Gold mineralisations in the Canan area, Lepaguare District, east-central Honduras: Fluid inclusions and geochemical constraints on gold deposition E. Salvioli-Mariani a, ⁎, L. Toscani a , T. Boschetti a , D. Bersani a , M. Mattioli b a Dipartimento di Fisica e Scienze della Terra “Macedonio Melloni”, Università di Parma, Viale Parco Area delle Scienze 157/A, 43124 Parma, Italy b Dipartimento di Scienze della Terra, della Vita e dell'Ambiente, Università di Urbino “Carlo Bo”, Campus Scientifico E. Mattei, 61029 Urbino, Italy abstract article info Article history: Received 17 November 2014 Revised 12 May 2015 Accepted 3 August 2015 Available online 5 August 2015 Keywords: Fluid inclusions Gold Sulphidation Canan Honduras Gold mineralisations in the Canan area (Honduras) occur within altered metamorphic rocks crossed by quartz veins which filled the fractures where the hydrothermal fluids carrying gold flowed. Quartz crystals of the veins contain abundant fluid inclusions which have been divided into four main types on the basis of the petro- graphic features and microthermometric data. The association of L-rich and V-rich inclusions with the same major components supports boiling at the time of entrapment. The trapped hydrothermal fluid consists of an aqueous solution (0.9–4.8 wt.% NaCl equivalent) plus a CO 2 –CH 4 -bearing bubble. Some fluid inclusions contain graphite of hydrothermal origin. Microthermometric and spectroscopic data on fluid inclusions indicate that hy- drothermal fluids carrying gold were at T = 300 °C, P = 500–1400 bar, log fO 2 ~ −37.6 ± 2.5 and with a pH value of 2.9 ± 0.4. Large amounts of sulphides (mainly pyrite) are associated with gold. We infer that Au was transported as Au–S complex, in particular as Au(HS)°. The activity of sulphur in the hydrothermal fluids was at least 10 −2 . The precipitation of gold can be related to several processes that reduced the stability of AuHS°: 1) boiling and vapour loss following the pressure drop caused both by fracture opening and fluid uprise, 2) sulphidation as a result of the presence of Fe 2+ (and other metal cations) from the mineralogical alteration (mainly of biotite and chlorite) in the wall-rocks and 3) hydrothermal alteration of feldspars and micas into ka- olinite and diaspore with increase in pH of the hydrothermal fluids. The mineralogical, petrological, geochemical features and the geological setting are broadly consistent with those of orogenic-type gold deposits. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Over the past decades, several studies on the relationships between the gold deposits hosted in quartz veins and alteration halos due to hydrothermal fluid infiltration have been published (e.g., Andrada de Palomera et al., 2012; Boiron et al., 1991; Cepedal et al., 2013; Esmaeily et al., 2012; Garofalo et al., 2002; Phillips and Powell, 2009). Intensive host-rock alteration around the quartz veins shows distinct mineralogical changes that are indicative of metasomatic processes due to hydrothermal fluids. The amount of precipitation of native elements and the type of hydrothermal alteration minerals are strongly dependent on the physical–chemical nature of the mineralising fluids and the host-rock composition. In several gold deposit, the mineral as- semblages occurring in the quartz veins and in the associated altered wall-rocks have been described (e.g., Botros, 2004; Callaghan, 2001; Deksissa and Koeberl, 2005; Miur, 2002). On the contrary, the chemical features of the fluids associated with the gold deposition and rock alter- ation are not yet fully understood (Klein et al., 2002; Yang et al., 2006; Su et al., 2008). The study of fluid inclusions in minerals from hydrothermal veins is very important to infer the composition of the fluids that have deposited gold and other associated metals. The fluid inclusions contain low- salinity mixed aqueous–carbonic fluids, where H 2 O and CO 2 are the major molecular components, CH 4 is a common minor component, and N 2 is present in trace (Groves et al., 2003, and references therein; Ridley and Diamond, 2000). The CO 2 concentration is always greater than 5 mol%; the relative amounts of H 2 O, CO 2 , and CH 4 may vary as a consequence of phase separation (boiling) during pressure fluctuations (Spooner et al., 1987). The aqueous component of the fluids contains 1–15 wt.% NaCl equivalent (Ridley and Diamond, 2000). Other types of fluids are H 2 O-poor carbonic fluids and low- to moderate-salinity aqueous fluids. Pure carbonic fluids or pure aqueous low-salinity fluids are rare (Ridley and Diamond, 2000). However, there is no scientific consensus regarding the origin of Au-carrying fluids. In the orogenic gold deposits, the distinction between magmatic and metamorphic ori- gin for fluids is difficult due to the close association between magmatic and metamorphic rocks and the strong structural control. Furthermore, in such a complex situation, fluids from different sources may exten- sively mix along their pathways (Ridley and Diamond, 2000). The Honduras region (Central America) is a well-known metallogenic province, which is represented by several areas of hydrothermally altered Journal of Geochemical Exploration 158 (2015) 243–256 ⁎ Corresponding author. E-mail address: emma.salviolimariani@unipr.it (E. Salvioli-Mariani). http://dx.doi.org/10.1016/j.gexplo.2015.08.003 0375-6742/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Geochemical Exploration journal homepage: www.elsevier.com/locate/jgeoexp