pseudobug

Don't laugh too much.

<a href="http://www.pathlights.com/ce_encyclopedia/04earth4.htm" target="_blank">"Genesis Rock" formed in under three minutes.</a>

[ February 16, 2002: Message edited by: pseudobug ]</p>

bluefugue

If rock was supposedly originally formed by a fiat of Yahweh, why would we expect this process to be duplicable under natural circumstances? Are we to suppose creation of rock by fiat is a repeatable process? Perhaps the creation of Adam out of dirt is repeatable too. Let's start analyzing clumps of dirt in the lab and see if any spontaneously turn into humans. (Uh oh, that sounds suspiciously like a creationist strawman of abiogenesis. )

John Solum

I'm not going to write a detailed refutation of that site since several already exist.

<a href="http://66.186.202.216/polohalo/poindex.htm" target="_blank">http://66.186.202.216/polohalo/poindex.htm</a>

<a href="http://www.talkorigins.org/faqs/po-halos.html" target="_blank">http://www.talkorigins.org/faqs/po-halos.html</a>

<a href="http://www.csun.edu/~vcgeo005/creation.html" target="_blank">http://www.csun.edu/~vcgeo005/creation.html</a>

From the YEC Geoscience Research Institute:
<a href="http://www.grisda.org/origins/15032.htm" target="_blank">http://www.grisda.org/origins/15032.htm</a>

I do want to make a few comments about the website.

1) YECs are inconsistent with their claims about the constancy of radioactiv decay rates. On one hand they argue that they could have changed (invalidating radiometric dating), and on the other, they argue that they haven't (Po halos). Either decay rates are constant, or they aren't.

2) The polonium halos occur in rocks that are associated with deposits of U-238 of which Po-218, 241, and 210 are daughter isotopes.

3) The Po halos that Gentry examined aren't in primary rocks, they occur in intrusions into primary rocks, and so the Po halo-bearing rocks aren't primary.

4) Granites don't just occur in Precambrian rocks, they also occur in what creationists would classify as "Flood rocks", which makes Gentry's claim that granite can't form naturally hard to support.


The term "totally solid mineral" is ridiculous. Do they suppose that mica is partially liquid? (actually, I think they're referring to the fact that micas have a very pronounced cleavage direction, while fluorite's cleavage is less pronounced-that doesn't help there case though). Also, at the scale at which the halos form, no material is unflawed. At the microscopic scale, all materials have defects, even glass what appears to be "solid, thick, unflawed glass." In fact it was studies of glass milk bottles that led to the realization that all materials have defects. Finally, fluorite is a secondary mineral that usually forms from hydrothermal fluids. If the Po halos are found in secondary minerals, then clearly the halos aren't remnants of the creation event. I also want to point out that if Po halos can form in secondary minerals, then since the Po wasn't there to begin with, there has to be a way for it to migrate into minerals (this migration was likely of Radon-222, a gas, which decayed to form Po-218, 214, and 210). This makes it difficult to support the position that Po haloes in mica are primary.

[ February 17, 2002: Message edited by: John Solum ]</p>

ps418

JohnS:
3) The Po halos that Gentry examined aren't in primary rocks, they occur in intrusions into primary rocks, and so the Po halo-bearing rocks aren't primary.

Indeed. Some of Gentry's halos were not even from granite, but from pegmatite veins which cross-cut older metamorphosed sedimentary and igneous formations. His interpretation of the haloes is of course ruled out by basic structural relationships, such as one might learn in the first week of an introductory geology class.

Wakefield describes his attempts to inform Gentry about the evidence from the sedimentary rocks. I found this most amusing:

"In his book Gentry talks of 'pristine sedimentary' created rocks which look as though they were intruded by granites. When Gentry phoned me (unfortunately, Gentry has never responded to my letters in any manner other than with phone calls) after I sent him a copy of this paper in preliminary form, I asked him about these sedimentary rocks. He claimed that metasedimentary rocks show no clear origin because of their recrystallization. Because his response was so patently false, I told him that many of these metasedimentary rocks show clear and unambiguous sedimentary features, like clastic grains, cobbles, ripple marks, mudcracks, bedding plains and, most important, stromatolites. He had no answer."

To quote Collins, this is not science, but merely a monumental example of the Omphalos argument.


Other problems:

Contact aureoles around many granites require long-periods of high heat, which is inconsistent with the granitic body cooling below closure temperature within 3 minutes. Some aureoles are up to 1000m thick!

<a href="http://www.tulane.edu/~sanelson/geol212/contactmeta.htm" target="_blank">http://www.tulane.edu/~sanelson/geol212/contactmeta.htm</a>
<a href="http://geology.csupomona.edu/drjessey/class/GSC425/Ig-Met23.html" target="_blank">http://geology.csupomona.edu/drjessey/class/GSC425/Ig-Met23.html</a>

Many granites contain inclusions of older country rock. I've seen some great photos of big chunks of banded gneiss 'floating' in granitic matrix. If granites are creation rocks, where the hell did those banded gneiss come from?

There are also examples, as John suggests, of *fossiliferous* inclusions in granite, which shows that granites are not simply creation rocks. Collins' list several examples of this:

" the Donegal granites in northwest Ireland intrude and enclose inclusions of sedimentary rocks of Cambrian age, illustrating that the granites are younger than the Cambrian deposits, whose contacts with the granites have a high-temperature metamorphic aureole (Pitcher and Berger, 1972). The same kinds of metamorphic contact-relationships are found in the granites that intrude fossil-bearing sediments in Maine, Connecticut, and Rhode Island (Harrison et al., 1983).

"The Narragansett Pier granite in Rhode Island surrounds inclusions of Pennsylvanian metamorphosed sediments containing flora fossils, Annularia stellata (Brown et al., 1978). The flora fossils are now totally carbonized as graphite, indicating the high temperature of the granite body that metamorphosed the sedimentary inclusions. The fact that the granite contains inclusions of these fossil-bearing sediments makes the granite younger than these supposed "Flood" sediments.

"The Sierra Nevada granite intrusions in California also have intruded and metamorphosed supposed 'Flood sediments' in roof pendants containing Ordovician graptolite fossils (Frazier et al., 1986) and Pennsylvanian brachiopod fossils (Rinehart and Ross, 1964; Rinehart et al., 1959). In other places, the Sierran granites have intruded and metamorphosed "Flood sediments" containing Triassic ammonites (coiled cephalopods) (Smith, 1927).

"A granite in the Mojave desert in California near Cadiz intrudes Cambrian limestone containing stromatolite fossils. At the contact, this limestone is converted to marble with high-temperature metamorphic minerals, but remnants of the stromatolites can still be found (Richard Squires, oral communication, 1998). Thus, it is very clear from the above examples that some granite masses are the same age as or even younger than the 'Noachian Flood deposits.'"


Brown, A., Daniel, P., and Barghoorn, E. S., 1978, Pennsylvanian fossils from metasediments within the Narragansett Pier granite, Rhode Island: Geological Society of America Abstracts with Programs, v. 10, n. 2, p. 34-35.

Frazier, M., Stevens, C. H., Berry, W., Smith, B. M., and Varga, R., 1986, Relationship of the Sierran Coyote Creek pendant to the adjacent Inyo Mountains, east-central California: Geological Society of America Abstracts with Programs, v. 18, n. 2, p. 106.

Harrison, W., Flower, M., Sood, M., Tisue, M., and Edgar, D., 1983, Crystalline rocks of northeastern United States: ANL/ES- Argonne National Laboratory, v. 137, p. 414.

Pitcher, W. S., and Berger, A. R., 1972, The Geology Of Donegal: A Study Of Granite Emplacement And Unroofing: New York, Wiley Interscience, 435 p.

Rinehart, C. D., and Ross, D. C., 1964, Geology and mineral deposits of the Mount Morrison quadrangle, Sierra Nevada, California: U. S. Geological Survey Professional Paper 385, 106 p.

Smith, J. P., 1927, Upper Triassic marine invertebrate faunas of North America: U. S. Geological Survey Professional Paper 141, 262 p.

Another observation falsifying the instant granite scenario is the radiometrically-dated cooling history of granitic bodies. It is possible to determine the cooling history of igneous bodies by dating different minerals within the body. Because these minerals have different closure temps, they can be used to determine when the melt passed certain temperatures. Results from such thermochronologic studies shows that granites do in fact originate from high-temp magmas that cooled slowly over time.

As an example, Joe Meert describes evidence for the cooling history of the Carion Pluton in Madagascar.

<a href="http://baby.indstate.edu/gga/pmag/radiomet.htm" target="_blank">http://baby.indstate.edu/gga/pmag/radiomet.htm</a>
Meert writes:


"Closure temperature of isotopic systems also provides a check of radiometric dates. In slowly-cooled igneous bodies such as granites, different minerals become closed systems at different temperatures (McDougall and Harrison, 1999). This is due, at least in part, to the fact that the minerals crystallize at different temperatures. The temperatures at which minerals close is easily verifiable through experimentation and this has been conducted numerous times including the famous experiments of Bowen. Therefore, if a body has indeed cooled slowly then the radiometric dates from that rock should demonstrate such a cooling trend.

"The Carion pluton in central Madagascar is approximately 20 kilometers in diameter and is the subject of an ongoing paleomagnetic study (Meert et al., in press). The rocks have been dated using both the U-Pb system and the 40Ar/39Ar system on a variety of minerals. The following table outlines the closure temperatures of the various minerals used in the Carion study along with their ages. Details regarding closure temperature studies can be found in McDougall and Harrison (1999).

Isotopic System /Closure Temperature/Age

Zircon U-Pb 850 +/- 50 C 532.1 +/- 5 Ma

Hornblende 40Ar/39Ar 500+/-50 C 512.7 +/-1.3Ma

Biotite 40Ar/39Ar 350+/-50 C 478.9 +/-1.0Ma

K-spar 40Ar/39Ar 200+/-25 C 435.0 +/-10Ma

K-spar 40Ar/39Ar 100+/-25 C 410 +/-10Ma



"Note that the ages of the minerals yields a cooling-curve that is consistent with the experimentally-derived closure temperatures of the isotopic systems**. Had decay rates not been constant, then we might expect to see a gross discordance of mineral ages in this study. Instead, we see a very nice cooling curve for this magma. The story doesn't end there however! This study also included a look at the paleoposition of Madagscar at the time this rock cooled. This is done through the study of paleomagnetism. Madagascar was thought to be a part of a larger supercontinent called Gondwana during this time period. A reference curve for Gondwana has been developed that basically traces the paleoposition of Gondwana during the time interval from 550-475 Ma (Meert et al., in press). If Madagascar was indeed a part of this supercontinent, then the paleomagnetic directions for Madagascar should be indentical to the directions from other continents that make up Gondwana. Since magnetic minerals in the Carion rocks lock in their directions at temperatures between 550-450 C (in this study), then the age of magnetization is about 511 +/- 10 Ma. The position of Mdagascar should match up with other 510 Ma directions from Gondwana---and they do!."

[ February 17, 2002: Message edited by: ps418 ]</p>

ps418

Its even worse than that. Any change in decay constants compromises the identification of the haloes in the first place. Gentry is identifying the halos based on their diameter, yet the diameter of the halos is partly a function of decay rate! R.H. Brown, on the GRISDA page above, points out:

"Halo identification is achieved through the measurement of the halo diameter. The size of the halo and the half-life of the isotope producing it are related. Assuming that the half-life of the parent isotope has remained constant throughout the formation of the halo, the initial energy of the alpha particles that produced the halos can be determined, and hence the parent radioactive isotope identified.

"In making this identification, Gentry assumes, as do other scientists, a constancy of radioactive decay rate for polonium. However, Gentry also wants to invoke periods of time that '... may have been accompanied by an increased, nonuniform radioactive decay rate' (p. 134). If there were periods of nonuniform decay rates, identification of any pleochroic halo from its ring diameter would be questionable at best!

"All available data indicate that halo ring diameter increases with increase in decay rate. Either the rates remain constant or they do not. Evidence from other sources suggests that the decay rates have remained constant for all radioactive isotopes. Several problems arise when one attempts to invoke increased decay rates while at the same time keeping the halo diameters constant! Such inconsistency cannot be considered as a satisfactory argument.

Valentine Pontifex

This is a very interesting observation and off-hand I don't recall anyone mentioning it. Though I suppose I might have forgotten since it has been a while since I read anything on the halo issue. It might make a good point if anyone ever writes an FAQ on constant decay rates for Talk.Origins. (I know there is a sci.physics FAQ but it really does not address the creationists.)

BTW, did you ever see the following:
<a href="http://www.talkorigins.org/origins/postmonth/mar01.html" target="_blank">Modifications of Nuclear Beta Decay Rates</a>

Valentine Pontifex

So the YECs have unwittingly stumbled upon powerful evidence that the decay rates have stayed relatively constant since the formation of the rock!?!

This could make a good FAQ.

BTW, since I mentioned it earlier:
<a href="http://www.public.iastate.edu/~physics/sci.physics/faq/decay_rates.html" target="_blank">sci.physics FAQ on constant decay rates</a>

John Solum

Patrick
This is very true, and as LordValentine pointed out, YECs inadvertently stumbled across a way to check the constancy of decay rates. I'm curious to see how YEC organizations will react. If they accept Gentry's work they have to accept radiometric dating, and if they reject radiometric dating, they have to reject Gentry's work.

Thanks for the references to Phanerozoic granites. Assuming that YECs would classify Phanerozoic rocks as Flood rocks (or at least the Paleozoic and Mesozoic), I'm curious about how they can explain Phanerozoic intrusions that are involved in Phanerozoic unconformities. The time needed for granite to cool is a classic problem with YEC. John Woodmorappe and Andrew Snelling wrote an article a few years back in which they stated that large intrusions could be cooled in a few hundred years through convective cooling. Let's assume that they're right (I don't think they are) and that granitic intrusions can cool in a few hundred years. Now, consider this hypothetical scenario: a granite is intruded into Devonian age rocks (which would be classified as Flood rocks) that are unconformably overlain by Permian rocks (also classified as Flood rocks), and the granite is cut by the unconformity (indicating that the granite was at the surface when the unconformity formed). Since the granite had cooled by the time the unconformity formed, using Woodmorappe and Snelling's calculations, a gap of at least hundreds of years must exist between the Devonian rocks and the Permian rocks. Since YECs would classify rocks of those ages as Flood rocks, either the Flood was hundreds of years long or either the pre-Devonian or post-Permian age rocks weren't deposited by the Flood (which leaves YECs with the problem of explaining how those rocks were formed).

LordValentine
I've seen that one before, but the sci.physics FAQ is new to me. Thanks a lot for posting it, it's a great resource.

I saw an FAQ somewhere that was titled "Using YEC to refute YEC", (I can't remember where, I'll try to find it). Using Po-haloes to refute claims about variable decay rates would be right in line with that.

ps418

Originally posted by John Solum:
I'm curious about how they can explain Phanerozoic intrusions that are involved in Phanerozoic unconformities. The time needed for granite to cool is a classic problem with YEC. John Woodmorappe and Andrew Snelling wrote an article a few years back in which they stated that large intrusions could be cooled in a few hundred years through convective cooling. Let's assume that they're right (I don't think they are) and that granitic intrusions can cool in a few hundred years. Now, consider this hypothetical scenario: a granite is intruded into Devonian age rocks (which would be classified as Flood rocks) that are unconformably overlain by Permian rocks (also classified as Flood rocks), and the granite is cut by the unconformity (indicating that the granite was at the surface when the unconformity formed). Since the granite had cooled by the time the unconformity formed, using Woodmorappe and Snelling's calculations, a gap of at least hundreds of years must exist between the Devonian rocks and the Permian rocks.

If the pre-Permian granite is truncated by the unconformity, then not only do you have the cooling-time for the granite, you also have the erosion time to truncate the granite.

The problem would be even worse if the pre-Permian granite was capped by a thick (&gt;10m) grus or kaolinitic weathering horizon, since these would require 10 - 100k years to develop, even under ideal conditions.

On the rapid cooling of igneous bodies proposed by Snelling and Woodmorappe. Their calculations do not 'solve' the problem of cooling large igneous bofies, because they assume hydrothermal cooling conditions that do not apply to many large igneous bodies. Whether or not a granitic magma was in fact hydrothermally cooled can be deduced from isotopic evidence (depletion of O18) and other lines of evidence (association with metal deposits, etc). And of course in many cases the actual cooling history of many ignoues bodies can be deduced by dating minerals and plotting the dates against their experimentally-determined closure temp, as Meert's example shows.

Patrick

[ February 18, 2002: Message edited by: ps418 ]

[ February 18, 2002: Message edited by: ps418 ]</p>

John Solum

Hi Patrick,

Your comments about the formation of a weathering horizon are correct, and are certainly worth pointing out, but what I was attempting to do is to show that the YEC "model" of granite formation can be refuted solely using YEC research.

I also agree that if granites were convective cooled, that there should be some evidence of that process (the stable isotopes (although I'd think the change in isotopic composition would be related to the composition of the convecting fluid) and mineralization you mentioned as well as alteration of the intrusion).

You're also mostly correct about the determination of the cooling history of intrusions, but I'd like to point out that the ages aren't crystallization ages (i.e., the ages don't all represent the time when the mineral crystallized from the magma), they're cooling ages, representing the time when an already-crystalline mineral cools below its closure temperature. For example, a mineral crystallizes, then after that it passes through its closure temperature, the "clock" begins. If the temperature is maintained above the closure temperature, but below the crystallization temperature, then the mineral will not be a closed system and the "clock" will not start. You have to remember the geothermal gradient (~25 deg C/km), so at the depths at which the intrusion crystallizes, the ambient temperature will be fairly high. I think this is why Joe Meert's graph levels off at ~100 deg C. That was the ambient temperature of the rock into which the granite was intruded (which equates to a depth of ~4km). So, the higher temperature part of Joe's curve is most likely associated with the crystallization of the magma, and the lower temperature part isn't.

With all that said, the cooling histories of rocks that are currently being uplifted (or were uplifted in the past) provide information about uplift rates (since the closure temperature can be turned into a depth through the geothermal gradient), which is something that's good to know. Determination of uplift rates is a pretty hot area of research right now, and it's why people look at some systems with really low closure temperatures like U/Th/He.

EDIT:

I just thought of an easier way to make my point. The granite doesn't cool to 0 deg. C, it cools to the temperature of the surround crust, which is a function of the depth at which the granite exists (the geothermal gradient is ~25 deg. C/km). A granite that's at 4 km will cool to 100 deg C, and so on.

[ February 20, 2002: Message edited by: John Solum ]</p>