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Departamento de Ingeniería Minera, Escuela Universitaria de Ingeniería Técnica Minera, C/ Jesús Rubio 2, 24004 León, Spain
Department of Geology and Geophysics, University of Adelaide, South Australia 5005, Australia
Departamento de Física-Geología, Universidad de Las Palmas de G.C., Aptdo. 550, 35080 Las Palmas de Gran Canaria, Spain
Departamento de Ingeniería Geológica, Escuela Técnica Superior de Ingenieros de Minas, C/ Ríos Rosas 21, 28003 Madrid, Spain
Corresponding author: e-mail, dimfgf{at}unileon.es
The Zn-Pb deposits of the southeastern area of the Picos de Europa province display an epigenetic hydrothermal mineralization of moderate temperature hosted by intensely dolomitized limestones of Carboniferous age. They are structurally and lithologically controlled since the three phenomena of fracturing, dolomitization, and mineralization are interrelated. Two types of mineralization have been found: type I, granular dark brown-colored sphalerite, galena, and dolomite, and type II, toffee-colored sphalerite, galena, and calcite. Type II mineralization is later than type I.
The Aliva and Andara deposits are the two largest in the Picos de Europa area, and both contain type I and type II styles of mineralization. Fluid inclusion studies indicate that the mineralizing solutions for both stages were similar and had trapping temperatures between 170° and 200°C and salinities around 15 wt percent NaCl equiv. However, microthermometric data from sphalerite (I and II), dolomite I, calcite II, and fluorite samples show various stages of circulation and trapping of brines with spatial and temporal variations in salinity and temperature.
Calcite and dolomite from the mineralization have 
13CPDB
values between 1 and 2.9 per mil (13C
CO2
= –0.8–1.1
), and 18OSMOW
values between 11.5 and 16.2 per mil (18OH2O
varied from 0.7–1.9). Sulfides show 34S
values between 12.9 and –16.8 per mil (34Sfluid
for the Aliva deposit ranged between 13.4 and –2.5). The combined stable
isotope data indicate evolved marine waters. Isotope evidence suggests that the
mineralizing fluids were probably formation waters of the Palentine zone and the
Picos de Europa province sediments. During the Permian, possibly during
extensional tectonic phases, these brines moved toward and through the Picos de
Europa province along late Hercynian fractures giving rise to the Zn-Pb
mineralization.
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