U-Pb data of Au-Pd-Pt-bearing quartz-hematite veins, Quadrilátero Ferrífero, Minas Gerais, Brazil

Fluid inclusions hosted in specular hematite from auriferous (jacutinga) and barren veins in the Quadrilátero Ferrífero either contain fluid inclusions assemblages of high-temperature aqueous carbonic and multiphase high-salinity, high-temperature aqueous inclusions or multiphase aqueous fluid inclusions showing narrow ranges of salinity and homogenization temperatures. Fluid inclusions in quartz and hematite are characterized by uniform Na/K ratios and considerable SO

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contents indicating similar formation conditions and perhaps fluid origin from a common source. The formation of specular hematite veins may be related to retrograde metamorphic fluids being released during the Brazillian orogenic cycle (600–700 Ma). The Pb isotopic characteristics of all jacutinga-type samples is readily reconciliated in a simple model that (i) involves different Palaeoproterozoic or Archaean source lithologies for lead and gold and that (ii) possibly reflects contrasting depths of fluid percolation during the Braziliano, orogeny and (iii) heterogeneous Au distribution in the greenstone source.