Copper exploration in Chile: best geosciences needed for ore discovery in a mature terrain

AUTHORS: Sergio L. Rivera

ABSTRACT:The analysis, from the geologic perspective, of two recent exploration discovery cases in Chile highlights its key role in exploring mature areas. New ideas, generated from the best available geosciences knowledge, expands the search space and re-opens the potential for new discoveries in a very complex and evolving exploration environment. In adverse conditions for Greenfields exploration in 2008 Codelco discovered the Casualidad IOCG type deposit. Systematic application of geological ideas, starting from regional targeting, through identificationexamination of areas of interest and subsequent discovery drilling, was based on the use of frontier genetic concepts and derived critical factors. Continued research helped to establish relations between IOCG and porphyry systems, as well as vertical and lateral alteration-mineralization zonation, thus adding new knowledge and expanding the exploration horizons for these copper deposits in similar metallogenic environments. In 2005 Codelco conducted an exploration program looking for the southern extension of the Andina mine, at the giant Rio Blanco-Los Bronces District. As the main result La Americana deep ore body was discovered. Its dominant mineralization style is different from the most typical magmatic and hydrothermal breccias controlling high grade bodies, exploited within the district and shows a consistent porphyry type mineralization-alteration zoning which can be reconstructed following a more than 1.5 km vertical mineralized column. This mineralizationalteration style was not previously recognized and all the genetic models were based mostly in the breccia events. The new geologic data permits to establish a new framework for relations between different styles of mineralization in porphyritic systems and to extrapolate these new ideas to explore along the Miocene porphyry belt, as well as in similar mineralized environments in the Andean region. It is due to new ideas that mineral exploration survives during dry periods of low discovery rate. This is a fundamental matter to take into account in the exploration strategies of mature terrains like Chile. The application of geosciences, at the edge and one step ahead of the state of knowledge, allows for discoveries both in Greenfield as well as in Brownfield environments. Extensive collaboration between industry and research is a prerequisite to reinforce the pipeline with the most productive new ideas based on the best geosciences development.

KEYWORDS: Copper exploration; Chile, ore discovery, Casualidad IOCG deposit, Rio Blanco-Los Bronces district, La Americana copper deposit, applied geosciences, Brownfield exploration; Greenfield exploration, industry-investigation collaboration

EAN: SGA_2011_A005
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