A major objective of this volume is to compile, integrate and correlate a wide variety of geologic, tectonic and mineral resource data onto a single geo-referenced backdrop. Its conception followed a phased approachas the data was migrated and assembled onto thematic GIS maps. Our purpose was to investigate what geological and tectonic processes have taken place and how the features represented therein might reflect bigger scale geodynamic processes. Secondly, we wanted to see to what extent rocks and broad environmental controls can be used to assess conditions for development (and preservation) of ore, oil and gas generating systems in Brazil. Thirdly, we wanted to observe and note for the record all procedures taken with regard to data management and interrogation of data bases so that our modeling could be replicated elsewhere.
The first results of the research are here documented in the form of a book accompanied by a DVD which includes the 2002 edition of the Geology, Tectonics and Mineral Resource Maps of Brazil. Significantly enough, the compilation of data was accompanied by a series of regional-scale traverses and complementary sampling of crustal sequences for isotope work. Many of the analyses, however, were not finished in time to be included in this edition due to logistical difficulties and to a great deal of painstaking work which is still in progress.
Points of controversy and uncertainty abound in Brazilian Geology as well as in regard the genesis of its mineral deposits, including oil. Rather than attempting to resolve controversies, this contribution presents a snapshot of CPRM data bases and a summary of the authors' understanding of the Brazilian Geology on a wide perspective. There will be doubtless skepticism in certain quarters regarding the correctness of the databases; we are keenly aware of their shortcomings, some related to omissions, others to matters of balance in emphasis.
Certain interpretations and specific data will inevitably be in error, and might possibly enrage some experts with first hand local knowledge. To these people we can only offer an advance apology and extend our invitation to discuss the matter and set the record straight.
This book is made up of twelve chapters and includes the work of about sixty authors. Most of them belong to the staff of the Brazilian Geological Survey, but several are known experts from Petrobrás, National Nuclear Energy Commission (CNEN), University of Brasilia (UnB), University of São Paulo (USP) and independent consultants.
The text was organized in five parts. The first two parts of the book, with six chapters, present an overview of the geologic and tectonic framework of the Brazilian territory and its marginal basins, together with a discussion of geochemical and geophysical constraints of selected areas. New Sm-Nd and SHRIMP data on crystalline basement rocks are presented and integrated with existing geologic information in an attempt to delineate chrono-tectonic provinces. The interrogation of the various datasets on a GIS environment sharpened our perceptions and improved our interpretations of geologic terranes, leading to a better understanding of the evolution of the crustal and mantle-derived sequences within the Brazilian Platform. These first six chapters provide an overview of the basement characteristics into which the mineral deposits described and discussed in the following five chapters were emplaced.
The third part of the book deals with the distribution of mineral resources in time and space, the discussion being focused on metallogenic associations observed in specific geological environments. At the outset, the exercise was fostered by the desire to investigate the degree to which tectonic-mineral deposit relationship concepts might be used in natural resource assessments or in planning of exploration programs.
The fourth part of the book deals with energy and industrial mineral resources, emphasizing specific geological environments and associated mineral resources. Examples of mineral deposits and occurrences have been catalogued on a comprehensive database. The fifth and last part of the book focus on the methodologies used and procedures taken with regard to data management, in order to facilitate interested readers to optimize their search procedures.
Like in the methodology adopted in continental countries such as Canada and Australia, the concept of chrono-tectonic provinces was used in this synthesis and in the compilation of the new "Carta Geológica do Brasil ao Milionésimo". The structural provinces of Almeida et al. (1977 and 1981) were in part modified for the Amazon Craton in order to express the present understanding of the Brazilian Geological Survey.
The other provinces follow, in a general way, the limits presented by those authors, with some local adjustments. This was the case of the western segment of the reworked Archean/Paleoproterozoic basement of the Mantiqueira Province in Minas Gerais State. Owing to conveniences related to the local data integration, this domain was incorporated to the eastern border of the São Francisco Province.
The formal limit of the São Francisco Province (or Craton) were revised in Alkmin et al. (1983), as shown in Figure VII.4. Provinces are here characterized as regions with discrete stratigraphic, tectonic, magmatic, metamorphic and geomorphic features that are distinctive of those from the confining units (Fig. 0.1).
The limits chosen for the Provinces may have well defined geological character (faults and fault zones, metamorphic fronts, hinterland terrains, erosional limits of sedimentary areas) or be poorly defined (arbitrary or transitional limits assumed in view of inadequate knowledge base).
Building on the concept of Provinces, two first-order tectonic-stratigraphic groupings are recognized. On the one hand, (i) the north-northeast region represented by the Amazon Craton Super-province, made up of seven provinces, essentially pre-Brasiliano , built from east to southwest from the Achaean to the Mesoproterozoic and correlated to continents in the northern hemisphere. In that region, Neoproterozoic litho-structural units are minor and peripheric.
On the other hand, (ii) the central and central-oriental portions of Brazil (Provinces 5, 6, 7 and 8 in Fig. 0.1) are essentially Brasiliano in age, comprising of a mosaic of pre-Brasiliano nucleii surrounded by Brasiliano-age mobile belts correlated to continents in the southern hemisphere, mainly in African territory. The remaining provinces (1, 2, 3 and 4) represent diverse Fanerozoic sedimentary basins.
The stratigraphic column adopted in this work (Fig. 0.2) was translated and adapted from the International Stratigraphic Chart compiled by J. Remane, A.F Muret,. and G.S Odin, published by UNESCO and IUGS (International Union for Geological Sciences) in the year 2000 and other sources consulted.
The Portuguese denominations of the Fanerozoic Units have been translated by geologists Eduardo Camozzatto, João Orestes S. Santos and Pércio Branco; whilst the translation of the Precambrian Units follows Fuck, R. A. (1991), in Revista Brasileira de Geociências 21(2):182-183. The expression Tertiary, still largely used, was omitted in this and other recent versions of stratigraphic maps, corresponds to the Paleogene, Neogene and Cenozoic ages.
The information contained in this volume represents the state of the art of geological knowledge in the Brazilian territory and adjoining ocean floor according to CPRM - Geological Survey of Brazil, at the end of the year 2002.
The thematic maps presented herewith as print files at the 1:2.500.000 scale were derived from data and information structured in a Geographic Information System (GIS) and consistent at the 1:1.000.000 scale.
The data base was compiled from digital data at several scales of knowledge and many formats that were generalized, filtered, and digitally combined for representation at the 1:1.000.000 and 1:2.500.000 scales.
For printed maps the Polyconic cartographic projection system was used, with Latitudinal origin at the Equator and Longitudinal origin at the 54º Central Meridian West of Greenwich, Elipsoid UGGI67, South American Planialtimetric Datum 1969 - SAD69. Geodesic values in GIS refer to the same elipsoid and planialtimetric datum.
The plan metric base maps used were derived by generalization of base maps of the Brazilian Institute of Geography and Statistics - IBGE that were prepared in partnership with the Brazilian Agency of Electric Energy - ANEEL and CPRM - Geologic Survey of Brazil after the International Map of the World at the 1:1.000.000 scale.
The data are presented as shapefiles (ESRI - ArcView) linked to dbf-type tables derived from a relational data base developed in Oracle and nominated Geobank.
The entity relationship model adopted in Geobank for the topics Geology and Tectonics encompasses information on lithologies, stratigrafic units, metamorphism, sedimentary structures, depositional environment and depositional systems. The topic Mineral Resources includes information on geochemical association, metallogeny and typology of mineral resource occurrences.
The topic Geology comprises data and information generated in the course of mapping and applied geologic studies undertaken, in several scales since 1970, by CPRM as well public domain bibliographic references.
Considerable advances have taken place in the geologic cartography of Brazil since the last integrated geologic map was issued in 1981, at the 1:2.500.000 scale. In that period CPRM carried out systematic mapping at 1:100.000, 1:250.000 and 1:500.000 scales over ca. 3,000,000 km².
The amount of information available for geologic units mapable, at the 1:2.500.000 scale, imposes upon the legend adopted for the Geology Map of Brazil, where over 1200 litho-stratigraphic units are described for the eight litho-structural units.
The diversity of the bio-stratigraphy preserved in the course of geologic time is shown in a specific table and the physiography of the adjoining ocean floor is represented in the Tectonic Map by bathymetry features, main structures and magnetic anomalies associated to accretion of ocean floor material.
Most data used in this work was generated as part of CPRM´s Basic Geologic Mapping Program of Brazil (PLGB), created in 1986, with positioning precision consistent with the scale used in this work. In the absence of recent information, updated versions of geologic maps produced in the 70's were used.
The preparation of such updated versions counted on new data generated in the course of Geology-Metallogeny Integration Projects undertaken by CPRM after 1991 as well as public domain data. The updated maps were geo-referenced relative to the new planimetric base maps which have adequate positioning precision at this scale of work. Unpublished geocronologic data obtained by CPRM in the course of 2001 and 2002 have also been incorporated.
The topic Tectonics encompasses data and information used in the Geology Map and the litho-stratigraphy of the Tectonic Provinces of Brazil was classified according to the prevailing tectonic regime as understood by the Project coordinators.
In the Tectonic Map of Brasil distinction was made to units that belong to compressive tectonic regimes, units that belong to extensive tectonic regimes (intra-plate and passive margin) and surface cover, thus allowing for an intuitive reading of the geotectonic evolution of Brazil in the course of geologic time.
In the Tectonic Map the Fanerozoic Sedimentary Basins of Brazil are overlapped by isopac maps and depicted individually in schematic geologic sections, in chrono-stratigrafic correlation diagrams for intracratonic basins, and in crono-tectonic correlation tables for rift-type and passive margin basins.
The Map on Energy and Industrial-Mineral Resources of Brazil was prepared on the basis of the relative positioning of over eighty minerals of industrial or agricultural use, in addition to coal, oil and natural gas, relative to crono-stratigraphy.
Chrono-stratigraphic charts derived from the Geology theme are presented for the main Fanerozoic Basins in Brazil and files with mineral resource data pertaining to the theme include information on 324 oil and/or gas fields. The data were compiled after several data bases owned by CPRM, after public domain data, and after information provided by Petrobrás - Petróleo Brasileiro SA.
The Mineral Resource and Metallogenic Association Maps of Brazil was compiled by positioning the occurrence of over seventy-five mineral commodities in relation to paleo-environments derived from the Tectonics theme. Ore deposits and mineral occurrences are classified according to their characteristics, economic status and substance.
Thematic maps on Building Materials, Mineral Resources of Industrial Use, Mineral Resources used in Agriculture and Energy Mineral Resources are presented, and a greater amount of detail is provided for ca. two thousand selected deposits or occurrences.
Data files regarding mineral resources were compiled from several databases proprietary to CPRM (which also incorporate public-domain data) and the National Department of Mineral Production - DNPM. The database assembled herewith includes over 31,000 items which are still being corrected. It is estimated that some 4 % of the items contain location, status, or substance classification errors.
To the database updated and published for the first time in 2001, were incorporated: i) Landsat images mosaic with 500m resolution; ii) digital elevation model with the same resolution; and, iii) integration of magnetometric and gamaspectrometric data from the CPRM database in GEOTIFF format.
BIZZI, Luiz Augusto (Ed.) et al. Geologia, Tectônica e Recursos Minerais do Brasil: texto, mapas e SIG . [Geology, Tectonics and Mineral Resources of Brazil: text, maps and GIS]. Brasília: CPRM-Serviço Geológico do Brasil, 2003. 673 p. il. 1 DVD.
ISBN 852300790-3.