ASSESSMENT OF GEODYNAMIC CONTROLS ON CENOZOIC MINERALIZATIONS OF THE ANDEAN CORDILLERA BETWEEN 0°-40°S USING BRGMS GIS ANDES©

This study focuses on the geodynamic controls on Cenozoic ore formation in the Andean Cordillera between 0-40°S. It assesses the advantages and limits when exploring for added-value in a continent-scale GIS (GIS Andes from BRGM) containing a mineral deposits data base of over 3000 deposits, carefully described in about 40 fields of information in fixed format. Advanced querying of attribute information on geological, commodity, and age themes allows the deposits to be displayed in time and space, and to become associated with the convergence parameters and the subduction zone evolution in the geodynamic development of the Andean convergent margin.

In the present-day configuration the mineral deposits of the Andes Cordillera show a zoning parallel to the mountain belt. This is probably controlled and accentuated by the subduction of the Nazca oceanic plate below the South American continent, and further influenced by a segmentation in the distribution of the mineralized districts due to transversal discontinuities of various origins.

The study has constructed eleven time slice maps in GIS format from the Paleocene to the Quaternary. They visualize multiple metallogenic, geological, geochemical and geophysical data layers projected in their present-day position. The time slice maps highlight that firstly, steep to intermediate subduction favors Cu-porphyry emplacement. Additional local structural phenomena further determine the further presence or absence of Mo and Au. Secondly, a suggested relationship between slab angle decrease and the presence of ore deposit generating intrusives is re-confirmed. Local stress variations and crustal thickness further determine the type of magmatically related deposits. Thirdly, it is presented that changes in slab dip angle, faulting activity, and inferred state of stress are all generally controlled by convergence velocity and direction, but not in all cases. The parameters may control unidirectional or bi-vergent along strike development of deposits over time.