Uranium series dating of speleothems define

uranium series dating of speleothems define

Pottery figurines have been unearthed in central China's Hunan Province, local archaeologists said. Among the pieces found in the Sunjiagang site of Changde City was a human-shaped figure that was about 4,000 years old. The statue is about the size of an adult's palm, and its face is well-preserved. Some pottery birds were found in the Tanglin relic site about 50 kilometers away.
     "These figurines were used in sacrificial rituals," said Wang Liangzhi, who headed the archaeological team. Guo Weimin, head of the Hunan provincial institute of cultural relics and archaeology, said that the discovery is helpful for studying the prehistorical culture of central China.

Comprehensive data on the chemical element Uranium is provided on this page; including scores of properties, element names in many languages, most known nuclides of Uranium. Common chemical compounds are also provided for many elements. In addition technical terms are linked to their definitions and the menu contains links to related articles that are a great aid in one's studies.

rare metallic element, 1797, named 1789 in Modern Latin by its discoverer, German chemist and mineralogist Martin Heinrich Klaproth (1743-1817), for the recently found planet Uranus (q.v.).

uranium u·ra·ni·um (yu-rā'nē-əm)
n.
Symbol U
An easily oxidized radioactive toxic metallic element having 16 known isotopes, of which U 238 is the most naturally abundant. Atomic number 92; atomic weight 238.03; melting point 1,135°C; boiling point 4,151°C; specific gravity 18.95; valence 2, 3, 4, 5, 6.

A chemical element that is naturally radioactive . An isotope of uranium, uranium 235, is the main fuel for nuclear reactors and atomic bombs . Its symbol is U. ( See fission and chain reaction .)

Geologic time describes the immense span of time—billions of years—revealed in the complex rock surface of Earth. Geologists have devised a geologic time scale that divides Earth's history into units of time. These units are eras, periods, and epochs. A unit is defined in terms of the fossils or rock types found in it that makes it different from the other units. Eras, the four largest time blocks in the scale, are named to indicate the fossils they contain: Precambrian (before ancient life), Paleozoic (ancient life), Mesozoic (middle life), and Cenozoic (recent life). The last three eras are then subdivided into 11 periods. The two most recent periods are further subdivided into seven epochs.

Before the eighteenth century, ideas about time and the history of Earth came mostly from religious theories. Many people believed Earth was only a few thousand years old. They also believed that all the physical features of Earth—mountains, valleys, oceans, rivers, continents—were the same as they had always been. Everything that existed on Earth was the same as it had been in the beginning.

In the eighteenth century, geologists began to theorize that Earth's lifetime was immense. However, since they lacked sophisticated scientific measuring devices, they could only offer educated guesses. They compared the rock record from different parts of the world and estimated how long it would take natural processes to form all the rocks on Earth.

Since that time, geologists have learned to study the strata, or the thousands of layers of sedimentary rock that make up the Earth's crust. Over the course of history, the natural weathering of Earth's surface created sediments (rock debris) that settled in layers on the surface. As the layers built up, the underlying layers were compressed together to form sedimentary rock. A basic geological assumption is that lower layers of rock almost always formed before higher layers.

The fossils of changing lifeforms found in the different strata also help geologists determine the long history of Earth. Determining the age of strata by looking at the fossils, position, grain size, minerals, color, and other physical properties contained within them is known as relative dating.

Geologists easily identify rocks containing fossils of primitive life-forms as being older than rocks containing fossils that are more evolved or advanced. However, the method of relative dating is exactly that, relative. It is not absolute. In addition, complex lifeforms have existed on Earth for only the last 600 million years. Therefore, their fossils represent less than 15 percent of Earth's history.

A more specific and far-reaching method to assign dates to layers of rocks and events that have occurred in Earth's history is absolute dating. This method employs the natural process of radioactive decay.

There are three operating uranium mines in Australia: Ranger in Northern Territory, Olympic Dam in South Australia, and Beverley with Four Mile in South Australia. Four Mile has final processing through the Beverley plant. Honeymoon was shut down in 2013 pending improved uranium prices, and the main Beverley (and North Beverley) wellfields were also shut down soon after that.

Calendar year 2012 U 3 O 8 production: 3710 t from Ranger, 3992.5 t from Olympic Dam, 386.7 t from Beverley, 154.6 t from Honeymoon, total 8244 tonnes (6990.6 tU).

The Ranger mine and associated town of Jabiru is about 230 kilometres east of Darwin, surrounded by the Kakadu National Park, a major tourist attraction. This is a monsoonal part of Australia, with pronounced wet season from December to April. The first two orebodies are now mined out and work is under way to develop an underground mine, though in the longer term the Jabiluka orebody, 20 km away on a contiguous lease, is a more significant prospect (see Uranium Deposits paper). The mining authority runs to January 2021, 40 years from commencement.

History:  
In 1969 the Ranger orebody was discovered by a Joint Venture of Peko Wallsend Operations Ltd (Peko) and The Electrolytic Zinc Company of Australia Limited (EZ). In 1974 an agreement set up a joint venture consisting of Peko, EZ and the Australian Atomic Energy Commission (AAEC).

In 1978, following a wide ranging public inquiry (the Ranger Uranium Environmental Inquiry) and publication of its two reports (the Fox reports), agreement to mine was reached between the Commonwealth Government and the Northern Land Council, acting on behalf of the traditional Aboriginal land owners. The terms of the joint venture were then finalised and Ranger Uranium Mines Pty Ltd was appointed as manager of the project.

Late in 2005 there was a rearrangement of ERA shares which meant that Cameco, Cogema and a holding company (JAURD) representing Japanese utilities lost their special unlisted status and their shares became tradable. The three companies then sold their shares, raising the level of public shareholding to 31.61%.

Until 1990 all ERA sales of uranium concentrate were from Ranger production. Over several years the spot price of uranium concentrates was below the cost of production at Ranger, which made it advantageous over 1990-97 for ERA to purchase supplies from third parties. In 1994 the level of 1510 tonnes just exceeded that year's mine production. Further purchases were made 2001-05. The third party concentrates concerned mostly came from Kazakhstan. In 2011 ERA purchased 2126 t U 3 O 8  to meet its sales commitments, including 1636 tonnes for actual 2011 sales. In 2012 about 500 t was purchased (387 t to end June). ERA sales are mostly under contracts with customers who are prepared to pay a price premium for long-term security of supply.



Uranium | Define Uranium at Dictionary.com

Comprehensive data on the chemical element Uranium is provided on this page; including scores of properties, element names in many languages, most known nuclides of Uranium. Common chemical compounds are also provided for many elements. In addition technical terms are linked to their definitions and the menu contains links to related articles that are a great aid in one's studies.