Icelandic rift relocations: Melting models and geochemical observations

Abstract

Rift relocations are distinctive features associated with plume-ridge interaction. The underlying processes controlling these relocations are not well understood. Observations of crustal thickness and basalt composition have been commonly used to investigate plume-ridge interaction. We present the first quantitative model of variations in melt production rates and composition during a rift relocation cycle including the growth and death of spreading centres.

The two dimensional time-dependent model of passive upwelling beneath a spreading ridge is based on simple corner flow. The resulting thermal and melting structure is calculated and used to predict the variation in crustal thickness and composition through time.

The results of the model are compared to geochemical and geophysical observations of the current rift relocation in southern Iceland and a palaeo-rift relocation in northern Iceland. A comparison is also made with the abandoned Phoenix Ridge, Drake Passage, Antartica. The geochemical observations are consistent with smaller degrees of melting, strongly influenced by deep mantle melting and we hope to confirm this using the model.