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Old 05-26-2010, 08:46 PM   #944174  /  #51
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That's what Humphreys says, but not what his results show according to the graphs. At least, I think that's the argument. I'm not sure if I'm following it at this stage.
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Old 05-26-2010, 08:53 PM   #944186  /  #52
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Originally Posted by JonF View Post
The "defect bend" is where the amounts of "tightly bound" and "loosely bound" helium released become comparable and then the "tightly bound" helium release essentially disappears. Dr. Loechelt has demonstrated, in several ways and quantitatively, that the amount of "loosely bound" helium (and therefore the "defect bend") is insignificatn and may be ignored.
What is the physical justification for this? Pretend you're doing your PhD viva.
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Old 05-26-2010, 09:02 PM   #944198  /  #53
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Quote:
Originally Posted by VoxRat View Post
Quote:
Originally Posted by JamesBannon View Post
...
I think the argument is that a single diffusion model is adequate if one disregards the initial release of Helium during the heating ramp (because that's when the majority of the loosely bound Helium is released). Humphreys got it wrong by including the Helium released at lower temperatures.
Well, Humphreys thinks he's answered these concerns because he did not include the helium released in the first 9 steps (up to 450˚C):
Quote:
Loechelt is right in claim (A), but wrong in claim (B). He overlooked part of one of his own quotes, in which an expert pointed out that loose helium would only affect the initial steps of the laboratory measurement, because after the initial steps the loose helium would be gone. That is one reason diffusion experts recommend ignoring the initial steps. Our experimenter recommended that, and that is exactly what we did.35 Thus he felt free to tell us that the rates he measured were accurate depictions of the leakiness for the other 98% of the helium. Ironically, our expert is one of those that Loechelt cites in his section about this issue. Loechelt either completely misunderstood the experts, or he deliberately distorted their meaning.
I think I agree with Voxrat here (wow did that feel weird to type) ... Or at least I THINK I agree with Voxrat here if I understand him correctly.
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Old 05-26-2010, 09:11 PM   #944216  /  #54
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OK ... Dr. Loechelt ... please explain something to me ... Dr. Humphreys says you overlooked part of one of your own quotes. Which part of which quote does he think you overlooked and what is he talking about and what is your response to his criticism? Put it in laymanspeak please. I'm a busy, distracted guy who only vaguely remembers material science class and calculus class. My engineering degree is 25 years old and I never used it for anything except to get into Air Force flight school. :-)
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Old 05-26-2010, 10:19 PM   #944322  /  #55
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Dave Hawkins, the busy, distracted guy:
Quote:
Dr. Humphreys says you overlooked part of one of your own quotes. Which part of which quote does he think you overlooked and what is he talking about and what is your response to his criticism?
Minimal courtesy here, Dave, would be to link to or quote from where Humphreys makes this claim.

Other people are busy and distracted, too, and don't have any more time than you do to do the work to respond to your vaguely-phrased and unannotated concerns...
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Old 05-26-2010, 10:20 PM   #944326  /  #56
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Wouldn't the obvious way to find out what Humphreys thinks involve, say, asking Humphreys?
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Old 05-26-2010, 10:43 PM   #944352  /  #57
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Quote:
Originally Posted by Steviepinhead View Post
Dave Hawkins, the busy, distracted guy:
Quote:
Dr. Humphreys says you overlooked part of one of your own quotes. Which part of which quote does he think you overlooked and what is he talking about and what is your response to his criticism?
Minimal courtesy here, Dave, would be to link to or quote from where Humphreys makes this claim.

Other people are busy and distracted, too, and don't have any more time than you do to do the work to respond to your vaguely-phrased and unannotated concerns...
So I have to link to a post that's just two posts higher up?
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Old 05-26-2010, 10:56 PM   #944367  /  #58
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Two posts higher up than your query for Dr. Loechelt would be jet black's comment.

If you meant something in the material you quoted from voxrat, that's the post immediately above yours. Immediately does not mean "two posts higher up." Apparently this is what you did mean:
Quote:
He overlooked part of one of his own quotes, in which an expert pointed out that loose helium would only affect the initial steps of the laboratory measurement, because after the initial steps the loose helium would be gone.
In which case, it's still up to you to provide enough context from Humphreys that YOU can tell Dr. Loechelt which one of the latter's quotes Humphreys is talking about. If YOU can't tell, why should Dr. Loechelt be able to? If Humphreys can't adequately cite and quote so that he can be followed, why should we trust him as to anything he says, or claims to say, or claims somebody else said...?

If you meant something else, it doesn't appear to be on this page at all, much less "two posts higher up."



The minimal courtesy would involve mentioning that the claimed Humphreys quote in question is on the same page, post number x.
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Old 05-26-2010, 11:16 PM   #944377  /  #59
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Quote:
Originally Posted by VoxRat View Post
Quote:
Originally Posted by JonF View Post
...
The "defect bend" is where the amounts of "tightly bound" and "loosely bound" helium released become comparable and then the "tightly bound" helium release essentially disappears. Dr. Loechelt has demonstrated, in several ways and quantitatively, that the amount of "loosely bound" helium (and therefore the "defect bend") is insignificatn and may be ignored.....
This is where it gets a little confusing, because it sounds like the bottom line is that a single-domain model would be OK after all - since the neglected additional domain(s) is (are) indeed negligible.

I wonder if JonF &/or Dr. Loechelt can make enough sense of this question to offer an answer?
The neglected domains are negligible when calculating helium release in the wild based on a previously developed model of diffusion rate as a function of temperature. The neglected domains are not negligible when developing a model of diffusion rate as a function of temperature and using data measured at temperatures low enough for releases from the two domains are comparable without accounting for the presence of two domains.

At the "low" temperature (about 1/T > 1.8 in Loechelt's graph above) the amount of helium released from the "loosely bound" domain is comparable to the amount of helium released from the "tightly bound" domain. [i]The data points bending over to the right are in a sense artifacts, because they do not represent what would be measured if we could measure over long periods at realistic pressures in the wild[i]. (At least that's my understanding). If we could measure in the wild, we would see the points continuing along the red and yellow lines. (Loechelt gave a reference above)

Dr. Loechelt developed the yellow line from data from Reiners in 2004, using a single-domain model and only data from temperatures > 300C (I don't have readily accessible conversions here) where the release was predominantly from the "tightly bound" domain. Reiners didn't do any measurements below 300C. Loechelt has also used Humphreys' data to derive a similar line (not graphed anywhere as far as I know) from all of Humphreys' data using a model that accounts for the presence of the two domains.
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Old 05-26-2010, 11:37 PM   #944382  /  #60
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Quote:
Originally Posted by VoxRat View Post
Quote:
Originally Posted by JamesBannon View Post
...
I think the argument is that a single diffusion model is adequate if one disregards the initial release of Helium during the heating ramp (because that's when the majority of the loosely bound Helium is released). Humphreys got it wrong by including the Helium released at lower temperatures.
Well, Humphreys thinks he's answered these concerns because he did not include the helium released in the first 9 steps (up to 450˚C):
Quote:
Loechelt is right in claim (A), but wrong in claim (B). He overlooked part of one of his own quotes, in which an expert pointed out that loose helium would only affect the initial steps of the laboratory measurement, because after the initial steps the loose helium would be gone. That is one reason diffusion experts recommend ignoring the initial steps. Our experimenter recommended that, and that is exactly what we did.35 Thus he felt free to tell us that the rates he measured were accurate depictions of the leakiness for the other 98% of the helium. Ironically, our expert is one of those that Loechelt cites in his section about this issue. Loechelt either completely misunderstood the experts, or he deliberately distorted their meaning.
I don't have the data handy, but I believe the temperature was not monotonically increasing.

Posted from the other thread:

Quote:
Originally Posted by Dave Hawkins
Humphreys ...
Quote:
He overlooked part of one of his own quotes, in which an expert pointed out that loose helium would only affect the initial steps of the laboratory measurement, because after the initial steps the loose helium would be gone.
Quote he's referring to (?) ...

Quote:
it suggests that only a small proportion of gas resides in domains that exhibit anomalously high diffusivity, and therefore this phenomenon may not significantly affect the bulk closure temperature or He diffusion properties of most natural zircons. (Reiners, 2005, p. 154)
If this is the quote Humphreys is referring to, then it does indeed appear that Loechelt overlooked this or misunderstood it.
No, he hasn't overlooked it or misunderstood it. It's a quote-mine. Note the "...may not ...". Let's look at it in context:

Quote:
Originally Posted by Reiners
It is important to note that most available He diffusion experiments for zircon display anomalously high diffusivity in the earliest stages of step-heating. This behavior has also been observed in other minerals and is not well understood, and could have a range of origins, including effects from geometric vagaries of natural grain morphology, localized high-diffusivity from small high radiation-damage zones, crystallographically anisotropic diffusion, or inhomogeneously distributed He. Reiners et al. (2004) compared these non- Arrhenius features of the diffusion experiments with forward models of degassing from multiple domains of different sizes. These features could be matched well by positing small fractions of gas (2–4%) in domains with length-scales that are a factor of about 25–200 times smaller than the bulk grains themselves (Fig. 3). Zircons with a wide range of ages and radiation dosages exhibited approximately the same degree of non-Arrhenius behavior in initial diffusion steps. Although such modeling does not prove such a mechanism for these non-Arrhenius effects, it suggests that only a small proportion of gas resides in domains that exhibit anomalously high diffusivity, and therefore this phenomenon may not signifi cantly affect the bulk closure temperature or He diffusion properties of most natural zircons.

Although Reiners et al. (2004) suggested that the anomalously high and non-Arrhenius diffusion seen in early stages of step heating experiments can be explained in ways that may not be important for most thermochronometric applications, this has yet to be proven. These and other features of He diffusion in zircon (and in other minerals) such as erratic behavior in some samples, are not easily explained and their origins may yet prove to be important in understanding anomalous ages and model thermal histories. One potential concern for step-heating diffusion studies of the type shown here, and which is common to most other He diffusion studies, is the possibility for crystallographic modifications during experiments themselves. If heating at experimental temperatures and durations changes crystallographic features that affect diffusivity (e.g., by causing annealing), it is conceivable that such stepheating experiments may underestimate He diffusivity in natural zircons. Other important unresolved questions include the role of localized radiation damage zones in crystals whose bulk compositions would not suggest signifi cant damage, the possibility of anisotropic diffusion, the interaction of microstructures, inclusions, or fission-tracks with migrating He, the possible role of pressure in He diffusion, and He solubility in zircon.
It means that there may not be enough "loosely bound" helium to have a significant effect on how things happen in the wild.

In laboratory experiments which liberate a little "loosely bound" helium (because there isn't much) and also liberate a little "tightly bound" helium (because it's tightly bound), that little amount of "loosely bound" helium can strongly affect a single-domain model such as Humphreys'. The amounts released from the two groups are comparable, they're both small for different reasons. If you're going to do a single-domain model you need to ensure that the helium you're measuring comes from only one domain. Humphreys didn't,:


Quote:
Originally Posted by Loechelt
As can be seen, 30% of the loosely-bound helium (orange triangles) survived the first heating ramp at 15 hours, and 15% even survived the second heating ramp at 30 hours. Therefore, enough loosely-bound helium remained to explain the low-temperature diffusivity through-out the entire experiment. Although the exact gas release values at any given time step are sensitive to the assumptions used in constructing the multidomain model, most notably the partitioning fraction between the two helium domains, it does demonstrate that it is possible for a fraction of the loosely-bound helium to remain throughout the entire experiment, contrary to Humphreys’ unsubstantiated claims.
{emphasis added}

It might be possible to model the Fenton Hill zircons with reasonable accuracy with a single-domain model, because there's so little "loosely bound" helium. I don't know. {I know now; the answer it is possible}.But it's certainly impossible to model the Fenton Hill zircons with a single-domain model based on measurements of helium outgassing from two domains in comparable quantities because the "loosely bound" helium skews the calculation of the model parameters, and skews them a lot. Loechelt has demonstrated that Humphreys did exactly that. Humphreys has not made any substantive response.

Of course, as Reiners et. al. demonstrated in 2005, a multidomain model is needed for highly accurate modeling of helium diffusion in zircons. Humphreys has ignored this important and obviously relevant finding.

And, of course, Davie won't understand a word of this. But others may.

More at A Response to the RATE Team Regarding Helium Diffusion in Zircon
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Old 05-27-2010, 12:56 AM   #944447  /  #61
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Thanks, Jon, I was following the argument after all. It seems to me that the two-domain diffusion model was necessary to highlight the mistakes made by Humphreys. There is also the question of precisely where the "cut off" temperature will be. Presumably, this is going to vary for individual crystals, and since there is no a priori method of determining exactly how much Helium will be loosely bound, the two-domain modelling would still be necessary.

Since Dave seems somewhat reluctant to answer my question, perhaps either yourself or Dr Loechelt could oblige? Is there any a priori justification in Humphreys conclusion that all of the Helium released from the crystals would be endogenous? (I suppose this question is related to the Carbon-14 in coal thread).
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Old 05-27-2010, 01:13 AM   #944467  /  #62
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Originally Posted by JamesBannon View Post
Thanks, Jon, I was following the argument after all. It seems to me that the two-domain diffusion model was necessary to highlight the mistakes made by Humphreys. There is also the question of precisely where the "cut off" temperature will be. Presumably, this is going to vary for individual crystals, and since there is no a priori method of determining exactly how much Helium will be loosely bound, the two-domain modelling would still be necessary.
AFAIK there are good reasons for believing the "loosely bound" helium is always much much less than the "tightly bound" helium.

Quote:
Since Dave seems somewhat reluctant to answer my question, perhaps either yourself or Dr Loechelt could oblige? Is there any a priori justification in Humphreys conclusion that all of the Helium released from the crystals would be endogenous? (I suppose this question is related to the Carbon-14 in coal thread).
Well, given a randomly chosen zircon the probability it's been exposed to a concentration of helium that would reverse the diffusion is pretty low. But there are known to be helium sources near Fenton Hill. I think that it's still pretty unlikely for the Fenton Hill zircons, but it's a low-probability possibility that should be considered and discussed. IMHO.
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Old 05-27-2010, 04:37 AM   #944851  /  #63
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It appears that Dr. Henke, a geologist, is not a diffusion expert as Dr. Loechelt is.

The effects of pressure in the field may or may not be important

All the stuff about mica is basically arm-waving. Nowhere is there any data supporting a quantitative equivalence between zircons under pressure and mica under pressure. Mica certainly is quite physically different from zircon.

It does seem that lab diffusion experiments under vacuum are standard and justified. So I think that there's no need to do the experiments at pressure.

The "defect bend" is where the amounts of "tightly bound" and "loosely bound" helium released become comparable and then the "tightly bound" helium release essentially disappears. Dr. Loechelt has demonstrated, in several ways and quantitatively, that the amount of "loosely bound" helium (and therefore the "defect bend") is insignificatn and may be ignored.

I don't know about Humphreys' prediction of the location of the "defect bend". I have the paper but I can't access it right now, and Dr. Loechelt might have some comment.
Ok so i think im getting this. (technical stuff is hard for me) So do i have this correct : Humphreys results are wrong but they are wrong for the reasons that Dr Loechelt suggests not the reasons Dr Henke suggest? (at least not the vaccuum reason?)
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Old 05-27-2010, 06:24 AM   #944926  /  #64
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Originally Posted by JamesBannon View Post
Thanks, Jon, I was following the argument after all. It seems to me that the two-domain diffusion model was necessary to highlight the mistakes made by Humphreys. There is also the question of precisely where the "cut off" temperature will be. Presumably, this is going to vary for individual crystals, and since there is no a priori method of determining exactly how much Helium will be loosely bound, the two-domain modelling would still be necessary.
Yes James, I think your synopsis is better than what I was planning to write. (I am too wordy at time.) Basically, there are more right ways to model the data than wrong ways. Humphreys and company just happened to do it wrong.

Right Ways

1. Use a single-domain model and extract the diffusion parameters from the high-temperature data.

2. Use a multi-domain model and extract the diffusion parameters over the entire temperature range.

Wrong Way

3. Use a single-domain model and extract the diffusion parameters from the low-temperature data.

You are also correct that the cut-off temperature cannot be exactly known in advance. In principle, there can be variability from sample to sample. Having said this, I think it is more than coincidence that in Reiners (2004), they never bothered taking the temperature below 300 C, and in Humphreys (2004), the cut-off is right around 300 C. Coincidence or experience?

Speaking of experience, I find these series of quotes by Humphreys interesting.

Quote:
The Nevada zircon data did not extend to low enough temperatures to compare them with the He Retentions. (Humphreys, D.R., 2005. Young helium diffusion age of zircons supports accelerated nuclear decay. In Vardiman et al. (2005), Chapter 2, p. 38.)
The "Nevada zircon data" refers to a 2002 paper by Peter Reiners. Humphreys is complaining that his diffusion experts did not take the temperature below 300 C.

Quote:
After that, in the summer and fall of 2002, we tried several times to get lower-temperature zircon data. (Humphreys, D.R., 2005. Young helium diffusion age of zircons supports accelerated nuclear decay. In Vardiman et al. (2005), Chapter 2, p. 41.)
Humphreys was not satisfied that the original helium diffusion experiment performed by his experts only went down to 300 C.

Quote:
This time we asked the experimenter (a) not to etch the crystals in HF (unnecessary anyhow because no sieving was needed) and (b) to get zircon diffusivities at lower temperatures. (Humphreys, D.R., 2005. Young helium diffusion age of zircons supports accelerated nuclear decay. In Vardiman et al. (2005), Chapter 2, p. 43.)
Three times Humphreys insists on going to lower temperatures. Notice it is the amateurs telling the experts what to do, not the other way around. I wonder what his diffusion experts thought? But they were under contract, and as the saying goes, the customer is always right. What did they find at lower temperatures?



Just below 300 C, the Arrhenius curve begins to deviate from a straight line. This exactly the point at which Fechtig and Kalbitzer advise the users of their diffusion method to ignore the data. (Fechtig, H., Kalbitzer, S., 1966. The diffusion of argon in potassium-bearing solids. In Potassium Argon Dating, Schaeffer, O.A., Zähringer, J. (Ed.), Springer-Verlag, New York, p. 101.) Coincidence? Or did Farley and Reiners know that they were wasting their time (but someone elses money) by investigating here?

Quote:
Originally Posted by JamesBannon View Post
Since Dave seems somewhat reluctant to answer my question, perhaps either yourself or Dr Loechelt could oblige? Is there any a priori justification in Humphreys conclusion that all of the Helium released from the crystals would be endogenous? (I suppose this question is related to the Carbon-14 in coal thread).
I think most of the helium was endogenous. The zircon crystal has a high affinity for radioactive elements like uranium and thorium, which usually makes it more radiogenic than its host rock. Most of the helium was probably generated inside the crystal by radioactive decay.

An intersting prediction of my multi-domain diffusion model, however, is that the "loosely-bound" helium could not have survive inside the crystals for 1.5 billion years. Then why was any found in the RATE samples? I believe that the "loosely-bound" helium was exogenous, and that the "tightly-bound" helium was endogenous. All takes is about 0.3% "loosely-bound" exogenous helium to account for the low temperature tail in the diffusion experiment. This is a very reasonable background helium level for this rock formation, based upon whole rock elemental analysis. That 0.3% "loosely-bound" exogenous helium would be trapped inside the zircons by the host rock until crushed and heated under vacuum in the diffusion experiment. Then it would escape, manifesting itself as a low-temperature tail in the Arrhenius curve. Seeing a small quantity of helium being so quickly released at low temperatures, Humphreys concluded that all the helium must also be so "loosely-bound" in the crystal at low temperatures, and constructed his model accordingly. He totally ignored the temperature dependence of the majority of "tightly-bound" helium that was liberated at high temperatures. Herein lies the fatal error.
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Old 05-27-2010, 06:33 AM   #944931  /  #65
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Quote:
Originally Posted by Steviepinhead View Post
Dave Hawkins, the busy, distracted guy:
Quote:
Dr. Humphreys says you overlooked part of one of your own quotes. Which part of which quote does he think you overlooked and what is he talking about and what is your response to his criticism?
Minimal courtesy here, Dave, would be to link to or quote from where Humphreys makes this claim.

Other people are busy and distracted, too, and don't have any more time than you do to do the work to respond to your vaguely-phrased and unannotated concerns...
Dave,

I have to agree with Stevie here. Your promise earlier in this thread was to "walk us through" any rebuttal that Humphreys had published regarding his critics. Now you are asking one of his critics to "walk you through" his rebuttal. The other reason I agree with Stevie is that you place the entire burden of proof on me. I object to that. If you compare the amount and quality of material I have posted online in comparison to Humphreys' few short paragraphs written against me, I think it is only fair to expect Humphreys to provide more information for his readers to understand the point he was trying to make.
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Old 05-27-2010, 07:37 AM   #944950  /  #66
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Ok sorry to ask another strupid question but i was just re reading this thread and I noticed on the first page Dr Loechelt posted this graph , I this graph from Humphreys experiment or is it Dr Loechelts corrected one, basically im asking is it right ot wrong coz I dont understand it. I know I seem like an idiot and im sorry its just hard for me to understand this stuff.
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Old 05-27-2010, 08:01 AM   #944959  /  #67
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I'm gonna hazard a guess that this graph is Dr. Loechelt's comparison of the data from the various papers cited in the top right corner of the graph. I'm sure that the graph has been sourced any number of times by now, but the thread -- together with it's predecessor -- has gotten to be a long one, with a variety of different graphs assuming center stage at various times, and at times more than once...

But I could easily be wrong, and am interested in knowing the right answer as well.

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Old 05-27-2010, 09:23 AM   #944984  /  #68
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CRAP! I just realised thats the wrong graph! I meant to ask about this graph!
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Old 05-27-2010, 09:38 AM   #944990  /  #69
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Well, it's another pretty one, for sure.
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Old 05-27-2010, 12:07 PM   #945075  /  #70
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Ok sorry to ask another strupid question but i was just re reading this thread and I noticed on the first page Dr Loechelt posted this graph , I this graph from Humphreys experiment or is it Dr Loechelts corrected one, basically im asking is it right ot wrong coz I dont understand it. I know I seem like an idiot and im sorry its just hard for me to understand this stuff.
asking questions about things you don't understand is the very opposite of being an idiot the cleverest people in the world do that all the time.
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Old 05-27-2010, 01:12 PM   #945126  /  #71
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OK ... Dr. Loechelt ... please explain something to me ... Dr. Humphreys says you overlooked part of one of your own quotes. Which part of which quote does he think you overlooked and what is he talking about and what is your response to his criticism? Put it in laymanspeak please. I'm a busy, distracted guy who only vaguely remembers material science class and calculus class. My engineering degree is 25 years old and I never used it for anything except to get into Air Force flight school. :-)
OK guys, really ... how tough can this be to figure out what I'm talking about here? All you have to do is look at the previous post (sorry, I said earlier it was two posts up). But here's a link ... http://talkrational.org/showthread.p...198#post944198 ... it obviously would be more appropriate to ask Humphreys these questions, but he's not here and you are. So ... can you answer them?
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Old 05-27-2010, 01:27 PM   #945145  /  #72
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Dr. Loechelt ...
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He totally ignored the temperature dependence of the majority of "tightly-bound" helium that was liberated at high temperatures. Herein lies the fatal error.
How do you figure that he totally ignored this? My understanding of this "low temperature tail" is that it's the "defect portion" of the curve. I see no evidence that Humphreys ignored this. In fact, he discussed it at length and even extrapolated it to calculate what temperature would be required for the Old Earth model to work. Very cold BTW ... sub-zero.
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Old 05-27-2010, 01:42 PM   #945164  /  #73
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Dr. Loechelt ...
Quote:
He totally ignored the temperature dependence of the majority of "tightly-bound" helium that was liberated at high temperatures. Herein lies the fatal error.
How do you figure that he totally ignored this? My understanding of this "low temperature tail" is that it's the "defect portion" of the curve. I see no evidence that Humphreys ignored this. In fact, he discussed it at length and even extrapolated it to calculate what temperature would be required for the Old Earth model to work. Very cold BTW ... sub-zero.
Dave,
This is the type of "analysis" that people get frustrated with.

LINK to Humphreys paper where he says this stuff.
THEN copy the pertinent paragraphs into a quote.
THEN explain how those paragraphs, contained in the linked paper, support your point.

THEN, for extra credit, copy the parts of Loechelt's paper (with a link of course) that you think doesn't address (i.e. mentions but doesn't really rebut) Humphreys work.

THAT is a minimum of effort that people are asking for. Otherwise people will have to sift through your statement and try to find the Huphreys paper they think is the correct one and then come back and ask you "Is this the right paper Dave?" and then find the quotes that you think mention this stuff and then ask "Is this the right quotes Dave?"

Do you get it? An extra one minute on your end moves the whole conversation along much quicker and leads to less confusion for all.
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Old 05-27-2010, 01:46 PM   #945168  /  #74
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Dr. Loechelt ...
Quote:
He totally ignored the temperature dependence of the majority of "tightly-bound" helium that was liberated at high temperatures. Herein lies the fatal error.
How do you figure that he totally ignored this? My understanding of this "low temperature tail" is that it's the "defect portion" of the curve. I see no evidence that Humphreys ignored this. In fact, he discussed it at length and even extrapolated it to calculate what temperature would be required for the Old Earth model to work. Very cold BTW ... sub-zero.
And the reason for that is because his model over-estimated the amount of Helium retained in the Zircon crystals. Look at the curves around the defect bend.
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Old 05-27-2010, 02:16 PM   #945194  /  #75
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Quote:
Originally Posted by Dave Hawkins View Post
OK ... Dr. Loechelt ... please explain something to me ... Dr. Humphreys says you overlooked part of one of your own quotes. Which part of which quote does he think you overlooked and what is he talking about and what is your response to his criticism? Put it in laymanspeak please. I'm a busy, distracted guy who only vaguely remembers material science class and calculus class. My engineering degree is 25 years old and I never used it for anything except to get into Air Force flight school. :-)
OK guys, really ... how tough can this be to figure out what I'm talking about here? All you have to do is look at the previous post (sorry, I said earlier it was two posts up). But here's a link ... http://talkrational.org/showthread.p...198#post944198 ... it obviously would be more appropriate to ask Humphreys these questions, but he's not here and you are. So ... can you answer them?
Ok, so you don't know the quote, you don't know what Humphreys is talking about, you pretty obviously won't understand any response, and you don't bother giving us a link to where Humphreys said that anyway...

So... how the living fuck is anyone supposed to answer your questions???


Dave... go ask Humphreys what he's talking about first, THEN come back and start asking questions. There is no point answering them if you don't know what the damned questions mean in the first place!





Oh, and Dave? Just for your information, those bloody questions have indeed been answered already... you've just simply ignored them and insisted that someone answer them.

Again...

And again...

AND again........
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