Pb isotope insight into the formation of the Earth's first stable continents
The formation of stable buoyant continental crust during the Archaean Eon was fundamental in establishing the planet's geochemical reservoirs. However, the processes that created Earth's first continents and the timescales over which they formed are debated. Here, we report the Pb isotope...
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ELSEVIER
2022
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| Online Access: | http://purl.org/au-research/grants/arc/DP200101104 http://hdl.handle.net/20.500.11937/90872 |
| _version_ | 1848765447614234624 |
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| author | Hartnady, Michael Kirkland, Christopher Smithies, R. Hugh Johnson, S.P. Johnson, Tim |
| author_facet | Hartnady, Michael Kirkland, Christopher Smithies, R. Hugh Johnson, S.P. Johnson, Tim |
| author_sort | Hartnady, Michael |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | The formation of stable buoyant continental crust during the Archaean Eon was fundamental in establishing the planet's geochemical reservoirs. However, the processes that created Earth's first continents and the timescales over which they formed are debated. Here, we report the Pb isotope compositions of K-feldspar grains from 52 Paleoarchaean to Neoarchaean granites from the Pilbara Craton in Western Australia, one of the world's oldest and best-preserved granite–greenstone terranes. The Pb isotope composition of the Pilbara K-feldspars is variable, implying the granites were derived from crustal precursors of different age and/or variable time-integrated 238U/204Pb and 232Th/204Pb compositions. Trends to sub-mantle 207Pb/206Pb ratios preclude the influence of 4.3 Ga crustal precursors. In order to estimate crustal residence times we derive equations to calculate source model ages in a linearized Pb isotope evolution system. The best agreement between the feldspar Pb two-stage source model ages and those derived from zircon initial Hf isotope compositions requires crustal precursors that separated from a chondritic mantle source between 3.2 and 3.8 Ga, and rapidly differentiated to continental crust with 238U/204Pb and 232Th/238U ratios of ∼14 and 4.2–4.5, respectively. The preservation of Pb isotope variability in the Pilbara Paleoarchaean granites indicates their early continental source rocks were preserved for up to 500 Ma after their formation. The apparent longevity of these early continental nuclei is consistent with the incipient development of buoyant melt-depleted cratonic lithosphere during the Eoarchaean to Paleoarchaean. |
| first_indexed | 2025-11-14T11:35:24Z |
| format | Journal Article |
| id | curtin-20.500.11937-90872 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| language | English |
| last_indexed | 2025-11-14T11:35:24Z |
| publishDate | 2022 |
| publisher | ELSEVIER |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-908722023-05-09T04:24:30Z Pb isotope insight into the formation of the Earth's first stable continents Hartnady, Michael Kirkland, Christopher Smithies, R. Hugh Johnson, S.P. Johnson, Tim Science & Technology Physical Sciences Geochemistry & Geophysics early Earth Pb isotopes crustal evolution Pilbara Craton Eoarchaean MC-ICP-MS IN-SITU ANALYSIS PILBARA CRATON HF ISOTOPES OXYGEN ISOTOPES CORE FORMATION LU-HF CRUST ZIRCON CONSTRAINTS The formation of stable buoyant continental crust during the Archaean Eon was fundamental in establishing the planet's geochemical reservoirs. However, the processes that created Earth's first continents and the timescales over which they formed are debated. Here, we report the Pb isotope compositions of K-feldspar grains from 52 Paleoarchaean to Neoarchaean granites from the Pilbara Craton in Western Australia, one of the world's oldest and best-preserved granite–greenstone terranes. The Pb isotope composition of the Pilbara K-feldspars is variable, implying the granites were derived from crustal precursors of different age and/or variable time-integrated 238U/204Pb and 232Th/204Pb compositions. Trends to sub-mantle 207Pb/206Pb ratios preclude the influence of 4.3 Ga crustal precursors. In order to estimate crustal residence times we derive equations to calculate source model ages in a linearized Pb isotope evolution system. The best agreement between the feldspar Pb two-stage source model ages and those derived from zircon initial Hf isotope compositions requires crustal precursors that separated from a chondritic mantle source between 3.2 and 3.8 Ga, and rapidly differentiated to continental crust with 238U/204Pb and 232Th/238U ratios of ∼14 and 4.2–4.5, respectively. The preservation of Pb isotope variability in the Pilbara Paleoarchaean granites indicates their early continental source rocks were preserved for up to 500 Ma after their formation. The apparent longevity of these early continental nuclei is consistent with the incipient development of buoyant melt-depleted cratonic lithosphere during the Eoarchaean to Paleoarchaean. 2022 Journal Article http://hdl.handle.net/20.500.11937/90872 10.1016/j.epsl.2021.117319 English http://purl.org/au-research/grants/arc/DP200101104 http://purl.org/au-research/grants/arc/LP180100199 http://creativecommons.org/licenses/by/4.0/ ELSEVIER fulltext |
| spellingShingle | Science & Technology Physical Sciences Geochemistry & Geophysics early Earth Pb isotopes crustal evolution Pilbara Craton Eoarchaean MC-ICP-MS IN-SITU ANALYSIS PILBARA CRATON HF ISOTOPES OXYGEN ISOTOPES CORE FORMATION LU-HF CRUST ZIRCON CONSTRAINTS Hartnady, Michael Kirkland, Christopher Smithies, R. Hugh Johnson, S.P. Johnson, Tim Pb isotope insight into the formation of the Earth's first stable continents |
| title | Pb isotope insight into the formation of the Earth's first stable continents |
| title_full | Pb isotope insight into the formation of the Earth's first stable continents |
| title_fullStr | Pb isotope insight into the formation of the Earth's first stable continents |
| title_full_unstemmed | Pb isotope insight into the formation of the Earth's first stable continents |
| title_short | Pb isotope insight into the formation of the Earth's first stable continents |
| title_sort | pb isotope insight into the formation of the earth's first stable continents |
| topic | Science & Technology Physical Sciences Geochemistry & Geophysics early Earth Pb isotopes crustal evolution Pilbara Craton Eoarchaean MC-ICP-MS IN-SITU ANALYSIS PILBARA CRATON HF ISOTOPES OXYGEN ISOTOPES CORE FORMATION LU-HF CRUST ZIRCON CONSTRAINTS |
| url | http://purl.org/au-research/grants/arc/DP200101104 http://purl.org/au-research/grants/arc/DP200101104 http://hdl.handle.net/20.500.11937/90872 |