14. Thermoluminescence Characteristics of Yanzhuang Meteorite

Early work on meteorite thermoluminescence, influenced by pottery dating and dosimetry applications, demonstrated a relationship between natural thermoluminescence and 1 the orbital perihelion of a meteorite and 2 the terrestrial age time since fall of a meteorite. For 14 years natural TL measurements were routinely made on newly recovered Antarctic meteorites to help identify unusual thermal and radiation histories, and to sort them by terrestrial age and perihelion. Two examples of the value of such data are presented, an Antarctic meteorite that underwent a major orbit change prior to fall and the collection mechanics of meteorites at the Lewis Cliff collection site. A second major area of focus for meteorite TL, that has no non-meteorite heritage, is the use of their induced TL to provide an extraordinarily sensitive and quantitative means of exploring metamorphic intensity and palaeothermometry. While especially valuable for unequilibrated ordinary chondrites, these types of measurement have proved useful with virtually every major class of meteorite, asteroidal and planetary. The challenge now is to extend the technique to small particles, micrometeorites, interplanetary dust particles, and cometary particles. Terrestrial age measurements using natural thermoluminescence of a drained zone under the fusion crust of Antarctic ordinary chondrites. Determination of trapping parameters of the high temperature thermoluminescence peak in equilibrated ordinary chondrites. Radiatiation Measurements 33 1 : —, DOI

TL/OSL (Thermoluminescence/Optically Stimulated Luminescence)

Radiometric dating , radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon , in which trace radioactive impurities were selectively incorporated when they were formed. The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay. Together with stratigraphic principles , radiometric dating methods are used in geochronology to establish the geologic time scale.

Using thermoluminescence, Sutton was able to precisely date the age of the impact to 49, +/- years before present. In addition to the Coconino and.

Cite Download Share Embed. Thermoluminescence and fusion crust studies of meteorites. The thermoluminescence TL of meteorites has been examined with apparatus designed with emphasis on linear heating of the sample. The type of TL i. The applications that have been made concern three phases of a meteorite’s arrival on Earth; its preatmospheric shape, the temperature gradients produced by heating during atmospheric passage, and the terrestrial age of meteorites for which the fall was not observed.

It has been found possible to measure terrestrial ages for some meteorites that have been on the Earth several hundred years. It appears probable that shock considerably increases the rate of decay of TL. The extent to which high temperatures experienced by the surface of the meteorite during its atmospheric passage have penetrated into the matrix suggests luminous flight times in the order of 10 seconds, but the gradients tend to be 3 – 5 times less than those predicted theoretically.

They appear to have the same dependence on the orientation of the meteorite as the temperature gradients determined from the fusion crust; the steepest gradients being experienced at the front of the meteorite.

The Dating Game

Widoczny [Schowaj] Abstrakt. Terrestrial age meas-urements using natural thermoluminescence of a drained zone un-der the fusion crust of Antarctic ordinary chondrites. Determination of trapping parameters of the high temperature thermoluminescence peak in equilibrated ordinary chondrites.

McKeever, S.W.S. McKeeverDating of meteorite falls using thermoluminescence: application to Antarctic meteorites. Earth Planet. Sci. Lett., 58 (), pp.

Petrology Tulane University Prof. Stephen A. Nelson Radiometric Dating Prior to the best and most accepted age of the Earth was that proposed by Lord Kelvin based on the amount of time necessary for the Earth to cool to its present temperature from a completely liquid state. Although we now recognize lots of problems with that calculation, the age of 25 my was accepted by most physicists, but considered too short by most geologists. Then, in , radioactivity was discovered. Recognition that radioactive decay of atoms occurs in the Earth was important in two respects: It provided another source of heat, not considered by Kelvin, which would mean that the cooling time would have to be much longer.

It provided a means by which the age of the Earth could be determined independently. Principles of Radiometric Dating. Radioactive decay is described in terms of the probability that a constituent particle of the nucleus of an atom will escape through the potential Energy barrier which bonds them to the nucleus.

Applied Optics

Luminescence dating is based on the principle that certain naturally occurring minerals e. Depending on the type of stimulation source, the phenomenon is termed thermally stimulated luminescence TL or optically stimulated luminescence OSL. Luminescence dating requires a proper resetting of the previously acquired pre depositional luminescence in the natural minerals into a very low level natural zeroing event , either by exposure to sun light during pre-depositional transportation by wind, water etc.

Following the natural zeroing event and subsequent burial, the natural minerals begin luminescence acquisition afresh from the ionizing radiation alpha, beta and gamma constantly provided by the decay of radioactive elements U, Th, K40, Rb present in the sediments and also from the cosmic rays. For calculating the age, the radiation energy stored in the mineral known as Paleodose and the annual radioactivity rate annual dose from the surrounding sediments has to be calculated.

The time elapsed since sedimentation, i.

geosciences, the natural TL dating technique was used by Sutton [] to date Meteor Crater. The calculated age based on this method was.

The most common method for dating artifacts and biological materials is the carbon 14 C method. However, it poses a serious problem for deep-time advocates because it cannot be used for dating anything much older than 50, years. After that time virtually all measureable 14 C should be gone. Many archaeologists use this method to date pottery and, consequently, the sedimentary layers in which they appear. Pottery contains certain crystalline materials.

The longer the pottery is in the ground, the more radiation dose it will absorb, causing more electrons to be excited into trap states. When scientists pull pottery from the ground, they use heat or lasers to de-excite these electrons out of their trap states back to their original state. This causes the electrons to give off light. Scientists measure the amount of light to get the total measured radiation dose TMRD.

At this point, the method seems to be a straightforward concept. However, problems arise from assuming a uniform radiation dose rate over any significant period of time and assuming that the TMRD resulted from the object or artifact being in a strictly constrained environment identical to that in which it was found. Both assumptions become less realistic with the passage of time. For example, a lithium fluoride crystal can preferentially respond to gamma thermal neutron, beta proton, or alpha particle radiation depending on whether it is constructed from 6 Li or 7 Li or a mixture of the two and what trace elements are included in its matrix.

Like most dating methods used by secularists, many assumptions are built into their speculations and hypotheses.

Thermoluminescence measurements in various wavelengths: potential for meteorites dating

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Thermoluminescence dating in the Region The processes by which the TL clock in sediments is reset include volcanic heating, meteorite impact.

Sengupta 1 , N. Bhandari 2 and S. The fusion crust of eight Antarctic meteorite finds show natural thermoluminescence TL levels about times higher than the levels in the fusion crust of freshly fallen meteorites, Dhajala, Jilin and Bansur. If it is assumed that this TL is due to cosmic ray received on the surface of Antarctica, the terrestrial residence times of the meteorites is calculated to lie between 10 4 – 10 5 years. Strictly, these periods represent lower limits of terrestrial ages of these meteorites, and are generally consistent with terrestrial ages calculated from cosmogenic radionuclides.

The interior material of a chondrite typically has about Gy dose equivalent of natural thermoluminescence accumulated due to ambient cosmic ray irradiation in the interplanetary space. The cosmic ray dose rate near 1 A. This slow fading of natural TL, TL NTL , has been used to estimate the terrestrial ages of chondrites [1 – 3] Since all the chondrites do not have identical NTL at the time of fall, because of its dependence on perihelion distance and extent of shock experienced by the meteorite, coupled to the variability of anomalous fading rates on the earth, this method leads to terrestrial age estimates which have been found not to be precise, and sometimes unreliable [2,3].

The meteorites undergo severe frictional heating of their surface during their passage through the earth’s atmosphere, resulting in the formation of fusion crust. It is estimated that the temperature of the surface exceeds o C, resulting in vapourisation of surface material and melting, and recrystallisation of material just below the surface, upto several millimetres [4] The fusion crust is usually sub millimeter and occasionally 2 millimeter thick, but the heat conducts down to several centimeters in favourable cases [5,6] where NTL is partially erased.

The fusion crust and the material just below it are thus expected to have no natural thermoluminescence at the time of fall. During the past decade, many meteorites have been recovered from the Antarctic ice shelf where they have been found lying on the surface of ice.

Radiometric dating

How do scientists find the age of planets date samples or planetary time relative age and absolute age? If carbon is so short-lived in comparison to potassium or uranium, why is it that in terms of the media, we mostly about carbon and rarely the others? Are carbon isotopes used for age measurement of meteorite samples?

We hear a lot of time estimates, X hundred millions, X million years, etc. In nature, all elements have atoms with varying numbers of neutrons in their nucleus.

Hütt, G. and Smirnov, A., Thermoluminescence dating in the Soviet Union, PACT Sears, D. W., Thermoluminescence of meteorites: relationships with their K-Ar.

Peer-Reviewed Articles. Sears, D. Nature Physical Science, , Earth Planet Sci. Meteoritics , 9 , Nature , , Mills, A. E : Sci. Vaz, J. Meteoritics , 12 , Bagolia, C.

Aspects of Archaeology: Thermoluminescence Dating


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