Contents lists available at ScienceDirect Ore Geology Reviews journal homepage: www.elsevier.com/locate/oregeorev Multi-isotope survey on the metallogenesis of the hydrothermal Co-Ni deposits in the Alpine Central Pyrenees of Spain J. Manuel a,b , I. Subías c, ⁎ , I. Fanlo c , E. Arranz c , F. Gervilla d,e a FERROANGOL, Caixa Postal 2692, Rua Joao de Barros 26, Luanda, Angola b Dpto. Geologia, Universidade Agostinho Neto, Avenida 4 De Fevereiro 71 244, Luanda, Angola c Departamento de Ciencias de la Tierra, Universidad de Zaragoza, Pedro Cerbuna, 12, 50009 Zaragoza, Spain d Departamento de Mineralogía y Petrología, Universidad de Granada, Avda. Fuentenueva s/n, 18071 Granada, Spain e Instituto Andaluz de Ciencias de la Tierra (UGR-CSIC), Avda. Palmeras, 4, Armillas, 18100 Granada, Spain ARTICLE INFO Keywords: Co-Ni High-T deposits Black shales REE Isotopes Dating ABSTRACT Thrust systems, related to thin-skinned tectonics are the main structural control for the development of Co-Ni deposits (Co-Ni arsenides, diarsenides and sulpharsenides) in the Alpine Central Pyrenees. Co-Ni ores occur in the hanging wall of these thrusts, hosted either by carbonate (San Juan de Plan and Crescencia mines) or siliciclastic rocks (Solita Mine), whereas the footwall is formed by black shales. Previous studies have applied graphite geothermometry and crystal-chemical criteria (the presence of alloclasite and the extent of the co- baltite–gersdorffite solid-solution) to determine that the complex assemblages of the studied deposits were formed at temperatures between 300 °C and 600 °C. The possible sources of the mineralizing fluids and metals have been investigated with a multi-isotope approach. Stable isotope data (C, O) support a primary magmatic source for the ore-forming fluids although interaction with both the Variscan black shales and carbonate host- rocks is also evidenced. Nd and Sr isotope compositions suggest that these fluids reacted with basement silici- clastic and igneous lithologies (and to a lesser extent with carbonate rocks). This reaction scavenged sulfur from the Variscan basement as a whole (positive δ 34 S values) and specifically from the underlying local black shales (negative δ 34 S values) and local magmatic rocks (δ 34 S values close to 0‰). Metals were extracted also from the Variscan black shales underneath each deposit, as suggested by the close correspondence between the metal ratios in the Co-Ni deposits and in the underlying black shales. The ore-forming activity responsible for the studied Co-Ni deposits spans an age range (Upper Cretaceous, 86 ± 27 Ma) similar to that of other high temperature events, developed in a context of thinned crust in the Pyrenean realm (i.e. High T/low P metamorphism, mantle exhumation and alkaline magmatism). These pro- cesses promoted high temperature hydrothermalism and formation of ore deposits, prior to the tectonic inver- sion and thrusting during the compressive stage. 1. Introduction The Pyrenean Axial Zone (PAZ) is the geotectonic unit that contains the greatest variety of mineralization types in the Pyrenees. It includes a wide range of metal commodities such as lead-zinc, fluorite, barite, silver, gold, tungsten, lithium and REE, formed by distinct geological processes (Pouit, 1986; Romer and Soler, 1995; Alfonso and Melgarejo, 2008; Subías and Fernández-Nieto, 1995; Johnson et al., 1996; Subías et al., 1997; Fanlo et al., 1998; Mateo et al., 2010, among others). Despite this diversity, the PAZ has been of minor mining importance with only few economically significant deposits so far. Recent mineralogical and microtextural investigations have been carried out on a Co deposit in Silurian terranes of San Juan de Plan (Fanlo et al., 2004), on a Co deposit related to an unconformity above Silurian black shales (Manuel, 2015) and on a small Ni occurrence in Devonian terranes (Crescencia mine; Fanlo et al., 2006). These studies demonstrated that the main assemblage of ore minerals formed at temperatures between 300 °C and 600 °C that are maybe related to a residual magmatic fluid migrating through the sedimentary pile. Nevertheless, textural relationships among ore minerals in Crescencia mine display signs of re-equilibration processes, which lead to changes in composition of ore minerals (Fanlo et al., 2006). So, we must evaluate if the deduced temperatures are the con- sequence of re-equilibration or, on the contrary, they are the result of a https://doi.org/10.1016/j.oregeorev.2018.01.030 Received 7 June 2017; Received in revised form 20 January 2018; Accepted 25 January 2018 ⁎ Corresponding author. E-mail address: isubias@unizar.es (I. Subías). Ore Geology Reviews 94 (2018) 225–238 Available online 03 February 2018 0169-1368/ © 2018 Elsevier B.V. All rights reserved. T