Granites of the intracontinental termination of a magmatic arc: an example from the Ediacaran Araçuaí orogen, southeastern Brazil Leonardo Gonçalves a, ⁎, Fernando F. Alkmim a , Antônio C. Pedrosa-Soares b , Ivo A. Dussin b , Claudio de M. Valeriano c , Cristiano Lana a , Mahyra Tedeschi b a Departamento de Geologia, Escola de Minas, Universidade Federal de Ouro, Morro do Cruzeiro, 35400-000 Ouro Preto, MG, Brazil b Universidade Federal de Minas Gerais, Programa de Pós-Graduação em Geologia, CPMTC-IGC-UFMG, Av. Antônio Carlos 6627, Pampulha, 31270-901 Belo Horizonte, MG, Brazil c TEKTOS, Geotectonics Study Group, Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524/4006-A, 20559-900 Rio de Janeiro, RJ, Brazil abstract article info Article history: Received 28 January 2015 Received in revised form 7 July 2015 Accepted 29 July 2015 Available online 29 August 2015 Handling Editor: A.S. Collins Keywords: Granites Magmatic arc termination Ediacaran Rio Doce arc Araçuaí orogen The Araçuaí orogen of southeastern Brazil together with the West Congo belt of central West Africa form the Araçuaí–West Congo orogen generated during closure of a terminal segment of the Neoproterozoic Adamastor Ocean. Corresponding to an embayment in the São Francisco–Congo Craton, this portion of the Adamastor was only partially floored by oceanic crust. The convergence of its margins led to the development of the Rio Doce magmatic arc between 630 Ma and 580 Ma. The Rio Doce magmatic arc terminates in the northern portion of the Araçuaí orogen. Granitic plutons exposed in the northern extremity of the arc provide a rare opportunity to study magmatism at arc terminations, and to understand the interplay between calc-alkaline magma produc- tion and crustal recycling. The plutons forming the terminus of the arc consist of granodiorites, tonalites and monzogranites similar to a magnesian, slightly peraluminous, calcic- (68%) to calc-alkaline (24%), with minor alkali-calcic (8%) facies, medium- to high-K magmatic series. Although marked by negative Nb–Ta, Sr and Ti anomalies, typically associated with subduction-related magmas, the combined Sr, Nd and Hf isotopic data char- acterize a crustal signature related to anatexis of metamorphosed igneous and sedimentary rocks, rather than fractional crystallization of mantle-derived magmas. Zircon U–Pb ages characterizes two groups of granitoids. The older group, crystallized between 630 and 590 Ma, experienced a migmatization event at ca. 585 Ma. The younger granitoids, emplaced between 570 and 590 Ma, do not show any evidence for migmatization. Most of the investigated samples show good correlation with the experimental compositional field of amphibolite dehydration-melting, with some samples plotting into the field of greywacke dehydration-melting. The studied rocks are not typical I-type or S-type granites, being particularly similar to transitional I/S-type granitoids de- scribed in the Ordovician Famatinian arc (NW Argentina). We suggest a hybrid model involving dehydration- melting of meta-igneous (amphibolites) and metasedimentary (greywackes) rocks for magma production in the northern termination of the Rio Doce arc. The real contribution of each end-member is, however, a challeng- ing work still to be done. © 2015 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. 1. Introduction Major and trace element data, together with Lu–Hf in zircon, whole- rock Sm–Nd and Rb–Sr isotopes provide sensitive discriminators of tec- tonic and/or magmatic processes operating above subduction zones and within collisional orogens (Rudnick, 1995; Kemp and Hawkesworth, 2003; Kemp et al., 2006; Liu et al., 2013; Niu et al., 2013). These chemistry and isotope datasets can also be used to discriminate between a range of geological processes involved in the pre-collisional to collisional stages of an orogenic belt evolution, such as crustal reworking, crust–mantle inter- actions, and production of juvenile magmas from the mantle. The Araçuaí orogen of southeastern Brazil and the West Congo belt of southwestern Africa once lie in the central portion of West Gondwana (Alkmim et al., 2001). Together, they form the Araçuaí–West Congo orogen (AWCO), generated during closure of a terminal branch of the Neoproterozoic Adamastor Ocean (Pedrosa-Soares et al., 1992, 2001; Brito Neves et al., 1999; Cordani et al., 2003; Alkmim et al., 2006). Em- placement of ophiolite slivers, development of intra-oceanic and continental-margin magmatic arcs, and collision of the plates represent- ed by the São Francisco–Congo, Paranapanema, Rio de la Plata and Kalahari cratons record the Adamastor Ocean closure from the Cryogenian to Ediacaran periods (e.g., Pedrosa-Soares et al., 1998, 2011; Campos-Neto, 2000; Alkmim et al., 2001, 2006; Basei et al., Gondwana Research 36 (2016) 439–458 ⁎ Corresponding author. Tel.: +55 31 87101840. E-mail addresses: leonardogeologo@hotmail.com, leonardo@degeo.ufop.br (L. Gonçalves), ffalkmim@gmail.com (F.F. Alkmim), pedrosa@pq.cnpq.br (A.C. Pedrosa-Soares), ivodusin@yahoo.com.br (I.A. Dussin), cmval@uerj.br (C.M. Valeriano), cristianodeclana@gmail.com (C. Lana), mahyratedeschi@gmail.com (M. Tedeschi). http://dx.doi.org/10.1016/j.gr.2015.07.015 1342-937X/© 2015 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr