93
2 Geochemistry of U in Natural Waters and Sediments
Minas Gerais State in Brazil had been an important gold mining center for
Portuguese people in eighteenth century. However, the radioactivity observed in
their lands in the early twentieth century coupled to its use for the energy generation
brought a new scenario to the state that plunged into the “nuclear era” and served to
the development of several geochemical studies focusing the presence of U in natural waters and sediments. The interest for radioactive elements there started in 1929
with the pioneering studies held by Djalma Guimarães in Brazilian Geological and
Mineralogical Service (SGMB), who proposed a new method for the separation of
a high-grade pure U for use in geochronological determinations. In 1935, Ouro
Preto, also in Minas Gerais State, was the birthplace of a complete laboratory for
mineral analysis that began in 1941 a systematic analytical study of minerals and
radioactive waters of that state. Djalma Guimarães in 1948 observed the radioactivity in some rocks of the alkaline suite of the Poços de Caldas plateau, as well as in
Minas Gerais State, which was associated with zirconium ore, thus, awakening new
interest in more specific investigations at that region.
Morro do Ferro consists of a hill situated near the center of the Poços de Caldas
plateau that initially drew the attention of mining prospectors due to the abundant
occurrence of magnetite veins and dikes. In 1935, the Minas General Company
obtained concession for the extraction of iron and associated minerals at Morro do
Ferro area. In the 1950s and early 1960s, preliminary ground investigations of the
Morro do Ferro area were carried out by the National Research Council (CNPq),
National Commission of Nuclear Energy (CNEN), and National Department of
Mineral Production (DNPM) in collaboration with the US Geological Survey
(USGS). In 1953, these investigations revealed by aerial radiometric surveys a
strong radioactive anomaly of the deposit that is almost entirely due to thorium and
its daughter products, associated with rare-earth elements and minor uranium
(Tolbert 1955; Wedow 1967). These early investigations included ground surveys,
drilling, trenching, gallery construction, geochemical analysis, and mineralogical
studies, with a view to evaluating the potential of the ore body. In 1970, it was discovered the Osamu Utsumi Mine in Cercado field at Caldas municipality, distant
about 25 km south of the Poços de Caldas city. Such mine was the first in Brazil that
produced “yellow cake” (uranium concentrate), originating the Poços de Caldas
Mineral-Industrial Complex (CIPC) that belonged to Brazilian Nuclear Industry
(INB).
New interest in Morro do Ferro area arose in the 1970s with the suggestion that
the deposit could be used as a natural biosphere analogue for a radioactive waste
repository as the activity in soils of the area was so high that the natural foliage
could easily be autoradiographed. The Biophysics Institute (Federal University of
Rio de Janeiro (UFRJ)) and the Institute of Environmental Medicine (New York
Medical Center), in collaboration with the Pontifical Catholic University (PUC) of
Rio de Janeiro and CNEN, realized several studies focusing the radionuclide
mobility.
Biogeochemistry of Uranium in Tropical Environments
2 Geochemistry of U in Natural Waters and Sediments
Minas Gerais State in Brazil had been an important gold mining center for
Portuguese people in eighteenth century. However, the radioactivity observed in
their lands in the early twentieth century coupled to its use for the energy generation
brought a new scenario to the state that plunged into the “nuclear era” and served to
the development of several geochemical studies focusing the presence of U in natural waters and sediments. The interest for radioactive elements there started in 1929
with the pioneering studies held by Djalma Guimarães in Brazilian Geological and
Mineralogical Service (SGMB), who proposed a new method for the separation of
a high-grade pure U for use in geochronological determinations. In 1935, Ouro
Preto, also in Minas Gerais State, was the birthplace of a complete laboratory for
mineral analysis that began in 1941 a systematic analytical study of minerals and
radioactive waters of that state. Djalma Guimarães in 1948 observed the radioactivity in some rocks of the alkaline suite of the Poços de Caldas plateau, as well as in
Minas Gerais State, which was associated with zirconium ore, thus, awakening new
interest in more specific investigations at that region.
Morro do Ferro consists of a hill situated near the center of the Poços de Caldas
plateau that initially drew the attention of mining prospectors due to the abundant
occurrence of magnetite veins and dikes. In 1935, the Minas General Company
obtained concession for the extraction of iron and associated minerals at Morro do
Ferro area. In the 1950s and early 1960s, preliminary ground investigations of the
Morro do Ferro area were carried out by the National Research Council (CNPq),
National Commission of Nuclear Energy (CNEN), and National Department of
Mineral Production (DNPM) in collaboration with the US Geological Survey
(USGS). In 1953, these investigations revealed by aerial radiometric surveys a
strong radioactive anomaly of the deposit that is almost entirely due to thorium and
its daughter products, associated with rare-earth elements and minor uranium
(Tolbert 1955; Wedow 1967). These early investigations included ground surveys,
drilling, trenching, gallery construction, geochemical analysis, and mineralogical
studies, with a view to evaluating the potential of the ore body. In 1970, it was discovered the Osamu Utsumi Mine in Cercado field at Caldas municipality, distant
about 25 km south of the Poços de Caldas city. Such mine was the first in Brazil that
produced “yellow cake” (uranium concentrate), originating the Poços de Caldas
Mineral-Industrial Complex (CIPC) that belonged to Brazilian Nuclear Industry
(INB).
New interest in Morro do Ferro area arose in the 1970s with the suggestion that
the deposit could be used as a natural biosphere analogue for a radioactive waste
repository as the activity in soils of the area was so high that the natural foliage
could easily be autoradiographed. The Biophysics Institute (Federal University of
Rio de Janeiro (UFRJ)) and the Institute of Environmental Medicine (New York
Medical Center), in collaboration with the Pontifical Catholic University (PUC) of
Rio de Janeiro and CNEN, realized several studies focusing the radionuclide
mobility.
Biogeochemistry of Uranium in Tropical Environments