Advancements in cosmogenic 38Ar exposure dating of terrestrial rocks
© 2017 Elsevier Ltd Cosmogenic exposure dating of Ca-rich minerals using 38 Ar on terrestrial rocks could be a valuable new dating tool to determine timescales of geological surface processes on Earth. Here, we show that advancement in analytical precision, using the new generation multi-collector...
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| Format: | Journal Article |
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Pergamon
2017
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| Online Access: | http://purl.org/au-research/grants/arc/DP160102427 http://hdl.handle.net/20.500.11937/58002 |
| _version_ | 1848760152599035904 |
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| author | Oostingh, K. Jourdan, Fred Danisik, Martin Evans, Noreen |
| author_facet | Oostingh, K. Jourdan, Fred Danisik, Martin Evans, Noreen |
| author_sort | Oostingh, K. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | © 2017 Elsevier Ltd Cosmogenic exposure dating of Ca-rich minerals using 38 Ar on terrestrial rocks could be a valuable new dating tool to determine timescales of geological surface processes on Earth. Here, we show that advancement in analytical precision, using the new generation multi-collector ARGUSVI mass spectrometer on irradiated pyroxene and apatite samples, allows determination of cosmogenic 38 Ar abundances above background values, as well as discrimination of 38 Ar/ 36 Ar ratios (1s absolute precision of ±0.3%) from the non-cosmogenic background value. Four statistically significant cosmochron ( 38 Ar/ 36 Ar vs 37 Ar/ 36 Ar) diagrams could be constructed for southeast Australian pyroxene samples from the Mt Elephant scoria cone for which a combined apparent exposure age of 313 ± 179 ka (2s) was obtained when using a 38 Ar production rate (Ca) of 250 atoms /g Ca/ yr. This exposure age overlaps within error with the known 40 Ar/ 39 Ar eruption age of 184 ± 15 ka (2s). Although apatite shows much larger 38 Ar abundances than pyroxene, our modelling and analyses of unirradiated apatite suggest that apatite suffers from both natural and reactor-derived chlorogenic as well as natural nucleogenic contributions of 38 Ar. Hence, we suggest that cosmogenic 38 Ar exposure dating on irradiated Ca-rich (and eventually K-rich), but Cl-free, terrestrial minerals is a potential valuable and accessible tool to determine geological surface processes on timescales of a few Ma. Calculations show that with the new generation multi-collector mass spectrometers an analytical uncertainty better than 5% (2s) can be achieved on samples with expected exposure ages of > 4 Ma. |
| first_indexed | 2025-11-14T10:11:14Z |
| format | Journal Article |
| id | curtin-20.500.11937-58002 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T10:11:14Z |
| publishDate | 2017 |
| publisher | Pergamon |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-580022023-08-02T06:39:10Z Advancements in cosmogenic 38Ar exposure dating of terrestrial rocks Oostingh, K. Jourdan, Fred Danisik, Martin Evans, Noreen © 2017 Elsevier Ltd Cosmogenic exposure dating of Ca-rich minerals using 38 Ar on terrestrial rocks could be a valuable new dating tool to determine timescales of geological surface processes on Earth. Here, we show that advancement in analytical precision, using the new generation multi-collector ARGUSVI mass spectrometer on irradiated pyroxene and apatite samples, allows determination of cosmogenic 38 Ar abundances above background values, as well as discrimination of 38 Ar/ 36 Ar ratios (1s absolute precision of ±0.3%) from the non-cosmogenic background value. Four statistically significant cosmochron ( 38 Ar/ 36 Ar vs 37 Ar/ 36 Ar) diagrams could be constructed for southeast Australian pyroxene samples from the Mt Elephant scoria cone for which a combined apparent exposure age of 313 ± 179 ka (2s) was obtained when using a 38 Ar production rate (Ca) of 250 atoms /g Ca/ yr. This exposure age overlaps within error with the known 40 Ar/ 39 Ar eruption age of 184 ± 15 ka (2s). Although apatite shows much larger 38 Ar abundances than pyroxene, our modelling and analyses of unirradiated apatite suggest that apatite suffers from both natural and reactor-derived chlorogenic as well as natural nucleogenic contributions of 38 Ar. Hence, we suggest that cosmogenic 38 Ar exposure dating on irradiated Ca-rich (and eventually K-rich), but Cl-free, terrestrial minerals is a potential valuable and accessible tool to determine geological surface processes on timescales of a few Ma. Calculations show that with the new generation multi-collector mass spectrometers an analytical uncertainty better than 5% (2s) can be achieved on samples with expected exposure ages of > 4 Ma. 2017 Journal Article http://hdl.handle.net/20.500.11937/58002 10.1016/j.gca.2017.07.043 http://purl.org/au-research/grants/arc/DP160102427 Pergamon restricted |
| spellingShingle | Oostingh, K. Jourdan, Fred Danisik, Martin Evans, Noreen Advancements in cosmogenic 38Ar exposure dating of terrestrial rocks |
| title | Advancements in cosmogenic 38Ar exposure dating of terrestrial rocks |
| title_full | Advancements in cosmogenic 38Ar exposure dating of terrestrial rocks |
| title_fullStr | Advancements in cosmogenic 38Ar exposure dating of terrestrial rocks |
| title_full_unstemmed | Advancements in cosmogenic 38Ar exposure dating of terrestrial rocks |
| title_short | Advancements in cosmogenic 38Ar exposure dating of terrestrial rocks |
| title_sort | advancements in cosmogenic 38ar exposure dating of terrestrial rocks |
| url | http://purl.org/au-research/grants/arc/DP160102427 http://hdl.handle.net/20.500.11937/58002 |