This study will investigate the isotopic compositions (Rb-Sr, Sm-Nd, Pb, and O) of volcanism in the central Mexican volcanic Belt (MVB) where a diverse volcanic suite has been characterized, yet no isotopic data is available. This project will contribute to current understanding of subduction-related processes by evaluating the genesis and evolution of three compositionally distinct volcanic series that have erupted contemporaneously in this region. The first goal of this is to determine whether geochemically diverse volcanism in the central MVB can be attributed to systematic variations in the characteristics of the mantle source. The central MVB is an optimal place to study the connection between mantle processes and volcanism in subduction-related arcs for three significant reasons. 1. The exposure of fresh lavas and scoriae is excellent and three distinct compositional types have already been well characterized with respect to age, volume, and distribution. 2. The tectonic setting is constrained including slab angle, depth to slab, and convergence rate. 3. The shallow (sub-horizontal) subduction angle produces an ~200 km wide arc, which provides excellent spatial resolution to expose the systematic spatial distribution of the three volcanic series. The second goal is to investigate the modification of mantle-derived magmas during their ascent through the crust, and evaluate the contribution of crystal fractionation and crustal assimilation to their evolution. Isotopic data, major and trace element geochemical data, and storage constraints (T, P, fO2, and wt% H2O) available from high quality water-saturated phase equilibria experiments, will allow quantification of the time-scales of some of these magmatic processes. The third goal of this project will be to use the isotopic compositions of the crustally contaminated lavas to expose information about the basement terranes through which they have erupted. This data will be used to constrain the boundaries between the basement terranes of central Mexico. This work will be conducted at the University of Colorado, Boulder in collaboration with Professor G. Lang Farmer, an expert in the application of radiogenic isotope data to igneous petrology, sedimentary provenance determinations, and the tectonic evolution of the Earth's crust. Additionally, all of the necessary equipment and facilities will be readily available to the PI at University of Colorado, Boulder and CIRES (Cooperative Institute for Research in Environmental Sciences). The training of the investigator has been that of classical igneous petrology with emphasis on experimental studies and fieldwork. The POWRE award will allow the PI to optimize this necessary relocation by providing the opportunity for her to pursue new collaborations and skills, as well as contribute her unique perspective to the field of isotope geochemistry. The research will involve her in learning new analytical techniques (mass-spectrometry) and provide her with experience in the application of isotope geochemistry to a variety of problems, vastly increasing her versatility as a petrologist.