Unconventional non-magmatic sulfur source for the Mazarrón Zn–Pb–Cu–Ag–Fe epithermal deposit (SE Spain)

Esteban-Arispe, I., Velasco, F., Boyce, A. J. , Morales-Ruano, S., Yusta, I. and Carrillo-Rosúa, J. (2016) Unconventional non-magmatic sulfur source for the Mazarrón Zn–Pb–Cu–Ag–Fe epithermal deposit (SE Spain). Ore Geology Reviews, 72, pp. 1102-1115. (doi: 10.1016/j.oregeorev.2015.10.005)

Abstract

The present study shows the existence of textural, mineralogical, microthermometric and isotopic data that evidences processes such as thermochemical sulfate reduction (TSR) that are not typical features of volcanic-hosted epithermal deposits formed at shallow submarine and/or subaerial environments. Geological evidence and mineralogical, fluid inclusion temperature and geochemistry data suggest that the Mazarrón Zn–Pb–Cu–Ag–Fe deposit is a volcanic-hosted epithermal deposit. It is hosted by dacites with different alteration halos: K–Ar dating of illite from the argillic alteration gives an age of 9.7 ± 1.2 Ma, which suggests that mineralization took place very close to the volcanism. The fluid inclusion study in the ore veins shows epithermal temperatures (between 190 and 260 °C), but moderate salinities, between 12 and 18 wt.% NaCl eq., compatible with mixing between surface waters and polygenic deep hydrothermal fluids. Evolution of the hydrothermal activity shows the existence of three stage of mineralization: in the first and last stages, with Fe-sulfides as main phases, mineralization was mainly formed by interaction between basinal fluids that leached Triassic sulfates (+ surface waters), and C-bearing reduced deep waters. During interaction of both fluids, the sulfur was subjected to extreme and geologically unusual fractionation under TSR conditions, with ranging from − 2.9 to + 28.4‰ δ34S, reaching exceptional values up to + 53‰ δ34S. The intermediate stage is mainly formed by sphalerite–galena–chalcopyrite–fahlore bearing sulfides; this event is compatible with the influx of a magmatic fluid discharge. Finally, this study suggests that Mazarrón could be classified as an intermediate sulfidation deposit.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Boyce, Professor Adrian
• Authors: Esteban-Arispe, I., Velasco, F., Boyce, A. J., Morales-Ruano, S., Yusta, I., and Carrillo-Rosúa, J.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Ore Geology Reviews
• Publisher: Elsevier B.V.
• ISSN: 0169-1368
• ISSN (Online): 1872-7360
• Published Online: 09 October 2015