Isochron dating methods forummember phpu
Bulk samples usually have low Rb/Sr ratios, yielding ages of low precision, while separated minerals in many achondrites yield Rb)Sr ages below 4.5 Byr, indicative of disturbance.
The Sm)Nd system in separated minerals from achondrites is more resistant to re-setting, yielding better age estimates.
So, the question is, how are these basaltic rock datings done?
Moose Professor, geology, Whatsamatta UEvolution - Changes in the environment, caused by the interactions of the components of the environment."Do not meddle in the affairs of cats, for they are subtle and will piss on your computer." - Bruce Graham"The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness." - John Kenneth Galbraith"Yesterday on Fox News, commentator Glenn Beck said that he believes President Obama is a racist. Combined with Google Site Search I come up with: The first accurate measurement of meteorite initial ratios was made by Papanastassiou et al. These differ from chondritic meteorites in showing evidence of differentiation after their accretion from the solar nebula. 231Pa and 230Th chronology of mid-ocean ridge basalts.
To be fair, every time you watch Glenn Beck, it does get a little easier to hate white people." - Conan O'Brien "I know a little about a lot of things, and a lot about a few things, but I'm highly ignorant about everything." - Moose Well, I'mmore on the amateur thoretical side. However, they may not have participated in the full planetary differentiation process which generated iron meteorites.
However, the good agreement between the Sm–Nd and Pb–Pb dates has served the important function of confirming the 147Sm half-life of 106 Byr. Nd isotope ratios are affected by the choice of normalising factor for mass fractionation. One example is a dating study on the Deccan basalts (Allegre et al., 1999). 1, the isochron gave a precise age of 65.6 " 0.3 Myr, in excellent agreement with previous K–Ar and Ar–Ar ages averaging 64.5 " 1.5 Myr. Chronology and chemical history of the parent body of basaltic achondrites studied by the 87Rb)87Sr method. 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. In order to make this determination, Papanastassiou et al. analysed whole-rock samples from seven different basaltic achondrites, yielding an isochron (Fig.