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"Doctor! It hurts when I do this! «bonk»" "So don't do that then!" One way around the issue of an unknown initial distribution of isotopes is to not do that. One of the most reliable mechanisms for dating the Earth is uranium-lead dating of zircons. Uranium can take the place of zirconium in the zircon crystal because of the chemical similarity of uranium ...


5

1) D* (radiogenic isotope) and Dref (stable reference isotope) are two isotopes of the same element. P is the radioactive parent of D*, and is a different element. Chemical fractionation between P and Dref occurs as the rock solidifies because different elements are preferentially incorporated in different minerals depending on how well their ionic radii and ...


4

For detailed information, see Isotopes of the Earth's Hydrosphere, especially chapter 3 which is "Isotopic Composition of Ocean Water". At the surface, deuterium fraction is maximized in regions of high evaporation, and minimized in areas with ice. In the deep ocean, there is about 2% above average deuterium in arctic, and 2% below average near ...


3

The reliability is dependent on the quality, (for instance is the mineral reworked or porous and thus prone to contamination), and size of the sample, (small samples result in poorer measurement). There is also of course the date range issue, use a sample that is too old or too new and the amount of each element is so tiny it can't accurately be measured. ...


3

Suppose you purify a sample of uranium 238, removing all of the lead. Half of those U-238 atoms will have decayed into lead 4.468 billion years from now. If the lead is removed from that half-uranium/half-lead sample 4.468 billion years from now, half of the U-238 atoms in that purified sample will have decayed into lead in yet another 4.468 billion years. ...


1

There are three ways samples of the mantle could arrive on the surface of the Moon. Drilling deep holes into the mantle, take a sample and send to the surface. As ejecta from a large deep impact crater, particularly where the crust is thin. During volcanic eruptions, the upward moving magma tears of chunks of mantle from the walls of the volcanic "vent&...


1

Potassium 40 has a half life of 1,300,000,000 years, which means that within that time half of the 11 percent which you refer to will have decayed to form Argon 40. Potassium 40 has two modes of decay, which is unusual for a radioactive isotope. Only 11 percent of it becomes argon 40, the remaining 89 percent decays by a different mode and becomes Calcium ...


1

How many have been validated by historic calibration, and what proportion (if any) yielded inconsistent results? Often with an item that they want tested, a specific date isn't available so calibration isn't possible, but calibration can be done when dates are known. Tree rings are most common and (though I've not read of this being done), samples from ...


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