Numerical Modelling of Radiogenic Ingrowth and Diffusion of Pb in Apatite Inclusions with Variable Shape and U-Th Zonation
The fundamental premise of apatite U-Th-Pb thermochronology is that radiogenic Pb is redistributed by volume diffusion. In practice, it is often additionally assumed that crystals (1) lose radiogenic Pb to an infinite reservoir, (2) have a simple geometry and (3) are chemically homogeneous. Here we...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-03-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/11/4/364 |
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| author | Daniil V. Popov Richard A. Spikings |
| author_facet | Daniil V. Popov Richard A. Spikings |
| author_sort | Daniil V. Popov |
| collection | DOAJ |
| description | The fundamental premise of apatite U-Th-Pb thermochronology is that radiogenic Pb is redistributed by volume diffusion. In practice, it is often additionally assumed that crystals (1) lose radiogenic Pb to an infinite reservoir, (2) have a simple geometry and (3) are chemically homogeneous. Here we explore the significance of the latter three assumptions by numerical modelling of Pb radiogenic ingrowth and diffusion in apatite inclusions within other minerals. Our results indicate that the host minerals are likely to hamper diffusive Pb loss from the apatite inclusions by limiting the Pb flux across their boundaries, and thus the thermal histories that are reconstructed assuming a fully open boundary may be significantly inaccurate, precluding a meaningful interpretation. We also find that when apatite boundaries are flux-limited, heterogeneities in U and Th concertation within apatite have subordinate effect on bulk-grain U-Th-Pb dates and can cause intra-grain U-Th-Pb dates to increase towards the boundaries. Finally, we show that it is important to correctly account for crystal geometry when modelling intra-grain U-Th-Pb dates. We suggest that the effect of surrounding minerals on diffusive Pb loss from apatite (and loss of other radiogenic isotopes from other minerals) should be examined more closely in future research. |
| first_indexed | 2024-03-10T12:45:24Z |
| format | Article |
| id | doaj.art-44ca2b5c5f2a467481102eb7b696e3d3 |
| institution | Directory Open Access Journal |
| issn | 2075-163X |
| language | English |
| last_indexed | 2024-03-10T12:45:24Z |
| publishDate | 2021-03-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Minerals |
| spelling | doaj.art-44ca2b5c5f2a467481102eb7b696e3d32023-11-21T13:31:32ZengMDPI AGMinerals2075-163X2021-03-0111436410.3390/min11040364Numerical Modelling of Radiogenic Ingrowth and Diffusion of Pb in Apatite Inclusions with Variable Shape and U-Th ZonationDaniil V. Popov0Richard A. Spikings1Department of Earth Sciences, University of Geneva, 13 Rue des Maraichers, CH-1205 Geneva, SwitzerlandDepartment of Earth Sciences, University of Geneva, 13 Rue des Maraichers, CH-1205 Geneva, SwitzerlandThe fundamental premise of apatite U-Th-Pb thermochronology is that radiogenic Pb is redistributed by volume diffusion. In practice, it is often additionally assumed that crystals (1) lose radiogenic Pb to an infinite reservoir, (2) have a simple geometry and (3) are chemically homogeneous. Here we explore the significance of the latter three assumptions by numerical modelling of Pb radiogenic ingrowth and diffusion in apatite inclusions within other minerals. Our results indicate that the host minerals are likely to hamper diffusive Pb loss from the apatite inclusions by limiting the Pb flux across their boundaries, and thus the thermal histories that are reconstructed assuming a fully open boundary may be significantly inaccurate, precluding a meaningful interpretation. We also find that when apatite boundaries are flux-limited, heterogeneities in U and Th concertation within apatite have subordinate effect on bulk-grain U-Th-Pb dates and can cause intra-grain U-Th-Pb dates to increase towards the boundaries. Finally, we show that it is important to correctly account for crystal geometry when modelling intra-grain U-Th-Pb dates. We suggest that the effect of surrounding minerals on diffusive Pb loss from apatite (and loss of other radiogenic isotopes from other minerals) should be examined more closely in future research.https://www.mdpi.com/2075-163X/11/4/364apatiteinclusionU-Th-PbthermochronologyPbdiffusion |
| spellingShingle | Daniil V. Popov Richard A. Spikings Numerical Modelling of Radiogenic Ingrowth and Diffusion of Pb in Apatite Inclusions with Variable Shape and U-Th Zonation Minerals apatite inclusion U-Th-Pb thermochronology Pb diffusion |
| title | Numerical Modelling of Radiogenic Ingrowth and Diffusion of Pb in Apatite Inclusions with Variable Shape and U-Th Zonation |
| title_full | Numerical Modelling of Radiogenic Ingrowth and Diffusion of Pb in Apatite Inclusions with Variable Shape and U-Th Zonation |
| title_fullStr | Numerical Modelling of Radiogenic Ingrowth and Diffusion of Pb in Apatite Inclusions with Variable Shape and U-Th Zonation |
| title_full_unstemmed | Numerical Modelling of Radiogenic Ingrowth and Diffusion of Pb in Apatite Inclusions with Variable Shape and U-Th Zonation |
| title_short | Numerical Modelling of Radiogenic Ingrowth and Diffusion of Pb in Apatite Inclusions with Variable Shape and U-Th Zonation |
| title_sort | numerical modelling of radiogenic ingrowth and diffusion of pb in apatite inclusions with variable shape and u th zonation |
| topic | apatite inclusion U-Th-Pb thermochronology Pb diffusion |
| url | https://www.mdpi.com/2075-163X/11/4/364 |
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