CO 2 fluid inclusion barometry in mantle xenoliths from central Mexico: A detailed record of magma ascent Gilles Levresse a, ⁎, Karina Elizabeth Cervantes-de la Cruz a , José Jorge Aranda-Gómez a , María Guadalupe Dávalos-Elizondo a , Sergio Jiménez-Sandoval b , Francisco Rodríguez-Melgarejo b , Leticia Araceli Alba-Aldave c a CGEO-UNAM; Campus Juriquilla, Juriquilla, Querétaro 76320, Mexico b Centro de Investigación y de Estudios Avanzados del I.P.N., P.O. Box l 1-798, Querétaro 76001, Mexico c Instituto de Geología-UNAM; Distrito Federal, 04510, Mexico abstract article info Article history: Received 23 April 2015 Accepted 18 November 2015 Available online 30 November 2015 Chemical equilibrium and CO 2 fluid inclusion barometry are complementary techniques, as they register differ- ent geological processes. Chemical equilibrium barometry records the pressure at the site where the xenoliths were incorporated into the transporting magma, but it is not a sensible technique to document magma ascent. CO 2 fluid inclusion pore pressure in xenoliths does not register the P–T conditions in the source area, but it allows illustrating a fairly detailed record of different geological processes that occurred during the magma transport to the surface and as the eruption proceeded. Mantle xenoliths from Ventura–Espíritu Santo and Santo Domingo volcanic fields contain dominant CO 2 pseudosecondary and secondary fluid inclusions trapped in cpx and ol. Cpx chemical equilibrium pressures indicate a maximum pressure of 10 kbar for the source area. Pore pressures obtained in CO 2 pseudosecondary and secondary fluid inclusions show a distribution with three maximum peaks at ca. 8, 5–7, and less than 3 kbar. A comparison with geophysical models for the area where the xenoliths- bearing volcanoes are located shows that the three peaks in the pore pressures correspond to three physico- chemical transitions within the continental crust. Likewise, the pore pressure suggests that rapid magma ascent is momentarily interrupted by these discontinuities, a fact that allows the formation of new fluid inclusions and the re-equilibration of some of the inclusions already present in the primary minerals of the xenoliths. © 2015 Elsevier B.V. All rights reserved. Keywords: Maar Xenoliths P–T evolution Fluid inclusions barometry Mexico 1. Introduction Xenoliths included in the pyroclastic successions of mafic alkalic maars are fairly well preserved rock samples from otherwise unreach- able regions in the upper mantle and lower crust beneath the volcanoes that brought them to the surface. The rapid ascent of intraplate mafic magmas allows that the included mantle and crustal xenoliths arrive to the surface with minimum mineralogical changes associated with re-equilibration and/or serpentinization (e.g. Spera, 1984; Luhr and Aranda-Gómez, 1997; Peslier et al., 2015). However, these xenoliths commonly display some changes, such as interstitial glass or “spongy” border zones in pyroxenes, induced by localized partial melting produced by decompression and/or by reaction of the xenoliths with the host magma. These secondary features overprinted on the meta- morphic mineral paragenesis and/or textures suggest a more complex ascent history (Nielson-Pike and Schwarzman, 1976). Putirka (2008) inferred various pressures recorded in the Hawaiian lavas with the pyroxene + liquid equilibrium methodology. The author interprets the different pressures obtained as the record of magma ascent from the Moho depth and its transit through the plastic flow to brittle faulting transition (Rutter, 1986) in the middle crust, which is influenced by changes of the mechanical properties of the rocks where the volcanic conduit crosses. Fluid inclusions provide a large amount of valuable information on the origin and forming condition of host minerals and rocks where they occur. Most mantle-derived minerals contain CO 2 as a dominant component in their fluid inclusions, although CO 2 is not the only com- ponent (e.g. Roedder, 1965, 1983; Andersen and Neumann, 2001; Hidas et al., 2010; Berkesi et al., 2012; Frezzotti et al., 2012a; Frezzotti and Touret, 2014). The density of CO 2 in a CO 2 fluid inclusion in a mantle mineral is a well-proven geobaromter. Estimation of depth from which the mantle rocks are carried up by ascending magma provides impor- tant information about the chemical–physical properties of the mantle (Longpré et al., 2014). Fluid inclusions found in peridotite xenoliths can be used to infer key information regarding the depth of xenolith en- trapment in ascending host magma and about the nature of the metaso- matic agents that may have modified the original lithology in the source area (Peccerillo et al., 2006). To understand the origin and evolution of the xenoliths and the ascent history of the magmas, only unmodified Journal of Volcanology and Geothermal Research 310 (2016) 72–88 ⁎ Corresponding author. E-mail address: glevresse@geociencias.unam.mx (G. Levresse). http://dx.doi.org/10.1016/j.jvolgeores.2015.11.012 0377-0273/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Volcanology and Geothermal Research journal homepage: www.elsevier.com/locate/jvolgeores