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<front>
<journal-meta>
<journal-id journal-id-type="publisher">EGUsphere</journal-id>
<journal-title-group>
<journal-title>EGUsphere</journal-title>
<abbrev-journal-title abbrev-type="publisher">EGUsphere</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">EGUsphere</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub"></issn>
<publisher><publisher-name>Copernicus Publications</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/egusphere-2026-4403</article-id>
<title-group>
<article-title>Analytical strategies for &lt;sup&gt;207&lt;/sup&gt;Pb/&lt;sup&gt;235&lt;/sup&gt;U carbonate geochronology</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Szymanowski</surname>
<given-names>Dawid</given-names>
<ext-link>https://orcid.org/0000-0001-9524-5710</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Guillong</surname>
<given-names>Marcel</given-names>
<ext-link>https://orcid.org/0000-0002-6920-3362</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Vermeesch</surname>
<given-names>Pieter</given-names>
<ext-link>https://orcid.org/0000-0003-3404-1209</ext-link>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Hopley</surname>
<given-names>Philip J.</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Department of Earth and Planetary Sciences, ETH Zurich, 8092 Zurich, Switzerland</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Department of Earth Sciences, University College London, London WC1E 6BT, United Kingdom</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>School of Natural Sciences, Birkbeck, University of London, London WC1E 7HX, United Kingdom</addr-line>
</aff>
<pub-date pub-type="epub">
<day>07</day>
<month>08</month>
<year>2026</year>
</pub-date>
<volume>2026</volume>
<fpage>1</fpage>
<lpage>25</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2026 Dawid Szymanowski et al.</copyright-statement>
<copyright-year>2026</copyright-year>
<license license-type="open-access">
<license-p>This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit <ext-link ext-link-type="uri"  xlink:href="https://creativecommons.org/licenses/by/4.0/">https://creativecommons.org/licenses/by/4.0/</ext-link></license-p>
</license>
</permissions>
<self-uri xlink:href="https://egusphere.copernicus.org/preprints/2026/egusphere-2026-4403/">This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-4403/</self-uri>
<self-uri xlink:href="https://egusphere.copernicus.org/preprints/2026/egusphere-2026-4403/egusphere-2026-4403.pdf">The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-4403/egusphere-2026-4403.pdf</self-uri>
<abstract>
<p>&lt;p style=&quot;font-weight: 400;&quot;&gt;In carbonate U&amp;ndash;Pb geochronology, unknown initial &lt;sup&gt;234&lt;/sup&gt;U/&lt;sup&gt;238&lt;/sup&gt;U disequilibria can be debilitating for the accuracy of &lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt;238&lt;/sup&gt;U dates. Even if residual &lt;sup&gt;234&lt;/sup&gt;U/&lt;sup&gt;238&lt;/sup&gt;U disequilibrium can be measured precisely enough to perform accurate corrections, beyond ca. 1.5 Ma (depending on the magnitude of initial excess/deficit of &lt;sup&gt;234&lt;/sup&gt;U) the expansion of uncertainties due to the disequilibrium correction may make carbonate &lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt;238&lt;/sup&gt;U dates prohibitively imprecise. An alternative approach utilising the &lt;sup&gt;207&lt;/sup&gt;Pb/&lt;sup&gt;235&lt;/sup&gt;U system is arguably more accurate, however the lower abundance of &lt;sup&gt;235&lt;/sup&gt;U and &lt;sup&gt;207&lt;/sup&gt;Pb relative to &lt;sup&gt;238&lt;/sup&gt;U and &lt;sup&gt;206&lt;/sup&gt;Pb inevitably results in larger analytical data-point uncertainties. Here we explore analytical strategies that maximise the potential of the &lt;sup&gt;207&lt;/sup&gt;Pb/&lt;sup&gt;235&lt;/sup&gt;U system for carbonate geochronology. ID-TIMS and LA-ICPMS are considered the most useful, and complementary, techniques. ID-TIMS offers the ultimate precision and accuracy combined with the ability to filter data for contamination using &lt;sup&gt;208&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb, but it requires mg-sized samples that limit the spatial resolution and the spread of data along the isochron. Optimised LA-ICPMS with large spot sizes may be a quick alternative with better spatial control and enhanced spread of data along the isochron, but &lt;sup&gt;208&lt;/sup&gt;Pb normalisation imposed by the difficulty of analysing &lt;sup&gt;204&lt;/sup&gt;Pb may add noise to the results. Overall, precise &lt;sup&gt;207&lt;/sup&gt;Pb/&lt;sup&gt;235&lt;/sup&gt;U carbonate geochronology is feasible and with minor analytical adjustments it can be adopted broadly instead of the &lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt;238&lt;/sup&gt;U method. Future work on carbonates should obtain additional compositional information that will allow robust identification of domains contaminated with extraneous Pb.</p>
</abstract>
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<funding-group>
<award-group id="gs1">
<funding-source>Eidgenössische Technische Hochschule Zürich</funding-source>
<award-id>ETH Career Seed Award</award-id>
</award-group>
</funding-group>
</article-meta>
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