precision 40Ar / 39Ar data. We explore sources of geologic uncertainty and reiterate the importance of systematic uncertainties in comparing U–Pb and 40Ar / 39Ar datasets.
Nicholas P. McKay, Julien Emile-Geay, and Deborah Khider
Geochronology, 3, 149–169, https://doi.org/10.5194/gchron-3-149-2021, https://doi.org/10.5194/gchron-3-149-2021, 2021
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This paper describes geoChronR, an R package that streamlines the process of quantifying age uncertainties, propagating uncertainties through several common analyses, and visualizing the results. In addition to describing the structure and underlying theory of the package, we present five real-world use cases that illustrate common workflows in geoChronR. geoChronR is built on the Linked PaleoData framework, is open and extensible, and we welcome feedback and contributions from the community.
Leonie Peti, Kathryn E. Fitzsimmons, Jenni L. Hopkins, Andreas Nilsson, Toshiyuki Fujioka, David Fink, Charles Mifsud, Marcus Christl, Raimund Muscheler, and Paul C. Augustinus
Geochronology, 2, 367–410, https://doi.org/10.5194/gchron-2-367-2020, https://doi.org/10.5194/gchron-2-367-2020, 2020
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Orakei Basin – a former maar lake in Auckland, New Zealand – provides an outstanding sediment record over the last ca. 130 000 years, but an age model is required to allow the reconstruction of climate change and volcanic eruptions contained in the sequence. To construct a relationship between depth in the sediment core and age of deposition, we combined tephrochronology, radiocarbon dating, luminescence dating, and the relative intensity of the paleomagnetic field in a Bayesian age–depth model.
Roger Powell, Eleanor C. R. Green, Estephany Marillo Sialer, and Jon Woodhead
Geochronology, 2, 325–342, https://doi.org/10.5194/gchron-2-325-2020, https://doi.org/10.5194/gchron-2-325-2020, 2020
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The standard approach to isochron calculation assumes that the distribution of uncertainties on the data arising from isotopic analysis is strictly Gaussian. This excludes datasets that have more scatter, even though many appear to have age significance. Our new approach requires only that the central part of the uncertainty distribution of the data defines a "spine" in the trend of the data. A robust statistics approach is used to locate the spine, and an implementation in Python is given.
Simon J. E. Large, Jörn-Frederik Wotzlaw, Marcel Guillong, Albrecht von Quadt, and Christoph A. Heinrich
Geochronology, 2, 209–230, https://doi.org/10.5194/gchron-2-209-2020, https://doi.org/10.5194/gchron-2-209-2020, 2020
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The integration of zircon geochemistry and U–Pb geochronology (petrochronology) allows us to improve our understanding of magmatic processes. Here we could reconstruct the ~300 kyr evolution of the magma reservoir that sourced the magmas, fluids and metals to form the Batu Hijau porphyry Cu–Au deposit. The application of in situ LA-ICP-MS and high-precision CA–ID–TIMS geochronology to the same zircons further allowed an assessment of the strengths and limitations of the different techniques.
Julia Kalanke, Jens Mingram, Stefan Lauterbach, Ryskul Usubaliev, Rik Tjallingii, and Achim Brauer
Geochronology, 2, 133–154, https://doi.org/10.5194/gchron-2-133-2020, https://doi.org/10.5194/gchron-2-133-2020, 2020
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Our study presents the first seasonally laminated (varved) sediment record covering almost the entire Holocene in high mountainous arid Central Asia. The established floating varve chronology is confirmed by two terrestrial radiocarbon dates, whereby aquatic radiocarbon dates reveal decreasing reservoir ages up core. Changes in seasonal deposition characteristics are attributed to changes in runoff and precipitation and/or to evaporative summer conditions.
Jon Woodhead and Joseph Petrus
Geochronology, 1, 69–84, https://doi.org/10.5194/gchron-1-69-2019, https://doi.org/10.5194/gchron-1-69-2019, 2019
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Recently developed methods for in situ U–Pb age determination in carbonates have found widespread application, but the benefits and limitations of the method over bulk analysis approaches have yet to be fully explored. Here we use speleothems – cave carbonates such as stalagmites and flowstones – to investigate the utility of these in situ dating methodologies for challenging matrices with low U and Pb contents and predominantly late Cenozoic ages.
Cited articles
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Short summary
The U–Pb method is one of the most powerful and versatile methods in the geochronological toolbox. With two isotopes of uranium decaying to two different isotopes of lead, the U–Pb method offers an internal quality control that is absent from most other geochronological techniques. U-bearing minerals often contain significant amounts of Th, which decays to a third Pb isotope. This paper presents an algorithm to jointly process all three chronometers at once.
The U–Pb method is one of the most powerful and versatile methods in the geochronological...
