Details

Autor(en) / Beteiligte

• Hole, M J
• Millett, J M

Titel

Controls of Mantle Potential Temperature and Lithospheric Thickness on Magmatism in the North Atlantic Igneous Province

Ist Teil von

• Journal of petrology, 2016-02, Vol.57 (2), p.417-436

Erscheinungsjahr

2016

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Modelled primary magma compositions of Palaeogene basalts from the North Atlantic Igneous Province (NAIP) require melting at mantle potential temperatures (T sub(P)) in the range 1480-1550 degree C. Modern lavas from Icelandic rift zones require T sub(P)1500 degree C and those from the rift flanks T sub(P)1450 degree C. Secular cooling of the NAIP thermal anomaly was therefore of the order of 50 degree C over the past 61 Myr. There were systematic variations in T sub(P) of 50-100 degree C from the centre of the thermal anomaly to its margins at any one time, although limits on the stratigraphical distribution of T sub(P) determinations do not rule out thermal pulsing on a timescale of millions of years. Variation in extent of melting at similar T sub(P) was controlled by local variability in lithospheric thickness. In the west of the NAIP, lithosphere thickness varied from 90km at Disko Island to 65km at Baffin Island, with similar thickness variations being evident for magmatism in the Faroe Islands, Faroe-Shetland Basin and the British Palaeogene Igneous Province (BPIP). Mean pressure of melting was greater than or equal to the final pressure of melting; the two values converge for melting columns with a melting interval of <1.5GPa, regardless of T sub(P). The majority of the BPIP magmas were generated in the garnet-spinel transition in the upper mantle. Calculated and observed rare earth element distributions in NAIP lavas are entirely consistent with the melting regimes derived from major element melting models. This allows a calibration of rare earth element fractionation and melting conditions that can be applied to other flood basalt provinces.