Uraninite dating

THOR1ANITE. This mineral of thorium oxide, ThO , is isomorphous with uraninite and occurs in black, nearly opaque cubic crystals in Ceylon and in Madagascar. Often containing rare-earth metals and uranium, the ore is strongly radioactive. Because of its radioactivity, it is valuable in helping to date the relative ages of rocks in which it occurs. 

Hurtado J. M., Chatterjee N., Ramezani J., Hodges K. V., and Bowring S. A. (xxxx) Electron microprobe chemical dating of uraninite as a reconaissance tool for leucogranite geochronology. Earth Planet. Sci. Lett, (in preparation). 

Helium was recognised as an element in 1895, but the history of its discovery dates back a further 30 years. The bright yellow He lines in the solar spectrum were first noted, but not identified, in 1868. In 1888, helium liberated when uraninite is treated with acid was mistaken for another inert gas, nitrogen. 

A sample of uraninite, a uranium-containing mineral, was found on analysis to contain 0.214 g of lead for every gram of uranium. Assuming that the lead all resulted from the radioactive disintegration of the uranium since the geological formation of the uraninite and that all isotopes of uranium other than can be neglected, estimate the date when the mineral was formed in the earth s crust. The half-life of is 4.5 x 10 years. 

Named after the planet Uranus. Yellow-colored glass, containing more than 1% nranium oxide and dating back to A.D. 79 has been found near Naples, Italy. Klaproth recognized an nnknown element in pitchblende (uraninite or uranium oxide) and attempted to isolate the metal in 1789. The metal was first isolated in 1841 by Peligot, who rednced the anhydrons chloride nsing potassium. 

Apart from zircon, other common accessory minerals that can be used for U/Th-Pb dating are monazite, rutile, titanite, apatite and allanite results on rarer minerals such as columbite-tantalite, perovskite, baddeleyite and the uranium ore minerals uraninite and davidite have also been reported. 

Table 9. Dating of uraninites with concordant ages by U-Th-Pb method... 

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