Botanical prospecting for uranium
Encyclopedia
Botanical prospecting for uranium is a method of finding uranium
deposits either by observation of plant life growing on the surface, or by geochemical analysis of plant material.
The history of uranium
prospecting
, especially in the Colorado Plateau
of North America, has seen several methods of identifying likely ore body
locations. The use of radiation detectors, such as Geiger counters and scintillation counter
is one such method. Another method widely used relies on knowledge of the geologic history of an area, such as locating a geologic formation
known to host ore deposits.
Each method begins with the identification of an area of interest. This area is then gridded off, which allows the prospector to map samples to specific locations on the ground.
, looks for physiologic and morphologic changes in plants growing in or around ore bodies. A survey of plants in the gridded area is conducted. Comparison of normal growth habits and rates is done with known normal plants, and areas with high rates of change in either physiology or morphology indicate likely spots for further prospecting. This method is time consuming, and is not useful in all areas.
to the surface, where it is concentrated in growing areas of the plant. Juniper
or saltbrush are usually used, as they are known uranium
concentrators. Samples of tree branch tips and leaves are taken from each area in the grid. These samples are then sent to a laboratory for analysis. Concentrations of more than 1 part in a million-(> 1 ppm) of uranium
indicate likely areas to investigate further, through drilling or digging. This method provides information about likely ore bodies down to a depth of between 50 and 70 feet, and is generally good in areas where mineralized beds form broad flat benches, so that a grid pattern can be used.
in an area of interest. Some uranium
ore bodies contain higher concentrations of certain elements, such as selenium
, than the surrounding host rock in which they are found. Certain plants that concentrate these elements act as indicator species for likely ore body locations. Mapping these plants provides information about areas in which further prospecting should be done. For example, in areas such as the Colorado Plateau
, various species of Astragalus
are selenium concentrators (A. pattersoni, A. preussi, A. thompsonae). Other indicator plants for sulfur
and calcium
, such as Eriogonum inflatum and Oenothera
caespitosa help to identify likely areas also, especially in conjunction with the selenium
indicators.
, such as in South Australia
or Saskatchewan
, Canada
, other plants would naturally be used.
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
deposits either by observation of plant life growing on the surface, or by geochemical analysis of plant material.
The history of uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
prospecting
Prospecting
Prospecting is the physical search for minerals, fossils, precious metals or mineral specimens, and is also known as fossicking.Prospecting is a small-scale form of mineral exploration which is an organised, large scale effort undertaken by mineral resource companies to find commercially viable ore...
, especially in the Colorado Plateau
Colorado Plateau
The Colorado Plateau, also called the Colorado Plateau Province, is a physiographic region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. The province covers an area of 337,000 km2 within western Colorado, northwestern New Mexico,...
of North America, has seen several methods of identifying likely ore body
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...
locations. The use of radiation detectors, such as Geiger counters and scintillation counter
Scintillation counter
A scintillation counter measures ionizing radiation. The sensor, called a scintillator, consists of a transparent crystal, usually phosphor, plastic , or organic liquid that fluoresces when struck by ionizing radiation. A sensitive photomultiplier tube measures the light from the crystal...
is one such method. Another method widely used relies on knowledge of the geologic history of an area, such as locating a geologic formation
Geologic formation
A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties...
known to host ore deposits.
United States
During the early efforts to locate uranium deposits in the United States, the U.S. Geological Survey conducted studies of prospecting through botanical surveys. These studies examined three methods.Each method begins with the identification of an area of interest. This area is then gridded off, which allows the prospector to map samples to specific locations on the ground.
Plant morphology variations
The first method, not widely used in the Colorado PlateauColorado Plateau
The Colorado Plateau, also called the Colorado Plateau Province, is a physiographic region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. The province covers an area of 337,000 km2 within western Colorado, northwestern New Mexico,...
, looks for physiologic and morphologic changes in plants growing in or around ore bodies. A survey of plants in the gridded area is conducted. Comparison of normal growth habits and rates is done with known normal plants, and areas with high rates of change in either physiology or morphology indicate likely spots for further prospecting. This method is time consuming, and is not useful in all areas.
Deep-rooted plants
The second method uses a survey of deep-rooted plants in an area of interest. This works because the plant roots carry uraniumUranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
to the surface, where it is concentrated in growing areas of the plant. Juniper
Juniper
Junipers are coniferous plants in the genus Juniperus of the cypress family Cupressaceae. Depending on taxonomic viewpoint, there are between 50-67 species of juniper, widely distributed throughout the northern hemisphere, from the Arctic, south to tropical Africa in the Old World, and to the...
or saltbrush are usually used, as they are known uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
concentrators. Samples of tree branch tips and leaves are taken from each area in the grid. These samples are then sent to a laboratory for analysis. Concentrations of more than 1 part in a million-(> 1 ppm) of uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
indicate likely areas to investigate further, through drilling or digging. This method provides information about likely ore bodies down to a depth of between 50 and 70 feet, and is generally good in areas where mineralized beds form broad flat benches, so that a grid pattern can be used.
Indicator plant species
The third method looks for concentrations of indicator plant speciesIndicator species
An indicator species is any biological species that defines a trait or characteristic of the environment. For example, a species may delineate an ecoregion or indicate an environmental condition such as a disease outbreak, pollution, species competition or climate change...
in an area of interest. Some uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
ore bodies contain higher concentrations of certain elements, such as selenium
Selenium
Selenium is a chemical element with atomic number 34, chemical symbol Se, and an atomic mass of 78.96. It is a nonmetal, whose properties are intermediate between those of adjacent chalcogen elements sulfur and tellurium...
, than the surrounding host rock in which they are found. Certain plants that concentrate these elements act as indicator species for likely ore body locations. Mapping these plants provides information about areas in which further prospecting should be done. For example, in areas such as the Colorado Plateau
Colorado Plateau
The Colorado Plateau, also called the Colorado Plateau Province, is a physiographic region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. The province covers an area of 337,000 km2 within western Colorado, northwestern New Mexico,...
, various species of Astragalus
Astragalus
Astragalus is a large genus of about 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae, subfamily Faboideae. The genus is native to temperate regions of the Northern Hemisphere...
are selenium concentrators (A. pattersoni, A. preussi, A. thompsonae). Other indicator plants for sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
and calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
, such as Eriogonum inflatum and Oenothera
Oenothera
Oenothera is a Genus of about 125 species of annual, biennial and perennial herbaceous flowering plants, native to North and South America. It is the type genus of the family Onagraceae, the Evening Primrose Family. Common names include evening-primrose, suncups, and sundrops.The species vary in...
caespitosa help to identify likely areas also, especially in conjunction with the selenium
Selenium
Selenium is a chemical element with atomic number 34, chemical symbol Se, and an atomic mass of 78.96. It is a nonmetal, whose properties are intermediate between those of adjacent chalcogen elements sulfur and tellurium...
indicators.
Other regions
In areas outside the Colorado PlateauColorado Plateau
The Colorado Plateau, also called the Colorado Plateau Province, is a physiographic region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. The province covers an area of 337,000 km2 within western Colorado, northwestern New Mexico,...
, such as in South Australia
South Australia
South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories.South Australia shares borders with all of the mainland...
or Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, other plants would naturally be used.