Jennings, Eleanor S. and Gibson, S.A. and Maclennan, J. (2019) Hot primary melts and mantle source for the Paraná-Etendeka flood basalt province: new constraints from Al-in-olivine thermometry. Chemical Geology 529 , p. 119287. ISSN 0009-2541.
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Other (Supplemental data table S1, accompanies Jennings et al. (2019), Chemical Geology)
Supplementary table S1 data.xls - Supplemental Material Download (78kB) |
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Other (Supplemental data table S2, accompanies Jennings et al. (2019), Chemical Geology)
Supplementary_table S2 count_times.xlsx - Supplemental Material Download (8kB) |
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Other (Supplemental data table S3, accompanies Jennings et al. (2019), Chemical Geology)
Supplementary_table S3 petrolog.xlsx - Supplemental Material Download (8kB) |
Abstract
Continental flood basalts (CFB) are amongst the most voluminous volcanic eruptions in Earth’s history. They are rapidly emplaced, and in rare cases the thick lava piles are associated with primitive magmas that have high MgO contents. The compositions of these primitive melts are consistent with a deep-sourced, high-temperature mantle plume origin. Whilst the association of CFBs with impacting mantle plumes is widely accepted, the magnitude of the thermal anomaly is not yet resolved. The development of Al-in-olivine thermometry, however, allows the crystallisation temperature of (near-)liquidus olivine to be determined without using the composition of the co-existing melt. This provides both a robust minimum estimate of mantle temperature and a value from which potential temperature (TP) can be back-calculated. This technique has previously confirmed that crystallisation temperatures in CFB settings can be a few hundred degrees greater than those estimated for MORB, and the results hint at a diversity in crystallisation temperatures between different CFB settings. In this study, we re-assess the TP of the mantle source of the Paraná-Etendeka CFB province by applying the Al-in-olivine thermometer to olivine-spinel pairs from picrites and ferropicrites. We show that the mean crystallisation temperatures of olivine with Fo>90 in the picrites is 1458 °C, with a maximum temperature of 1511 °C. Using the mean value, we calculate a preferred TP of 1623 °C, for an assumed lithospheric thickness of 50 km and magma emplacement pressure of 0.5 GPa. This represents a thermal anomaly of around +300 °C relative to ambient mantle, and confirms that the mantle source of the Paraná-Etendeka CFB is the second hottest known from Phanerozoic Large Igneous Provinces, after the Caribbean Large Igneous Province. The ferropicrites record a cooler mean olivine crystallisation temperature of 1296 °C. Given that these low-volume melts derive from deeper and earlier melting of mantle pyroxenite, their temperature is not directly comparable to that of the picrites but they appear to require a somewhat cooler mantle source – perhaps found at the front or edges of a rising plume head.
Metadata
| Item Type: | Article |
|---|---|
| Keyword(s) / Subject(s): | olivine, thermometry, Al-in-olivine, continental flood basalt, Paraná-Etendeka, mantle plume, mantle temperature |
| School: | Birkbeck Faculties and Schools > Faculty of Science > School of Natural Sciences |
| Depositing User: | Dr Eleanor Jennings |
| Date Deposited: | 02 Sep 2019 10:57 |
| Last Modified: | 02 Aug 2023 17:53 |
| URI: | https://eprints.bbk.ac.uk/id/eprint/28741 |
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