First reference of pyrite framboids in a Hg-Sb mineralization: The Valle del Azogue mineral deposit (SE Spain)

The Valle del Azogue mineral deposit is an interesting example of Upper Miocene, Hg-Sb-(base metal sulfides) hydrothermal mineralization in SE Spain. The cap of the deposit is a hydrothermal breccia, stretching approximately 1 km N-S, NE-SW and 500 m E-W. It consists of kaolinite, quartz, baryte, calcite, sericite, gypsum and minor base-metal sulfides (sphalerite, pyrite), and exhibits significant anomalies of Fe (Fe (Fe2O3 > 6 wt %), Mn (>600 ppm), Ba (>4000 ppm), Hg (>3000 ppm), Sb (>10,000 ppm), Zn (>2000 ppm), Ag (>100 ppm), As (> 800 ppm) and Pb (>1200 ppm). Beneath the hydrothermal breccia a mineralized stockwork exists displaying a simple paragenesis of quartz, baryte, stibnite, cinnabar, sphalerite, siderite, chalcopyrite and pyrite. Vein-related hydrothermal alteration is poorly developed and it is only represented by the presence of silica followed by sericite. The most peculiar characteristic of the Valle del Azogue is that it is the first place where pyrite framboids have been found forming part of a Hg-Sb mineralization. In this work, new data about the Valle del Azogue mineral deposit are given taking into account its metallogenetic position in the regional mineralizing hydrothermal framework. In addition, the detailed study of the pyrite framboids is carried out, stressing their main mineralogical, textural and chemical characteristics, and proposing the existence of an evolutional textural pattern from the typical spheroidal framboids to the development of euhedral pentagonal pyrite monocrysts.