Contents lists available at ScienceDirect Chemie der Erde journal homepage: www.elsevier.com/locate/chemer Petrology, phase equilibria modelling, noble gas chronology and thermal constraints of the El Pozo L5 meteorite Pedro Corona-Chávez a, ⁎ , María del Sol Hernández-Bernal b , Pietro Vignola c , Rufino Lozano-Santacruz d , Juan Julio Morales-Contreras e , Margarita Reyes-Salas d , Jesús Solé-Viñas e , José F. Molina f a Universidad Michoacana de San Nicolás de Hidalgo, Instituto de Investigaciones en Ciencias de la Tierra, Edificio U, Ciudad Universitaria, Morelia, 58020, Mexico b Universidad Nacional Autónoma de México, Escuela Nacional de Estudios Superiores, Unidad Morelia, 58190, Mexico c Consiglio Nazionale delle Ricerche (CNR) – Istituto per la dinamica dei processi ambientali, via Botticelli 23, 20133 Milan, Italy d Universidad Nacional Autónoma de México, Instituto de Geología, Circuito interior Ciudad Universitaria, 04510, Mexico e Universidad Nacional Autónoma de México, Instituto de Geofísica, Unidad Morelia, 58190, Mexico f Departamento de Mineralogía y Petrología, Universidad de Granada, Spain ARTICLE INFO Keywords: Ordinary chondrite El Pozo Petrology Metamorphism Phase equilibria modelling Thermobarometry Cosmogenic ages ABSTRACT We present the results of physical properties, petrography, bulk chemistry, mineral compositions, phase relations modelling and Noble gases study of the meteorite El Pozo. The petrography and mineral compositions indicate that the meteorite is an L5 chondrite with a low shock stage of S2-S3. Heterogenous weathering was pre- ferentially along shock structures. Thermobarometric calculations indicate thermal equilibrium conditions be- tween 768 °C and 925 °C at ∼4 to 6 kb, which are substantially consistent with the petrological metamorphism type 5. A pseudosection phase diagram is relatively consistent with the mineral assemblage observed and PT conditions calculated. Temperature vs. fO 2 diagram shows that plagioclase compositional stability is very sen- sitive to Tschermack substitution in orthopyroxene, clinopyroxene and X An plagioclase during the high tem- perature metamorphic process. Based on noble gases He, Ne, Ar and K contents a cosmogenic exposure age CRE of 1.9 Myr was calculated. The 21 Ne would be totally cosmogenic, with no primordial Ne. The 21 Ne/ 22 Ne value (0.97) is higher than solar value. According to the cosmogenic Ne content, we argue that El Pozo chondrite originally had a pre-atmospheric mass of 9–10 kg, which would have been produced by a later collision after the recognized collision of the L-chondrite parent body ∼470 Ma ago. 1. Introduction Metamorphic or equilibrated chondrites (e.g. petrologic type 4–6), provide understanding about size and heating events acquired during accretional, collisional and fragmental processes (Grossman and Brearley, 2005; Huss et al., 2006). Although the degree of meta- morphism of chondrites groups is commonly referred to reliable clas- sification of petrologic types (Van Schmus and Wood, 1967), many textural and mineral reaction details are not well understood (Dunn et al., 2010). Ordinary chondrites show a vast variety of bulk chemistry that can lead to significant differences during the multiple metamorphic reaction series. Consequently, detailed textural and metamorphic phase equilibria modelling studies of natural ordinary chondrites could pro- vide new insights about reaction of solids metamorphic chondrites (Johnson et al., 2016). Two pieces totalling 460 g of the El Pozo meteorite were found in the Chihuahua State, Mexico (Grossman, 2000). Based on the pre- liminary mineralogy: olivine Fa 23.6 and pyroxene Fs 22.2 (Sánchez–Rubio and Reyes–Salas in Grossman 2000; Sánchez-Rubio et al., 2001), El Pozo meteorite is considered to be an ordinary chondrite belonging to the L group and petrologic type 5. Hernández-Bernal and Solé (2010) reported a whole rock K–Ar age of 3103 ± 16 Ma. A comparative Raman (RMP), infrared (IR) and X-ray diffraction (XRD) study identi- fied a common mineral assemblage of ordinary chondrite (Ostrooumov and Hernández-Bernal, 2011). However, petrography, modal abun- dances of minerals and bulk chemistry in the El Pozo chondrite are not yet described. In this work, we provide the first physical, chemical, petrological https://doi.org/10.1016/j.chemer.2017.12.003 Received 21 June 2017; Received in revised form 18 December 2017; Accepted 21 December 2017 ⁎ Corresponding author. E-mail addresses: pcorona@umich.mx (P. Corona-Chávez), msol_hernandez@enesmorelia.unam.mx (M.d.S. Hernández-Bernal), pietroevignola@gmail.com (P. Vignola), rufino@unam.mx (R. Lozano-Santacruz), moralesjuanjulio@gmail.com (J.J. Morales-Contreras), adelars@unam.mx (M. Reyes-Salas), jsole@unam.mx (J. Solé-Viñas), jfmolina@ugr.es (J.F. Molina). Chemie der Erde xxx (xxxx) xxx–xxx 0009-2819/ © 2018 Elsevier GmbH. All rights reserved. Please cite this article as: CORONA-CHÁVEZ, P., Chemie der Erde (2018), https://doi.org/10.1016/j.chemer.2017.12.003