Re: [asa] Kirk on C14 contamination

The really unfortunate thing about the "scoffer" charge is its emotional
power. In context, it's clear that the "scoffers" are denying that God will
judge in the future. The author assures the Christian community that the
apparent delay in Christ's coming isn't an indication that God will not
judge; God has judged in the past, and He will judge again. The reference
to the flood does create some interesting and difficult hermeneutical
questions, but the charge of "scoffer" to anyone who denies a global flood
obviously misuses the text. Yet it's a very scary thing, particularly for
people such as myself raised in a conservative evangelical tradition, to
have to stand up to the charge of being a last-days "scoffer."

On Dec 3, 2007 7:32 PM, Steven M Smith <smsmith@usgs.gov> wrote:

>
> Kirk,
>
> I read your RATE post on TheologyWeb <
> http://www.theologyweb.com/campus/showthread.php?t=103916> and
> Baumgardner's reply both on TheologyWeb <
> http://www.theologyweb.com/campus/showpost.php?p=2140732&postcount=10> and
> Answer in Genesis <
> http://www.answersingenesis.org/articles/2007/11/30/feedback-rate-contamination>
> websites.
>
> First, thank you for your excellent postings and reasoned exchanges.
> Congratulations for presenting an argument so cogent that Dr. Baumgardner
> felt compelled to join your thread to defend his views.
>
> Second, I wish to commend you on your civility in response to
> Baumgardner's "less-than-professional" attacks on your character and
> scientific qualifications. Your posts are an excellent example of how
> scientists conduct a civil argument in publications. I highly recommend
> this TheologyWeb thread to anyone interested in the RATE research.
> (Unfortunately, to get to the good exchanges between Kirk & Baumgardner you
> will have to wade through some petty bickering by a few other
> less-well-behaved participants.)
>
>
> As I was catching up on reading some of the past ASA posts, I just noticed
> a question on this thread that was directed toward me.
>
>
> >> "In regard to 14C production due to the presence of uranium in crustal
> >> environments, I treat that topic in detail in section 7 of my chapter
> and
> >> show the maximum plausible 14C production rate, given measured
> >> neutron fluxes in deep mines and measured reaction cross sections,
> >> is more than four orders of magnitude too small to account even for
> >> the small measured 14C levels in diamonds. This same analysis also
> >> applies to coal. "
>
> [Let me add a little bit more of the Baumgardner quote that was not
> included in the previous post - SMS.]
>
> "Uranium concentrations in coal are typically less than those measured for
> granite, which is the setting for most of the diamonds we studied. (See the
> USGS fact sheet on uranium concentrations in coal and granite in the
> References.)"
>
> > Maybe Steve Smith can answer this better, but I believe that his
> > estimates came from granites, but that coals can have orders of
> > magnitude higher levels of uranium and thorium. Steve--any comments?
>
> I can't comment directly on Baumgardner's treatment of neutron fluxes and
> his conclusion that this source of 14C production is too small to be
> considered. I have not read his Chapter 7 and I am not inclined to attempt
> a review of his math. I can, however, speak with some knowledge on the
> concentrations of uranium and thorium in various rocks since this pertains
> to my own specialization in mineral exploration geochemistry and
> environmental geochemistry of metals. From this I will then make a few
> general statements that may pertain to his treatment of neutron fluxes.
>
> When I initially read this paragraph by Baumgardner, the first thing that
> jumped out was the statement about their RATE diamonds from a granitic
> setting. At best, Baumgardner is a little sloppy on his terminology here.
> Diamonds are not mined from or generally found in granitic settings.
> Hardrock diamonds are mined from kimberlite, an ultramafic rock that is at
> the opposite end of the spectrum from granites. Now, I am familiar with the
> tendency of stone masons, geologic engineers, and geophysical modellers to
> refer to any hard crystalline igneous as "granite" but chemically, these two
> rock types are about as different as dark & light. (Some geologists refer
> to ultramafic rocks as "primitive" and to granites as "evolved" but that is
> another story.) So if you are going to talk about the chemistry of
> diamond-bearing kimberlite, you would not look at the chemistry of granite.
>
> So what about uranium & thorium contents? The average crustal abundances
> for uranium & thorium are estimated at about 2 and 8 parts-per-million
> respectively (2 ppm = 0.0002%). Granites are generally enriched in
> uranium & thorium with averages around 4 - 5 ppm U and 15 - 20 ppm Th.
> Occasionally, some individual "highly evolved" granites have even higher
> concentrations. Ultramafics, on the other hand, are depleted in uranium &
> thorium with abundance averages around 0.001 ppm U and 0.004 ppm Th
> (references available upon request). Thus if all of the observed neutron
> flux in deep mines is generated from the decay of U & Th, then that flux
> should be on the order of 1,000 times less in mine within a kimberlite than
> one in a granite. Of course the flux would be much higher in an uranium
> mine regardless of the source rock. Therefore, you should expect several
> orders magnitude for neutron flux rates in different mines. Note: If
> Baumgardner truly measured or used neutron flux rates from deep mines within
> granite then he could be overestimating the effects of U-Th radiation on the
> production of 14C in diamonds. Despite his error in rock identification,
> Baumgardner would see this as evidence in favor of his argument. To truly
> evaluate the effects of U-Th neutron fluxes on 14C contents in diamonds, one
> would need to measure the flux in the actual mine that produced the diamond.
>
> Unlike igneous rocks (granites or kimberlites) where the uranium content
> is primarily derived from their initial magma chemistry, the plant material
> that ultimately becomes coal is generally very low in uranium. The bulk of
> uranium in coal is secondary; it came from somewhere else -- either early in
> the swamp, during the formation of the peat, during the change to coal, or
> late after the coal has formed. The chemical behavior of uranium gives us
> some clues. Uranium is very slightly water soluble in oxidized
> (oxygen-rich) environments and insoluble in reduced (oxygen-poor)
> environments. Many secondary uranium deposits of economic significance are
> found near large quantities of weathered granite or volcanic ash of granitic
> composition. The working model for these uranium deposits is that
> oxygenated water (i.e. rainwater) seeps through these rocks dissolving
> trace quantities of uranium (originally around 4 - 5 ppm U in that granitic
> rock). The slightly uranium-enriched waters move out of the granite or ash
> into more permeable rock layers (usually sandstones) and move down gradient
> until the water reaches a reducing environment. At this point the uranium
> precipitates out of solution and is left behind as the water moves on.
> Eventually the uranium is enriched sufficiently at this oxidation-reduction
> boundary (known in chemistry as a redox front) to form a deposit, which may
> contain up to a few percent uranium and other associated metals. As long as
> the groundwater flow regime remains constant, the deposit actually migrates
> slowly through the sandstone as oxygenated waters re-dissolve the uranium at
> the back of the deposit and move it forward until it is again reduced. We
> call these occurrences "Roll-Front Uranium" deposits or sometimes just
> "sandstone uranium deposits."
>
> I digressed into this discussion of uranium geochemistry and ore deposits
> because the organic material preserved in rocks is one of these reducing
> agents that causes uranium to precipitate out of solution. Sometimes these
> sandstones contained coalified or partially petrified wood. Here in
> Colorado, some of the sandstone uranium mines have actually processed
> high-grade uranium-bearing petrified logs and even uranium-enriched dinosaur
> bones as part of their ore. I've seen reports of coalified logs containing
> >16% uranium (160,000 ppm U). (I have a specimen of hot radioactive
> petrified wood that I store in a lead-lined ammo box. I also commonly take
> a Geiger counter out with me when I take school kids, scout groups, college
> groups, museum groups, church groups, and friends on local field trips to
> see dinosaur bones in sandstones.) Thin layers of interbedded black shale
> (compressed organic-rich mud) or coal in these deposits may also form
> high-grade uranium zones. And at least one small coal bed in Wyoming was
> mined in the early 1960's as an uranium deposit.
>
> So can we say that coals are generally rich in uranium? (And should I be
> worried about the amount of uranium pouring out a coal-fired power plant
> near me?) The answer to both of these questions is ... with a few
> exceptions, probably not. Before the screams of protest get too loud, let
> me explain. The large seams of coal mined for power plants generally have
> uranium concentrations that are indeed lower than granite. The average
> abundance range of uranium in coals (collected from coal mines in the United
> States) is generally between <1 to 4 ppm U; thorium concentrations in coal
> also range from 1-4 ppm. According to the USGS Fact Sheet cited by
> Baumgardner <
> http://greenwood.cr.usgs.gov/energy/factshts/163-97/FS-163-97.html>, coals
> with more than 20 ppm uranium are rare in the United States. (I have met
> both authors of this USGS Fact Sheet and they don't appear any more abnormal
> than the rest of us scientists <grin>.) According to a report about uranium
> in coal for the National Uranium Resource Evaluation (NURE) program (Facer,
> J.R., Jr, 1979, GJBX-56(79)) 250 samples of "commercial grade coal and
> lignite" from the northern Great Plains of the U.S. had uranium
> concentrations from 0.1 - 7.5 ppm averaging 0.9 ppm. A subset of these
> coals from the Powder River Basin, a known uranium producing region, ranged
> from 0.4 - 1.1 ppm and averaged 0.8 ppm. The few coals in the U.S. that
> show higher uranium contents are (1) generally very thin and have high ash
> contents (i.e., not good for power plants); or (2) have a slightly
> enriched uranium zone near the surface of the coal bed where it is in
> contact with a very permeable sandstone or conglomerate. Apparently, the
> redox front does not move very far into a coal seam. I know of one
> exception where high uranium coal is being used for power plants and cooking
> fires. This one is in China. Unfortunately in this locality, the people
> are suffering & dying of arsenic poisoning from the coal emissions long
> before any of the other metals, like uranium, are affecting them.
>
> So now, let's get back to Baumgardner's argument. He is correct on this
> point. Most coals have less uranium & thorium contents than granite. Since
> his coal samples apparently come from a group of commercially mined U.S.
> coals, in all probability his samples have low uranium & thorium contents
> also. (Baumgardner could confirm this by submitting his samples to a
> commercial geochemical laboratory for U & Th analyses. With costs ranging
> between $10.00 and $60.00 per sample depending on the method and the amount
> of sample prep work needed, the analyses would be cheap compared to the
> radiocarbon work.)
>
> Finally, what can we say about his argument that ...
>
> >> "the maximum plausible 14C production rate, given measured neutron
> >> fluxes in deep mines and measured reaction cross sections,
> >> is more than four orders of magnitude too small to account even for
> >> the small measured 14C levels in diamonds. This same analysis also
> >> applies to coal."
>
> (1) Assuming that the neutron flux is due almost entirely to the decay of
> U & Th atoms, then the use of measured neutron fluxes from granites
> *overestimates* the production of 14C in coal or diamonds from these
> neutrons.
> (2) However, if the neutron flux measurements were done in deep mines
> within ultramafic rocks (i.e. diamond mines) then flux rate is appropriate
> for discussing diamonds but *could be 1,000 to 2,000 times too small* for
> average coal samples.
> (3) This entire argument assumes that Baumgardner's equations for 14C
> production rates, based on neutron flux measurements, are correct and that
> the equations contain no assumptions based only on a presumed 6,000 year-old
> earth. I did not evaluate his math for either situation.
>
> Steve
> [Disclaimer: Opinions stated in this post are my own and are not to be
> attributed to my employer.]
> _____________
> Steven M. Smith, Geologist, U.S. Geological Survey
> Box 25046, M.S. 973, DFC, Denver, CO 80225
> Office: (303)236-1192, Fax: (303)236-3200
> Email: smsmith@usgs.gov
> -USGS Nat'l Geochem. Database NURE HSSR Web Site-
> http://pubs.usgs.gov/of/1997/ofr-97-0492/
>
>

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Received on Mon, 3 Dec 2007 20:24:07 -0500