How does earthly age determine?
Crab of in relief settleclear lake how appraisal true bogus?
Although this is the problem of two wide of the mark, but they can use common tool however: Isotropy.
So, what is isotropy? How does isotropy determine again earthly age, how Where is appraisal crab producing area? Let small make up will tell you ~
We know, material is comprise by atom, and atom is comprise by the electron outside the nucleus and nucleus, nucleus is comprised by proton and neutron.
The atom that has certain proton number and certain neutron number is called namely a kind of nuclide, and the atom that has certain proton number is called a kind of element.
Namely same the atom of kind of element all has same proton number, and same kind nuclein has same proton number and identical neutron to count.
And alleged isotope, have identical proton number and the nuclide that different neutron counts namely. They have same proton number, it is so in periodic chart, they hold same position, reason calls isotropy.
We add opposite atomic weight to express different isotope in elemental symbol top left corner normally, be like: Oxygen - 18. Different element can have one or more isotope, be like calcium, there are 6 stable isotopes in nature: Calcic - 40, calcic - 42, calcic - 43, calcic - 44, calcic - 46, calcic - 48.
Because neuter atomic chemistry basically is,decide by the electron outside the nucleus, and number of the electron outside the nucleus is equal to the proton inside nucleus to count, so the different isotope of same element has very similar chemistry.
However, as a result of the difference of nucleus quality, in a few physico-chemical processes, often show slight difference again. The isotope of around of the physics that brings about as a result of this differentia different, chemical process comprises the phenomenon that produces difference to call isotropy fractional distillation.
This kind already the glamour place that the character that likeness has little difference again is isotropy.
What pledge according to isotropy radioactivity is different, we are isotropy system cent radio isotope and stable isotope.
The isotope of radioactivity cause of formation that radio isotope system produces by radio isotope and radioactivity disintegration is comprised.
And stable isotope is to show both neither has radioactivity is not by other the isotope that has emissive isotope disintegration to generate.
Of course, this differentiates and be opposite hourly, to studies time measure, radioactivity half-life the isotope with the very long or very short half-life of disintegration matrix also is considered as to stabilize isotropy.
[intellectual link: Radioactivity disintegration and half-life]
The nucleus of some nuclide is not stable, can initiative change is other nuclide, give out ray, this one process is called radioactivity disintegration, the nuclide that can produce disintegration says its have radioactivity. The nuclide before disintegration calls the parent, the nuclide that disintegration generates is called child body. To specific disintegration response, the disintegration of the mother's body of aleatoric amount comes the time that its content needs when remnant half only is constant, this calls half-life for a short while.
To radio isotope system, the application in geochemistry basically is to decide year. And to stabilizing isotropy, application basically is measure lukewarm, show a cause, show trace.
(one) the application of the radio isotope: Calm year
Alleged calm year, use the property of radio isotope disintegration namely, determine the age after the system is not exchanged with outside happening isotope.
The year that resembles can sending quantity estimation doctoral student through judgement is same. If assume the hair quantity before reading rich is fixed cost, as the addition of the time that read rich, hair quantity is reduced with a fixed rate, the specific value that can carry current hair capacity and initiative hair amount will figure the time that reads rich. (X)
Decide to isotropy year also be likeness, when the system is not exchanged with outside happening isotope, can regard " enter a school " , and isotropy matrix as time gradually disintegration decreases, resemble a hair same. So we should determine only the content of odd matrix in sample (current hair is measured) , the content that gives initiative the parent through estimation of a few means (initiative hair is measured) , the half-life as a result of isotropy disintegration (hair quantity reduces rate) it is foregone, so we can get sample is not exchanged with outside happening what measuring how many years, got sample thereby " the age " .
Our for instance familiar carbon - 14 calm year, determine namely the age after the system does not produce the exchange of carbolic isotope with the outside.
As a result of the action of cosmic ray, nuclear reaction can happen to make carbon in atmosphere - 14, think this one rate is roughly fixed normally; At the same time carbon - 14 produce disintegration, so the carbon in atmosphere - 14 can be in generate and certain stable state is reached in disintegration, the carbon in final air - 14 content are basic and changeless. After wood fell trees makes coffin, among them carbon will produce exchange with atmosphere no longer, after this carbon - 14 produce disintegration, decrease with fixed rate. We pass the carbon in measuring coffin - 14 content, the carbon in its and air - 14 content are comparative, foregone disintegration rate, can know coffin is the child of what time.
Decide year of way to other radio isotopes, the principle is more similar also, just should select different isotropy system according to different time measure.
If choose half-life is too short, so the content of the mother's body in sample is met very few, measure even then do not come out; If choose half-life is too long, so content of the mother's body did not change almost, also cannot decide the age.
For example earthly age is about to decide through U-Pb system.
Decide to isotropy year, compare a key among them is estimate to initiative content. Because most circumstance issues us not to know the initiative content of radioactivity matrix, so our need assumes through a lot of other way the content of the mother's body or the changeover that adopt formula, it is other and OK that the content of will initiative matrix becomes certain amount. Compare among them commonly usedly law of mode age law, the line when waiting waits.
Law of the line when waiting
(2) the application of stable isotope: Measure lukewarm, show a cause, show trace
To stabilizing the application of isotropy, the property that basically is the isotope that used same element has similar sex to have the characteristic of otherness again already. What write speech of the place in teaching material Geochemistry in its like W.M.White, thus Is It That One Group Of Isotope Geochemists Make Their Living By Measuring Isotope Fractionations While The Other Group Makes Their Living By Ignoring Them! (a flock of isotropy geochemistry homes are recumbent measure the fractional distillation of isotropy and live, and another group of fractional distillation that what lean is oversight isotope)
We first from measure lukewarm speak of. In some geology process, if isotropy exchange achieves a balance between two-phase (for example in seawater slow precipitation calcium carbonate) , and the function that balancing fractional coefficient is temperature, need to determine only so the temperature when the isotropy ratio difference between two-phase can get a balance.
[intellectual link: Balance fractional coefficient]
The business of the isotropy ratio between two-phase calls coefficient of isotropy fractional distillation, and between two-phase when achieving isotropy to exchange a balance, to same temperature, this one fractional coefficient is a constant, call coefficient of balance fractional distillation.
For example, in ancient climate research, the oxygen that connects deposit of regular meeting occurrence ocean - 18 isotope are right the graph of time, this kind of graph is the briny temperature chart to time actually. Because of generally speaking, we often think suppose oxygen of oxygen isotope ratio - 18/ oxygen - 16 to decide a value, and the seawater when deposit and deposit achieved oxygen isotope balance. So the change of the oxygen isotope ratio in deposit can represent the change of temperature.
This graph is isotope of the O in marine deposit follows the attempt that time change and C isotope change along with time since Paleocene, meaning discussing global climate change and isotope of global C loop, C changes at that time the relation between.
Want to allow to give temperature certainly, can expect this isotope system is incidental very big fractional distillation, such meetings are convenient to be being measured fractionally, decided temperature also is met more accurate. So, isotropy is measured lukewarm the characteristic that used isotropy chemistry to have petty difference namely, and show a cause, used the characteristic of chemistry likeness morely.
Alleged show a cause, indicate the origin of sample namely through some feature index. We expect this one index has very big difference in different source area while, had better return in migratory process can keep changeless. For example, where is the home town that we can judge him through the accent of a classmate. If tone of his pronunciation suffixation of a nonsyllabic r to nouns and sometimes verbs is more serious, likely northerly, if make the same score, become warped the tongue is not divided, most come from south, this shows a cause namely. The target that we choose is oral speech soundvoice, because differ on one hand,district accent differs, on the other hand " dialect did not change Mao Cui of hair on the temples " .
And the principle that isotropy shows a cause also to it similar. For example, isotope of the Sr in the natural environment of different place is comprised somewhat difference, sr isotope is general in course of efflorescent, biology at the same time do not produce remarkable fractional distillation, such Sr isotope can use area of the source that show trace.
A research that having makes clear, the Sr isotope composition in different water system has certain difference, and the comparison in the Sr isotope composition in the carapace of the crab that grows in water system and water system is adjacent, and the Sr isotope of different position comprises same crab to also agree quite. So Sr isotope has the latent capacity that indicates crab place of production. And Chinese division big metal stabilizes isotropy geochemistry lab (Www.metalisotopes.cn) the method that also trying development to use source of crab of Sr isotope appraisal one kind.
And alleged show trace, the property with the different feature of fractional distillation of the isotope in using different process namely, the process that will figure sample place is experienced. Because differ,the feature of isotropy fractional distillation that process place brings about has difference, through gauging these difference, can restrict conversely form, the geological process that experiences in migratory process. For example, can pass the Fe isotope in studying paddy earth, will figure the migratory rule of element of the Fe in paddy earth, provide a few guidance for agricultural activity.
Paddy earth section plane
Of course, afore-mentioned it is only very shallow and half-baked is generalized and classify, the isotropy method application in geochemistry domain is very wide, more system and comprehensive introduction read relevant book even.
(3) the research direction of isotropy geochemistry
Since isotropy has the application with magical so much, how should have the research of isotropy geochemistry so?
To this problem, everybody has his understanding. Isotropy domain is stabilized according to the metal only here (already the stable isotope system of the tantalum such as Cu, V, Zn, Ba, Si, Cd) for exemple, undertake a few simple specifications to this problem.
Want to study the metal stabilizes isotropy, need to establish the analytic method of high accuracy above all, can comprise the isotope of all sorts of sample in nature measure accurate.
On one hand, the opposite quality difference that the metal stabilizes isotropy system is lesser, the fractional distillation in nature is opposite lesser also, be less than the fractional distillation that causes in chemical extract process even.
On the other hand, a lot of tantalum are in nature content is very few, it is Ppm class even, in chemical flow be polluted easily. The analysis that so the metal stabilizes isotropy is not easy, all over the world a few labs can finish only minority the measurement of sample.
Accordingly, the development that analyses a method also is direction of a of isotropy geochemistry domain important research all the time.
Next, nature of Qing Dynasty wanting a unit of monthly interest rate the fractional mechanism in all sorts of processes, like adsorption, diffuse, crystallization, precipitation, melt. This need clears up different isotropy system to whether produce fractional distillation, produce how many fractional distillation, why to meet fractional.
Coequal and important return those who have isotropy application way to disentomb. Want the respective characteristic according to different isotope system, link real geoscience problem, use the tool of isotropy each fields in geochemistry.
Ca isotropy graph results from author
Isotope of the O in marine deposit and C isotope follow time change graph to result from Isotope Geochemistry of textbook of W.M.White isotope geochemistry
Paddy earth section plane results from the metal stabilizes isotropy geochemistry lab
The metal stabilizes parity to cultivate a graph to result from Gong Ying adds graduate student of Chinese family big doctor
Other result from network
Contribute: Xiao Zicong
The United States makes up: Li Ying
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