Isochron Dating

Home Feedback Links Books. All Rights Reserved. Unfortunately, and especially so in recent years, National Geographic magazine has increasingly deviated from the subject of geography and become a virtual propaganda mouthpiece for evolutionary speculations. Now even evolutionists have abandoned this creature, now called Paranthropus , as a missing link, but the effect was profound at the time. Later, as an adult and ex-evolutionist, Dr. A recent NG article [ 2 ] has presented the unsuspecting reader with a totally one-sided and uncritical portrayal of the dating methods used by conventional uniformitarian geologists. Evidently, NG is now being pressed into service as a cheerleader for the dogmas of the old Earth and Universe. To rectify this situation, I briefly outline here some of the many fallacies of isotopic dating [ 3 ] and discuss some recent developments in the field of age determination. The NG article lumps all dating methods together, regardless of their assumptions or the span of time supposedly measured by the dating method. Implicitly, it seems there is a deceptive equating of different dating methods.

Clocks in the Rocks

Email address:. Isochron dating uranium. Use today, near the radioactivity of rocks that has been appliedwith.

Thus the goal of garnet geochronology is not merely to date garnet growth; rather​, it is to geologic scatter and adherence to the isochron assumptions. (though.

With an accout for my. Isochron dating is a common technique of radiometric dating and is applied to date certain events, such as crystallization , metamorphism, shock events, and differentiation of precursor melts, in the history of rocks. Isochron dating can be further separated into mineral isochron dating and whole rock isochron dating ; both techniques are applied frequently to date terrestrial and also extraterrestrial rocks meteorites.

The advantage of isochron dating as compared to simple radiometric dating techniques is that no assumptions about the initial amount of the daughter nuclide in the radioactive decay sequence are needed. Indeed the initial amount of the daughter product can be determined using isochron dating. This technique can be applied if the daughter element has at least one stable isotope other than the daughter isotope into which the parent nuclide decays.

All forms of isochron dating assume that the source of the rock or rocks contained unknown amounts of both radiogenic and non-radiogenic isotopes of the daughter element, along with some amount of the parent nuclide. Thus, at the moment of crystallization, the ratio of the concentration of the radiogenic isotope of the daughter element to that of the non-radiogenic isotope is some value independent of the concentration of the parent.

Isochron dating

The following radioactive decay processes have proven particularly useful in radioactive dating for geologic processes:. Note that uranium and uranium give rise to two of the natural radioactive series , but rubidium and potassium do not give rise to series. They each stop with a single daughter product which is stable. Some of the decays which are useful for dating, with their half-lives and decay constants are:. The half-life is for the parent isotope and so includes both decays.

Initial isotope equilibrium: The assumption that at the time of formation of a rock, therein share the same Sr isotope composition; a prerequisite for an isochron.

The simplest form of isotopic age computation involves substituting three measurements into an equation of four variables, and solving for the fourth. The equation is the one which describes radioactive decay:. Solving the equation for “age,” and incorporating the computation of the original quantity of parent isotope, we get:. Some assumptions have been made in the discussion of generic dating, for the sake of keeping the computation simple.

Such assumptions will not always be accurate in the real world. These include:. If one of these assumptions has been violated, the simple computation above yields an incorrect age. Note that the mere existence of these assumptions do not render the simpler dating methods entirely useless.

Refuting “Radiometric Dating Methods Makes Untenable Assumptions!”

I am a student studying evolution, and I noticed your website. My real comment to you regards your statement about Mount St. You state that “radioactive measurements of these rocks show them to be millions of years old” And why shouldn’t they be? Even though you say that they were produced in days or hours, have you not considered where this stratified rock is from? It is from deep inside a volcano, and it doesn’t surprise me that the rock, lava, whatever, is millions of years old.

Dating minerals may provide age information on a rock, but assumptions must be Two isotope ratios need to be measured to determine an isochron date.

Here I want to concentrate on another source of error, namely, processes that take place within magma chambers. To me it has been a real eye opener to see all the processes that are taking place and their potential influence on radiometric dating. Radiometric dating is largely done on rock that has formed from solidified lava. Lava properly called magma before it erupts fills large underground chambers called magma chambers.

Most people are not aware of the many processes that take place in lava before it erupts and as it solidifies, processes that can have a tremendous influence on daughter to parent ratios. Such processes can cause the daughter product to be enriched relative to the parent, which would make the rock look older, or cause the parent to be enriched relative to the daughter, which would make the rock look younger.

Radioactive Dating Explained – Part 2

Isochron dating is a common radiometric dating technique applied to date natural events like the crystallization of minerals as they cool, changes in rocks by metamorphism, or what are essentially naturally occurring shock events like meteor strikes. Minerals present in these events contain various radioactive elements which decay and the resulting daughter elements can then be used to deduce the age of the mineral through an isochron.

The appeal of isochron dating is that it does not presuppose the initial amount of the daughter nuclide in the decay sequence.

This age is computed under the assumption that the parent substance (say, Radiometric dating is largely done on rock that has formed from solidified lava. What has to happen next to get an isochron is that the uranium or thorium has to​.

We dealt with the issues around radiocarbon dating here. That leaves a bunch more to cover. We can do that, because these are not assumptions. These are known issues with radiometric dating and have been dealt with ages ago. The first radiometric dating of rocks was done in Also in the 30s, geologists finally accepted the use of physics in their field and begun to accept that the age of the Earth was actually a measurable concept. What about those issues above? Well, there are two methods of using radiometric dating that deal with those issues.

RADIOACTIVE AGE ESTIMATION METHODS—Do they prove the Earth is billions of years old?

The technique uses a few key assumptions that are not always true. These assumptions are:. Assumption 2 can cause problems when analysing certain minerals, especially a mineral called sanidine. This is a kind of K-rich feldspar that forms at high temperatures and has a very disordered crystal lattice. This disordered crystal lattice makes it more difficult for Ar to diffuse out of the sample during analysis, and the high melting temperature makes it difficult to completely melt the sample to release the all of the gas.

Isochron dating overcom es the possible error caused by som e initial daughter in the Assumptions in isochron dating. The isochron method.

Potassium, an alkali metal, the Earth’s eighth most abundant element is common in many rocks and rock-forming minerals. The quantity of potassium in a rock or mineral is variable proportional to the amount of silica present. Therefore, mafic rocks and minerals often contain less potassium than an equal amount of silicic rock or mineral. Potassium can be mobilized into or out of a rock or mineral through alteration processes. Due to the relatively heavy atomic weight of potassium, insignificant fractionation of the different potassium isotopes occurs.

However, the 40 K isotope is radioactive and therefore will be reduced in quantity over time. But, for the purposes of the KAr dating system, the relative abundance of 40 K is so small and its half-life is so long that its ratios with the other Potassium isotopes are considered constant. Argon, a noble gas, constitutes approximately 0. Because it is present within the atmosphere, every rock and mineral will have some quantity of Argon.

Argon can mobilized into or out of a rock or mineral through alteration and thermal processes. Like Potassium, Argon cannot be significantly fractionated in nature. However, 40 Ar is the decay product of 40 K and therefore will increase in quantity over time. The quantity of 40 Ar produced in a rock or mineral over time can be determined by substracting the amount known to be contained in the atmosphere. This ratio is

Presentation 5 : Radiometric Dating – Part 1