Helium diffusion dating

16 Mar

The HAV of the quartz concentrate was determined via helium saturation of samples under controlled conditions and subsequent helium analysis as 0.066 ± 0.037% of the bulk sample volume (hereafter, mean values for the sequence are given).

The measurement of helium concentration in initial samples allowed us to determine the partial pressure of helium in the gas phase of HAV as 0.47 ± 0.16 atm; the concentration of helium in the pore water was calculated as the product of pressure and the Henry solubility constant corresponding to the conditions of natural rock occurrence: 0.0036 ± 0.0016 cm O).

In essence, the study argues that although Uranium-Lead (U-Pb) dating of the zircons suggests that ~1.5 billion years worth of uranium decay has indeed taken place, additional evidence shows that helium (a product of radioactive decay of uranium) has only been diffusing out of the minerals for about 6,000 years (±2,000 years).

My critique today is not so much about the rocks, the data, or even the interpretations of those data—it is about Ai G’s failure to work according to the scientific method. What is the clearest evidence that the Earth is less than 10,000 years old?

This effect is manifest in both date-effective uranium (e U) correlations among zircon grains from single hand samples and in diffusion experiments on pairs of crystallographically oriented slabs of zircon with alpha doses ranging from ∼10 α/g.

We interpret these results as due to two contrasting effects of radiation damage in zircon, both of which have much larger effects on He diffusivity and thermal sensitivity of the zircon (U-Th)/He system than crystallographic anisotropy.

Our model predicts that the bulk zircon (U-Th)/He closure temperature ( above this dose.

Linking this parameterization to one describing damage annealing as a function of time and temperature, we can model the coevolution of damage, He diffusivity, and (U-Th)/He date of zircon.