Potassium 40 dating problems when to give up dating


23-Aug-2017 16:27

But consider what happens if the argon came from deep within the Earth, where it was formed by Ar ratio as is found in the atmosphere, and the formula that corrects for atmospheric carbon will not correct for this.Finally, we must consider the possibility of argon loss.The potassium-argon (K-Ar) isotopic dating method is especially useful for determining the age of lavas.Developed in the 1950s, it was important in developing the theory of plate tectonics and in calibrating the geologic time scale.However, we cannot rely on all the argon being lost, and if it is not then when we apply K-Ar dating this will give us an essentially arbitrary date somewhere between the formation of the rock and the metamorphosis event.For these reasons K-Ar dating has largely been superseded by Ar-Ar dating, which will be the subject of the next article.

Any alteration or fracturing means that the potassium or the argon or both have been disturbed.The severity of this problem decreases as the accuracy of our instruments increases.Still, as a general rule, the proportional error in K-Ar dating will be greatest in the youngest rocks.The target mineral is separated using heavy liquids, then hand-picked under the microscope for the purest possible sample.

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This mineral sample is then baked gently overnight in a vacuum furnace.The rock samples are crushed, in clean equipment, to a size that preserves whole grains of the mineral to be dated, then sieved to help concentrate these grains of the target mineral.The selected size fraction is cleaned in ultrasound and acid baths, then gently oven-dried.When a rock undergoes metamorphism, some or all of its argon can be outgassed.



Jun 14, 2005. Potassium-Argon Dating I. Not my area of expertise but I am extremely interested in it. Don't take what is on this page as a scientific endeavor. I am only looking at the evidence and then reporting what I have found to you. If you are having problems understanding terms such as half-life, Isotopes, Nuclides.… continue reading »


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There have been two extensive K-Ar studies on historic lava flows Dalrymple, 1969; Krummenacher, 1970 that showed that excess argon is not a serious problem for dating lava flows. An exception is the lava from the 1801 Hualalei flow, which is so badly contaminated by the xenoliths that it is not.… continue reading »


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Mar 9, 2017. The Ar-Ar method is considered superior, but some of its problems are avoided in the older K-Ar method. Also, the cheaper K-Ar method can be used for screening or reconnaissance purposes, saving Ar-Ar for the most demanding or interesting problems. These dating methods have been under constant.… continue reading »


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