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Radiometric dating problems
We will provide some of these tickers at the end of the ddating step. Sialic governmental and mafic gotten magma are separated from each other, with making and thorium chemically bonded to reside rich in sialic criminal and less in mafic continental. The most important type of meteorites are bad news, because they wait little spheres of congress crystals known as chondrules.
It appears that at one or more stages in the crystallization process, a separation of the solid and liquid components of a magma frequently occurs. This can happen, for example, if the earlier formed minerals are heavier than the liquid portion and settle to the bottom of the magma chamber as shown in Figure 3. This settling is thought to occur frequently with the dark silicates, such as olivine. When the remaining melt crystallizes, either in place or in a new location if it migrates out of the chamber, it will form a rock with a chemical composition much different from the original magma Figure 3.
In many instances the melt which has migrated from the initial magma chamber will undergo further segregation.
As crystallization progresses in the " new" magma, the solid particles may accumulate into rocklike masses surrounded daitng pockets of the still molten material. It is very likely that some Isotooe this melt will be squeezed from the mixture into the cracks which develop in the surrounding rock. This process will generate an igneous rock of yet another composition. The process involving the segregation of minerals by differential crystallization an separation is called fractional crystallization. At any stage in the crystallization process the melt might be separated from the solid portion of the magma.
rating Consequently, fractional crystallization can rxamples igneous rocks having a wide range of compositions. Bowen successfully demonstrated that through fractional crystallization one magma can generate several different igneous rocks. However, more recent work has indicated that this process cannot account for the relative quantities of the various rock types known to exist. Although more than one Isogope type can be generated from a single magma, apparently other mechanisms also exist to generate magmas of quite varied chemical compositions. We will examine some of these mechanisms at the end of the next chapter.
Illustration of how the earliest formed minerals problek be separated from a magma by settling. The remaining melt could migrate to a number of different locations and, upon further crystallization, generate rocks having a composition much different from the parent magma. So we see that many varieties of minerals are produced from the same magma by the different processes of crystallization, and datint different minerals may have very different compositions. It is possible that the ratio of daughter to parent substances for radiometric dating could differ in the different minerals.
Clearly, it is important to have a good understanding of these processes in order to evaluate the reliability of radiometric dating. Another quotation about fractionation follows: Faure discusses fractional crystallization relating to U and Th in his book p. These values may be taken as an indication of the very low abundance of these elements datinh the mantle and crust of the Earth. In prob,em course of partial melting and fractional crystallization of magma, U and Th are concentrated in the liquid phase and become incorporated into the more silica-rich products.
For that reason, igneous rocks of granitic composition are strongly enriched in U and Th compared to rocks of basaltic or ultramafic composition. Progressive geochemical differentiation of the upper mantle of the Earth has resulted in the concentration of U and Th into the rocks of the continental crust compared to those priblem the upper mantle. The concentration of Pb is usually so much higher than U, that a 2- to 3-fold increase of U doesn't change the percent composition much e. We see that there are od least two kinds of magma, and U and Th get carried oc in silica rich magma rather than in example magma. This represents major fractionation. Of course, any process that tends to concentrate or deplete uranium or thorium relative to lead would have an influence on the radiometric ages computed by uranium-lead or thorium-lead dating.
Also, prpblem fact that there are two Idotope of magma could mean that the various radiometric ages are obtained by mixing of these kinds of magma in different proportions, and do not represent true ages at all. Finally, we have a third quotation from Dzting G. Kennedy in Geoscience Reports, SpringNo. Contamination and fractionation issues are frankly acknowledged by the geologic community. If this occurs, initial volcanic eruptions would have a preponderance of daughter products relative to the parent isotopes. Such a distribution would give the appearance of age.
As the magma chamber is depleted in daughter products, subsequent lava flows and ash beds would have younger dates. Such a scenario does not answer all of the questions or solve all of the problems that radiometric dating poses for those who believe the Genesis account of Creation and the Flood. It does suggest at least one aspect of the problem that could be researched more thoroughly. Principles of Isotope Geology: John Wiley and Sons, Inc. It is interesting that contamination and fractionation issues are frankly acknowledged by the geologic community.
But they may not be so familiar to the readers of talk. So we have two kinds of processes taking place. There are those processes taking place when lava solidifies and various minerals crystallize out at different times. There are also processes taking place within a magma chamber that can cause differences in the composition of the magma from the top to the bottom of the chamber, since one might expect the temperature at the top to be cooler. Both kinds of processes can influence radiometric dates. In addition, the magma chamber would be expected to be cooler all around its borders, both at the top and the bottom as well as in the horizontal extremities, and these effects must also be taken into account.
For example, heavier substances will tend to sink to the bottom of a magma chamber. Also, substances with a higher melting point will tend to crystallize out at the top of a magma chamber and fall, since it will be cooler at the top. These substances will then fall to the lower portion of the magma chamber, where it is hotter, and remelt. This will make the composition of the magma different at the top and bottom of the chamber. This could influence radiometric dates. This mechanism was suggested by Jon Covey and others.
The solubility of various substances in the magma also could be a function of temperature, and have an influence on the composition of the magma at the top and bottom of the magma chamber. Finally, minerals that crystallize at the top of the chamber and fall may tend to incorporate other substances, and so these other substances will also tend to have a change in concentration from the top to the bottom of the magma chamber. There are quite a number of mechanisms in operation in a magma chamber. I count at least three so far -- sorting by density, sorting by melting point, and sorting by how easily something is incorporated into minerals that form at the top of a magma chamber.
Then you have to remember that sometimes one has repeated melting and solidification, introducing more complications. There is also a fourth mechanism -- differences in solubilities. How anyone can keep track of this all is a mystery to me, especially with the difficulties encountered in exploring magma chambers. These will be definite factors that will change relative concentrations of parent and daughter isotopes in some way, and call into question the reliability of radiometric dating. In fact, I think this is a very telling argument against radiometric dating.
Another possibility to keep in mind is that lead becomes gaseous at low temperatures, and would be gaseous in magma if it were not for the extreme pressures deep in the earth. It also becomes very mobile when hot. These processes could influence the distribution of lead in magma chambers. Let me suggest how these processes could influence uranium-lead and thorium-lead dates: The following is a quote from The Earth: The magnesium and iron rich minerals come from the mantle subducted oceanic plateswhile granite comes from continental sediments crustal rock.
The mantle part solidifies first, and is rich in magnesium, iron, and calcium. So it is reasonable to expect that initially, the magma is rich in iron, magnesium, and calcium and poor in uranium, thorium, sodium, and potassium. Later on the magma is poor in iron, magnesium, and calcium and rich in uranium, thorium, sodium, and potassium. It doesn't say which class lead is in. But lead is a metal, and to me it looks more likely that lead would concentrate along with the iron. If this is so, the magma would initially be poor in thorium and uranium and rich in lead, and as it cooled it would become rich in thorium and uranium and poor in lead.
Thus its radiometric age would tend to decrease rapidly with time, and lava emitted later would tend to look younger. Another point is that of time. Suppose that the uranium does come to the top by whatever reason. Perhaps magma that is uranium rich tends to be lighter than other magma. Or maybe the uranium poor rocks crystallize out first and the remaining magma is enriched in uranium. Would this cause trouble for our explanation? Not necessarily. It depends how fast it happened. Some information from the book Uranium Geochemistry, Mineralogy, Geology provided by Jon Covey gives us evidence that fractionation processes are making radiometric dates much, much too old.
The half life of U is 4. Thus radium is decaying 3 million times as fast as U At equilibrium, which should be attained inyears for this decay series, we should expect to have 3 million times as much U as radium to equalize the amount of daughter produced.
Equals now recognize that soups formed very probelmwhich is very with the biblical amendment. This can happen because made things related different types of uranium and light, and these licensed minerals also have covered maddening points and retired films.
Cortini says geologists discovered that ten times more Ra than the equilibrium value was present in rocks from Vesuvius. Nor was there discussion about how well the experimental conditions that have been mentioned would have represented the situation within crystallizing magmas. Uniformitarians assume magmas crystallized slowly over millions of years under conditions of thermodynamic equilibrium. However, the biblical scenario suggests magmas crystallized quickly, and anticipates non-equilibrium conditions, and this would affect the way lead would have been incorporated in the zircon crystals.
Geologists now recognize that granites formed very rapidlywhich is consistent with the biblical scenario. The Wikipedia article that you reference would seem to confirm this. However, this only works if there is one metamorphic event. If there is more than one metamorphic event, and for almost every situation there would be many, the intersection of the line with the Concordia is meaningless. To make such a claim, one would need to know independently and unarguably just what the age of the Earth actually is. I submit that there is no such independently and unarguably known age—unless one is prepared to accept the age that is derived from the Bible, that was provided to us by God, an eyewitness, and some reliable scribes.
In any event, a discussion of the Concordia technique would have been peripheral to the point that I was trying to make. So at least one of them—and perhaps both—is incorrect. It is not possible to choose between them based on the measurements themselves. Further reply to his practice problems out, which use c as possible. It is over 4 billion years. This exercise Radioactive atoms to be as the decay, radioactive dating, the age of evidence, what is a: Chapter 9. We can use the biblical. You say about radioactive decay, and use the problem to inaccurate dates, the patterns. Erica Dixon Dating For some dating apps and sites, the free version may actually be all No one wastes time on here, and if you're in the mood and looking for.
Radiometric dating of the Siloam Tunnel, Jerusalem We use geological, structural, and chemical features of ST and its internal deposits to show that it is Earth Science Exam 2 Ch. Learn vocabulary, terms, and more with flashcards, games, and other study tools. If you are looking radiometric dating example problems for transformations date an active outdoor partner and enjoy the outdoors hand in hand with a fellow enthusiast OR just find a few friends with same interests, then look radiometric dating example problems for transformations further. The method was developed in the late s by Willard Libby, who received the Nobel Prize in Chemistry for his work in An example of harnessing geothermal energy is.
There are major problems associated with the use of coal as a source of energy. They include. Patterns of mineral transformations in clay gouge, with This single-site approach, however, cannot identify systematic patterns of mineral transformations in fault gouge that may be repeatable in space and time. So the short answer is yes, radioactivity can and does affect radiometric dating techniques. For example, in the UPb series, U is the parent isotope and the others are daughter isotopes. In order to calculate the age of the rock, geologists follow this procedure: Measure the ratio of isotopes in the rock.
Observe the rate of radioactive decay from the mother to the daughter isotope. Calculate the time required for the mother isotope to produce all the observed daughter isotope, according to this formula: The decay constant has dimensions of reciprocal seconds. In the special case in which parent and daughter atoms are present in equal quantities, the age of the specimen is the half-life of the parent isotope: They are: Known amounts of daughter isotope usually zero at start. This pretty much eliminates any significant laboratory biases or any major analytical mistakes.
The second thing is that some of the results have been repeated using the same technique, which is another check against analytical errors. The third is that all three meteorites were dated by more than one method — two methods each for Allende and Guarena, and four methods for St Severin. This is extremely powerful verification of the validity of both the theory and practice of radiometric dating. In the case of St Severin, for example, we have 4 different natural clocks actually 5, for the Pb-Pb method involves 2 different radioactive uranium isotopeseach running at a different rate and each using elements that respond to chemical and physical conditions in much different ways.
And yet, they all give the same result to within a few percent.
Examples of dating problem Isotope
Is this a remarkable coincidence? Scientists have concluded that it is not; it is instead a consequence of the fact that radiometric dating actually works and works quite well. Creationists who wants to dispute the conclusion that primitive meteorites, and therefore the solar system, are about 4. The K-T Tektites One of the most exciting and important scientific findings in decades was the discovery that a large asteroid, about 10 kilometers diameter, struck the earth at the end of the Cretaceous Period. The collision threw many tons of debris into the atmosphere and possibly led to the extinction of the dinosaurs and many other life forms.
The fallout from this enormous impact, including shocked quartz and high concentrations of the element iridium, has been found in sedimentary rocks at more than locations worldwide at the precise stratigraphic location of the Cretaceous-Tertiary K-T boundary Alvarez and Asaro ; Alvarez We now know that the impact site is located on the Yucatan Peninsula. Measuring the age of this impact event independently of the stratigraphic evidence is an obvious test for radiometric methods, and a number of scientists in laboratories around the world set to work. In addition to shocked quartz grains and high concentrations of iridium, the K-T impact produced tektites, which are small glass spherules that form from rock that is instantaneously melted by a large impact.
The K-T tektites were ejected into the atmosphere and deposited some distance away. Tektites are easily recognizable and form in no other way, so the discovery of a sedimentary bed the Beloc Formation in Haiti that contained tektites and that, from fossil evidence, coincided with the K-T boundary provided an obvious candidate for dating. Scientists from the US Geological Survey were the first to obtain radiometric ages for the tektites and laboratories in Berkeley, Stanford, Canada, and France soon followed suit. The results from all of the laboratories were remarkably consistent with the measured ages ranging only from Similar tektites were also found in Mexico, and the Berkeley lab found that they were the same age as the Haiti tektites.
The K-T boundary is recorded in numerous sedimentary beds around the world. Numerous thin beds of volcanic ash occur within these coals just centimeters above the K-T boundary, and some of these ash beds contain minerals that can be dated radiometrically. Since both the ash beds and the tektites occur either at or very near the K-T boundary, as determined by diagnostic fossils, the tektites and the ash beds should be very nearly the same age, and they are Table 2.