New data on the ophiolitic VMS deposits of Moeche (Cabo Ortegal Complex, NW Spain)

Castroviejo Bolibar, Ricardo and Tassinari, Colombo G. and Proenza, Joaquín (2006). New data on the ophiolitic VMS deposits of Moeche (Cabo Ortegal Complex, NW Spain). In: "12th Quadrennial IAGOD Symposium 2006", 21-24 Agosto 2006, Moscú.

Description

Title: New data on the ophiolitic VMS deposits of Moeche (Cabo Ortegal Complex, NW Spain)
Author/s:
  • Castroviejo Bolibar, Ricardo
  • Tassinari, Colombo G.
  • Proenza, Joaquín
Item Type: Presentation at Congress or Conference (Other)
Event Title: 12th Quadrennial IAGOD Symposium 2006
Event Dates: 21-24 Agosto 2006
Event Location: Moscú
Title of Book: 12th Quadrennial IAGOD Symposium 2006. Understanding the genesis of ore deposits to meet the demands of the 21st century
Date: 2006
Subjects:
Faculty: E.T.S.I. Minas (UPM)
Department: Ingeniería Geológica [hasta 2014]
Creative Commons Licenses: Recognition - No derivative works - Non commercial

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Abstract

As a result of the variscan collision, several allochtonous complexes were emplaced on the Iberian margin in Devonian times, among them the Cabo Ortegal Complex comprising the Moeche ophiolitic sequence. Copper has been won from several mines (Piquitos I & II, Barqueira, Maruxa) from disseminated ores and thin massive sulphide layers in the Moeche Unit, a strongly deformed meta-volcanic sequence comprising mainly quartz-chlorite schists and mylonites, which defines the top of the ophiolite. The ores were metamorphosed and strongly deformed under brittle conditions (for pyrite), but their textures are often apparently post-deformational, due to very common solution-transfer processes; they are composed mostly of pyrite and chalcopyrite, with minor sphalerite, pyrrhotite, etc., and with traces of native gold and PGE. The geology, mineralogy, and geochemistry of the orebodies relate closely to VMS of the Cu-Zn (Cyprus) type. Fluid inclusion studies allowed an estimation of metamorphic conditions at pressures of 2/2’5 kb and T 325/350ºC. New determinations using the chlorite geothermometer yield temperatures around 320 ºC, corresponding to pressures near 2 kb according to the isochores deduced from the fluid inclusion study, although in the Barqueira mine higher temperatures, up to 350 ºC, are found, corresponding to presssures up to 2’5 kb. Pb isotopic compositions of pyrite point to a double source of Pb, i.e. a main mantle and a subordinate crustal source. The values for 87SR/86Sr in pyrite support this interpretation, but some results suggest later mobilization in an open system, corresponding to solution-transfer. Age determinations of pyrite deduced from the Pb isotope uranogenic graph, ≈ 480 Ma, do not fit with the metamorphic ages published for the Moeche Unit, and might point to the age of Pb extraction from the mantle.

More information

Item ID: 10976
DC Identifier: http://oa.upm.es/10976/
OAI Identifier: oai:oa.upm.es:10976
Official URL: http://www.minsoc.ru/confs.php?id=22&cid=14
Deposited by: Biblioteca ETSI Minas y Energía
Deposited on: 04 Jun 2012 14:06
Last Modified: 20 Apr 2016 19:10
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