It has been found that the rates fluctuate for an unknown reason. In addition to the ages of Earth, Moon, and meteorites, radiometric dating has been used to determine ages of fossils, including early man, timing of glaciations, ages of mineral deposits, recurrence rates of earthquakes and volcanic eruptions, the history of reversals of Earth's magnetic field, and the age and duration of a wide variety of other geological events and processes.
That 'age,' however, "is based on interpretation of a very complicated data set," Mundil said.
We analyzed a variety of samples including glaucophane-bearing pelitic schist from the Itsuki area in Kyushu and the Toba area on the Kii Peninsula, and quartzite from the Anan area in eastern Shikoku.
The U-Pb age distributions reflect similar characteristics for all three areas, indicating significant peaks at 450-500 Ma and ∼ 600 Ma, with additional scattered ages of 800-1800 Ma, and ages older than 2000 Ma.
The Kurosegawa Tectonic Zone, which is one of the least geochronologically understood areas of the Japanese Islands, contains several rock types of contrasting ages in a serpentinite mélange.
This paper presents the U-Pb ages of detrital zircons in pelitic schists and quartzite from the Kurosegawa Tectonic Zone, where high-pressure/low-temperature metamorphic rock (e.g., blueschist) is one of the main constituents.
Lead zircon dating problems Aaron Cavosie, also a visiting professor at Wisconsin University's NASA Astrobiology Institute, said meteorite impacts were relevant to when habitable conditions existed on Earth, with cool surface conditions and water.
These meteorites, which are fragments of asteroids and represent some of the most primitive material in the solar system, have been dated by 5 independent radiometric dating methods.
This is dramatically illustrated by the contact metamorphic effects of a Tertiary granite stock on zircon crystals in surrounding regionally metamorphosed Precambrian sediments and volcanics.
Zircons are regarded as one of the best "clocks" used by geologists, who count the number of atoms of lead and uranium inside to determine when the zircon formed.
It may sound straight-forward, but there are many variables that have to be considered.
We recognize two major types of meteorites: The dating method is usually performed on the mineral zircon.
Geologists have tried various zircon treatments, including abrading the outer surfaces of the crystals, which are typically a tenth of a millimeter across, or leaching the crystals with strong acid.