Researchers from China have discovered naturally occurring uranium which was first thought to be non-existent, the People’s Daily Online reported.
The report said that the discovery was published as cover story in the latest issue of Geology (English version).
According to the research, the result provided important information that revealed the nature of hydrothermal uranium mineralization, which has great significance to study the origin of the uranium, as well as the formation and evolution of the Earth's heat.
Uranium is used as the basic element in the nuclear arms industry and the source of nuclear energy, in civilian and industrial use. Since uranium is widely distributed on Earth, it was assumed that uranium does not occur in nature in pure form because of its instability, but only in oxygen-containing minerals.
Led by president of the Beijing Institute of Geology, Li Ziying, the research team conducted a systematic study of the composition and the valence of uraninite in hydrothermal uranium deposits.
The study found that the uranium uraninite was not only in tetravalent and hexavalent form, but also existed as uranium metal (zero valence).
The research said that uranium remains in a metallic state or low valence state due to the strong reduction environment inside the Earth. Most of the uranium combines with oxygen to form tetravalent or hexavalent compounds when the uranium fluids are transported near the Earth's surface, in continuous increase of contact with oxygen.
The report said that the samples for Li's research were taken from two known mineral deposits in China: "Guidong 330" and "Zhuguang 302" in the northeast of Guangdong Province. The research team analyzed the samples using X-ray photoelectron spectroscopy.
Li said that only a portion of the uranium remains in its metallic state as he considers that the proportion of pure uranium, tetravalent and hexavalent in the field of hydrothermal uranium ore, may determine the depth of the ore formation.
The report added that the important discovery would provide essential understanding of the nature of hydrothermal uranium mineralization and the basic elements for ore control, which has an important practical value.