Features of the composition of the main rock-forming minerals of basalts and xenoliths of the Canary archipelago (Spain)

The article is devoted to studying the chemical composition of the main rock-forming minerals of basalts from the island of La Palma, xenolith from the island of Lanzarote of the Canary Archipelago (Spain). The main task of the research is the diagnosis of mineral composition of these rocks. Peridodite xenoliths can be of several types reflecting their mantle or crust origin. The chemical composition of the main rock-forming minerals is described, which testifies to a cumulative genesis of these formations in deep magmatic chambers with possible inclusion of xenogenic crystals from lithospheric mantle material. The main research methods were petrographic diagnostics and micro X-ray spectral analysis of the chemical composition of the main rock-forming minerals by Tescan Vega II LMU electron microscope equipped with INCA Energy 350 energy dispersive spectrometer (with Si (Li) Standart detector). We found that the olivines and pyroxenes of basalts were characterized by a typical composition of volcanic rocks, which had been formed in near-surface conditions or as a result of direct outpouring. Variations in the composition of plagioclase from labrador to oligoclase allowed classifying these formations as subalkaline bases characteristic of intraplate oceanic magmatism. The study of the petrostructure of peridotite xenolith and the composition of its constituent minerals revealed the peculiarities of their formation. There are several versions of the nature of peridotite xenoliths, reflecting their mantle or crustal origin. The obtained results suggested the cumulative genesis of these formations in deep magma chambers, with the possible involvement of xenogenic crystals from lithospheric mantle material. The magmatic nature of xenolith was supported by the presence of endiopside and plagioclase in the intergranular space of large olivine and orthopyroxene grains. The elements of intracrystalline deformations and their high magnesian composition, corresponding to restite hyperbasites of ophiolite association, can be used to explain the mantle nature of large crystals of olivine and orthopyroxene.