Potassium dating

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. 1979, 1986 © Harper Collins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Cite This Source potassium-argon dating A method of radiometric dating, involving analysis of the ratio of potassium 40 (a radioactive isotope of potassium) to argon (the product of radioactive decay of potassium 40) in a given sample.

Critical to these dating methods is the assumption that there was no radiogenic argon ( Hualalai basalt, Hawaii (AD 1800-1801) 1.6±0.16 Ma; 1.41±0.08 Ma Mt. Stromboli, Italy, volcanic bomb (September 23, 1963) 2.4±2 Ma Mt.

Etna basalt, Sicily (May 1964) 0.7±0.01 Ma Medicine Lake Highlands obsidian, Glass Mountains, California ( in the 1800-1801 Hualalai flow, Hawaii, resided in fluid and gaseous inclusions in olivine, plagioclase, and pyroxene in ultramafic xenoliths in the basalt, and was sufficient to yield "ages" of 2.6 Ma to 2960 Ma.

Geologists have used this method to date rocks as much as 4 billion years old.

It is based on the fact that some of the radioactive isotope of Potassium, Potassium-40 (K-40) ,decays to the gas Argon as Argon-40 (Ar-40).

In these materials, the decay product Ar is able to escape the liquid (molten) rock, but starts to accumulate when the rock solidifies (recrystallizes).

The amount of Argon sublimation that occurs is a function of the purity of the sample, the composition of the mother material, and a number of other factors.The geomagnetic polarity time scale was calibrated largely using K–Ar dating.Ar (argon), the atom typically remains trapped within the lattice because it is larger than the spaces between the other atoms in a mineral crystal.Any alteration or fracturing means that the potassium or the argon or both have been disturbed.The site also must be geologically meaningful, clearly related to fossil-bearing rocks or other features that need a good date to join the big story.Further confirmation comes from diamonds, which form in the mantle and are carried by explosive volcanism into the upper crust and to the surface. obtained a K-Ar isochron "age" of 6.0±0.3 Ga for 10 Zaire diamonds, it was obvious excess was inherited from the mantle source areas of the magmas. Snelling, "Discordant Potassium-Argon Model and Isochron ' Ages' for Cardenas Basalt (Middle Proterozoic) and Associated Diabase of Eastern Grand Canyon, Arizona," in R.

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