Questions tagged [isotopic]

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12
votes
1answer
275 views

How different is the proportion of heavy water ($\ce{^2H2O}$) in the different oceans?

The average proportion of naturally occurring semi-heavy water or deuterated water, $\ce{^2HHO}$ or $\ce{HDO}$, is about 1 molecule in 3200. The proportion comes from the fact that one hydrogen in ...
7
votes
1answer
137 views

How good is K-Ar dating?

I don't doubt that K-Ar dating of rocks is a sound method, but in discussions with skeptics it would be good to know just how reliable exactly? For example, has K-Ar been cross-checked with other rock ...
4
votes
1answer
137 views

How many $\ce{^{14}C}$ measurements have been made?

I know that the upper limit of radiocarbon dating is typically about 60,000 years, but how many radiocarbon dates have actually been measured? As of October 2015, how many $^{14}\ce C$ (radiocarbon) ...
3
votes
1answer
116 views

Why can isotopes reflect the age of the Earth rather than the age of the supernova that created them?

Radiometric dating is based on heavier elements decaying into lighter elements, for example uranium decaying to lead. But wasn't all uranium in the Solar System created in one or more supernova? And ...
2
votes
1answer
35 views

In radiometric isochron dating why is at t=0 D*/Dref=const but P/Dref not?

I am a physics graduate and trying to understand one of the assumptions made for isochron dating of rocks: at crystallization time of the rock, $t=0$, the ratio of the parent isotope to a stable ...
2
votes
1answer
41 views

Potassum-Argon Dating and Proportions of Daughter Products in Potassium 40 Decay Channel

So Potassium 40 decays in such a way that roughly 89% of it becomes Calcium 40 and 11% of it becomes Argon 40. When they list these figures are they implying that after 1 half-life, of the 50% of the ...
2
votes
0answers
23 views

Can zircons be analysed by the (U+Th)/He after being ablated for analysis of U-Pb?

I have zircons that have been mounted in a resin block. They have been polished to approximately half way through the zircons (as is convention) and they have been ablated to attain the U-Pb or Pb-Pb ...
1
vote
1answer
36 views

How do they get “deep lunar mantle” samples?

Phys.org's Study suggests Earth and Moon not identical oxygen twins says They found that the oxygen isotopic composition varied depending on the type of rock tested. This may be due to the degree of ...