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Spatial modeling of aerogeophysical data and interpretation of SAR images with application to geological and metallogenetic mapping of the central Bacajá Domain, State of Pará, Brazil

Author(s):
Cleyton de Carvalho Carneiro
Total Authors: 1
Document type: Doctoral Thesis
Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Geociências
Defense date:
Examining board members:
Lena Virgínia Soares Monteiro; Jurandir Zullo Junior; Henrique Llacer Roig; Marcelo Lacerda Vasquez
Advisor: Álvaro Penteado Crósta
Abstract

The Bacajá Domain is located in the eastern portion of the Amazonian Craton, within the Maroni-Itacaúnas Paleoproterozoic province or Transamazon. The current interpretation of the limits between different lithostratigraphic units was based mainly on airborne geophysical data acquired in the 1970s. Between 2004 and 2005 radar (SAR) data were acquired by the Amazon Protection System (SIPAM) and new geophysical data, comprising magnetic and gammaspectrometric data, were acquired by the Geological Survey of Brazil (CPRM). These new data are fundamentally important to advance the geological knowledge and to assess the mineral potential of this region. These data sets were analyzed and spatially modeled for generating geological maps and information on the gold potential of the central Bacajá Domain. The results suggest that the boundary between the Bacajá Domain and the Carajás Province is located between the Pacajá orthogneiss (Neoarchean) and Novolândia granulite (Riaciano). Using fuzzy logic modeling the more favorable areas to the occurrence of mafic and ultramafic rocks were defined, comprising amphibolite, diabase, gabbro and metagabbro. Using Self-organizing Maps (SOM), classes related to the main lithologies that occur in the central Bacajá Domain were defined. Gold occurrences are associated with areas whose gammaespectrometric signatures exhibit high potassium values, characterized also by NW-SE trending lineaments. These characteristics suggest the presence of extensional structures associated with shear zones in the areas of the mafic rocks belonging to the Três Palmeiras Sequence. Based on these results, new proposal is presented for the distribution of the main lithostratigraphic units of the central Bacajá Domain at the scale of 1:100,000 (AU)