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Author | Topic: Potassium Argon Sensitivity Analysis | ||||||||||||||||||||||||||||
Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
Hello to all. I am a registered mechanical engineer with a solid background in metrology, material science, nuclear physics, and material phase transformations. I am currently employed in a manufacturing industry.
I don't have a big dog in this fight over the age of the earth but I would like to perform a sensitivity analysis on the potassium-argon methodology. I liken it to a glass-manufacturing problem where you have to deal with gasses trapped inside molten silica and atmospheric contamination driven by partial pressure. As I see it I would like to evaluate the following variables for a sensitivity analysis, plugging into the radioactive decay formula: 1) How much atmospheric argon can be absorbed into molten silica over a long period of time at atmospheric pressure, and the temperature slightly above the melting point? I need this in ppm. 2) What is the range of K40 in current year magma samples in ppm and the corresponding A40 for the same samples with no atmospheric contamination? I will use the decay formulas and any other assumptions or correction factors deemed appropriate, and excess argon. I'll use the following methodology from Bureau Laboratories: http://geoinfo.nmt.edu/labs/argon/Methods/home.html PS: I think the assumption of zero captive argon in a lava sample is not a good assumption. I do not know how much this affects the result but I will evaluate that as a sensitivity. thanks to all
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Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
quote: The isochron method is based on variations in concentrations of the parent, the radioactive daughter, and the non-radioactive daughter in various minerals within the same sample. This is a little more involved, and I'm willing to take it on. The problem with the isochron method appears to be the assumption about proportional homogeniety of the different mineral mixtures relative to atmospheric argon. Apparantly another sample of "known age" must be used for comparison. http://geoinfo.nmt.edu/labs/argon/Methods/home.html# "In order for an age to be calculated by the 40Ar/39Ar technique, the J parameter must be known. For the J to be determined, a standard of known age must be irradiated with the samples of unknown age. Because this (primary) standard ultimately cannot be determined by 40Ar/39Ar, it must be first determined by another isotopic dating method. The method most commonly used to date the primary standard is the conventional K/Ar technique. The primary standard must be a mineral that is homogeneous, abundant and easily dated by the K/Ar and 40Ar/39Ar methods. Traditionally, this primary standard has been a hornblende from the McClure Mountains, Colorado (a.k.a. MMhb-1)." According to this laboratory, this is a foundational assumption that is necessary for using the original potassium argon method to be usable: "No non-atmospheric 40Ar was incorporated into the rock/mineral during or after its formation." Hence we are back to revisiting the assumptions of the "known standard," which must be validated by the originally proposed A40/K40 method applied to hornblende from Colorodo. So if atmospheric A40 enterred the system of the "known standard", I'm not so sure the original method or the isochron method can handle this very well, and would like to evaluate it. This is why I'd like to get a better handle on the solubility of atmospheric air into liquid glass. It must work something like oxygen diffusing into liquid water, which is sensitive to temperature, pressure, and time of exposure.
quote: I have friends in a university geology department that I plan to use as resources. I'd like to see a good sensitivity analysis as I do in engineering. If you happen to see one on the internet, I'd greatly appreciate you sharing it. Edited by Engineer, : added additional info on isochron method.
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Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
quote: Most Argon is 40Ar, whether in the earth or in the air. If argon is boiling off from inside the earth and then expelling itself with lava, how can it be assumed to be zero in the lava sample at the time of solidification? In glass manufacturing there is a considerable problem with gases in the molten silica, causing bubbles and loss of clarity. The gases want to disolve into the melted silica based on partial pressure, temperature, and solubility. If the gas would just expel itself to zero it would reduce chemical additions and process controls. Some of the clarity enhancing chemicals are rather toxic like arsenic. The cost savings would be nice, and safety would be improved. So how does the natural gas expulsion process benefits molten lava but not the glass manufacturing industry where gases want to enter the liquid silica. Maybe the quantities we are talking about here are orders of magnitude below a significant error. I can't know without making comparisons. What am I missing here? I think I need to be looking at concentrations of the trapped gases in ppm versus the amount of A40 produced by decay. PS: Thanks for the articles. I will study them. Edited by Engineer, : No reason given. Edited by Engineer, : No reason given. Edited by Engineer, : No reason given.
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Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
I notice that Helium is a good fining agent for removing bubbles from glass:
http://www.freshpatents.com/...dt20070802ptan20070175241.php Argon probably aids this as well. Interesting.
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Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
quote: I'm not an expert yet on dating methods, and it really doesn't bother me that the earth is over 4 billion years old.
quote: Actually I'm looking at this like any other engineering problem where I verify assumptions with data. I am quite familiar with the concept of closed systems, and I'm looking at those assumptions in the dating methods. I'm also pretty intimate with the concepts of arrhenius diffusivity in the process industries. Arrhenius equation - Wikipedia attached is an example of how CO2 invades polyethylene through diffusion: Page not found – Composite Agency polymer analysis One might assume polyethylene is a closed system but it is not, and it absorbs and releases gases and humidity in a matter of days. It can also be penetrated by liquid solution which carries chemicals with it. The only real difference I see between the outside surface of the earth and the inside of the earth is temperature, pressure, and solar radiation. Of course the outside also has an atmosphere and some chemical differences, but much if not all of it came from inside at some point in time. Perhaps I should be looking at another dating method. I've looked at the isochron method, and some of the theory behind it. I totally agree with physics -- the thing I question is assumptions and their basis going into the physics models. I don't think the rates of decay changed or anything like that. I'm more interested in validating closed system assumptions, before, during, and after a sample magma sample is deposited.
quote: quote: If the assumptions are consistent then the results should be consistent as well, regardless of the validity of the assumptions. The physical equations are correct, and should produce results that are equally valid to the assumptions going into them.
quote: quote: Having an independent method to verify a result is always good. What I really need to see is the data. How much of the chemicals for each testing method are present in pristine magma inside the earth today, and inside magma that erupts? Edited by Engineer, : No reason given.
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Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
quote: I don't need a ton of data. The data I originally asked for is in ppm for parent, daughter, etc. Isn't A40 like 1 x 10 exp-14 moles/mole in a typical volcanic rock sample or something like that? I'm sure it can vary, but how about an average sample such as something to be tested. This is the kind of data I'm talking about. We have a mass spectrometer at my quality lab. Also, I have to use optic devices to measure dust in the air that's less than 50 ppm. I work with this kind of data rather frequently, so it's not a big deal to me. By the way, I am a six sigma black belt and a certified quallity engineer, so I'm qualified to validate measurement and testing methods regardless of who is using them. Though I might not be well versed in geology, I am well versed in metrology and how it is used to make measurements. I consider geochemistry just another chemistry problem. In the end there is typically a "gold standard" somewhere for verifying results, and that's what I'm looking for as well as the equivalent of a certification which typically documents all of the methodology, its uses and known limitations, and a set of procedures that might read something like this: step 1 -- take geologic sample under CFR 123.4step 2 -- prepare example in lab under procedure CFR 456.7 step 3 -- set up mass spectrometer using procedure CFR 8910.11 etc etc etc I think I will take your advice and look at U-Pb concordia-discordia method instead. It sounds like you are proposing it as the gold standard. Edited by Engineer, : No reason given.
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Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
OK so I'm looking at the Uranium-Lead method which has assumptions about lead and uranium in zirconia crystals.
Interesting. I used to work in a vibration lab that used piezo materials in their vibration transducers. Lead zirconate titanate is a good piezo material: Lead zirconate titanate - Wikipedia I think the lead is right in there with the zirconium as a chemical compound. It appears to be. It appears to take an extremely high pressure to "push" lead into this structure. Edited by Engineer, : No reason given.
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Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
quote: Mechanical and electrical engineers design your dating equipment. We know what we are doing. We have to understand the process and the physical material to design the measuring equipment. It doesn't mean we understand it as well as the expert in that field, but we need a certain level of understanding of both capability and limitation. I'm thrown into a lot of problems where "I don't have a background" -- what's new for an engineer? You might be right about this one with dating where I've finally met my technical match, but currently I have two projects "not in my field", one belonging to a civil engineer and another belonging to an electrical engineer. I've also had to do nuke engineering and inferential statistics. On the civil engineering side, I have to figure out what causes floor coatings to fail on concrete. I've got the answer but it sure took a while. I've never taken a course in concrete mechanics. If you think concrete physics and chemistry is simple, think again. It's not. If you can design a floor coating that won't fail, then you will be quite wealthy. If you want to see a phase diagram that's totally whack, try taking a look at a solidus-liquidus graph in degrees baume for sulfuric acid -- not taught in mechanical engineering, that's for sure As far as molecular lattice and interstituals, it's not such a big stretch for someone with a materials science background. I'll look at the zirconium, which doesn't want interstitial lead for some apparent reason. I only had one course in phase transformations and lattice structures, so admittedly I'm a little weak there. As I said before, I want to see data, and I will look at whatever is provided. I think I am intelligent enough to evaluate it. It will, however, take time. I appreciate the resources, but just talking about it isn't enough. If some technical person in another discipline askes me about failure mechanics, I'd have a way to explain it with technical information. So often I've heard it said in my profession -- if someone can't explain something to a technically minded audience, then they really don't understand it themselves. If they understood it then they could explain it. I'm not saying that about the people on this forum, but I've always had to work with information that's "not in my field". The "you're to dumb to understand" approach, usually means someone has an agenda in my experience. I think I can understand anything given the time. Just give me the time to digest what's been provided. thanks. Edited by Engineer, : No reason given.
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Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
quote: They don't have the same lattice structure. That's a sufficient answer.
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Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
quote: If you have a better way for me to get the information I'm all ears. I don't think the internet is going to cut it.
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Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
quote: Just from reading his short discription, I wouldn't know the answer for certain, and I haven't run a mass spectrometer since college. Given that he has some answers that make sense I'd say he's either measuring the wrong element and he thinks it is the Thorium or something is wrong with the equipment settings. The easiest mistake is to misinterpret what the element or compond is. Elements and compounds can look so similar in a spectrometer analysis and yet be completely different in the diagnostic catalogue. As I said, I don't have enough information to say this with any certainty because I know nothing about how this particular test was performed. Edited by Engineer, : No reason given.
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Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
To answer your point, I will always be a deist because of my own personal experiences that predate my choice of a religion and relate to my own personal conscience and experience.
My choice of a religion is based on what I consider to be the best, though primitive, explanation of who the metaphysical entity is. Our predecessors have no words or even a conceptual understanding of nuclear decay or science, but prior to the birth of our universe these concepts aren't very useful either. Obviously our universe is finite on the time scale, and obviously it is highly ordered. On the otherhand I think a lot of "intelligent design" is nothing more than an attempt to rebutt science which in the end is destined to lose. When I get to the end of the study which will take a while, I will probably find out that the dating methods are contiguous. Consider the daunting task I had ahead of me, a mere mechanical engineer, to become a certified sig sigma black belt. Take a look at design of experiments (DOE) sec 7, and ANOVA in sec 6: http://www.asq.org/certification/six-sigma/bok.html
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Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
Jon F,
Congratulations on your advanced education. I was a candidate for the Georgetown Universiy NASA-Langly graduate program myself. I graduated magna cum laude in my undergrad curriculum. One question here, just for the record. As a nuclear engineering professional I understand that radiation exposure speeds up nuclear reaction. This is fundamental to nuclear power plant operation. http://www.world-nuclear.org/education/ral.htm
In the case of lava flow, we know that all surface substance is subject to radiation from the sun and other sources. Neutron bombardment speeds up nuclear reaction of the unstable isotopes. This fact allows us to generate heat in a nuclear reactor. So what is the assumption for environmental radiation exposure over the past 4 billion years? Are you assuming it is a constant, or is this just a noise factor with small relative contribution anyway? Edited by Engineer, : No reason given. Edited by Engineer, : No reason given. Edited by Engineer, : experimenting with html code Edited by Engineer, : Nuclear irradiation does not speed up nuclear decay, it acclerates fission. My error.
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Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
quote: This is a common problem I must endure everyday in my profession -- selling a highly technical project to a usually non-technical group of high level executives that hold the purse-strings for funding. I would start out by telling the non-technical executives how failure mechanics is useful to humankind -- how many lives it could have saved in certain situations -- by how it can save them from catastrophe and loses that their company has experienced. I would provide technical case studies where it has done so. Next, I would propose my plan to reduce such failures, their cost, and provide their proposed benefits. Then I would stand behind my promises with accountabilities that they can measure with financial results. Usually the executives are some of the most technically ignorant people around. They, however, must make the ultimate decisions and hold accountability. That's how it works in my world: good communication, good research, a good business case, and measurable results. I had to do something similar to this for my most recently funded project where we have concrete floor-coating failures that must be fixed or risk environmental contamination. The mid-level executives demanded the technical research to back my claims. Nobody has a satisfactory explanation in my opinion and I have to swag technical judgment into the solution. My reputation is always on the line, I have not been defeated yet, and I thank the creator for my successes. I am unrelenting, but I know when to quit. Edited by Engineer, : No reason given.
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Engineer Member (Idle past 5543 days) Posts: 65 From: KY, USA Joined: |
quote: I think the measurement systems will concur. I must prove it to myself. As an engineer I deal constantly with closed system and open system assumptions. Solar radiation on the earth is not a closed system and potentially could affect all surface measurements in some way. It might be miniscule, and even neutrons have a penetration limit, so it would have less effect as you go deeper into the earth's surface. K40 can change to A40 through irradiation as shown in this technical paper: http://geoinfo.nmt.edu/labs/argon/Methods/home.html
Other chemicals are produced as well. This is simply visiting the closed system assumption. Was the earth bombarded at one time, and would it even make a difference if it was? If it made a difference would it affect all measurement systems the same way? probably not. I still have to look. I'm sure I'm not the first to ask. Edited by Engineer, : added link
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