Mineralogical characterization of peridotite xenoliths from the Los Tormos volcano (Calatrava volcanic field)

Resumen

Peridotite xenoliths from the Los Tormos volcano (Calatrava volcanic field) provide significant information about the lithospheric mantle of Central Iberia. Studied samples are classified as spinel-bearing lherzolite, harzburgite and wehrlite. Chemical composition of olivine and two pyroxenes shows similar Mg# ranges, providing evidence of mineral equilibrium. Geothermobarometic estimates give depths in the spinel peridotite stability field (35-50 km, 10-15.2 kbar), and temperatures of 961-1185 °C. Major element mineral melting models in the lherzolite xenoliths record a low partial melting degree (up to 10%) although one harzburgite indicates a higher degree of melting (about 15%). The wehrlite sample could result from metasomatism by interaction with alkaline silica-undersaturated melts that replaced primary lherzolite orthopyroxene. Similar estimated pressures for peridotite mineral equilibration and for clinopyroxene megacryst/phenocryst crystallization in the host nephe- linite suggest the formation of mantle magma chambers, where alkaline magmas entrained megacrysts (cumulates) and peridotite wall-rocks.