Geochronology dating techniques

Posted by / 11-Oct-2019 15:57

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The isotopes the KAr system relies on are Potassium (K) and Argon (Ar).

The primary standard must be a mineral that is homogeneous, abundant and easily dated by the K/Ar and Ar methods.

Traditionally, this primary standard has been a hornblende from the Mc Clure Mountains, Colorado (a.k.a. Once an accurate and precise age is determined for the primary standard, other minerals can be dated relative to it by the Ar technique (e.g. However, while it is often easy to determine the age of the primary standard by the K/Ar method, it is difficult for different dating laboratories to agree on the final age.

Argon loss and excess argon are two common problems that may cause erroneous ages to be determined.

Argon loss occurs when radiogenic K by a fast neutron reaction) can be used as a proxy for potassium.

Therefore, mafic rocks and minerals often contain less potassium than an equal amount of silicic rock or mineral.

Potassium can be mobilized into or out of a rock or mineral through alteration processes.

Ar total fusion measures ratios, making it ideal for samples known to be very argon retentive (eg. Total fusion is performed using a laser and results are commonly plotted on probability distribution diagrams or ideograms.Multiple argon extractions can be performed on a sample in several ways.Step-heating is the most common way and involves either a furnace or a laser to uniformily heat the sample to evolve argon.uses cookies to personalize content, tailor ads and improve the user experience. By using our site, you agree to our collection of information through the use of cookies.

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Because this (primary) standard ultimately cannot be determined by Ar, it must be first determined by another isotopic dating method.

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