Jarosita y minerales afines en el depósito epitermal de Palai-Islica (Carboneras, Almería). Geoquímica e implicaciones genéticas

Abstract

En el presente trabajo se describen las características texturales, químicas e isotópicas de la jarosita y de distintos sulfatos relacionados del depósito epitermal de Au-Cu de Palai-Islica (Almería) y se discute su significado e implicaciones genéticas.

Barite and great quantities of Fe±Al sulfates (jarosite, natrojarosite, natroalunite and aluminite) together gypsum characterize the latest stages of the Au-Cu, Tertiary volcanic related, epithermal mineralisation of Palai-Islica. The Fe±Al sulfates present at the top of the mineralisation have a complex chemistry: an almost complete Na+-K+, an incomplete Fe3+-Al3+ solid solutions and uncommon substitution vector (PAsPbS-2(NaK)-1). The textural relations show an AlFe, accompanied for a pH decrease, and a more hypothetical KNa trends. The S and O isotope study is in accordance with a evolution from warm marine waters (± magmatic input) which precipitate barite after the ore episode to meteoric relatively cool waters. The product of these last waters are gypsum and the Fe±Al sulfates. As show the isotope results, the source of S for this sulfates is the oxidation of sulfides. In addition, a H2S input from hydrothermal fluids has also been deduced to exist since the great abundance of the sulphates, the scarcity of sulfide oxidation features and the presence of fluid inclusions in gypsum that not homogenize until gypsum dehydration.