As-(Ag) sulphide veins in the Spanish Central System: Further evidence for a hydrothermal event of Permian age

Tomás Martín-Crespo, Elena Vindel, José Angel López-García, Esteve Cardellach

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Abstract

The Spanish Central System (SCS) has been subjected to repeated deformation and fluid flow events which have produced both 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 study presents a multidisciplinary approach leading to the characterisation of the chemistry and age of the hydrothermal fluids that produced the As-(Ag) mineralised stockwork of Mónica mine (Bustaviejo, Madrid). Fluid inclusion data indicate the presence of 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 °C and 0.3 kbar. A second H2O-NaCl fluid is found in three types of fluid inclusions: a high temperature and low salinity type (340±20 °C; 0.8-3.1 wt.% eq. NaCl) also associated to ore stage I, a moderate temperature and very low salinity type (160-255 °C; 0-1.5 wt.% eq. NaCl) represented in ore stage III, and a very low temperature and hypersaline type (60-70 °C; 30-35 wt.% NaCl), unrelated to the mineralising stages and clearly postdating the previous types. 40Ar-39Ar dating on muscovite from the early As-Fe stage (I) has provided an age of 286±4 Ma, synchronous with the late emplacement phases of La Cabrera plutonic massif (288±5 Ma) and with other Permian hydrothermal events like Sn-W skarns and W-(Sn) sulphide veins. δ18O of water in equilibrium with stage I quartz (5.3-7.7‰), δD of water in equilibrium with coexisting muscovite (-16.0‰ to -2.0‰), and sulphide δ34S (1.5-3.6‰) values are compatible with waters that leached metamorphic rocks. The dominant mechanism of the As-(Ag) deposition was mixing and dilution processes between aqueous-carbonic and aqueous fluids for stage I (As-Fe), and nearly isobaric cooling processes for stages II (Zn-Cu-Sn) and III (Pb-Ag). The origin and hydrothermal evolution of As-(Ag) veins is comparable to other hydrothermal Permian events in the Spanish Central System. © 2004 Elsevier B.V. All rights reserved.
Original languageEnglish
Pages (from-to)199-219
JournalOre Geology Reviews
Volume25
Issue number3-4
DOIs
Publication statusPublished - 1 Oct 2004

Keywords

  • Fluid inclusions
  • Hydrothermal fluids
  • Permian
  • Spanish Central System
  • Stable isotopes

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    Martín-Crespo, T., Vindel, E., López-García, J. A., & Cardellach, E. (2004). As-(Ag) sulphide veins in the Spanish Central System: Further evidence for a hydrothermal event of Permian age. Ore Geology Reviews, 25(3-4), 199-219. https://doi.org/10.1016/j.oregeorev.2004.04.007