Extended correlation of the Paleogene Faroe Islands and East Greenland plateau basalts

TY - JOUR

T1 - Extended correlation of the Paleogene Faroe Islands and East Greenland plateau basalts

AU - Søager, Nina

AU - Holm, Paul Martin

PY - 2008

Y1 - 2008

N2 - New analytical data are presented for 13 enriched high-Ti tholeiitic basalts from the top of the Faroese lava pile that was formed by the time of break-up of the North Atlantic  56-55  Ma ago and are located on the eastern continental margin of the Atlantic Ocean. The samples fall in three groups according to their Nb/Zr/Y chemistry: High-Ti1, High-Ti2 and High-Ti3. The grouping is related to their stratigraphic position so that the High-Ti1 group is found lowest in the sampled profiles and the High-Ti3 group at the top with the High-Ti2 group in between. The High-Ti1 and High-Ti2 groups have 206Pb/204Pb = 17.59-18.30 while the High-Ti3 group has 206Pb/204Pb = 18.88-19.12. The three Faroese lava groups can be correlated with the East Greenland syn-breakup basalt formations using their geochemistry, lava morphology and phenocryst contents. The High-Ti1 group correlates with the Milne Land Formation and the High-Ti2 and High-Ti3 groups correlate with the Geikie Plateau Formation and Rømer Fjord Formation, respectively. The discovery of equivalents to the East Greenland Geikie Plateau Formation and Rømer Fjord Formation means that volcanism has proceeded longer than previously thought on the Faroe Islands but with a lot lower intensity than on the other side of the rift. This demonstrates that large parts of the km-thick volcanic successions of the North Atlantic LIP developed in parallel on the juxtaposed rifted continental margins during break-up, although the centre of eruptions moved away from the Faroe Islands during the last stages of volcanism.Pb-isotope ratios indicate that the High-Ti1, High-Ti2, Milne Land Formation and Geikie Plateau Formation have the same mantle source while the High-Ti3 and Rømer Fjord Formation also contain material from another mantle component. High-Ti1 and Milne Land Formation lavas have a higher content of most incompatible elements compared to High-Ti2 and Geikie Plateau Formation. This is unexpected because the Zr/Nb ratio indicates that the High-Ti2 and Geikie Plateau Formation lavas are formed by lower degrees of melting. An explanation may be that High-Ti1 and Milne Land Formation magmas fractionated significant amounts of clinopyroxene at the bottom of the crust before rising to higher crustal levels, whereas High-Ti2 and Geikie Plateau Formation magmas initially fractionated olivine at lower pressures.

AB - New analytical data are presented for 13 enriched high-Ti tholeiitic basalts from the top of the Faroese lava pile that was formed by the time of break-up of the North Atlantic  56-55  Ma ago and are located on the eastern continental margin of the Atlantic Ocean. The samples fall in three groups according to their Nb/Zr/Y chemistry: High-Ti1, High-Ti2 and High-Ti3. The grouping is related to their stratigraphic position so that the High-Ti1 group is found lowest in the sampled profiles and the High-Ti3 group at the top with the High-Ti2 group in between. The High-Ti1 and High-Ti2 groups have 206Pb/204Pb = 17.59-18.30 while the High-Ti3 group has 206Pb/204Pb = 18.88-19.12. The three Faroese lava groups can be correlated with the East Greenland syn-breakup basalt formations using their geochemistry, lava morphology and phenocryst contents. The High-Ti1 group correlates with the Milne Land Formation and the High-Ti2 and High-Ti3 groups correlate with the Geikie Plateau Formation and Rømer Fjord Formation, respectively. The discovery of equivalents to the East Greenland Geikie Plateau Formation and Rømer Fjord Formation means that volcanism has proceeded longer than previously thought on the Faroe Islands but with a lot lower intensity than on the other side of the rift. This demonstrates that large parts of the km-thick volcanic successions of the North Atlantic LIP developed in parallel on the juxtaposed rifted continental margins during break-up, although the centre of eruptions moved away from the Faroe Islands during the last stages of volcanism.Pb-isotope ratios indicate that the High-Ti1, High-Ti2, Milne Land Formation and Geikie Plateau Formation have the same mantle source while the High-Ti3 and Rømer Fjord Formation also contain material from another mantle component. High-Ti1 and Milne Land Formation lavas have a higher content of most incompatible elements compared to High-Ti2 and Geikie Plateau Formation. This is unexpected because the Zr/Nb ratio indicates that the High-Ti2 and Geikie Plateau Formation lavas are formed by lower degrees of melting. An explanation may be that High-Ti1 and Milne Land Formation magmas fractionated significant amounts of clinopyroxene at the bottom of the crust before rising to higher crustal levels, whereas High-Ti2 and Geikie Plateau Formation magmas initially fractionated olivine at lower pressures.

U2 - 10.1016/j.lithos.2008.10.002

DO - 10.1016/j.lithos.2008.10.002

M3 - Journal article

SN - 0024-4937

VL - 107

SP - 205

EP - 215

JO - Lithos

JF - Lithos

IS - 3-4

ER -