Temperature fluctuation of the Iceland mantle plume through time

Holly E Spice,Linda A Kirstein,J Godfrey Fitton

doi:10.1002/2015gc006059

Abstract

AbstractThe newly developed Al‐in‐olivine geothermometer was used to find the olivine‐Cr‐spinel crystallization temperatures of a suite of picrites spanning the spatial and temporal extent of the North Atlantic Igneous Province (NAIP), which is widely considered to be the result of a deep‐seated mantle plume. Our data confirm that start‐up plumes are associated with a pulse of anomalously hot mantle over a large spatial area before becoming focused into a narrow upwelling. We find that the thermal anomaly on both sides of the province at Baffin Island/West Greenland and the British Isles at ∼61 Ma across an area ∼2000 km in diameter was uniform, with Al‐in‐olivine temperatures up to above that of average mid‐ocean ridge basalt (MORB) primitive magma. Furthermore, by combining our results with geochemical data and existing geophysical and bathymetric observations, we present compelling evidence for long‐term (>107 year) fluctuations in the temperature of the Iceland mantle plume. We show that the plume temperature fell from its initial high value during the start‐up phase to a minimum at about 35 Ma, and that the mantle temperature beneath Iceland is currently increasing.

Highlights

Mantle plumes are buoyancy-driven flows originating from deep within the Earth and result in large mantle thermal anomalies
The North Atlantic Igneous Province (NAIP) is one of the best studied Large igneous province (LIP) on Earth, and it is generally accepted to be the result of a deep-seated mantle plume that presently underlies Iceland
Iceland is the only part of the NAIP (Figure 1) that remains active, and it represents the subaerial expression of an extensive basalt plateau formed as the result of the interaction of the mantle plume and the Mid-Atlantic spreading axis

Summary

Introduction

Mantle plumes are buoyancy-driven flows originating from deep within the Earth and result in large mantle thermal anomalies. (3) Overthickened (20–35 km) oceanic crust that forms the Greenland-Faeroe Ridge (GFR) and the Iceland-Faeroe Ridge (IFR) (Figures 1 and 2a), and is thought to be the result of plume-driven mantle upwelling [Shorttle and Maclennan, 2011] and anomalously hot material in the core of the Iceland plume tail [White and Lovell, 1997; Darbyshire et al, 1998] The distribution of these three types of crust is variable through time on a longer time scale than the crustal thickness variations recorded by the VSRs. The aim of this study is to use the newly developed Al-in-olivine thermometer to investigate the thermal evolution of the Iceland mantle plume throughout its lifetime and to test whether changes in the large-scale crustal architecture of the North Atlantic region are due to variations in mantle potential temperature (as is the case with the VSRs) as opposed variations in mantle fertility

North Atlantic Bathymetry and Mantle Melting

Estimating Magmatic Temperature

Relationship of Magmatic Temperature to Mantle Potential Temperature

Temporal Variation in the Composition of Reykjanes Ridge Basalts

Findings

Temperature of the Iceland Mantle Plume Through Time