Grenvillian massif-type anorthosite suite in Chiapas, Mexico: Magmatic to polymetamorphic evolution of anorthosites and their Ti-Fe ores A. Cisneros de León a,⇑ , B. Weber b , F. Ortega-Gutiérrez a , R. González-Guzmán b , R. Maldonado a , L. Solari c , P. Schaaf d , R. Manjarrez-Juárez b a Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510 Coyoacán D.F., Mexico b Departamento de Geología, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Baja California, Carretera Ensenada-Tijuana 3918, Zona Playitas, 22860 Ensenada, Baja California, Mexico c Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, 76230 Querétaro, Mexico d Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510 Coyoacán D.F., Mexico article info Article history: Received 21 July 2016 Revised 22 March 2017 Accepted 11 April 2017 Available online 18 April 2017 abstract Two meta-anorthosite inliers (20 km 2 each) were discovered on each side of the Polochic-Tonalá fault system within the Chiapas Massif Complex (CMC) in southeastern Mexico. The anorthosites occur com- monly associated to subordinate hornblendite, rutile-bearing ilmenitite, oxide-apatite-rich amphibolite and nelsonite. An absolute crystallization age for the anorthosite could not be precisely constrained due to the paucity and apparent resetting of the magmatic zircon. However, they are interpreted as rem- nants of a Proterozoic massif-type anorthosite complex older than 909 ± 27 Ma as suggested by U-Pb data and the striking geochemical similitudes (major, trace and REE, Sr-Nd isotopes; T DM = 1.39–1.45 Ga) to Stenian-Tonian massif-type anorthosites found elsewhere. A complex tectono-thermal history for the anorthosite suite is inferred from the discovery of abundant metamorphic zircon in all samples. Ubiquitous petrographic evidence suggests formation of secondary zircon from reactions involving bad- deleyite and srilankite (ZrTi2O 6 ) breakdown at different stages of the anorthosite suite evolution. Two generations of baddeleyite are recognized: (1) exsolution from igneous ilmenite and högbomite ([Mg, Fe 2+ ] 2 [Al,Ti] 5 O 10 ) during cooling, and (2) exsolution product from metamorphic rutile and högbomite during retrogression. U-Pb zircon data (LA-MC-ICPMS) of three comagmatic rocks, including one anortho- site sample, reflect the complex polymetamorphic nature observed in the petrographical evidence; con- cordant to sub-concordant ages spread in a range from 909 Ma to 242 Ma. Most U-Pb ages cluster around known regional metamorphic events at ’450 Ma and ’250 Ma. In addition, an age cluster at 600 Ma suggests a Neoproterozoic event, interpreted in terms of reheating of anorthosite during mafic intrusions associated to intra-plate rifting. Ó 2017 Elsevier B.V. All rights reserved. 1. Introduction Massif-type anorthosites are igneous rocks chiefly composed of plagioclase (>90%); together with mangerite, charnockite and gran- ite conform plutonic suites (AMCG) commonly found in Precam- brian terranes (2.1–0.9 Ga; Ashwal, 1993). The Grenville Orogeny (1.25–0.9 Ga) has been one of the main episodes of massif-type anorthosite magmatism on Earth. The distribution of these rocks as large belts and occurrence typically restricted to Stenian- Tonian times makes massif-type anorthosites excellent tracers in Rodinia supercontinent reconstructions (Li et al., 2008; Pisarevsky et al., 2003). However, their importance not only resides on its role in paleogeographic restorations, but also on their value as the main titanium ore deposit hosting rocks (Charlier et al., 2015). In Mexico, massif-type anorthosites and related rocks occur along a N-S trending region within isolated basement inliers. Expo- sures of massif-type anorthosites occur in the northern Tamaulipas state (Novillo Gneiss, Ortega-Gutiérrez, 1978; Trainor et al., 2011; inset Fig. 1); the central Hidalgo state (Huiznopala Gneiss, Lawlor et al., 1999) and in the southern Oaxaca state in the Guichicovi (Weber and Hecht, 2003; Weber and Köhler, 1999) and the Oaxa- can Complexes (Keppie et al., 2003; Ortega-Gutiérrez et al., 1995; Solari et al., 2003). http://dx.doi.org/10.1016/j.precamres.2017.04.028 0301-9268/Ó 2017 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: Institut für Geowissenschaften, Universität Heidel- berg, Im Neuenheimer Feld 236, 69120 Heidelberg, Germany. E-mail address: alejandro.cisneros@geow.uni-heidelberg.de (A. Cisneros de León). Precambrian Research 295 (2017) 203–226 Contents lists available at ScienceDirect Precambrian Research journal homepage: www.elsevier.com/locate/precamres