Modelling rock deformation mechanisms and genesis of ore deposits in shear zones, Carajás, Brazil
Final Report Abstract
The objective of the present pilot project was to check the feasibility of a detailed case study into the structural control of the Carajás Transcurrent System on the mineralization of the Alvo 118 deposit within the Carajás Mineral Province (Brazil), using methods of structural geology and petrology. The study was planned in cooperation with the universities of Belém (Brazil) and Durham (UK). The pilot project in the Mineral Province of Carajas (Amazon Region of North Brazil) was funded for a half-year period in order to do field work and examine drill cores with respect to mineralisation and deformation processes in the Archaean to Proterozoic Carajás Transcurrent System. This project was planned as accompanying the exploration of a new base metal mining prospect by the Brazilian Mining Company Vale (Companhia Vale do Rio Doce, former CVRD) operating in this mineral province. We expected (and had been promised) the release of the entire set of drilling records, large amounts of both oriented and non-oriented drill core samples and the creation of new road cuts, providing the only fresh outcrops in the area where rocks at the surface are strongly and intensely altered by tropical weathering. The first results from studying drill cores, a key outcrop and geometrical modelling of the drilling data were promising. After a personnel change inside the cooperating company, access to the field and to data became more difficult during the pilot project. Contrary to earlier statements, most oriented drill cores would not be made accessible, thus limiting the options for structural investigations. Furthermore, Vale reduced the priority for the exploration of the new base metal prospect “Alvo 118” after their discovery of a new major Ni deposit. Although the original research plan would very likely have been successful with access to all the data, the new situation was not encouraging. Faced with the obstacles and uncertainties described above, we decided not to develop the pilot project into a full-fledged longer-term project at this moment, despite the persisting scientific interest and promise of the topic.
