Tectono-Magmatic Activation of the South American Platform and Associated Mineralization

After a long period of relative tectonic stability, which lasted from the Silurian until the Jurassic, the eastern part of the South American platform underwent an important tectonic activation, which began toward the end of the Jurassic and produced notable effects in a large area extending from the Guiana Shield to the southern extremity of the platform, in Argentina. This event affected several geotectonic units of quite different age and origin, but was particularly intense in the last consolidated areas. The effects of the tectono-magmatic activation lasted until the Tertiary. The more important consequences of this event were:

1- Reactivation of large Precambrian faults in the basement and origin of new faults; large vertical displacement of blocks.
2 - Creation of a series of sedimentary basins on the down-faulted blocks. The sediments may exceed 6,000 m in thickness and include marine strata, beginning with the Aptian. The Paleozoic syneclises were reactivated.
3 - Intense magmatic activity. Intrusive and volcanic rocks of varied composition were formed in the whole area.
4 - Endogenous mineralization, mainly related to alkaline rocks. Commercial concentrations of Zr, Th, V, Mo, P, Ti, Nb, Fe, Ni, R.E., Ba and Fores were formed, possibly also Pb and Zn ores, as welI as diamonds. The sedimentary basins contain alI the commercial reserves of petroleum known in the eastern part of the platform, as welI as important deposits of gas, oil shales, sedimentary phosphates, salt, gypsum and barite.