La Palma

The Canary Islands are a chain of seven volcanic, hotspot-related islands off the coast of northwestern africa. The style, time relationship and chemistry of the volcanoes differes dramatically from the volcanoes in the Hawaiian Chain - with a much higher percentage of alkalic and evolved lavas. La Palma is one of the two westernmost and youngest islands in the Canary Island chain. The subarial portion of the island is composed almost entirely of basanite.

Mantle heterogeneities exist on scales that range from inter-oceanic scale to small veinlets in xenoliths brought to the surface in lava flows.  What is not as well known is the scale at which these heterogeneities  are sampled and preserved in basalts.  We report major, trace and Sr-Pb-Nd isotope  Fe2O3 vs MgO and differentiation modeling results for samples from three different stratigraphic sequences - purple circles represent borehole S-01 samples, blue diamonds represent samples from the top of Bejenado and yellow triangles represent samples from the underlying Cumbre Nueva sequence. Solid and dashed lines represent two differentiation models carried out with the MELTS software with two starting compositions from the more primitive borehole samples. compositions for samples from a stratigraphic sequence of primarily basanitic lavas from Bejenado volcano on La Palma, Canary Islands.  Variation is significant in major elements (MgO = 2.3 wt. % to 14.1 wt. %),  trace elements, both compatible (Ni = 5 ppm to 240 ppm) and incompatible (Ba = 271 ppm to 1020 ppm), and isotopes (206Pb/204Pb = 19.38 to 20.06; 87Sr/86Sr = 0.70299 to 70319; eNd = + 4.4 to +6.0). Major and trace elements define excellent differentiation trends, but there is no correlation between major element or isotope composition and stratigraphy. These variations indicate melting of a heterogeneous mantle over short length scales during the 10-20 kyr life of the BejenadoVolcano.

Isotopic composition vs. borehole depth for samples from Borehole S-O1. The figure to your left is the 206Pb/204Pb ratio and the figure to your right is the 87Sr/86Sr ratio.