Articles | Volume 1, issue 1
https://doi.org/10.5194/gchron-1-17-2019
© Author(s) 2019. 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-1-17-2019
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
26 Sep 2019
Research article |
| 26 Sep 2019
| 26 Sep 2019
Resolving the effects of 2-D versus 3-D grain measurements on apatite (U–Th) ∕ He age data and reproducibility
Department of Geological Sciences, University of Texas at Austin,
Austin, 78712, USA
Woods Hole Oceanographic Institution, Woods Hole, 02543, USA
now at: Department of Earth Sciences, University of Southern
California, Los Angeles, CA 90089, USA
Richard A. Ketcham
Department of Geological Sciences, University of Texas at Austin,
Austin, 78712, USA
Daniel F. Stockli
Department of Geological Sciences, University of Texas at Austin,
Austin, 78712, USA
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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.
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We use microCT scanning to improve the quality of 3He exposure ages measured in detrital magnetite. We show that the presence of inclusions can significantly increase the measured amount of 3He and thereby the exposure age. By prescreening magnetite with microCT and analyzing only inclusion-free grains, this problem can be avoided. We also calibrate the cosmogenic 3He production rate in magnetite relative to 10Be in quartz, which can be used for similar studies in the future.
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The article describes a course that we have developed at the University Centre in Svalbard that covers many aspects of Arctic Geology. The students experience this from a wide range of lecturers, focussing both on the small and larger scales, and covering many geoscientific disciplines.
Alyssa J. McKanna, Isabel Koran, Blair Schoene, and Richard A. Ketcham
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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.
David M. Whipp, Dawn A. Kellett, Isabelle Coutand, and Richard A. Ketcham
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Multi-thermochronometry, in which methods such as (U-Th)/He dating of zircon and apatite and apatite fission track dating are combined, is used to reconstruct rock thermal histories. Our ability to reconstruct thermal histories and interpret the geological significance of measured ages requires modeling. Here we use forward models to explore effects of grain size and chemistry on cooling ages and closure temperatures for the (U-Th)/He decay systems in apatite and zircon.
Renas I. Koshnaw, Fritz Schlunegger, and Daniel F. Stockli
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As continental plates collide, mountain belts grow. This study investigated the provenance of rocks from the northwestern segment of the Zagros mountain belt to unravel the convergence history of the Arabian and Eurasian plates. Provenance data synthesis and field relationships suggest that the Zagros Mountains developed as a result of the oceanic crust emplacement on the Arabian continental plate, followed by the Arabia–Eurasia collision and later uplift of the broader region.
Richard A. Ketcham and Murat T. Tamer
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We introduce a new model of how etching reveals damage tracks left by fissioning atoms, which accounts for variable along-track etching rates. This complete characterization explains many observations, including community difficulty in obtaining consistent track length measurements. It also provides a quantitative basis for optimizing etching procedures, discerning more about how radiation damage anneals, and ultimately deriving more reproducible fission-track ages and thermal histories.
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We have discovered a new way of measuring the three-dimensional distribution of radioactive elements in individual crystals by shining a very bright light on apatite crystals at the Advanced Photon Source at Argonne National Laboratory. This allows us to learn about the rates and timing of geologic processes and to help resolve problems that previously were unsolvable because we had no way to make this type of measurement.
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Pieter Vermeesch, Yuntao Tian, Jae Schwanethal, and Yannick Buret
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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.
Spencer D. Zeigler, James R. Metcalf, and Rebecca M. Flowers
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(U–Th) / He dating relies on proper characterization of apatite crystal dimensions so that eU concentrations and dates can be calculated accurately and precisely, but there is systematic error and uncertainty in geometric measurements. By comparing 2D microscopy to
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Natacha Gribenski, Marissa M. Tremblay, Pierre G. Valla, Greg Balco, Benny Guralnik, and David L. Shuster
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John J. Y. He and Peter W. Reiners
Geochronology, 4, 629–640, https://doi.org/10.5194/gchron-4-629-2022, https://doi.org/10.5194/gchron-4-629-2022, 2022
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Apatite helium thermochronology is a method that dates the time at which a rock (and the apatite crystals contained within) cooled below a certain temperature by measuring radioactive parent isotopes (uranium and thorium) and daughter isotopes (helium). This paper proposes a revision to a commonly used calculation that corrects raw data to account for instances when the analyzed apatite crystals are fragmented. It demonstrates the improved accuracy and precision of the proposed revision.
Stephen E. Cox, Hayden B. D. Miller, Florian Hofmann, and Kenneth A. Farley
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Noble gases are largely excluded from minerals during rock formation, but they are produced by certain radioactive decay schemes and trapped in mineral lattices. However, they are present in the atmosphere, which means that they can be adsorbed or trapped by physical processes. We present details of a troublesome trapping mechanism for helium during sample crushing and show when it can be ignored and how it can be easily avoided during common laboratory procedures.
David M. Whipp, Dawn A. Kellett, Isabelle Coutand, and Richard A. Ketcham
Geochronology, 4, 143–152, https://doi.org/10.5194/gchron-4-143-2022, https://doi.org/10.5194/gchron-4-143-2022, 2022
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Multi-thermochronometry, in which methods such as (U-Th)/He dating of zircon and apatite and apatite fission track dating are combined, is used to reconstruct rock thermal histories. Our ability to reconstruct thermal histories and interpret the geological significance of measured ages requires modeling. Here we use forward models to explore effects of grain size and chemistry on cooling ages and closure temperatures for the (U-Th)/He decay systems in apatite and zircon.
Cited articles
ASTM: E1441-11: Standard Guide for Computed Tomography (CT) Imaging, ASTM
International, West Conshohocken, PA, available at: https://doi.org/10.1520/E1441-11,
2011.
Bargnesi, E. A., Stockli, D. F., Hourigan, J. K., and Hager, C.: Improved
accuracy of zircon (U – Th)/ He ages by rectifying parent nuclide zonation
with practical methods, Chem. Geol. 426, 158–169,
https://doi.org/10.1016/j.chemgeo.2016.01.017, 2016.
Beucher, R., Brown, R. W., Roper, S. Stuart, F., and Persano, C.: Natural
age dispersion arising from the analysis of broken cystals: Part II.
Practical application to apatite (U-Th) ∕ He thermochronometry, Geochim.
Cosmochim. Ac., 120, 395–416,
https://doi.org/10.1016/j.gca.2013.05.042, 2013.
Blott, S. J. and Pye, K.: Particle shape: a review and new methods of
characterization and classification, Sedimentology, 55, 31–63,
https://doi.org/10.1111/j.1365-3091.2007.00892.x, 2008.
Brown, R. W., Beucher, R., Roper, S. Persano, C., Stuart, F., and
Fitzgerald, P.: Natural age dispersion arising from the analysis of broken
crystals. Part I: Theoretical basis and implications for the apatite
(U-Th) ∕ He thermochronometer, Geochim. Cosmochim. Ac., 122, 478–497,
https://doi.org/10.1016/j.gca.2013.05.041, 2013.
Browne, E.: Nuclear Data Sheets for A = 232, Nucl. Data Sheets, 107,
2579–2648, https://doi.org/10.1016/j.nds.2006.09.001, 2006.
Danisik, M., McInnes, B. I. A., Kirkland, C. L., McDonald, B. J., Evans, N.
J., and Becker, T.: Seeing is believing: Visualization of He distribution in
zircon and implications for thermal history reconstruction on single
crystals, Sci. Adv., 3, e1601121, https://doi.org/10.1126/sciadv.1601121, 2017.
Ehlers, T. A. and Farley, K. A.: Apatite (U-Th) ∕ He Thermochronometry:
Methods and Applications to Problems in Tectonic and Surface Processes,
Earth Planet. Sc. Lett., 206, 1–14, https://doi.org/10.1016/S0012-821X(02)01069-5, 2003.
Evans, N. J., McInnes, B. I. A., Squelch, A. P., Austin, P. J., McDonald, B. J.,
and Wu, Q.: Application of X-ray micro-computed tomography in (U-Th) ∕ He
thermochronology, Chem. Geol., 257, 101–113, https://doi.org/10.1016/j.chemgeo.2008.08.021,
2008.
Farley, K. A.: (U-Th) ∕ He Dating: Techniques, Calibrations, and Applications,
Rev. Mineral. Geochem., 47, 819–844,
https://doi.org/10.2138/rmg.2002.47.18, 2002.
Farley, K. A. and Stockli, D. F.: (U-Th) ∕ He Dating of Phosphates: Apatite,
Monazite, and Xenotime, Rev. Mineral. Geochem., 15, 559–577,
https://doi.org/10.2138/rmg.2002.48.15, 2002.
Farley, K. A., Wolf, R. A., and Silver, L. T.: The effects of long
alpha-stopping distances on (U-Th) ∕ He age, Geochim. Cosmochim. Ac., 60,
4223–4229, https://doi.org/10.1016/S0016-7037(96)00193-7, 1996.
Flowers, R. M.: Exploiting radiation damage control on apatite (U–Th)/He
dates in cratonic regions, Earth Planet. Sc. Lett., 277, 148–155,
https://doi.org/10.1016/j.epsl.2008.10.005, 2009.
Flowers, R. M. and Kelley, S. A.: Interpreting data dispersion and
“inverted” dates in apatite (U–Th)/He and fission-track datasets: An
example from the US midcontinent, Geochim. Cosmochim. Ac., 75,
5169–5186, https://doi.org/10.1016/j.gca.2011.06.016, 2011.
Flowers, R. M., Shuster, D. L., Wernicke, B. P, and Farley, K. A.: Radiation
damage control on apatite (U-Th) ∕ He dates from the Grand Canyon region,
Colorado Plateau, Geology, 35, 447–450,
https://doi.org/10.1130/G23471A.1, 2007.
Flowers, R. M., Ketcham, R. A., Shuster, D. L., and Farley, K. A.: Apatite
(U-Th) ∕ He thermochronometry using a radiation damage accumulation and
annealing model, Geochim. Cosmochim. Ac., 73, 2347–2365,
https://doi.org/10.1016/j.gca.2009.01.015, 2009.
Fox, M., Dai, J.-G., and Carter, A.: Badly behaved detrital (U-Th) ∕ He ages:
Problems with He diffusion models or geological models?, Geochem. Geophy.
Geosy., 20, 2418–2432, https://doi.org/10.1029/2018GC008102,
2019.
Gautheron, C., Tassan-Got, L., Barbarand, J., and Pagel, M.: Effect of
alpha-damage annealing on apatite (U–Th)/He thermochronology, Chem. Geol.,
266, 157–170,
https://doi.org/10.1016/j.chemgeo.2009.06.001, 2009.
Gautheron, C., Tassan-Got, L., Ketcham, R. A., and Dobson, K. J.: Accounting for long alpha-particle stopping distances in (U-Th-Sm)/He geochronology: 3D modeling of diffusion, zoning, implantation, and abrasion, Geochim. Cosmochim. Ac., 96, 44–56, https://doi.org/10.1016/j.gca.2012.08.016, 2012.
Glotzbach, C., Lang, K. A., Avdievitch, N. N., and Ehlers, T. A.: Increasing
the accuracy of (U-Th(-Sm))/He dating with 3D grain modelling, Chem. Geol,
506, 113–125, https://doi.org/10.1016/j.chemgeo.2018.12.032,
2019.
Guenthner, W. R., Reiners, P. W., Ketcham, R. A., Nasdala, L., and Giester, G.:
Helium diffusion in natural zircon: radiation damage, anisotropy, and the
interpretation of zircon (U-Th) ∕ He thermochronology, Am. J. Sci., 313,
145–198, https://doi.org/10.2475/03.2013.01, 2013.
Herman, F., Braun, J., Senden, T. J., and Dunlap, W. J.: (U-Th) ∕ He
thermochronometry: Mapping 3D geometry using micro-X-ray tomography and
solving the associated production-diffusion equation, Chem. Geol., 242,
126–136, https://doi.org/10.1016/j.chemgeo.2007.03.009, 2007.
Holden, N. E.: Total half-lives for selected nuclides, Pure Appl.
Chem., 62, 941–958, https://doi.org/10.1351/pac199062050941, 1990.
Hourigan, J. K., Reiners, P. W., and Brandon, M. T.: U-Th zonation-dependent
alpha-ejection in (U-Th) ∕ He chronometry, Geochim. Cosmochim. Ac., 69,
3349–3365, https://doi.org/10.1016/j.gca.2005.01.024, 2005.
Ketcham, R. and Cooperdock, E. H. G.: Apatite grains, Digital Rocks, https://doi.org/10.17612/CZYH-KC13, 2019.
Ketcham, R. A.: Computational methods for quantitative analysis of
three-dimensional features in geological specimens, Geosphere, 1, 32–41,
https://doi.org/10.1130/GES00001.1, 2005.
Ketcham, R. A. and Carlson, W. D.: Acquisition, optimization and
interpretation of X-ray computed tomographic imagery: Applications to the
geosciences, Comput. Geosci., 27, 381–400,
https://doi.org/10.1016/S0098-3004(00)00116-3, 2001.
Ketcham, R. A. and Mote, A. S.: Accurate measurement of small features in
X-ray CT data volumes, demonstrated using gold grains, J.
Geophys. Res., 124, 3508–3529, https://doi.org/10.1029/2018JB017083, 2019.
Ketcham, R. A. and Ryan, T. M.: Quantification and visualization of
anisotropy in trabecular bone, J. Microsc., 213, 158–171, https://doi.org/10.1111/j.1365-2818.2004.01277.x, 2004.
Ketcham, R. A., Slottke, D. T., and Sharp, J. M. J.: Three-dimensional
measurement of fractures in heterogeneous materials using high-resolution
X-ray CT, Geosphere, 6, 499–514, https://doi.org/10.1130/GES00552.1, 2010.
Ketcham, R. A., Gautheron, C., and Tassan-Got, L.: Accounting for long
alpha-particle stopping distances in (U-Th-Sm)/He geochronology: Refinement
of the baseline case, Geochim. Cosmochim. Ac., 75, 7779–7791,
https://doi.org/10.1016/j.gca.2011.10.011, 2011.
Le Roux, L. A. and Glendenin, L. E.: Half-life of 232Th, in
Proceedings of the National Meeting on Nuclear Energy, Pretoria, South
Africa, 83, 94, 1963.
McDannell, K. T., Zeitler, P. K., Janes, D. G., Idleman, B. D., and Fayon,
A. K.: Screening apatites for (U-Th) ∕ He thermochronometry via continuous
ramped heating: He age components and implications for age dispersion,
Geochim. Cosmochim. Ac., 223, 90–106.
https://doi.org/10.1016/j.gca.2017.11.031, 2018.
Reiners, P. W. and Brandon, M. T.: Using thermochronology to understand
orogenic erosion, Annual Rev. Earth Planet. Sc., 34,
419–466, https://doi.org/10.1146/annurev.earth.34.031405.125202, 2006.
Reiners, P. W. and Farley, K. A.: Influence of crystal size on apatite
(U-Th) ∕ He thermochronology: an example from the Bighorn Mountains, Wyoming,
Earth Planet. Sc. Lett., 188, 3–4, https://doi.org/10.1016/S0012-821X(01)00341-7,
2001.
Shuster, D. L. and Farley, K. A.: The influence of artificial radiation damage and thermal annealing on helium diffusion kinetics in apatite, Geochim. Cosmochim. Ac., 73, 183–196, https://doi.org/10.1016/j.gca.2008.10.013, 2009.
Shuster, D. L., Flowers, R. M., and Farley, K. A.: The influence of natural
radiation damage on helium diffusion kinetics in apatite, Earth Planet. Sc.
Lett., 249, 148–161, https://doi.org/10.1016/j.epsl.2006.07.028, 2006.
Sneed, E. D. and Folk, R. L.: Pebbles in the lower Colorado River, Texas a
study in particle morphogenesis, J. Geol., 66, 114–150,
https://doi.org/10.1086/626490, 1958.
Steiger, R. H. and Jäger, E.: Subcomission on geochronology: Convention
on the use of decay constants in geo- and cosmochronology, Earth Planet.
Sc. Lett., 36, 359–362, https://doi.org/10.1016/0012-821X(77)90060-7, 1977.
Stockli, D. F., Farley, K. A., and Dumitru, T. A.: Calibration of the
apatite (U-Th) ∕ He thermochronometer on an exhumed fault block, White
Mountains, California, Geology, 28, 11, 983–986,
https://doi.org/10.1130/0091-7613(2000)28<983:COTAHT>2.0.CO;2, 2000.
Stockli, D. F., Surpless, B. E., Dumitru, T. A., and Farley, K. A.:
Thermochronological constraints on the timing and magnitude of Miocene and
Pliocene extension in the central Wassuk Range, western Nevada, Tectonics,
21, 10-1–10-19, https://doi.org/10.1029/2001TC001295, 2002.
Surpless, B., Stockli, D. F., Dumitru, T. A., and Miller, E. L.: Two-phase
westward encroachment of basin and range extension into the northern Sierra
Nevada, Tectonics, 21, 2-1–2-13, https://doi.org/10.1029/2000TC001257,
2002.
Wilson, L. and Huang, T. C.: The influence of shape on the atmospheric
settling velocity of volcanic ash particles, Earth Planet. Sc. Lett., 44,
311–324, https://doi.org/10.1016/0012-821X(79)90179-1, 1979.
Zeitler, P. K., Herczeg, A. L., McDougall, I., and Honda, M.: U-Th-He
dating of apatite: A potential thermochronometer, Geochim. Cosmochim. Ac.,
51, 2865–2868,
https://doi.org/10.1016/0016-7037(87)90164-5, 1987.
Short summary
(U–Th) / He chronometry relies on accurate grain-specific size and shape measurements. Using > 100 apatite grains to compare
assumed2-D versus
true3-D grain shapes measured by a microscope and X-ray computed tomography, respectively, we find that volume and surface area both differ by ~ 25 % between the two techniques and directly affect mass and concentration measurements. But we found a very small effect on the FT correction (2 %) and no discernible impact on mean sample age or dispersion.
(U–Th) / He chronometry relies on accurate grain-specific size and shape measurements. Using...
