A história Natural do Grupo Serra Geral desde o Cretáceo até o Recente

Authors

  • Léo Afraneo Hartmann Universidade Federal do Rio Grande do Sul

DOI:

https://doi.org/10.5902/2179460X13236

Abstract

http://dx.doi.org/10.5902/2179460X13236

The natural history of the Serra Geral Group comprises a series of processes, starting with the partial melting of the asthenosphere, continuing with the upwelling and modification of magmas and reaching the effusion of the basalt lavas. It also includes interaction of these magmas with the surrounding crust, especially causing heating of the Guarani aquifer and pyrometamorphism of the sedimentary units of the Paraná Basin. This evolution culminates with the hydrothermal alteration and weathering of silica gossans over amethyst geode zones, recording in the gossans’ mud the local evolution of life and climate in the last 10 thousand years. Besides the well-studied magmatic processes, the distinctive formation of paralavas related  with methane combustion was identified, including re-melting of basalts at around 1,800oC. The re-melting may generate Au-EGP-Cu ore deposits in stratiform complexes. Hydrothermal alteration caused the filling of amygdales with zeolites and smectite, allowing the use of such basalts in the ‘rock for crops’ practice. Gem-quality amethyst and agate deposits are also hydrothermal in origin, as well as native copper (first hydrothermal event) and sand injections (second hydrothermal event). The natural history of the volcanic group is thus better understood; its study demands the description of many aspects of the planet’s dynamics, both in its interior and on the surface.

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Published

2014-10-31

How to Cite

Hartmann, L. A. (2014). A história Natural do Grupo Serra Geral desde o Cretáceo até o Recente. Ciência E Natura, 36(3), 173–182. https://doi.org/10.5902/2179460X13236