%0 Journal Article
%A Martín Crespo, Tomás
%A Vindel Catena, Elena
%A López García, José Ángel
%A Cardellach, Esteve
%T As–(Ag) sulphide veins in the Spanish Central System:further evidence for a hydrothermal event of Permian age
%D 2004
%@ 0169-1368
%U https://hdl.handle.net/20.500.14352/50080
%X The Spanish Central System (SCS) has been subjected to repeated deformation and fluid flow events which have producedboth sulphide-bearing and barren vein systems. Although several hydrothermal episodes took place between 300 and 100 Ma,fluid circulation during the Permian was especially important, giving rise to a range of different types of deposits. This studypresents a multidisciplinary approach leading to the characterisation of the chemistry and age of the hydrothermal fluids thatproduced the As–(Ag) mineralised stockwork of Mo´nica mine (Bustaviejo, Madrid). Fluid inclusion data indicate the presenceof two different fluids. An initial ore stage (I) formed from a low- to moderate salinity (3–8 wt.% eq. NaCl) H2O–NaCl–CO2–CH4 fluid, at minimum trapping temperature of 350±15 ºC and 0.3 kbar. A second H2O–NaCl fluid is found in three types offluid inclusions: a high temperature and low salinity type (340±20 ºC; 0.8–3.1 wt.% eq. NaCl) also associated to ore stage I, amoderate temperature and very low salinity type (160–255 ºC; 0–1.5 wt.% eq. NaCl) represented in ore stage III, and a verylow temperature and hypersaline type (60–70 ºC; 30–35 wt.% NaCl), unrelated to the mineralising stages and clearlypostdating the previous types. 40Ar–39Ar dating on muscovite from the early As–Fe stage (I) has provided an age of 286±4Ma, synchronous with the late emplacement phases of La Cabrera plutonic massif (288±5 Ma) and with other Permianhydrothermal events like Sn–W skarns and W–(Sn) sulphide veins. δ18O of water in equilibrium with stage I quartz (5.3–7.7x), δD of water in equilibrium with coexisting muscovite (-16.0‰ to -2.0‰), and sulphide δ34S (1.5–3.6‰) values arecompatible with waters that leached metamorphic rocks. The dominant mechanism of the As–(Ag) deposition was mixing anddilution processes between aqueous–carbonic and aqueous fluids for stage I (As–Fe), and nearly isobaric cooling processes forstages II (Zn–Cu–Sn) and III (Pb–Ag). The origin and hydrothermal evolution of As–(Ag) veins is comparable to otherhydrothermal Permian events in the Spanish Central System.
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