Uranium–lead dating in the context of "Radiometric dating"

The age of Earth is estimated to be 4.54 ± 0.05 billion years. This age represents the final stages of Earth's accretion and planetary differentiation. Age estimates are based on evidence from radiometric age-dating of meteoritic material—consistent with the radiometric ages of the oldest-known terrestrial material and lunar samples—and astrophysical accretion models consistent with observations of planet formation in protoplanetary disks.

Following the development of radiometric dating in the early 20th century, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old. The oldest such minerals analyzed to date—small crystals of zircon from the Jack Hills of Western Australia—are at least 4.404 billion years old. Calcium–aluminium-rich inclusions—the oldest known solid constituents within meteorites that are formed within the Solar System—are 4.5673 ± 0.00016 billion years old giving a lower limit for the age of the Solar System.

The South China Craton or South China Block is one of the Precambrian continental blocks in China. It is traditionally divided into the Yangtze Block in the NW and the Cathaysia Block in the SE. The Jiangshan–Shaoxing Fault represents the suture boundary between the two sub-blocks. Recent study suggests that the South China Block possibly has one more sub-block which is named the Tolo Terrane. The oldest rocks in the South China Block occur within the Kongling Complex, which yields zircon U–Pb ages of 3.3–2.9 Ga.

There are three important reasons to study the South China Block. First, South China hosts a great deal of rare-earth element (REE) ores. Second, the South China Block is a key component of the Rodinia supercontinent. Therefore, such study helps us understand more about the supercontinent cycle. Third, almost all major known clades of Triassic marine reptiles have been recovered from the South China sedimentary sequences. They are important to understand the marine recovery after the Permian-Triassic mass extinction.

Bertram Borden Boltwood (July 27, 1870 – August 15, 1927) was an American pioneer of radiochemistry.

Boltwood attended Yale University, became a professor there and in 1910 was appointed chair of the first academic department of radiochemistry. He established that lead (the metal) was the final decay product of uranium, noted that the lead-uranium ratio was greater in older rocks and, acting on a suggestion by Ernest Rutherford, he was the first to measure the age of rocks by the decay of uranium to lead, in 1907. He obtained results of 400 to 2200 million years, the first successful use of radioactive decay by Pb/U chemical dating. More recently, older mineral deposits have been dated to about 4.4 billion years old, close to the best estimate of the age of Earth.

Mare Imbrium /ˈɪmbriəm/ (Latin imbrium, the "Sea of Showers" or "Sea of Rains") is a vast lava plain within the Imbrium Basin on the Moon and is one of the larger craters in the Solar System. The Imbrium Basin formed from the collision of a proto-planet during the Late Heavy Bombardment. Basaltic lava later flooded the giant crater to form the flat volcanic plain seen today. The basin's age has been estimated using uranium–lead dating methods to approximately 3.9 billion years ago, and the diameter of the impactor has been estimated to be 250 ± 25 km. The Moon's maria (plural of mare) have fewer features than other areas of the Moon because molten lava pooled in the craters and formed a relatively smooth surface. Mare Imbrium is not as flat as it would have originally been when it first formed as a result of later events that have altered its surface. Mare Imbrium was the location of the first robotic rover deployed on an extraterrestrial body.

Lead (₈₂Pb) has four observationally stable isotopes: Pb, Pb, Pb, Pb. Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide. The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay chains: the uranium series (or radium series), the actinium series, and the thorium series, respectively; a fourth decay chain, the neptunium series, terminates with the thallium isotope Tl. The three series terminating in lead represent the decay chain products of long-lived primordial U, U, and Th. Each isotope also occurs, to some extent, as primordial isotopes that were made in supernovae, rather than radiogenically as daughter products. The fixed ratio of lead-204 to the primordial amounts of the other lead isotopes may be used as the baseline to estimate the extra amounts of radiogenic lead present in rocks as a result of decay from uranium and thorium. This is the basis for lead–lead dating and uranium–lead dating.

The longest-lived radioisotopes, both decaying by electron capture, are Pb with a half-life of 17.0 million years and Pb with a half-life of 52,500 years. A shorter-lived naturally occurring radioisotope, Pb with a half-life of 22.2 years, is useful for studying the sedimentation chronology of environmental samples on time scales shorter than 100 years.