Creation Science Rebuttals

Young-Earth Creationist 'Dating' of a Mt. St. Helens Dacite: The Failure of Austin and Swenson to Recognize Obviously Ancient Minerals

 

By Kevin R. Henke, Ph.D

 
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INTRODUCTION

Because radiometric dating utterly refutes their biblical interpretations, young-Earth creationists (YECs) are desperate to undermine the reality of these methods.  As part of their efforts, YEC Dr. Steve Austin and his associates at the Institute for Creation 'Research' (ICR) collected a dacite sample from Mt. St. Helens, Washington State, USA, which probably erupted in 1986 AD.  Austin et al. then ineffectively separated the sample into several mineral and glass 'fractions', submitted the dacite and its 'fractions' for potassium 40-argon 40 (K-Ar) dating, and subsequently used the bogus results to inappropriately attack the K-Ar method.  Austin's conclusions on this project are summarized at the ICR website.

The 'research' efforts of Austin and his colleagues and their 'expertise' in radiometric dating have been widely criticized, including by Joe Meert (also here), Karen Bartelt and company and myself at No Answers in Genesis and in my web debate with Dr. David Plaisted at Tim Thompson's 'Radiometric Dating Source List'.

Austin rarely responds to his critics.  However, non-geologist YECs, such as MD Keith Swenson at Is the Lava Dome at Mt. St. Helens Really a Million Years Old? and at the Answers in Genesis' website, have attempted to defend Austin's work.  Although Swenson accompanied Austin on a trip to Mt. St. Helens, there is no indication from his writings that Swenson is familiar with igneous petrology, geochronology or even geology in general.

 AUSTIN FAILED TO PROPERLY USE THE K-Ar METHOD

Considering that the half-life of potassium-40 (40K) is fairly long (1,250 million years, McDougall and Harrison, 1999, p. 9), the K-Ar method cannot be used to date samples that are much younger than 6,000 years old (Dalrymple, 1991, p. 93).  A few thousand years are not enough time for 40Ar to accumulate in a sample at high enough concentrations to be detected and quantified.  Furthermore, many geochronology laboratories do not have the expensive state-of-the-art equipment to accurately measure argon in samples that are only a few million years old.  Specifically, the laboratory personnel that performed the K-Ar dating for Austin et al. Specifically, personnel at Geochron Laboratories of Cambridge, Massachusetts, USA, performed the K-Ar dating for Austin et al. This laboratory no longer performs K-Ar dating.  However, when they did, their website clearly stated in a footnote that their equipment could not accurately date rocks that are younger than about 2 million years old ("We cannot analyze samples expected to be younger than 2 M.Y."; also see discussions by Bartelt et al.).  With less advanced equipment, 'memory effects' can be a problem with very young samples (Dalrymple, 1969, p. 48). That is, very tiny amounts of argon contaminants from previous analyses may remain within the equipment, which precludes accurate dates for very young samples.  For older samples, which contain more 40Ar, the contamination is diluted and has insignificant effects. Considering the statements at the Geochron website and the lowest age limitations of the K-Ar method, why did Austin submit a recently erupted dacite to this laboratory and expect a reliable answer???  Contrary to Swenson's uninformed claim that ' Dr Austin carefully designed the research to counter all possible objections', Austin clearly demonstrated his inexperience in geochronology when he wasted a lot of money using the K-Ar method on the wrong type of samples.

Austin's results on the Mt. St. Helens dacite, which are also listed by Swenson, are shown in the following table:

Notice that only one of Austin's dates is above the lower dating limit of approximately 2 million years established by Geochron Laboratories.  However, rather than dealing with this issue and critically evaluating Austin's other procedures (including the unacceptable mineral and glass impurities in his 'fractions'), YECs loudly proclaim that the results are discrepant with the 1986 AD eruption.  They then proceed to assault the validity of the K-Ar method.  That is, rather than rejecting Austin's bogus 'message,' YECs unfairly attack the K-Ar 'messenger.'

Considering that the dacite probably erupted in 1986 AD, Austin should have known that at least some of the samples would have given dates that were younger than 2 million years old and that Geochron Laboratories could not have provided reliable answers.  Therefore, it's not surprising that some of Austin's dates, such as the result for the amphiboles, etc., 'fraction,' have large +/- uncertainties. 

Without properly referencing Bartelt et al.'s report, Swenson comments on one of the many criticisms of Austin's 'research':

'One critic said that Dr Austin should not have sent young samples to the dating laboratory because it potentially puts "large error-bars on the data." By this reasoning, the method could not be used on any rocks, since, if we did not see the rocks form, how would we know whether they are young?'

 This is the old YEC 'only eyewitnesses can provide accurate histories' scam.  Obviously, Swenson, like many YECs, fails to realize that scientists can successfully unravel past events without witnessing them.  Forensic scientists frequently send criminals to prison without eyewitness testimony.  To be exact, the recent hideous actions of the Washington DC area (USA) sniper(s) illustrate how unreliable eyewitnesses can be and how important forensic science is in solving crimes and stopping killers.

In contrast to Austin et al.'s juvenile attacks on K-Ar dating, geochronologists confirm the reality of radiometric dates by using multiple methods (Baadsgaard et al., 1993; Stern et al., 1981, p. 5-6; and Foster et al., 1989; also see How Can Woodmorappe Sell Us a Bill of Goods if He Doesn't Know the Costs? and/or comparing their results with fossil, paleomagnetic or astronomical data (e.g., Harland et al., 1990; Hilgen et al., 1997, p. 2043; Renne et al., 1998, p. 121-122; Baadsgaard et al., 1988; Baadsgaard et al., 1993; Queen et al., 1996; Montanari et al., 1985; and Hirschmann et al., 1997; also see Radiometric Dating Does Work (link dead); Consistent Radiometric Dates; The Formation of the Hawaiian Islands; A Radiometric Dating Resource List; How Serious are Errors in Ar40-Ar39 Dates and How Good are Their Monitoring Standards?).  (Also see Radiometric Dating and the Geologic Time Scale: Circular Reasoning or Reliable Tools?, which refutes the nonsensical YEC claims that radiometric and fossil dating is based on 'circular reasoning').  To be exact, even without any radiometric dates, stratigraphic, fossil, and/or paleomagnetic data usually give geologists at least a rough idea of the ages of their samples.

 WHAT CAUSED THE 'OLD' DATES?

As mentioned above, we already know that Austin's application of the K-Ar method to this dacite sample was flawed from the beginning.  Nevertheless, what are some possible causes of Austin's old dates? 

Of course, some YECs might argue that God, for whatever reason, simply zapped some 40Ar into the various minerals during the 'Creation Week' about 6,000 years ago.  Obviously, this suggestion has absolutely no scientific support or merit.  Such ideas are flights of fantasy and not scientific hypotheses. Not even Austin endorses these untestable claims in his essay. 

Other YECs might argue that some of the minerals in the dacite began to grow sometime over the past 6,000 years.  However, without resorting to unproven miracles to speed up the decay rate of 40K, YECs still have the problem of explaining how all of that 40Ar could form in only 6,000 years.  Currently, the YEC 'RATE Committee' is attempting to 'solve' this problem (see Rate Group,  Rats in RATE's 'Research' and More Rats in RATE).

Using science, there are at least three hypotheses that may be purposed to explain why Austin obtained 'dates' of 340,000 to 2.8 million years from his samples: 

1. Argon gas ('excess' argon) was incorporated into the glass and minerals in the dacite as they formed in the parent melt.  The argon failed to degas from the minerals before the dacite solidified.

2. Because all but one of the dates in the above table are below the 2 million year lower dating limit established by Geochron Laboratories, the dates may be nothing more than contamination artifacts from the mass spectrometer at Geochron Laboratories.  The 2.8 million year old date also may have largely or entirely resulted from contamination.

3. IF the Geochron mass spectrometer was exceptionally clean on the day that Austin's samples were run (that is, IF hypothesis #2 is not a factor), the dates may be approximately accurate.  Even if the absolute values of the dates are highly erroneous, the relative order of the fractions' dates from oldest to youngest may be roughly correct.  That is, the various minerals (phenocrysts) in the dacite may have grown in the parent melt at different times and the entire crystallization process may have taken as much as a few million years.  Additionally, somewhat older xenoliths (foreign rocks) and xenocrysts (foreign minerals, Hyndman, 1985, p. 250) from the surrounding rocks may have been incorporated into the melt as it rose to the Earth's surface.

Any or all of these hypotheses are possible.  Austin strongly argues that steps were taken in his laboratory to protect the samples from contamination and that xenoliths (foreign rocks, hypothesis #3) were removed from the samples before analysis.  He also claims that microscopes were used to scan for 'foreign particles' (xenocrysts?, hypothesis #3) in the samples.  Of course, he and his assistants may have missed many of the xenocrysts if they were small.

Austin clearly ignores the possibility of contamination in the mass spectrometer (hypothesis #2) and the possibility that the phenocrysts in his samples may be much older than the 1986 AD eruption (hypothesis #3).   Austin simply assumes that the first explanation is correct and then he proceeds to use the 'presence' of 'excess argon' in his samples to question the reliability of all K-Ar dates on other rocks and minerals.  This is the logical fallacy of composition (Copi and Cohen, 1994).  The validity of either hypothesis #2 or #3 would provide additional evidence that Austin's application of the K-Ar method is flawed and that he has failed to prove that the K-Ar method is universally invalid.

ZONED GRAINS (PHENOCRYSTS) AND POSSIBLE XENOCRYSTS

Figure 4 in Austin's essay shows a thin section photograph of a portion of the 1986 dacite.  In the caption of Figure 4, Austin identifies the grains in the photograph as phenocrysts and microphenocrysts, which is probably generally correct.    Phenocrysts and microscopic phenocrysts (microphenocrysts) are crystals that grow in a melt (magma) deep within the Earth.   In some cases, the entire melt solidifies before reaching the Earth's surface and an intrusive igneous rock develops (Hyndman, 1985, p. 32).  Because intrusive rocks solidify deep within the Earth away from cool water and air, volcanic glass is absent and the grains may be fairly large (that is, easily reaching lengths of one centimeter or more).  In other cases, such as Austin's dacite, a partially crystallized melt erupts on the Earth's surface and produces a volcanic rock, which may be a mixture of rapidly quenched volcanic glass and coarser phenocrysts (Hyndman, 1985, p. 57). 

Although Austin and Swenson will not admit it, some of the grains in Figure 4 may be xenocrysts rather than phenocrysts.   In some cases, the magma may not be hot enough to melt or entirely dissolve the xenocrysts and they may survive after the melt cools.   For even the best mineralogists and petrologists, xenocrysts may be difficult to distinguish from phenocrysts (for example, Hyndman, 1985, p. 250). 

As clearly shown in Figure 4 of Austin's essay, many of the mineral grains are zoned.  The zoning appears as a series of concentric rings of various shades of gray within the grains (see the two obvious examples in the middle of Figure 4). Zoned crystals also may show Carlsbad twinning, which is typical of feldspars (Perkins and Henke, 2000, Plate 10; Klein and Hurlbut, 1999, p. 542).  In thin section and under crossed-polarized light, Carlsbad twinning has a 'half and half' appearance, where one half of the grain is darker than the other half (Perkins and Henke, 2000, Plate 10).   As the sample is rotated on a microscope stage, one twin will darken as the other lightens in crossed-polarized light.  A large grain with very noticeable Carlsbad twinning is located at the top of Figure 4. 

Plagioclase feldspar consists of a mixture (solid solution) of anorthite (CaAl₂Si₂O₈) and albite (NaAlSi₃O₈).  Well-established laboratory studies (Klein and Hurlbut, 1999, p. 318-326; Hyndman, 1985, p. 86-89) indicate that calcium-rich plagioclases crystallize in melts at higher temperatures than albite or sodium-rich plagioclases.  That is, as the magma cools, calcium-rich plagioclases crystallize first, which causes the remaining melt to become depleted in calcium and relatively enriched in sodium.   Once temperatures further decline, more sodium-rich plagioclase begins to solidify from the melt and may surround the calcium-rich grains.  This process produces zoning, where the older and more calcium-rich plagioclases are located in the core of the grains and the younger and more sodium-rich plagioclases occupy the rims.  Because of their crystalline and chemical differences, the calcium-rich plagioclase cores have somewhat different optical properties than the sodium-rich rims, which produce the noticeable concentric zoning in the grains in Austin's thin section photograph.

Besides plagioclase feldspars, chemicals in cooling magmas deep within the Earth may organize into pyroxenes, amphiboles and a large variety of other minerals.  In contrast, any melt that reaches the Earth's surface during an eruption will immediately quench into volcanic glass if it comes into contact with seawater or other surface waters.   The quenching process freezes the atoms in place and prevents them from organizing into crystals. In the presence of air, the lava may cool slowly enough that some VERY small minerals may grow.

The highly disorganized volcanic glass matrix in Austin's Figure 4 appears black or 'isotropic' in crossed-polarized light.   Unlike most minerals, which lighten and darken in crossed-polarized light as the microscope stage is rotated, volcanic glass always remains consistently dark under crossed-polarized light.  Furthermore, unlike disorganized and quickly chilled volcanic glass, well-zoned and developed feldspar crystals, such as those shown in Figure 4, don't form overnight.  On the basis of the glass and mineral textures and elementary melt chemistry, we know that the zoned plagioclases and other relatively large and well-developed minerals in Austin's dacite must have taken more time to grow than the surrounding glass matrix.  By using high-temperature ovens in undergraduate university laboratories or even crystal-growing kits and kitchen chemicals, a normally intelligent person can verify that coarse crystals take more time to grow than finer-grained materials.  Clearly, basic crystal chemistry and physics dictates that zoned and other relatively large phenocrysts grew deep within the Earth and existed before the glass matrix that rapidly formed during the 1986 eruption.   Nevertheless, it is clear from Austin's essay that he has failed to incorporate the obviously diverse ages of the phenocrysts and the volcanic glass into his explanation for the origin of the dacite.  Similarly, Swenson also fails to comprehend the indisputable history that is associated with the plagioclase zoning and to properly recognize the important age differences between the coarsest phenocrysts and the volcanic glass.

THE DIFFICULTY IN SEPARATING SILICATE MINERALS FROM SILICATE VOLCANIC GLASS

Obviously, if Austin wanted a sample that only represented the material that solidified during the 1986 eruption, he would have had to remove ALL of the plagioclase and other phenocrysts from the glass component.   Even when phenocrysts (as in Austin's Figure 4) and xenocrysts can be seen with an optical microscope, they can be extremely difficult, if not impossible, to effectively separate from the glass.  I've attempted to separate very fined-grained minerals from glass in coal ashes by using magnetic separation and hydrofluoric and other acids. It's not easy. Austin even admits that the dacite is 45% phenocrysts and 'lithic (rock) inclusions.'  Considering how messy this dacite is, separating the glass from the mineral matter may not even be possible for this sample.

Swenson wants us to believe that Austin's critics (including me) are simply using invalid 'rationalizations' when we criticize Austin's dating of inadequately pure mineral/glass fractions.  Although Austin claimed that he took precautions to avoid laboratory contamination and that he and his team removed the obvious xenoliths from the dacite sample, Austin's own words refute Swenson's illusions that the dacite mineral/glass 'fractions' were suitably 'pure' enough for testing the validity of the K-Ar method. Specifically, Austin admits that most of his fractions are impure when he includes the term 'etc.' after most of the mineral 'fractions' in his table (see above).  That is, his 'fractions' were really mixtures of volcanic glass, various mineral phenocrysts (including pyroxenes, amphiboles, metal oxides, and/or zoned plagioclases) and even possible xenocrysts.  Furthermore, Austin's descriptions in the following statements clearly indicate that he FAILED to adequately separate the phenocrysts and possible xenocrysts from the volcanic glass.  Austin admits:

'Although NOT a complete separation of non-mafic minerals, this concentrate included plagioclase phenocrysts (andesine composition with a density of about 2.7 g/cc) and the major quantity of glass (density assumed to be about 2.4 g/cc). NO ATTEMPT WAS MADE TO SEPARATE PLAGIOCLASE FROM GLASS, but further use of heavy liquids should be considered.' [my emphasis]

Because Austin did NOT separate the plagioclase from the glass, we would expect this sample to contain a mixture of young glass, plagioclases with relatively old calcium-rich cores and moderately old sodium-rich rims.   Because Austin clearly understands the heterogeneous composition of this 'fraction', he should have known that a K-Ar date on this mess would be meaningless.  Again, the mineral textures, as well as the laws of chemistry and physics, dictate that the calcium-rich plagioclase cores grew at higher temperatures before the sodium-rich rims and that glasses only formed once the melt erupted at the surface.

Austin also states:

'The 'heavy-magnetic concentrate' also had glassy particles (more abundant than in the 'heavy-nonmagnetic concentrate'). Mafic microphenocrysts within these glassy particles were probably dominated by the strongly magnetic Fe-Ti oxide minerals. The microscopic examination of the 'heavy-magnetic concentrate' also revealed a trace quantity of iron fragments, obviously the magnetic contaminant unavoidably introduced from the milling of the dacite in the iron mortar. No attempt was made to separate the hornblende from the Fe-Ti oxides, but further finer milling and use of heavy liquids should be considered.'

At this point Austin admits that the iron mortar probably contaminated his sample.  Although the contamination might have seriously affected any iron analyses, K and Ar analyses may not have been affected.

The description of another one of Austin's 'fractions' indicates that it is also highly impure:

'The 'heavy-nonmagnetic concentrate' (DOME-1H) was dominated by orthopyroxene with much less clinopyroxene, but had a significant quantity of glassy particles attached to mafic microphenocrysts and fragments of mafic phenocrysts along incompletely fractured grain boundaries. These mafic microphenocrysts and fragments of mafic phenocrysts evidently increased the density of the attached glass particles above the critical density of 2.85 g/cc, which allowed them to sink in the heavy liquid. This sample also had recognizable hornblende, evidently not completely isolated by magnetic separation.'

In another example of inadequate mineral/glass fractionation, Austin admits:

'The 'pyroxene concentrate' (DOME-IP) was dominated by orthopyroxene and much less clinopyroxene. Because it was composed of finer particles (170-270 mesh), it contained far fewer mafic particles with attached glass fragments than DOME-IH. This preparation is the purest mineral concentrate.'

Notice that Austin admits that the pyroxene aliquot was RELATIVELY pure. He DOES NOT claim that the pyroxene IS pure.  Therefore, instead of dating the ages of the pyroxenes, he probably dated a mixture of mostly pyroxenes along with other minerals and volcanic glass.   Again, a K-Ar date on such an impure 'fraction' would be meaningless and a waste of time and money.  That is, Austin is not dating the volcanic glass or the pyroxenes in the dacite, but artificial mixtures, which result from incomplete separations.

Finally, Austin states: 

'ALTHOUGH THE MINERAL CONCENTRATES ARE NOT PURE, and all contain some glass, an argument can be made that both mafic and non-mafic minerals of the dacite contain significant ⁴⁰Ar.'  [my emphasis] 

However, because Austin ignores the analytical inadequacies of Geochron's mass spectrometer (hypothesis #2), except for possibly the pyroxenes, there is no evidence that excess argon is present in any of the other mineral or glass components in this sample. 

Because Austin admits that his separations were impure, how can he, Swenson and other YECs justify their claims that these dacite samples were a fair test of the validity of the K-Ar method?   Why did Austin waste precious time and money analyzing samples that were known to contain mineral and glass impurities?  As a geologist, Austin should have known that minerals, especially zoned minerals, take more time to crystallize than quenched disorder glass.  How could he expect the relatively large and sometimes zoned minerals to be as young as the glass?!!

The following additional comments by Swenson demonstrate that he does not understand the mineralogy and chemistry of the dacite: 

'Another critic said that Dr Austin should only have dated the volcanic glass from his sample, because the glass would have solidified when the lava dome formed. However, Dalrymple [1969] found that even volcanic glass can give wrong ages and rationalized that it can be contaminated by argon from older rock material.'

I should state that Swenson did not have the courtesy to name this critic (it's me) or cite even one of my sources that criticize Austin's efforts.  In any debate, the debaters should provide the references or Internet links for their opponents so that the readers can evaluate both sides and really understand what's going on.

Clearly, Swenson simply assumes that the volcanic glass contains 'excess argon.' However, dating a mixture of older plagioclase and younger volcanic glass with inadequate equipment (hypothesis #2) does not prove that any of these components contain excess argon.  In his essay, Austin even admits that the glass still needs to be separated and analyzed for argon.  Furthermore, many studies (for example, the Haulalai basalt; Funkhouser and Naughton, 1968) demonstrate that Swenson and other YECs cannot automatically assume that modern volcanic glass contains excess argon.  Although hypothesis #1 is plausible, until the argon isotope concentrations of the PURE glass are accurately measured for Austin's dacite (if this is even possible) we cannot properly evaluate this hypothesis.

Because Swenson does not provide a page number for his citation of Dalrymple (1969), the identity of the volcanic glass with excess argon is uncertain.  Perhaps, Swenson was referring to the following statement from Dalrymple (1969, p. 51):

'The origin of the excess 40Ar is not entirely clear, but the discovery of excess 40Ar in Holocene quenched basalt glass [Dalrymple and Moore, 1968] indicates that radiogenic argon, released when older rocks are heated or melted, is dissolved in the melt and may be occluded by minerals as they crystallize.'

If Swenson is referring to this section, it's nothing more than an irrelevant red herring.  Unlike the Mt. St. Helens' dacite, this glass formed in SUBMARINE (ocean floor) basalts under high hydraulic pressures (Dalrymple and Moore, 1968).  Dalrymple (1969, p. 47) further states:

'Up to 2.6 x 10 to the -11 mole/gram of excess radiogenic 40Ar has been found in SUBMARINE basalts of Holocene age from Kilauea [Dalrymple and Moore, 1968; plus another reference], BUT IT'S OCCURRENCE THERE IS NOT SURPRISING IN VIEW OF THE HYDROSTATIC PRESSURE IN THE OCEAN DEPTHS and the rapidity with which SUBAQUEOUS flows are quenched.' [my emphasis]

Although high-pressure ocean water may prevent argon gas from escaping from the rims of a lava flow on the ocean floor, the centers of modern submarine flows typically provide K-Ar dates of 'zero years' (Young, 1982, p. 103).  Because the centers of the flows cool more slowly, any excess 40Ar and other gases can disperse out of the remaining melt before solidification. 

While YECs explain geology by invoking talking snakes, magical fruit, and a mythical 'Flood', Dalrymple (1969) discusses legitimate chemistry and fluid physics, which is hardly relying on flimsy 'rationalizations' or implausible excuses.  Furthermore, contrary to Swenson's claims, nothing in Dalrymple (1969) excuses Austin's sloppy approach to K-Ar dating.  In particular, YECs have no justification for automatically assuming that the dacite glass contains excess argon.  Even if the dacite glass does contain excess argon, Dalrymple (1969, p. 52) concluded that excess argon may have no effect on the volcanics if they were to age over millions of years:

'With the exception of the Hualalai flow [which contains noticeable ultramafic xenoliths, Dalrymple, 1969, p. 49], the amounts of excess 40Ar and 36Ar found in the flows with anomalous 40Ar/36Ar ratios were too small to cause serious errors in potassium-argon dating of rocks a few million years old or older.'

That is, as the volcanics age, the excess argon would be diluted into insignificance by the developing radiogenic 40Ar.   Furthermore, if abundant excess argon is present in older rocks, Ar-Ar dating and K-Ar isochron dating can detect and eliminate its effects (as examples, McDougall and Harrison, 1999, p. 123-130; Maluski et al., 1990). 

CONSIDERING THE RELEVANCE OF BOWEN'S REACTION SERIES (HYPOTHESIS #3)

Austin clearly believes that the ancient dates for his samples entirely resulted from excess argon (hypothesis #1):

'Phenocrysts of orthopyroxene, hornblende and plagioclase are interpreted to have occluded argon within their mineral structures deep in the magma chamber and to have retained this argon after emplacement and solidification of the dacite. The amount of argon occluded is probably a function of the argon pressure when mineral crystallization occurred at depth and/or the tightness of the mineral structure. Orthopyroxene retains the most argon, followed by hornblende, and finally, plagioclase.'

'These data suggest that whereas the orthopyroxene mineral structure has about the same or slightly less gas retention sites as does the associated plagioclase, orthopyroxene has a tighter structure and is able to retain more of the magmatic ⁴⁰Ar. Orthopyroxene retains the most argon, followed by hornblende, and finally, plagioclase. According to this interpretation, the concentration of ⁴⁰Ar* of a mineral assemblage is a measure of its argon occlusion and retention characteristics. Therefore, the 2.8 Ma "age" of the "pyroxene concentrate" has nothing to do with the time of crystallization.'

It's certainly plausible that some excess argon could accumulate in small fractures or defects within the crystalline structures of pyroxenes, amphiboles, feldspars and other minerals (Dickin, 1995, p. 248). While Austin claims that orthopyroxenes should retain the most argon followed by hornblende (an amphibole) and finally plagioclase, he provides no references to support this claim.  In reality, the crystalline structures of amphiboles, unlike feldspars and pyroxenes, contain open channels, which can hold argon gas and other fluids (Klein and Hurlbut, 1999, p. 488-493).   I'm skeptical that the defects and fractures in the orthopyroxenes and feldspars of Austin's dacites could hold more excess argon per mineral volume than the relatively large open structures within the hornblendes (Dickin, 1995, p. 248).  Therefore, IF hypothesis #1 was the only factor influencing the dates of Austin's samples, I would expect the hornblende-rich 'fraction' to provide an older date than the pyroxene- and feldspar-rich 'fractions.'  Because Austin's amphibole-rich 'fraction' has a younger 'date' than the pyroxene-rich 'fractions,' these results suggest that other factors (such as, hypotheses #2 and #3) and not just excess argon (hypothesis #1) could be affecting the dates.  From the above discussions, we already know that hypothesis #2 is a likely explanation for Austin's old dates.  To evaluate hypothesis #3, we should look at the crystallization order of the phenocrysts as suggested by Bowen's Reaction Series.

Bowen's Reaction Series is based on field observations and simple laboratory heating +/- pressure experiments.  The series states that certain minerals will crystallize in a melt at higher temperatures than other minerals.  That is, different minerals have different freezing points.  Mafic (magnesium and iron-rich) volcanic rocks, such as basalts, form from relatively hot melts (1200C and hotter, Hall, 1998, p. 29) and tend to have olivine, pyroxene, calcium-rich feldspars, and may be amphiboles.  Felsic (silica-rich) rocks, such as granites, form at cooler temperatures (perhaps as cool as 700^C, Hall, 1998, p. 29) and usually only contain minerals towards the bottom of the series, such as quartz, muscovite and K-feldspar.  The most common minerals in rocks of intermediate chemistry, such as dacites, are located towards the middle of the series. 

Bowen's Reaction Series is a very important concept that undergraduate students learn in their introductory physical geology courses.  To be exact, Bowen's Reaction Series was the one diagram that I was required to memorize when I took my first geology course in college.

Although Bowen's Reaction Series was established long ago by field and laboratory studies, Swenson, Austin and other YECs repeatedly fail to comprehend its importance and how it can produce ancient phenocrysts, which may affect the radiometric dating of very young samples.  In a young volcanic rock, such as the 1986 Mt. St. Helen's dacite, the calcium-rich plagioclases may have formed thousands or even a few million years ago.   Again, as a rock ages and 40Ar accumulates in both the glass and any 40K-bearing minerals, the differences in the ages of the materials becomes less significant.  That is, if the glass quenched in an eruption 300,000 years after the formation of the calcium-rich plagioclases, after 18.0 million years, the differences in the ages of the materials would only be 18.0 and 18.3 million years. (Also see: 'Magma Cooling' in More Errors on 'True.Origins': J. Sarfati's Support of Flood Geology, which exposes YECs Snelling's and Woodmorappe's errors and insufficient statements on the topic of magma cooling.)

Bowen's Reaction Series also predicts that pyroxenes will crystallize at higher temperatures before amphiboles.  Assuming that any argon contamination from Geochron's equipment (hypothesis #2) is negligible, we see that the dates in Austin's table are consistent with the crystallization order in Bowen's Reaction Series.  As expected, the purest pyroxene fraction provides an older date (2.8 +/- 0.6 million years) than the amphibole fraction (0.9 +/- 0.2 million years) in Austin's table.  That is, IF the dates are real, the pyroxenes formed in the melt before the amphiboles as predicted by the series. Because the pyroxenes solidify before most other minerals, it's also not surprising that the 'pyroxene, etc.' fraction, which contains more impurities than the somewhat purer 'pyroxene' fraction, provides a significantly younger date of 1.7 +/- 0.3 million years.  Depending upon the amount of zoned feldspars (which consist of older calcium-rich cores and younger sodium-rich rims) and the quantity of glass, amphibole and pyroxene impurities, the 'feldspar etc.' date could have any value between 0 and 2.8 million years under hypothesis #3.

On the basis of the following statements by Swenson, his gross misinterpretations of Dalrymple (1969), and his unwillingness to respond to my earlier statements on Bowen's Reaction Series and its possible relevance to Austin's results, it is clear that Swenson does not know what Bowen's Reaction Series is and how it can affect the age distributions of minerals in very young volcanic rocks:

'Others have claimed Dr Austin's dacite sample gave an old age because it contained old feldspar crystals. They said that Dr Austin should have known they were old because the crystals were large and zoned. However, Dr Austin's results (Table 1) show that the wrong ages were not confined to one particular mineral. The idea that the age of a mineral can be anticipated by its size or colour is incorrect. Dalrymple [1969], for example, found that the wrong ages in his samples were unrelated to crystal size, or any other observable characteristic of the crystal.'

Contrary to Swenson's implications, mineral zoning is much more than a color property.  As discussed earlier, zoning and crystal growth are extremely important in understanding phenocryst ages. 

Based on the statements in his essays, Swenson simply assumes that excess argon is present in all of the components of the dacite and that any statements on the lack of a relationship between excess argon and crystal size in Dalrymple (1969) automatically apply to Austin's dacite.  Again, because Swenson does not provide any page numbers when referring to Dalrymple (1969), we can only guess which sections of Dalrymple's article he is citing.  Dalrymple (1969, p. 51) says:

'Damon et al. [1967] have suggested that large phenocrysts in volcanic rocks may contain excess 40Ar because their size could prevent their being completely degassed before the flow cools.  The results for the Mt. Lassen plagioclase and the Mt. Etna 1792 flow, which contains a HIGH percentage of large phenocrysts, appear to support their contention.  However, a SINGLE plagioclase phenocryst with a diameter of one cm [centimeter] from the 1964 eruption of Surtsey gave a 40Ar/36Ar ratio indistinguishable from air argon, as did 10 whole-rock samples with abundant large plagioclase phenocrysts...[reference to the appendix of the paper].  Thus, for THESE experiments there does not appear to be any correlation of excess 40Ar with large phenocrysts or with any other petrological or petrographic parameter.'  [my emphasis]

Clearly, whether amphibole, pyroxene, plagioclase or other phenocrysts are effectively degassed or not during eruptions is a complex and, perhaps, unpredictable issue.  Nevertheless, as discussed in Dalrymple (1969, p. 52), excess argon is often in small concentrations that would not significantly affect any dates on samples that are at least several million years old.  Furthermore, if excess argon is relatively abundant in older samples, Ar-Ar dating and K-Ar isochron dating can detect and eliminate its effects (as examples, McDougall and Harrison, 1999, p. 123-130; Maluski et al., 1990). 

POSSIBLE XENOCRYSTS

Swenson confidently proclaims:

'Some have argued that the magma (underground lava) must have picked up chunks of old rock as it moved through the Earth. They claim that these pieces of old rock (xenoliths) contaminated the sample and gave the very old age. This criticism is unfounded because Dr Austin was particularly careful to identify xenoliths and ENSURE NONE were included in the sample.' [my emphasis]

In his report, Austin refers to the presence of 'lithic inclusions' in his samples.  Austin cites a reference by Heliker (1995), which indicates that 3% of the Mt. St. Helens lava dome is 'lithic inclusions': 

' The data of Table 3 seem to argue that very different mineral phases of the dacite each contain significant ⁴⁰Ar. Although the mineral concentrates are not pure, and all contain some glass, an argument can be made that both mafic and non-mafic minerals of the dacite contain significant ⁴⁰Ar. The lithic inclusions in the lava dome might be thought to be the contaminant, in which case they might add "old" mafic and non-mafic minerals to the young magma. It could be argued that gabbroic clumps in the magma disaggregated as the fluidity of the magma decreased with time, thereby adding an assortment of 'old' mineral grains. However, Heliker [1995] argues that the gabbroic inclusions are not XENOLITHS from the aged country rock adjacent to the pluton, but CUMULATES formed by crystal segregation within a compositionally layered pluton. These inclusions are, therefore, regarded as a unique association within the recent magmatic system.' [Austin's emphasis]

Even IF 1) Austin's summation of Heliker (1995) is absolutely accurate and no gabbro xenoliths or xenoliths of any other lithologies were present in the dacite, 2) Austin succeeded in removing all of the 'lithic inclusions' from his samples as Swenson claims, 3) no microscopic xenocrysts were hiding in this messy dacite, and 4) hypothesis #2 was not a factor, Austin would still need to specify the lifespan of the 'recent magmatic system.' In geology, magmatic systems may remain molten and grow phenocrysts over hundreds of thousands to several million years ('Magma Cooling' in More Errors on "True.Origins": J. Sarfati's Support of Flood Geology).  Again, Figure 4 by itself illustrates that ancient phenocrysts were present in the dacite, which would invalidate Austin's dates.

DATING VOLCANIC ROCKS

Although Austin failed to properly fractionate and date the minerals and glass in Mt. St. Helens dacite, many scientists have been able to isolate specific minerals from older volcanics and successfully date them.  Although xenocrysts and xenoliths are very common in the Peach Springs Tuff, Nielson et al. (1990), which is misquoted by YEC Woodmorappe (1999), were able to find suitably pure (free of xenoliths and xenocrysts) samples of the tuff at Kingman, Arizona.  Unlike Austin, Nielson et al. (1990) recovered and successfully dated mineral samples.  Not surprisingly, YEC Woodmorappe (1999) fails to mention that Nielson et al.'s (1990) samples provided very precise Ar-Ar radiometric dates of 18.26 - 18.60 million years old, which were consistent with the stratigraphy.  Because Nielson et al.'s samples were pure and were taken from a fairly old volcanic tuff, the dates were not significantly affected by various minerals crystallizing in the parent magma at different times. When confronted by Nielson et al. (1990) and countless other successful dating studies from the literature, YECs have no choice but to admit that the dates are real or they must invoke non-scientific and less noble options, such as ignoring the old dates, invoking baseless accelerations in radioactive decay rates, invoking excess argon when its obviously not present, misquoting the geochronologists, accusing the geochronologists of dishonesty, or invoking Woodmorappe's financially prohibitive Crap Shoot.

WHAT'S THE ULTIMATE ORIGIN OF THE EXCESS 40Ar?

Even if excess argon is present in a sample, YECs must still explain the ultimate origin of 40Ar.   The Earth's atmosphere currently contains relatively abundant concentrations of argon (0.934%; Krauskopf and Bird, 1995, p. 301).  Where did all of this argon come from if the Earth is only a few thousand years old?  In nature, 40Ar is only known to originate from the radioactive decay of 40K.   Some YECs might argue that the 40Ar could have come from the decay of another, unidentified isotope(s).  However, this is easier to say than to prove.  Any advocates of unidentified parent isotopes need to identify these isotopes, produce any evidence of their former existence, and derive the appropriate decay reactions for them.

Other YECs might simply ignore the problem by saying that God created the 40Ar out of nothing 6,000 to 10,000 years ago.   Again, this is an unproven fantasy and not science.  Still others on the RATE committee believe that, for some reason, God increased the decay rate of 40K and produced excess 40Ar during the 'Creation Week,' the 'Fall of Adam and Eve' and/or 'Noah's Flood.'  However, the RATE committee members readily recognize that such accelerations in decay rates would produce deadly amounts of heat and radiation that would threaten to kill Noah and sterilize the entire planet (Vardiman, 2000, p. 3). 

Rather than invoking unproven miracles and plastering over the issue with 'God did it', scientists seek more profound, meaningful and useful natural answers.  Currently, the only reasonable explanation for the presence of abundant terrestrial 40Ar is that the Earth is ancient.  A natural and long-term origin for 40Ar through the decay of 40K is further supported by 40Ar > 36Ar in the Earth's atmosphere.  In contrast, stellar atmospheres have 36Ar > 40Ar (Krauskopf and Bird, 1995, p. 576), which is consistent with stellar evolution (Faure, 1998, p. 18).  Although the Sun is much larger than the Earth, silicates and 40K are more concentrated on Earth.  The Sun mostly consists of hydrogen and helium, whereas the Earth has too little mass to retain large concentrations of these volatile elements.  Instead, the relatively low mass of the Earth and its relatively close proximity to the Sun has resulted in silicon, potassium, iron and other less volatile elements concentrating in it.  Rather than dealing with this evidence, Austin simply states that the origin of the excess 40Ar requires 'more study'.  In other words, YECs need more time to invent excuses to explain how abundant 40Ar could ever form on an Earth that is supposedly only 6,000 to 10,000 year old.

'RATIONALIZING' RADIOMETRIC DATES?

Woodmorappe (1999), Swenson, and other YECs frequently accuse geochronologists of 'rationalizing away' any anomalous radiometric dates.   However, how is the obvious mess in Austin's Figure 4 a 'rationalization'?   Why would we expect a young dacite that is full of zoned phenocrysts to give one uniform date? How is the reality of Bowen's Reaction Series a 'rationalization'?   How are the limitations of Geochron's equipment a 'rationalization'?

Rather than appropriately dealing with the complexities in samples like the dacite shown in Austin's Figure 4, YECs often irrationally dismiss evidence of ancient rocks and minerals by using groundless and improbable miracles (see It'll Take a Miracle to Save Their Science)  Real scientists are expected to provide natural and reasonable hypotheses for their results, whether their results were anticipated or not.  Certainly, there are times when scientists obtain anomalous results and they can only say 'we don't know why we got these results'.  These mysteries then provide new avenues for further research.   Nevertheless, the bogus K-Ar results from Austin's dacite are obvious and Austin et al. and not the K-Ar method are to blame.

CONCLUSIONS

Figure 4 in Austin's report, by itself, indicates that ancient zoned grains (phenocrysts and perhaps some xenocrysts) were common in Austin's dacite from Mt. St. Helens.  It's also obvious from Austin's text that he was unsuccessful in adequately separating the volcanic glass from the much older minerals.  Austin should have known that if he wanted to date the 1986 AD eruption the phenocrysts needed to be entirely removed from his 'fractions' and that another method besides K-Ar dating would have been required.   Furthermore, when Austin submitted his samples to Geochron Laboratories, he failed to heed warnings from the laboratory about the limitations of their equipment.   Both Austin and Swenson ignored the implications of zoned minerals and Bowen's Reaction Series on the age of the dacite.  Obviously, it's Austin's improper use of the K-Ar method and not the method itself that is flawed.  Rather than recognizing the flaws in Austin's essay, Swenson simply parrots Austin's erroneous claims without really understanding the chemistry and mineralogy of dacites. 

REFERENCES

Baadsgaard, H.; J.F. Lerbekmo; and I. McDougall, 1988, 'A Radiometric Age for the Cretaceous - Tertiary Boundary Based upon K-Ar, Rb-Sr, and U-Pb Ages of Bentonites from Alberta, Saskatchewan, and Montana', Can. J. Earth Sci., v. 25, p. 1088-1097.

Baadsgaard, H.; J.F. Lerberkmo; J.R. Wijbrans; C.C. Swisher III; and M. Fanning, 1993, 'Multimethod Radiometric Age for a Bentonite near the Top of the Baculites reesidei Zone of Southwestern Saskatchewan (Campanian-Maastrichtian Stage Boundary?)', Can J. Earth Sci., v. 30, p. 769-775.

Copi, I.M. and C. Cohen, 1994, Introduction to Logic, 9th ed., MacMillan: New York.

Dalrymple, G.B., 1969, '40Ar/36Ar Analyses of Historic Lava Flows', Earth Planet. Sci. Lett., v. 6, p. 47-55.

 Dalrymple, G.B., 1991, The Age of the Earth, Stanford University Press, Stanford, CA. 

Dalrymple, G.B. and J.G. Moore, 1968, 'Argon 40: Excess in Submarine Pillow Basalts from Kilauea Volcano, Hawaii', Science, v. 161, p. 1132. 

Damon, P.E., A.W. Laughlin and J.K. Percious, 1967, Problem of Excess Argon-40 in Volcanic Rocks, Int. Atomic Energy Agency, Vienna.

Dickin, A.P., 1995, Radiogenic Isotope Geology, Cambridge University Press, New York.  

Faure, G., 1998, Principles and Applications of Geochemistry, Prentice Hall, Upper Saddle River, NJ. 

Forster, D.A.; T.M. Harrison and C.F. Miller, 1989, 'Age, Inheritance, and Uplift History of the Old Woman-Piute Batholith, California and Implications for K-feldspar Age Spectra', J. of Geol., v. 97, p. 232-243.

Funkhouser, J.G. and J.J. Naughton, 1968, 'Radiogenic Helium and Argon in Ultramafic Inclusions from Hawaii', J. Geophys. Res. v. 73, n.14, p. 4601-4607.

Hall, A., 1996, Igneous Petrology, 2nd ed., Longman, England. 

Harland, W.B.; R.L. Armstrong; A.V. Cox; L.E. Craig; A.G. Smith and D.G. Smith, 1990, A Geologic Time Scale 1989, Cambridge University Press, Cambridge. 

Heliker, C., 1995, 'Inclusions in Mount St. Helens dacite erupted from 1980 through 1983', J. of Volcanology and Geothermal Research, v. 66, p. 115-135. 

Hilgen, F.J.; W. Krijgsman and J.R. Wijbrans, 1997, 'Direct Comparison of Astronomical and 40Ar/39Ar Ages of Ash Beds', Geophys. Research Lett., v. 24, n. 16, p. 2043-2046. 

Hirschmann, M.M.; P.R. Renne; and A.R. McBirney, 1997, '⁴⁰Ar/³⁹Ar Dating of the Skaergaard Intrusion', Earth Planetary Sci. Lett., v. 146, p. 645-658. 

Hyndman, D.W., 1985, Petrology of Igneous and Metamorphic Rocks, 2nd ed., McGraw-Hill, New York. 

Klein, C. and C.S. Hurlbut, Jr., 1999, Manual of Mineralogy (after James D. Dana), 21st ed., John Wiley & Sons, New York.  

Krauskopf, K.B. and D.K. Bird, 1995, Introduction to Geochemistry, 3rd ed., WCB McGraw-Hill, Boston. 

Maluski, H., P. Monie, J.R. Kienast, and A. Rahmani, 1990, 'Location of Extraneous Argon in Granulitic-facies Minerals: A Paired Microprobe-laser probe 40Ar/39Ar Analysis', Chem. Geol. (Isotop. Geosci. Sec.), v. 80, p. 193-217. 

Montanari, A.; R. Drake; D.M. Bice; W. Alvarez; G.H. Curtis; B.D. Turrin and D.J. DePaolo, 1985, 'Radiometric Time Scale for the Upper Eocene and Oligocene Based on K/Ar and Rb/Sr Dating of Volcanic Biotites from the Pelagic Sequence of Gubbio, Italy', Geology, v. 13, Sept., p. 596-599. 

McDougall, I. and T.M. Harrison, 1999, Geochronology and Thermochronology by the 40Ar/39Ar Method, Oxford University Press, New York.  

Nielson, J.E.; D.R. Lux; G.B. Dalrymple, and A.F. Glazner, 1990, 'Age of the Peach Springs Tuff, Southeastern California and Western Arizona', J. Geophys. Res., v. 95, n. B1, p. 571-580.

Perkins, D. and K.R. Henke, 2000, Minerals in Thin Section, Prentice-Hall, Upper Saddle River, NJ.

Queen, M.; L.M. Heaman; J.A. Hanes; D.A. Archibald and E. Farrar, 1996, '40Ar/39Ar Phlogopite and U-Pb Perovskite Dating of Lamprophyre Dykes from the Eastern Lake Superior Region: Evidence for a 1.14 Ga Magmatic Precursor to Midcontinent Rift Volcanism', Can. J. Earth Sci., v. 33, p. 958-965.  

Renne, P.R.; C.C. Swisher; A.L. Deino; D.B. Karner; T.L. Owens and D.J. DePaolo, 1998, 'Intercalibration of Standards, Absolute Ages and Uncertainties in 40Ar/39Ar Dating', Chem. Geol., v. 145, p. 117-152. 

Stern, T.W.; P.C. Bateman; B.A. Morgan; M.F. Newell and D.L. Peck, 1981, 'Isotopic U-Pb Ages of Zircon from the Granitoids of the Central Sierra Nevada, California', U.S. Geological Survey Professional Paper n. 1185, 17 p. 

Vardiman, L., 2000, 'Introduction', in Radioisotopes and the Age of the Earth, L. Vardiman, A.A. Snelling and E.F. Chaffin (eds.), Institute for Creation Research, El Cajon and Creation Research Society, St. Joseph, Mo. 

Woodmorappe, J., 1999, The Mythology of Modern Dating Methods, Institute for Creation Research, El Cajon, CA.  

Young, D.A., 1982, Christianity and the Age of the Earth, Zondervan, Grand Rapids, MI.

 

 

 

 

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