Constraining magmatic differentiation at Teide/Pico Viejo and associated rift zones, Tenerife, Canary Islands

Abstract

To unravel magma chamber processes and eruption triggers at the central volcanic complex Pico Teide/Pico Viejo (TPV) and its adjacent rift zones on Tenerife, we investigated 52 samples for their Sr isotope composition in feldspar phenocrysts. Processes such as magma mixing and contamination can be masked in whole-rock analyses, which merely represent the integrated average of all component parts involved (crystals, liquid, xenoliths). As feldspar crystals record prolonged crystallisation histories, we employ a microanalytical approach to resolve magmatic processes. LA-MCICPMS represents the best means to a) yield a stratigraphy of Sr isotope ratios over core-to-rim profiles of single phenocrysts, i. e. a ‘timeline’ of the magma’s isotopic evolution and b) to carry out a large number of analyses in a relatively short time. 87Sr/86Sr has been analysed in plagioclase phenocrysts of the most recent eruptive products on Tenerife that built the TPV-complex and effused from the rift zones to the NW and NE over the last 35,000 yrs [1]. No correlation between 87Sr/86Sr and An content has been detected in feldspars of these deposits, in concordance with the results from other localities such as Merapi or Krakatau [2; 3]. Crystal populations are found to be very heterogenous amongst the sample suite and also within single samples [cf. 4], The latter may range from no significant variation in 87Sr/86Sr and An in some crystals to significant rises and subsequent falls of 87Sr/86Sr independent of associated An variations in others. A wide array of processes including FC, AFC and magma mixing is suggested to influence the evolution of TPV and rift zone lavas, demonstrating a complex interplay of differentiation processes within the TPV plumbing system.