Contents lists available at ScienceDirect Journal of South American Earth Sciences journal homepage: www.elsevier.com/locate/jsames Geochemistry of Mesozoic volcanic rocks from the Fresnillo area (Chilitos Formation), Zacatecas, Mexico: Implications for the magma source and tectonic setting Sanjeet K. Verma a,∗ , Erik Emmanuel M. Torres b , Vivek P. Malviya c , José Ramón Torres-Hernández d , Darío Torres-Sánchez b , Beatriz A. Rivera-Escoto e , Pankaj Mehta f a División de Geociencias Aplicadas, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), Camino a la Presa San José 2055, San Luis Potosí 78216, Mexico b Posgrado de la División de Geociencias Aplicadas, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), Camino a la Presa San José 2055, San Luis Potosí 78216, Mexico c 24E Mayur Residency Ext., Indra Nagar, Lucknow 226015, India d Instituto de Geología, Universidad Autónoma de San Luis Potosí, Manuel Nava No. 5. Zona Universitaria, 78240, San Luis Potosí, S.L.P., Mexico e División de Materiales Avanzados, Instituto Potosino de Investigación en Ciencia y Tecnología (IPICYT), Camino a la Presa San José # 2055, Col. Lomas 4a Sec., San Luis Potosí, SLP 78216, Mexico f Department of Environmental Sciences, Central University of Jammu, J&K, 181143, India ARTICLEINFO Keywords: Geochemistry Volcanic rocks Back-arc basin Petrogenesis Tectonic setting Chilitos Formation ABSTRACT Geochemical data from Early Cretaceous volcanic rocks (ultra-basic, basic, intermediate) from the Fresnillo area (Chilitos Formation), Zacatecas, are presented in this study. These rocks are characterized by variable SiO 2 = 38.1–61.7 wt %, Al 2 O 3 = 17.5–27.2 wt %, and MgO = 0.21–6.4 wt % with the Mg# = 20.6–78.9. They are infuenced by variable degrees of hydrothermal alteration, being the propylitic more dominant than argillic alteration. The geochemistry displays strong enrichment in light rare earth elements (LREEs) and large ion lithophile elements (LILEs). Moreover, a depletion in high feld strength elements (HFSEs; e.g., Nb, Ta, Ti) and nearly fat heavy rare earth element (HREE) patterns are observed. Negligible or absence negative Eu anomalies indicate that fractional crystallization of plagioclase played an insignifcant role during the magma evolution. The geochemical features suggest that volcanic rocks are derived from partial melting of an enriched mantle source that has experienced assimilation (low degree) and fractional crystallization. The low La/Nb (0.68–2.23) and Nb/Y (0.19–0.69) ratios, relatively high Zr/Y (3.68–10.56) and Th/Ta (1.03–3.65) ratios, and progressively enriched normalized patterns clue an island arc and most likely a back-arc basin environment for the Chilitos Formation in the Fresnillo area. New multidimensional discrimination diagrams indicate a mid-ocean ridge to island arc setting. A new tectono-magmatic model combined with previous geological observations indicate that the Chilitos Formation was formed in a back-arc tectonic setting and was part of the Guerrero terrane during the Late Jurassic to Early Cretaceous time. 1. Introduction The Fresnillo area is situated in the state of Zacatecas on the Mexican plateau and is bounded by the Mesa Central and Sierra Madre Occidental provinces (Fig. 1a and b). This area is a historically im- portant center for silver, lead, and zinc production (MacDonald et al., 1986) and contains a variety of fresh and hydrothermally altered ig- neous rocks. The oldest units in the area are Mesozoic marine sediments and mafc rocks that are unconformably overlain by mid-Paleogene felsic volcanics (Lang et al., 1988). Previous studies performed in the Fresnillo area have focused mainly on its regional geology, cartography, stratigraphy (Martínez, 1973; de Cserna, 1976; García et al., 1991; Romàn and Rìos Vasquez, 2004) and metallogeny (MacDonald et al., 1986; Lang et al., 1988; Ruvalcaba-Ruiz and Thompson, 1988; Lucio, 1990; Simmons, 1991; Velador et al., 2010). De Cserna (1976) pre- sented the area's general geology and explained the volcano-sedimen- tary succession in the Fresnillo area that is tentatively correlated with the Chilitos Formation and is mainly composed of pillowed basalt, https://doi.org/10.1016/j.jsames.2019.102351 Received 22 July 2019; Received in revised form 4 September 2019; Accepted 4 September 2019 ∗ Corresponding author. E-mail addresses: sanjeet.verma@ipicyt.edu.mx, sanjeet_vrm@yahoo.com (S.K. Verma). Journal of South American Earth Sciences 96 (2019) 102351 Available online 10 September 2019 0895-9811/ © 2019 Elsevier Ltd. All rights reserved. T