Changing compositions in the Iceland plume; Isotopic and elemental constraints from the Paleogene Faroe flood basalts
Elemental and Sr, Nd, Hf and high precision Pb isotopic data are presented from 59 low-Ti and high-Ti lavas from the syn-break up part of the Faroe Flood Basalt Province. The depleted MORB-like low-Ti lavas erupted in the rift zone between the Faroe Islands and central East Greenland around the time...
| Published in: | Chemical Geology |
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| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
2011
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| Subjects: | |
| Online Access: | https://curis.ku.dk/portal/da/publications/changing-compositions-in-the-iceland-plume-isotopic-and-elemental-constraints-from-the-paleogene-faroe-flood-basalts(3d4cb450-5722-4da0-b40f-e2ab54718732).html https://doi.org/10.1016/j.chemgeo.2010.11.017 |
| Summary: | Elemental and Sr, Nd, Hf and high precision Pb isotopic data are presented from 59 low-Ti and high-Ti lavas from the syn-break up part of the Faroe Flood Basalt Province. The depleted MORB-like low-Ti lavas erupted in the rift zone between the Faroe Islands and central East Greenland around the time of break up of the North Atlantic have isotopic end-member compositions different from the depleted Iceland lavas. We suggest that the main low-Ti mantle component is NAEM (North Atlantic End-Member (Ellam and Stuart, 2000, J. Petrol. 41, 919) and that the 207Pb/204Pb value of the component should be 15.35 and eHf=+16.5. NAEM is the main depleted component in the early Iceland plume. This is supported by high mantle potential temperatures (up to 1550 °C) calculated for the source of the low-Ti basalts. The unique mantle isotopic composition of NAEM with low 206Pb/204Pb (17.5) and ¿7/4Pb (-3.8) precludes a derivation from recycled MORB lithosphere. Instead we suggest that NAEM represents a plume component of recycled depleted Archean lithospheric mantle that was further depleted ~500 Ma ago, possibly in connection with the recycling process. Two other isotopic end-members are required to explain the variation of the Faroe low-Ti basalts: (1) The Faroe depleted component (FDC), with 87Sr/86Sr=0.7025, eNd=+11, eHf=+19.5, 206Pb/204Pb=18.2, 207Pb/204Pb=15.454 and 208Pb/204Pb=37.75, which is similar in composition to some Atlantic MORB and is regarded as a local upper mantle source. (2) An enriched EM-type component similar in geochemistry to the Icelandic Öræfajökull lavas. This component is believed to be recycled pelagic sediments in the plume but it can alternatively be a local crustal or lithospheric mantle component. The enriched Faroe high-Ti lavas erupted inland from the rift have isotopic compositions very similar to the enriched Icelandic neo-volcanics and these lava suites apparently share the two enriched plume end-members IE1 and IE2 (Geochim. Cosmochim. Acta 68, 2, 2004). The lack of mixing between high and ... |
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