Isochron dating methods forummember phpu
Oldest reliable 40Ar/39Ar ages for terrestrial rocks: Barberton Mountain komatiites.
The isotopic abundance of 142Nd in the Juvinas meteorite.
Age spectrum results from the better of two basaltic komatiite samples are shown in Fig. In contrast to the komatiites, these samples display significant excess argon in the low- and high-temperature gas releases, with an integrated age of 3778 Myr.
But I now see members referring to radiometric datings of oceanic crust rocks that I must presume to be basaltic.
I have done searches to try to determine how these datings are done, but have never been able to find anything.
The latter examples led workers to suspect that Ar redistribution was occurring within the sample, possibly during the irradiation process. Arrows separate successive gas releases with identical ages. The amount of ocean floor material recovered which is fresh (unaltered) enough for dating is limited, so most attention has been focussed on dating terrestrial sections (such as basic lavas) which yield a good magnetostratigraphy.
The K)Ar method is really the only geochronometer capable of dating young basic rocks. Age of the Deccan traps using 187Re–187Os systematics.