Radiometric dating and old ages in disarray
A review of Radioisotopes and the Age of the Earth, Volume II: Results of
a Young-Earth Creationist Research Initiative, edited by Larry Vardiman, Andrew
A. Snelling and Eugene F. Chaffin
Institute for Creation Research, El Cajon, CA, and Creation Research Society, Chino
Valley, AZ, 2005
by Michael J. Oard
The long-awaited results of an eight-year, $1.25 million research project have finally
been published by the RATE group. RATE stands for radioisotopes and the age of the
earth, and was a joint project between the Institute for Creation Research (ICR)
and the Creation Research Society (CRS). This review will cover volume II of the
technical RATE book. The RATE group presented their findings to an audience of about
2,000 people in El Cajon, California, on 5 November 2005. A DVD of the event is
now available.1
Volume I of RATE was published in 2000 as an introduction and outline of the research
plan.2 Volume II does not
supersede the first volume; there is much background information on radiometric
dating. The 100-page glossary at the end of volume I is needed for the non-specialist
to digest volume II.
A popular level book by Don DeYoung and a popular-level DVD, both titled Thousands
… Not Billions, cover the main results.3,4
These publications are a little heavy for the layman, but the layman can still understand
the basics of the important results of the RATE project. In the DVD, Humphreys shows
a lucid animation of only 6,000 years of helium leakage out of zircons while 1.5
Ga of radioactivity transpired. Baumgardner’s carbon-14 results were also
well animated.
Introduction
Biblical creationists have long realized that the millions and billions of years
resulting from radiometric dating was one of our major challenges. Similar to Larry
Vardiman in his introduction to the RATE project at the 5 November conference, I
saw that radiometric dating is the basis for upholding the hypotheses of evolution
and the supposed old age of the earth. Radiometric dating is a key area leading
to unbelief in the Bible.
As a result, I spent the better part of two years studying dating method with the
goal of doing research on this problem. Then I found out that ICR was planning a
major project on radiometric dating. So, I switched to other challenges, since ICR
was better equipped and positioned to meet the challenge of radioisotopes. My study
certainly was not a waste of time, since the earth sciences are filled with the
results of dating methods, which guide many uniformitarian ideas in the earth sciences.
Besides, it helps me review the results of the RATE project.5
Instead of radiometric dating being a challenge to creationists, it is now a challenge
to uniformitarians.
The technical RATE books are not for new creationists or for someone with little
background in geophysics or geochronology or nuclear physics. They are in-depth
studies, as one would expect for the results of a research project that challenges
radiometric dating. Many exciting results have come out of the RATE project. Instead
of radiometric dating being a challenge to creationists, it is now a challenge to
uniformitarians. But there are a few perplexing results for the creationist
to think through.
After a preface by John Morris, chapter 1 is an introduction by Larry Vardiman giving
the history of the RATE project, the key research results, and the significance
of the project. He has a section on the future of RATE in which unanswered questions
will be pursued as special projects, while other major research initiatives are
developed. There is a thought-provoking appendix by the late Henry Morris on creationist
peer review. He argued that overall peer review is needed and quite beneficial to
the creationist movement, but there are shortcomings, as most all creationist and
secular scientists realize.
Accelerated radiometric decay from helium diffusion
There are many assumptions behind radiometric dating, but there are three main ones.
Uniformitarian scientists assume (1) the initial isotope amounts are known, (2)
the decay rate has remained constant at today’s rate, and (3) the sample has
remained in a closed system for millions and billions of years. Evidence is presented
that all three assumptions are violated in various contexts, but the RATE project
concludes that the assumption of constant decay at today’s rates is the most
significant wrong assumption. The RATE group has discovered that one or more periods
of accelerated radiometric decay occurred in the past.
The RATE group has discovered that one or more periods of accelerated radiometric
decay occurred in the past.
The most powerful evidence is described in chapter 2 by Russ Humphreys on his results
of helium diffusion out of zircons from the Precambrian granite at Fenton Hills,
New Mexico. This chapter is a masterpiece on how a research project should be written:
clear with colour pictures, non-dogmatic style, systematic development with great
graphics, and objections answered. At first, Humphreys was concerned about the diffusion
rate in biotite that surrounded the relatively large zircon crystals. Did the biotite
slow helium diffusion out of zircons? The RATE team subsequently found out, by subcontracting
the diffusion experiment to a secular scientist critical of creationists, that the
diffusion of helium through biotite is insignificant compared to diffusion out of
the zircon crystals. So, the main variable is the helium diffusion rate out of zircon
crystals, which depends upon the temperature.
Humphreys found only about 6,000 (± 2,000) years of helium diffusion out
of zircon crystals while at the same time the zircons underwent 1.5 Ga
of radioactive decay—assuming current rates! There is way too much helium
in the zircons for the alleged age. Accelerated radioactive decay sometime in the
past is thus strongly supported. The uniformitarian diffusion rate predicted from
the radiometric ‘age’ is about 5 orders of magnitude too slow! Humphrey’s
results are actually conservative, because the uniformitarian scientists believe
that several heating pulses occurred during 1.5 Ga of geological time, which would
have driven off even more helium. Humphreys deals with objections in appendix D
at the end of his chapter. Most of these objections seem like uniformitarian red
herrings.
Humphrey’s experimental results are enough to show that absolute radiometric
dates by uniformitarian scientists are wrong.
Radiohalos offer further support for accelerated radioactive decay
Two hourglasses representing two methods of dating the same rock. In the first,
1.5 Ga worth of radiometric decay at today’s rates has occurred, while in
the second, only 6,000 years of helium diffusion has taken place.
In chapter 3, Andrew Snelling summarizes his results on uranium and polonium radiohalos
in biotite. There is much to digest in this chapter. To form a radiohalo, there
must be over 109 atoms concentrated into a very tiny spot, about 1 μm
in diameter. There cannot be too many atoms or the alpha damage causes a dark diffuse
sphere, making it difficult to recognize the type of halo. With 238U
halos, colouration initially develops after 100 Ma worth of alpha decay, becomes
darker after about 500 Ma worth, and very dark after about 1 billion worth at today’s
rates. Within the biblical time frame, halos provide further evidence for accelerated
radiometric decay.
The uniformitarian problem with halos is that the half-lives of polonium are much
too short for the assumed slow cooling of magma. The polonium isotopes have decay
half lives of 164 microseconds for 214Po, 3.1 minutes for 218Po,
and 138 days for 210Po.
Snelling discovered that polonium halos are commonly found adjacent to
uranium halos along the same biotite cleavage plane at an average distance
of only 1 mm—strong evidence that the polonium originated from the decay of
uranium. However, there are some polonium halos that are several kilometres from
the nearest uranium source, which would suggest rapid transport. Polonium-210 halos
were much more abundant than halos from other polonium isotopes, as expected from
its longer half life, and they are generally 6 to 12 times more abundant than 238U
halos. Polonium halos were much more abundant in granites that intruded Paleozoic
and Mesozoic sedimentary rocks from the Flood than assumed pre-Flood and post-Flood
granites. Snelling concludes that there was about 500 Ma worth of radiometric decay
during the Flood.
Snelling developed a model in which 238U decays within relatively tiny
zircon crystals in the biotite, and the radioactive daughter isotopes 222Rn
and polonium diffuse out of the zircon. Pressurized hydrothermal fluids moving through
the biotite cleavage planes pick up the daughter isotopes, progressively depositing
polonium at the same location. What causes more than 109 atoms of the
polonium to be deposited in a tiny spot? Snelling surmises that the polonium bonded
to sulfur ions. Although there were no sulfur compounds at the centre of the polonium
halo, there was a small empty spot, indicating that the sulfur compounds probably
leached out of the biotite.
No halos are formed above the annealing temperature of 150°C. But, once the
granite cooled below the annealing temperature, alpha decay from both the uranium
and polonium atoms started forming the halos. Because of the short half-lives of
the polonium isotopes, especially 214Po, large quantities of polonium
had to be transported very rapidly, and the polonium halos had to form within a
few hours to a few days. Since uranium supplies the polonium, the uranium halo had
to form almost at the same time as the polonium halo, requiring accelerated
radiometric decay. If the cooling were very slow, as uniformitarians assert, most
of the uranium, radon and polonium would have decayed, leaving little left to form
a halo in the narrow window of hydrothermal transport below 150°C. This suggests
that the granite magma solidified and cooled below the annealing temperature
in around 6 to 10 days!
Only one sample of ‘post-Flood Cenozoic granite’ from the Cascade Mountains
of Washington, USA, had polonium halos, suggesting that this granite is a Flood
rock. Radiohalos are more prolific in ‘Flood’ granites than ‘pre-Flood’
Precambrian granites. Snelling attributes the low number of halos in Precambrian
granites to the annealing caused by the heat of accelerated decay during the Flood.
Snelling considers the finding of abundant polonium halos in ‘Flood’
granites as evidence that the polonium was emplaced by hot hydrothermal fluids.
This is contrary to Robert Gentry’s claim of granites created solid and remaining
solid during the Flood—a concept that I believe has not yet been falsified,
although RATE members believe so. However, Gentry’s hypothesis has been significantly
weakened. Gentry did have problems with the geology of his samples, some even coming
from pegmatite dikes and granites that intruded Flood sedimentary rocks.
One of the most interesting results is that Snelling found radiohalos in metamorphic
rocks, including, gneiss, schist, and biotite garnet eclogite. There are also many
polonium halos in pegmatites, probably due to their high uranium content. These
results suggest that metamorphic rocks and pegmatites also cooled very rapidly.
Fission tracks reinforce accelerated nuclear decay
A) In Snelling’s model, hydrothermal fluids rapidly transport
Rn and Po from zircons containing U to sites with S forming PoS. These sites average
1 mm apart. B) Once the temperature drops below 150°C, alpha
decay starts damaging the crystal. C) With further passing of time
and more alpha decay, both 238U and in this case 210Po fully
form. Since all Po halos have to form rapidly, especially 214Po halos,
100 Ma to 1 Ga of radioactive decay has to occur at the same time from the U within
the zircon crystal. This shows that the decay of U was greatly accelerated.
Fission tracks are not caused by radioactive beta or alpha decay, but when the whole
atom, mainly 238U, splits apart into two fragments. As 238U
in relatively large zircon crystals breaks apart, the two atoms recoil from each
other, damaging the crystal lattice in a straight line. The nuclear decay rate for
fission is much less than the radioactive decay rate. The zircon crystals are treated
with acid to etch and enlarge the damage tracks so that they can better be seen
under a microscope. The fission tracks are counted, and the age of the zircon crystal
is deduced, based on the half-life for uranium fission. However, the number of tracks
depends not only on the age, but also on the temperature history of the sample and
the cooling rate. High temperature, long time periods, and slow cooling anneal a
higher proportion of fission tracks. These variables are spelled out in the appendix
to chapter 4.
Many sources of error are inherent in fission track dating, in particular the low
annealing temperature, possible errors during etching, and others. There is also
a fudge factor called the ‘zeta calibration’ which calibrates the results
to material of ‘known age’—which is circular reasoning. The lab
that Snelling employed did use the zeta calibration, but kept the same value for
all the samples, so that the effect of the calibration was less significant.
Snelling gathered zircon crystals from several volcanic tuffs around the Grand Canyon
and the Colorado Plateau. The tuff samples were extracted from the Cambrian Tapeats
Sandstone and Muav Limestone in the western Grand Canyon, the upper Mesozoic Morrison
Formation, and the mid to upper Cenozoic Peach Spring tuff in western Arizona and
southeast California.
The Tapeats and Muav Formation tuffs exhibited a wide range of fission track ‘ages’.
The ‘ages’ ranged from near zero to about 900 Ma and did not
match the uniformitarian results. Uniformitarian scientists came up with a number
of reasons for the age spread, such as differential annealing and inherited zircons
from other sources. This makes one wonder about the integrity of all uniformitarian
dates. Are all dates a pick-and-choose process, so that results close to the expected
age are chosen while reasons are deduced for rejecting results that do not agree?
In regard to fission track ages, uniformitarian scientists commonly appeal to annealing
events to cover unexpected results. Snelling apparently accepts some of this uniformitarian
reasoning, especially that the divergent dates on the Cambrian samples are due to
annealing. Although annealing of zircons is supposed to occur at temperatures between
about 200°C to 300°C, the uniformitarian scientists deduced that the Cambrian
formations were never above 130°C. So, how can the Cambrian tuff zircons be
annealed? Snelling suggests that the heat of accelerated nuclear decay annealed
the tracks, but this brings up a problem. How can the heat of accelerated decay
be used when a mechanism is required during the Flood to take away the huge amount
of heat?
The average of the Morrison Formation fission tracks ages was close to
the expected age, but the spread was also quite large.
The Miocene Peach Springs tuff had a narrow spread close to the assumed uniformitarian
date of about 20 Ma. Snelling assumes that the Peach Springs tuff is post-Flood.
If it was formed post-Flood, then accelerated decay continuedafterthe Flood—a
questionable interpretation. I take this result to mean that the Peach Springs tuff
is from the Flood. However, Snelling cautions that even Pleistocene samples can
show a million years worth of nuclear and radioactive decay (but one wonders how
much fudging, assumptions and circular reasoning are involved in Pleistocene samples).
We certainly need more research on this subject.
Snelling interprets the fission track results as physical evidence of millions of
years of nuclear decay (nuclear referring to fission) that corresponds to millions
of years of radiometric decay during the Flood. So, fission tracks reinforce Snelling’s
halo results that there was about 500 Ma worth of nuclear and radiometric decay
during the Flood, since there is no doubt that the Cambrian and Morrison Formation
tuffs are from the Flood.
Different dating methods result in different dates on the same rock
Artist’s impression of fission tracks on etched and polished zircon crystal
from a sample of the Peach Springs Tuff obtained from an outcrop in the Snaggletooth
area of southern California close to the Arizona border.
In chapter 5, Steven Austin examined the consistency of four main radiometric dating
methods on Precambrian samples from two locations. The samples were collected from
the Beartooth Mountains amphibolite and the Bass Rapids diabase sill in Grand Canyon.
Austin used the isochron technique that employs different minerals from the same
rock. The isochron method is considered superior because a straight line on the
isochron plot informs us that two of the three main assumptions of radioactive dating
(the closed system and initial conditions assumptions) are supposed to be validated.
Snelling takes Austin’s study a step further in chapter 6 by analyzing igneous
rocks of many supposed ages, ranging from the recent to the Precambrian. He reinforces
Austin’s results in chapter 5. Snelling also obtained some very anomalous
dates. For instance, some 20th century lava flows from Mt Ngauruhoe,
New Zealand, gave a Rb-Sr isochron age of 133 Ma, a Sm-Nd isochron age of 197 Ma,
and a Pb-Pb age of 3.908 Ga for the cooling time of the modern lavas! Snelling makes
a case that the millions and billions of years for these rocks is likely inherited
from the mantle and/or due to Flood accelerated decay. There may also be some mixing
of magma. In a summary statement, Snelling writes of the significance of these results
for radiometric dating:
‘All these considerations—isochron discordances, inheritance of mantle
source isotopic signatures, and mixing of crustal contamination—must render
radioisotope “dating” highly questionable at best, and useless at worst,
as the absolute “dating” method is so unanimously and forthrightly claimed
to be’ (p. 456).
Both studies discovered that dates from the different methods on the same rock disagree
by a large amount! Moreover, there are systematic relationships between
the methods. The alpha emitters gave older ages than and the beta emitters, and
the longer the half-life, the older the radiometric ‘age’. Snelling
and Austin suggest that a relationship may exist between the atomic weight of the
parent radioisotopes: the greater the weight the greater the isochron ‘age’.
They concluded that only accelerated radiometric decay, which affected each element
and each type of decay differently, explains the anomalous results.
Snelling goes further and suggests that we can use radiometric dates in a relative
sense, based on 3–4 Ga of accelerated decay during creation and 500 Ma of
decay during the Flood. Within the Creation-Flood model, a rock with a radiometric
‘age’ of say 1 billion years would be older than one with a radiometric
‘age’ of 300 million years. But he also states that because of inheritance
and mixing, there will be many anomalies to a relative ‘age’ progression.
I would like to see more research on this relative age suggestion.
Possible mechanism for accelerated radiometric decay
Chapter 7 was the most difficult chapter for me to comprehend, probably because
I know little of theoretical nuclear physics. In this chapter Eugene Chaffin presents
theoretical considerations for accelerated decay. Chaffin essentially suggests a
number of possibilities for accelerated decay. It is especially commendable that
Chaffin has published his ideas in the standard physics literature.
One possibility for accelerated decay is a slight variation in the strength of the
nuclear or strong force that would cause a dramatic increase in alpha decay—around
5 to 8 orders of magnitude! Alternatively, if the alpha energy increases by only
10%, the decay constant increases by about 5 orders of magnitude. These ideas have
the most potential.
Chaffin then describes a possibility from the highly speculative string theory.
He argues that if the radii of compact extra dimensions can be changed, then the
strength of the strong force can be changed. The weak force determines beta decay
and may also be changed by considering ‘forbidden decays’, as well as
string theory. These concepts are highly theoretical and speculative. The different
mechanisms causing accelerated alpha and beta decay would likely explain the different
isochron ages from these two mechanisms applied to the same rock.
Carbon-14 everywhere
Chapter 8 presents John Baumgardner’s carbon-14 results on coal, diamonds,
and other carbon samples. 14C is ubiquitous in the ‘old’
material studied. Even the uniformitarian geologists have reported such results
numerous times. Baumgardner sent carbon samples to an AMS dating lab. If a sample
is over 100,000 years old, there should be no detectible 14C. All his
samples still contained measurable 14C. So, all these ‘old’
samples must be less than 100,000 years old!
The uniformitarian scientists of course cry ‘contamination’, but their
claim becomes hollow when considering diamonds. It would indeed be difficult to
contaminate a diamond, as it is the hardest substance known!
Furthermore, Baumgardner finds no correlation between the 14C
abundance in coal and its putative age in the geological timescale, offering support
that the coal samples are all the same age (e.g. the time of the Flood).
Then if a more realistic past 14C /12C ratio is substituted
in the dating equation, the dates telescope to a maximum date of around 5,000 years!
This is the Flood model version in which much more 12C existed before
the Flood and was taken out of the biosphere by subsequent Flood burial.
Baumgardner takes his measurements a step further. He measured Precambrian 14C
/12C and got a mean of 0.062 % of the modern carbon ratio (pmc). Phanerozoic
ratios average about 0.292 pmc with a wide variation: significantly greater than
Precambrian. Six diamonds from kimberlite pipes and one placer deposit gave an average
ratio of about 0.12 pmc. He then dated 6 more placer diamonds and obtained an average
14C /12C ratio of about 0.2 pmc with a wide spread of values,
significantly different than the first sample of diamonds.
How does he explain all these different average values? He suggests that accelerated
radiometric decay, which produces an extreme neutron flux, formed 14C
in about the right ratios in his various samples. Baumgardner suggests that the
diamonds from kimberlite pipes were less influenced by accelerated decay than the
placer diamonds, a deduction that needs more research.
Baumgardner’s research provides an example of what would result if creationists
could ask the research questions, instead of evolutionists holding the purse strings
to taxpayer dollars. We would likely find ready answers to ideas that at
first appear contradictory to the Bible. For the 14C challenge, we would
long ago have found young 14C ages and had answers to why uniformitarian
14C dates are ‘old’. This example indicates that with more
research using the creation/Flood model, instead of the evolution/uniformitarian
model, we should be able to find answers to many other current challenges in the
earth sciences.
Genesis 1–2:3 is historical narrative
Chapter 9 summarizes the results of the new topic added late in the RATE project—the
grammatical analysis of poetic and historical texts by Steven Boyd. In analyzing
poetic and historical texts, he found that historical texts predominantly use the
preterite verb form (one type out of four), while poetic texts hardly use it at
all. Boyd’s analysis and research are superb; the difference between historical
narrative and poetic texts is stark. Genesis 1–2:3 uses predominantly preterite verbs.
So the probability that these verses are historical narrative is in the neighbourhood
of 99.99%. Genesis is real history, intended to be read as real history! A larger
glossary would have been helpful, since Boyd uses many Hebrew grammatical terms
that would be unfamiliar to non-Hebraists.
RATE problems
The last chapter discusses three problems with the conclusions of the RATE project.
The first problem is theological. Four billion years worth of radioactive decay
does not seem to deserve God’s praise of very good. But, I agree
with the RATE group that this is likely a terminology problem. Change the word ‘decay’
to ‘transformation’ would rid the terminology of ominous connotations.
Such accelerated elemental transformations likely were part of God’s process
of creation of matter during the first few days. Rather, the Fall resulted in death
of humans and animals called nephesh chayyāh (Hebrew נֶפֶשׁ חַיָּה), and radioactive atoms
do not qualify as nephesh chayyāh!
The RATE group concludes that there was about 4 Ga of accelerated decay at creation
and about 500 Ma worth at the time of the Flood. However, the amount of heat released
by this amount of decay during the Flood would raise the crust to 22,000
K, more than enough to melt the whole crust and boil away the oceans! This is called
the heat problem.
However, we are still here, so the Flood heat must have been removed somehow. Conduction,
convection, and radiation of heat are all orders of magnitude too slow. Humphreys
suggests a hypothesis that God also ‘stretched out the heavens’ during
the Flood, as well at creation. This stretching of the universe during the Flood
would absorb the heat by the work of expansion and cool the granite magmas in 6
to 10 days. The problem with this idea is that material with little radioactivity
would freeze, including the oceans. I am skeptical of this hypothesis but am open
to further research. I also noted that heat from accelerated decay is called upon
to explain some the results of the RATE project, while the effects of the cooling
mechanism were not considered. As for a cooling mechanism, I can just as well believe
that God caused a miracle to absorb the heat, after all God was involved
in the Flood.
The third problem is the radiation given off by accelerated radiometric decay during
the Flood. 500 Ga worth of decay during the Flood would zap the inhabitants of the
ark with gamma radiation. The water of the Flood would provide much protection,
but it may not be sufficient (water contains radioactive tritium (3H)
for one thing). Furthermore, just the radioactive potassium-40 in the bodies of
those animals and the people on the ark would kill them when decay accelerated.
Although I believe the evidence for accelerated radiometric decay in earth’s
past is very convincing, I would like to see further research on the heat and radiation
problem during the Flood. I believe it is possible that all the decay occurred during
the first few days of the creation, but this would be difficult to demonstrate,
since Snelling provides a strong case for accelerated decay during the Flood from
halos and fission tracks. From the field of geomorphology, I have observed copious
evidence that granites were uplifted solid late in the Flood (a hypothesis not without
its problems). This evidence is independent of the reasons why Gentry believes that
granites were created solid. Solid uplift of batholiths and plutons has always made
me question whether granites were ever molten, but if the granites solidified
in 6 to 10 days early in the Flood, then Snelling’s evidence for Flood accelerated
decay actually would fit with what I see in the field.
I would also like to see the helium diffusion research replicated on one more granite
drill core. Although I wouldn’t expect any significant difference, it always
helps to tighten up the statistics and quiet critics with more than one sample.
Several assumptions in Snelling’s great research and provocative interpretations
should be better justified, for instance the classification of granites into pre-Flood,
Flood, and post-Flood. Snelling believes that some of the Precambrian granites were
the original creation rocks and were uplifted solid during the Flood. Although he
has a section on the upward intrusion of liquid granite during the Flood, I believe
the idea needs more research. Are S-type granites, derived from Flood sediments
real, or just a geochemical deduction from the plutons of southeast Australia?6–8
Summary
The RATE books and DVDs are an excellent addition to the creationist bookshelf.
They provide strong evidence that uniformitarian radiometric ‘ages’
are wrong, and that accelerated radiometric decay occurred in the earth’s
past. The RATE group is to be commended for providing solutions to the challenge
of radiometric dating. Especially valuable is the variety of means used to disseminate
the RATE results. The reader can choose the means most applicable to his background.
The research is not finished. I look forward to further research on new questions.
Related articles
Further reading
Related resources
References
- RATE Group, RATE Premier Conference: Thousands …
Not billions (DVD), Institute for Creation Research, El Cajon, CA, 2006. Return to text.
- Vardiman, L.V., Snelling, A.A. and Chaffin, E.F. (Eds),
Radioisotopes and the Age of the Earth: A Young-Earth Creationist Research Initiative,
Institute for Creation Research and Creation Research Society, El Cajon, CA, and
Chino Valley, AZ, 2000. Return to text.
- DeYoung, D., Thousands … Not Billions: Challenging
an Icon of Evolution Questioning the Age of the Earth, Master Books, Green
Forest, AR, 2005 Return to text.
- RATE Group, Thousands … Not Billions: Challenging
an Icon of Evolution Questioning the Age of the Earth (DVD), Institute for
Creation Research, El Cajon, CA, 2005. Return to text.
- Oard, M.J., Review of Radioisotopes
and the Age of the Earth by Vardiman, Snelling and Chaffin, Journal of
Creation 15(2):31–32, 2001. Return to
text.
- Collins, W.J., Evaluation of petrogenetic models for Lachlan
Fold Belt granitoids: Implications for crustal architecture and tectonic models,
Australian Journal of Earth Sciences 45:483–500,
1998. Return to text.
- Chappell, B.W. and White, A.J.R., Two contrasting granite
types: 25 years later, Australian Journal of Earth Sciences 48:489–499,
2001. Return to text.
- Clemens, J.D., S-type granitic magmas—Petrogenetic issues,
models and evidence, Earth-Science Reviews 61:1–18,
2003. Return to text.
|
