Original paper

The origin of the tourmaline-turquoise association hosted in hydrothermally altered rocks of the Kuh-Zar Cu-Au-turquoise deposit, Damghan, Iran

Taghipour, Batoul; Mackizadeh, Mohammad Ali

Abstract

The Kuh-Zar Cu-Au-turquoise deposit is located within the Torud-Chah Shirin magmatic arc (middle Eocene). The rocks exposed in the mining area consist of andesite, dacite, pyroclastics and diorite to granodiorite. Petrological studies show they have a typical arc geochemical signature. Based on their main mineral assemblages that encompass quartz, sericite, pyrite, tourmaline, alunite, turquoise, jarosite, the following hydrothermal alteration zones have been identified: propylitic, argillic, phyllic, advanced argillic and sillicic. The rare association of tourmaline and turquoise is an outstanding feature of this deposit. Electron probe microanalysis indicates that the tourmaline belongs to the schorlite-dravite group. The B-bearing fluids were sourced from metapelites and metapsammites coexisting with Al- saturated phases. It is probable that the tourmaline was generated from hydrothermal fluids affecting sericites from the phyllic alteration zone. Mineral reactions and stable isotope data (δ18O and δD) for turquoise indicate that a final oxidation stage of primary sulfides resulted in the development of an acid-sulfate mineral assemblage (including turquoise) on overgrowing pre-existing mineral assemblages.

Keywords

advanced argillicalterationo and h stable isotopetourmalineturquoise