Petrological Relationships between Mantle Xenolths and their Host Magmas in the Alkaline Province Mexico
Primitive Mantle normalized patterns are similar to extension-related mafic magmas. These patterns indicate that host magmas were generated in a highly-incompatible elements enriched Mantle zone. This is supported by an enrichment in light REE ([La/Yb]N = 10.827.1) and the behavior of immobile trace elements. The tectonomagmatic discrimination diagrams indicate that host magmas were generated in an intraplate environment.
Using a REE partial melting model, it was pointed out that Mantle represented by the xenoliths cannot reproduce the REE-patterns of the host magmas. After the application of an inverse melting model, the host magmas were generated in the spinel lherzolite stability field, in a more enriched zone (highly incompatible elements).
The xenoliths are spinel-lherzolites, harzburgites and rare dunites. They have are protogranular, nevertheless, a few xenoliths displayed protogranular- porphyroclastic transitional textures, indicating that the xenoliths come from stable zones with little or no deformation. The mineralogy (olivine + orthopyroxene + clinopyroxene ± spinel) is typical of unaltered Mantle nodules. The core and rim compositions in olivine range from Fo86 to Fo92, whereas orthopyroxenes are characterized by En8791 and clinopyroxenes by En4345-Fs2.749.31-Wo4951. Chromiferous spinels have Mg/(Mg + Fe+2) = 0.700.81 and Cr/(Cr + Al) = 0.100.35.
Primitive Mantle-normalized multielements diagrams and Chondrite-normalized REE patterns for xenoliths, pointed out that they represent an enriched Mantle for the SSCC area, and a lesser enriched Mantle for the ST.
The xenoliths equilibrated at 820-1190°C and from 10-25 kbar.