Strontium Isotope Geochemistry and Petrogenesis of the Early Tertiary Lava Pile of the Isle of Skye, Scotland, and other Basic Rocks of the British Tertiary Province: an Example of Magma--Crust Interaction

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Abstract
Most of the flows in the Palaeocene lava pile remnant of Skye are members of the Skye Main Lava Series (SMLS), comprising transitional basalts and two associated suites of evolved lavas. The first suite evolves through Fe-rich hawaiites and mugearites to benmoreites, and the second suite evolves through Fe-poor intermediates to trachytes. Ca-rich, alkali-poor olivine tholeiites (the Preshal Mhor magma type) occur as sparse flows in the stratigraphically highest parts of the lava pile remnant and are abundant in the dyke swarm transecting it. Initial 87Sr/86Sr ratios ranging from 0.70308 to 0.70571 in 45 SMLS samples show no significant correlation with degree of zeolitization (H2O+), silica saturation, or 87Rb/86Sr. A moderately good negative correlation with total Sr confirms published Pb-isotope evidence of interaction with ancient, sialic crust. Details of the (87Sr/86Sr)l versus Sr pattern are consistent with previous hypotheses that the SMLS basalt-benmoreite suite evolved at a depth near the Moho, whilst the low-Fe trend to trachyte resulted from near-surface basalt fractionation.

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