Potassium-Argon Dating Methods



Argon–argon dating

The older method required splitting samples into two 40ar 39ar dating method separate potassium and argon measurements, while the newer method requires only one rock fragment or mineral grain and uses a single measurement of argon isotopes. The sample is generally crushed and single crystals of a mineral or fragments of rock hand-selected for analysis.

These are then irradiated to produce 39 Ar from 39 K. The sample is then degassed in a high-vacuum mass spectrometer via a laser or resistance furnace. Heating causes the crystal structure of the mineral or minerals to degrade, and, as the sample melts, trapped gases are released. The gas 40ar 39ar dating method include atmospheric gases, such as carbon dioxide, water, nitrogen, and argon, and radiogenic gases, like argon and helium, generated from regular radioactive decay over geologic time.

The J factor relates to the fluence of the neutron bombardment during the irradiation process; a denser flow of neutron particles will convert more atoms of 40 K to 40 Ar than a less dense one. However, in a metamorphic rock that has not 40ar 39ar dating method its closure temperature the age likely dates the crystallization of the mineral.

Thus, a granite containing all three minerals will record three different "ages" of emplacement 40ar 39ar dating method it cools down through these closure temperatures. Thus, although a crystallization age is not recorded, the information is still useful in constructing the thermal history of the rock. Dating minerals may provide age information on a rock, but assumptions must be made.

Minerals usually only record the last time they matchmaking by name and birthdate down below the closure temperature, and this may not represent all of the events which the rock has undergone, and may not match the age of intrusion. Thus, discretion and interpretation of age dating is essential. This technique allows the errors involved in B2 matchmaking dating to be checked. Argon—argon dating has the advantage of not requiring determinations of potassium.

Modern methods of analysis allow individual regions of crystals to be investigated. This method is important as it allows crystals forming and cooling during different events to be identified. One problem with argon-argon dating has been a slight discrepancy with other methods of dating. Thus the Cretaceous—Paleogene extinction when the dinosaurs died out - previously dated at Similarly, the Permian-Triassic extinction is now dated at From Wikipedia, the free encyclopedia.

Ludwig, Absolute Ages Aren't ExactlyScience Kerr, Two Geological Clocks Finally Keeping the Same TimeScience Retrieved from " https: Navigation menu Personal tools Not logged in Talk Contributions Create account Log in. Views Read Edit View history. Navigation Main page Contents Featured content Current events Random article Donate to Wikipedia Wikipedia store. Interaction Help About Wikipedia Community portal Recent changes Contact page. Tools What links here Related changes Upload file Special pages Permanent link Page information Wikidata item Cite this page.

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Radioactive Dating