Isotope constraints on the genesis of the Arroyo Rojo VMS deposit (Tierra del Fuego, Argentina).

BIEL, C.; COLáS, V.; SUBíAS, I.; ACEVEDO, R.D.; BILLSTRöM, K.

Mineral deposit research for a high-tech world. Volcanic-hosted base and precious metal deposits.

SGA

Lugar: Upsala; Año: 2013; p. 1 - 4

The Arroyo Rojo deposit is the most importantpolymetallic, volcanic-hosted massive sulphide close tothe town of Ushuaia in the rhyolitic belt of the Andes of theTierra del Fuego. This deposit is hosted by a volcanic andvolcanoclastic sequence, Middle Jurassic in age. This Zn-Pb-Cu deposit display a lenticular morphology developedas a stacked lenses-style, with disseminatedmineralization at both footwall and hanging-wall. The oresand host-rocks have one penetrative tectonic foliation andhave been metamorphosed to greenschist facies.Associated hydrothermal alteration follows a strataboundmodel.Stable isotopes point toward mineralizing fluids derivationfrom interaction and re-equilibration with the siliciclasticportion of host formation, with sulphur derived from amixture of biogenic reduction of seawater sulphate insome restricted to closed ambient with probably magmaticinfluence, and heavier ä34SCDT values derived by leachingof sulphide from detrital rocks. Lead and strontiumisotopes indicate that metals were leached fromsedimentary rocks. This process allowed re-equilibrationand homogenization of hydrothermal fluids. In short, theweight of geological, mineralogical and isotopic evidencespoints to a sulphide deposition in a brine pool.