Abstract
Two drillings carried out at Cerro Prieto (Province of Malaga), together with additional geophysical data, revealed the existence of an igneous body formed of rock-types previously unknown in the Subbetic zone. The recovered rocks, emplaced under hypoabyssal conditions, are predominantly porphyric, containing olivine, diopside and TiO2-rich phlogopite phenocrysts (up to 1-2 mm in size) within a micro-to-hypocrystalline groundmass composed of alkali-feldspar, diopside, phlogopite and abundant magnetite, and could be classified as alkali minettes lam- prophyres. They contain numerous xenocrysts corroded by the magma and centimetric ultrafemic xenoliths deriv- ing from the mantle. Clinopyroxenes yield crystallisation temperatures from about 1150 to 1320o C and pressures ranging from about 4 to 17 kbar, suggesting 50 km as the minimum depth of the magma sources. The chemical compositions of these lamprophyres are similar to intra-plate alkali-basalts, derived from oceanic-island-basaltic-type highly metasoma- tized mantle sources. 40 Ar/ 39 Ar dating of a phlogopite mineral separate gave an age of 217±2.5 Ma. However, these 1 4
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