Geochemistry of the Ore Fluids in the Bonfim and Itajubatiba Gold Skarn Deposits, Northeastern Brazil: A PIXE Method Study

Abstract

Skam deposits are characterised by their high variety of metals and contents. The variety of metals become an interesting economic characteristic of these deposits, that could be an important source of many metals. In this scenario, each particular skam can show different geochemical associations. Different ore types and their complex geochemical association reflect the parental fluid, the composition of the host rocks and the temperature and pressure of ore formation (Meinert, 1992). The characterisation of the ore fluids can give fundamental information to elaborate a metaUogenic model and to provide important criteria for ore exploitation, in each particular deposit. Detailed characterisation of the ore fluids composition can be obtained by mineral chemistry and fluid inclusions studies of the ore paragenesis. The advance of new techniques allows, for example, to measure traces elements in minerals, in a non destructive way. That is the case of the PIXE Method (Particle Induced X-Ray Emission), where the highly intense photon beam from the synchrotron allows deep atoms to be excited by the photons remaining after the attenuation by the matrix (Volfinger et al., 1997). This contribution reports PIXE analyses carried out on the samples from the ore paragenesis of two gold skarn deposits, in Northeastern Brazil: Itajubatiba (Au) and Bonfim (W-Au). The principal objective is to determine the composition of the ore fluids and their geochemical association. Its purpose is to estab-lish a geochemical and metallogenic model for these deposits and elaborate some be used in a more rational exploitation of them.