0
Generally speaking, helium diffusion doesn't really affect the radiometric dating of a zircon crystal. The reason that helium diffusion isn't a factor is that helium diffusion isn't a reliable method of dating the crystal, and it usually isn't used. Other radiometric means are applied to this purpose, and uranium-lead is probably the most common. This dating method (U-Pb) has been around for a long time, and it is highly refined. Let's dig around a bit and see what's up.
It was just after the turn of the 19th century that investigators considering the nature of radioactive materials thought of the method of radiometric dating. (Yes, that's right. Radiometric dating has been around for a hundred years or so.) The uranium-lead dating method has been a favorite because the uranium and lead (as well as the products of their decay) aren't really able to "escape" the confines of the zircon crystal matrix. Helium, which is formed during the alpha decay of uranium and its daughter products as they transform into lead, is also produced. But helium diffusion can generally be ignored when doing U-Pb dating. It's a good thing, too, and here's why.
Helium is an inert gas and is not "bound" into the crystal structure of the zircon crystal. Further, it has a pronounced ability to diffuse, and it can move through and actually escape the zircon. Lots of variables contribute to the diffusion of helium through and out of a zircon, and thermal conditions will dramatically affect helium diffusion. As a zircon crystal lies entombed in rock that is heating and cooling in response to geologic processes, helium will diffuse (increasingly and decreasingly) in response. But the uranium and its daughters produced in radioactive decay can't really do that. They're stuck. Most investigators will ignore helium when doing radiometric dating because there are too many things that can affect its concentration. Further, these things (save the very highest thermal conditions) don't significantly affect the elements in the U-Pb decay chain.
Variability in the helium concentration in zircons is subject to many difficult-to-model variables to make it a top notch radiometric dating tool. On the other hand, U-Pb dating works extremely well for most applications where the age of a zircon needs to be determined. We should also note that the decay chains of U-238 and U-235 are different, and each can be considered separately when running a mass spectrographic analysis of a zircon. That gives us a two-in-one way to calculate the age of a sample by looking at the U-238 and U-235 decay chains independently. We can compare the results of U-238 - Pb-206 and U-235 - Pb-207 side by side and state with good accuracy the age of zircons millions and even billions of years old. Variables that affect helium diffusion (and therefore helium concentrations) can generally be ignored with U-Pb dating.
There is some talk recently about the use of helium concentration in zircons to determine age, but the diffusion of helium within zircon is not that well understood. Additionally, it is difficult to quantitatively assess the variables to obtain an accurate age of the crystal. It is far easier (owing to the "confinement" of the uranium and its daughters as well as the lead) to use U-Pb dating techniques. The recent to-do over helium dating is primarily being supported by those who wish to overturn the estimates of the age of earth that have been broadly accepted by almost all scientists. Very few investigators doubt the veracity of the earth's age (set at about four and a half billion years) which has been estimated using radiometric decay in gelogic samples. Those few who believe in a young earth have grabbed onto the terrible science (it's worse than just bad) offered by a few investigators (who should know better) that casts doubt on the general view of the age of the earth. Helium diffusion doesn't in zircon generally doesn't affect the calculation of the age of a sample using standard radiometric techniques. Links have been provided below to related questions and other articles directly relative to this issue.
What else can I help you with?
When could diffusion be dangerous?
pollution that can make us medically unwell is an effect of diffusion
Is water freezing into ice an example of diffusion?
These are two different processes. Diffusion is when two substance mix together, evaporation is when a liquid turns into a gas. If diffusion where to effect evaporation it would be to do with changing the properties of the liquid being evaporated.
What is the effect of size of uptake on diffusion in agar?
larger the size, the smaller the surface area to volume ratio, hence the slower the rate of diffusion into the agar jelly :)
Does color effect the growth of a crystal?
Yes, I found out that the less color a crystal has the more it will grow.
Does distance effect rate o diffusion?
Yes, distance does affect the rate of diffusion. Generally, the greater the distance, the slower the rate of diffusion because particles have to travel a longer distance to reach their destination. This means that it takes more time for molecules to move across a greater distance through a medium.
What are the effect of ozone diffusion and green house effect?
Ozone diffusion and greenhouse effect increase the temperature on earth. This can cause various natural calamities.
How do temperature effect the rate of diffusion?
higher temp = higher rate of diffusion
What effect does NaCl have on glucose diffusion?
No it does not
When could diffusion be dangerous?
pollution that can make us medically unwell is an effect of diffusion
Does diffusion effect cell size?
Yes
How did cultural diffusion effect ancient Greece?
it had no effect
What is the effect of the density of liquid on the rate of diffusion?
The increase in density will decrease the rate of diffusion. There is an inverse relation between density and rate of diffusion.
What effect the size of crystal?
Temperature.
Does food coloring effect crystal growth?
no
Does sucrose have an effect in diffusion?
Sucrose can affect diffusion as it can slow down the movement of molecules across a membrane. This is because sucrose is a larger molecule compared to other substances commonly involved in diffusion. It can create a barrier that hinders the rate of diffusion.
How does diffusion effect cells?
I think you mean how does it affect cells but im not sure
Is water freezing into ice an example of diffusion?
These are two different processes. Diffusion is when two substance mix together, evaporation is when a liquid turns into a gas. If diffusion where to effect evaporation it would be to do with changing the properties of the liquid being evaporated.
