Metallogenesis of Zn-Pb Carbonate-Hosted Mineralization in the Southeastern Region of the Picos de Europa (Central Northern Spain) Province: Geologic, Fluid Inclusion, and Stable Isotope Studies

摘要

The Zn-Pb deposits of the southeastern area ofthe Picos de Europa province display an epigenetichydrothermal mineralization of moderate temperature hosted byintensely dolomitized limestones of Carboniferous age. They arestructurally and lithologically controlled since the threephenomena of fracturing, dolomitization, and mineralization areinterrelated. Two types of mineralization have been found: typeI, granular dark brown-colored sphalerite, galena, and dolomite,and type II, toffee-colored sphalerite, galena, and calcite. TypeII mineralization is later than type I.The Aliva and Andara deposits are the two largest in the Picosde Europa area, and both contain type I and type II styles ofmineralization. Fluid inclusion studies indicate that themineralizing solutions for both stages were similar and hadtrapping temperatures between 170 deg C and 200 deg C andsalinities around 15 wt percent NaCl equiv. However;microthermometric data from sphalerite (I and II), dolomite I,calcite II, and fluorite samples show various stages ofcirculation and trapping of brines with spatial and temporalvariations in salinity and temperature.Calcite and dolomite from the mineralization have#delta#~(13)C_(PDB) values between 1 and 2.9 per mil(#delta#~(13)C_(#SIGMA#_CO2) valence –0.8-1.1 perthousand), and #delta#~(18)O_(SMOW) values between 11.5and 16.2 per mil (#delta#~(18)O_(H_2O varied from 0.7-1.9per thousand). Sulfides show #delta#~(34)S values between 12.9and -16.8 per mil (#delta#~(34)S_(fluid) for the Aliva depositranged between 13.4 and-2.5 per thousand). The combinedstable isotope data indicate evolved marine waters. Isotopeevidence suggests that the mineralizing fluids were probablyformation waters of the Palentine zone and the Picos de Europaprovince sediments. During the Permian, possibly duringextensional tectonic phases, these brines moved toward andthrough the Picos de Europa province along late Hercynianfractures giving rise to the Zn-Pb mineralization.