Tectonic Study of Brazil
Summary
This study which will be of interest primarily to mining companies uses GETECH's unique and comprehensive gravity and magnetic datasets and the geological expertise of Reis–Coward Associates
This study can be used to identify:
- deformation within the ocean crust resulting in volcanism, strike-slip faulting, extension and compression. This helps to explain the temporal and spatial location of alkaline volcanism and provides a model for kimberlite emplacement
- cratonic boundaries both in the upper and lower crust. New tectonic models have been proposed for the structures of the Amazonian and Sao Francisco cratons and their major shear zones
- a new kinematic model for mineralisation to help identify new prospective areas
- the locations of large crustal shears or fractures, important in kimberlite exploration
Geophysical Data Sources
Gravity: Over 1 million gravity stations were used to generate a 30km grid of Bouguer anomaly to map crustal thickness. GETECH's reprocessed offshore satellite gravity data have been used to identify plate tectonic fracture zones that relate to onshore tectonics.
Aeromagnetic: The data cover onshore Brazil as a 1km grid of total magnetic intensity. The data comprise CPRM data from GETECH's SAMMP study augmented with new 1km grid of all Petrobras (pre-1995) onshore data.
A suite of derivatives and transforms of these datasets provide the main geophysical basis of the geophysical interpretation
Gravity was used to image the plate tectonic reconstruction of the South Atlantic at ~80 Ma in order to analyse the structural and mineral relationships between Brazil and the conjugate areas of Africa
The study identifies the:
- Different terranes from Archean (c 2600 Ma), Early Proterozoic (c 2000 Ma), Middle Proterozoic (c 1200 Ma) and the Late Proterozoic or Brasilian (c 600 Ma)
- Nature of the terrane boundaries (major strike slip or thrust zones) and possible suture zones
- Tectonic fabrics of each unit
- Correlations with conjugate tectonic units in Africa, prior to the opening of the South Atlantic
- Effects of the Paleozoic and Mesozoic basin development and of Atlantic rifting and magmatism
- Locations of the main known mineral deposits
Deliverables
ArcGIS products containing;
- images of the aeromagnetic data and their principle derivatives
- lineament analysis of the geophysical data
- regional gravity and crustal thickness topography
- Distribution of Archean crust, Archcean structures and areas where the Archean rocks have been overprinted by subsequent tectonism
- Distribution of Lower Proterozoic fabrics and shear zones
- Distribution of Pre-Brasilian (c 600 Ma) cratons, the nature of Brasilian orogenic boundaries and the major structures within the orogenic belts
- Distribution of known mineral deposits
- Plate tectonic relationships and conjugate structures on the West African margin
Technical Report as hard copy and PDF file
Optional Products
- Country-wide compilation of aeromagnetic surveys as profile line data and grids
- Unique gravity database of over 500,000 gravity stations
