http://www.mantleplumes.org/WebpagePDFs/Mexico2.pdf
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Introduction
The Trans-Mexican Volcanic Belt (TMVB) is the Neogene volcanic arc built on the southern edge of the North American plate (Ferrari et al., 1999) (Figure 1). TMVB volcanism presents a wide range of chemical compositions. The geochemical signature of fluids from the subducting plate varies strongly and lavas with a slab melting fingerprint have been reported from several locations. Small amounts of lavas with an intraplate (or OIB) signature are found side by side with those with a subduction signature and with similar ages. In addition, seismicity associated with the subducting Cocos plate is abundant in the forearc region but ends rather abruptly just to the south of the TMVB at around 100 km depth (Figure 1) where the upper mantle has a relatively low density and high temperature. The geochemical diversity and absence of seismicity beneath the TMVB prompted several workers to develop genetic models at variance with a classic subduction scenario.
http://www.mantleplumes.org/Mexico2.html
