Constraints on the origin of the cenozoic intraplate aldama volcanic field, tamaulipas, NE Mexico

The Cenozoic Aldama Volcanic Field (8-0.24 Ma) is located on the southeastern margin of the Sierra de Tamaulipas and is the largest field of the Eastern Mexican Alkaline Province. It contains cinder cones, tuff rings, maars, and simple cones, as well as widespread lava flows. The volcanic rocks are geochemically characterized as alkali basalts, subalkaline basalts, trachybasalts (potassic and hawaiites), latites to trachytes, and grouped in six rock types according to their Mg-content and normative composition: (a) Alkaline near-primary rocks, (b) Alkaline basic rocks, (c) Alkaline intermediate rocks, (d) Subalkaline near-primary rocks, (e) Subalkaline basic rocks, and (f) Subalkaline intermediate rocks.Trace elements and isotopic ratios show that the source of the basaltic melts displays asthenospheric characteristics and stability conditions, indicating that the partial melting (<5%) occurred in lithospheric levels within the spinel stability depth. The coexistence in time and space of alkaline and subalkaline rocks could be explained by selective alkali metasomatism of a regional HFSE and REE-enriched OIB-like source. The magma generation occurred in a typical continental intraplate setting, associated with mantle disturbances produced by the eclogitization and detachment of the Hess conjugate subducted under NE Mexico. Some alkaline and subalkaline melts evolved to intermediate members by fractional crystallization.