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Woodmorappe (1979, p. 122) attacks the
validity of Rb-Sr isochron dating by claiming that the Pahrump Group 'Diabase' in
California has been dated at 'no less than 34 billion years', which is approximately twice
the age of the Big Bang and more than 7 times the age of the Earth!! Of course, both geologists and YECs agree that a
'date' of 34 billion years for this rock is completely ridiculous. Geochronologist Dalrymple (1984, p. 77-79)
discusses the origin of this 'date' and denounces Woodmorappe (1979, p. 122) for
misreading a 87Sr/86Sr vs. 87Rb/86Sr plot for the Pahrump Group 'Diabase'. The original sources of the Pahrump Group
'Diabase' Rb-Sr diagram are Wasserburg et al. (1964, p. 4397) and Faure and Powell (1972,
p. 101-102). The diagram of the 'diabase' shows a terrible scatter and does NOT provide an
isochron and an associated Rb-Sr date. Radiometric
dating on related rocks, however, suggests that the 'diabase' is about 1.2 billion years
old (Dalrymple, 1984, p. 79).
On the original diagram, Wasserburg et al.
(1964, p. 4398) drew in age-meaningless reference isochrons of 1, 2, and 3 "billion
years" to highlight the bad scatter of the data points. Later, Faure and Powell (1972, p. 101) used
alternative reference isochrons of '34 billion years' and '1.09 billion years' to better
bracket the large scatter of points. Obviously,
these various reference isochrons have NO time meaning.
Reference isochrons are simply drawn into the diagrams as guides for the reader in
much the same way that a flying pilot may refer to the position of another plane as being
between '9 and 11 o'clock' from her position. In this case, the '9 to 11 o'clock' has no
time meaning but simply indicates that the other plane is from the left to the front left
of the pilot. Certainly, the ability of Wasserburg et al. (1964, p. 4398) and Faure and
Powell (1972, p. 101) to draw in various reference isochrons shows how worthless the data
really are in this case. However, because
Woodmorappe (1979, p. 122) wants radiometric dating to look as bad as possible, he
improperly cites the 34 billion year old reference isochron as if it were the optimal
Rb-Sr 'date' for the 'diabase' and ignores the 1.09 billion year reference isochron and
the actual age estimate of approximately 1.2 billion years.
Computer scientist and creationist Dr. David
Plaisted also cites the discussions of the Pahrump Group 'Diabase' in Woodmorappe (1979,
p. 122) as a supposed example of the unreliability of the Rb-Sr method. When discussing the 'diabase' diagram, Dr.
Plaisted at
A Reply to Dr.
Henke and Others states:
'However, Dr.
Henke is not giving the whole story here. It follows from the mathematical properties of
isochrons that if an isochron, even with carefully selected samples, gives a Rb/Sr age of
34 billion years, then at least one of the samples must have a Rb/Sr age of 34 billion
years or larger, and probably at least one more has a Rb/Sr age nearly this large or
larger. In fact, from Dalrymple (1984, p. 79), three of the 8 samples have Rb/Sr ages of
nearly 34 billion years or larger. Thus we still have a serious anomaly to contend with.'
According to Faure and Powell (1972, p. 102),
the scattered points on the Rb-Sr diagram probably resulted from 87Sr contamination from
an adjacent granite or gneiss during Mesozoic metamorphism.
Millions of years of 87Rb decay are required to produce a significant amount
of 87Sr in the surrounding rocks. The
Mesozoic metamorphic event probably dislodged some 87Sr from a large number of mineral
grains in the granite and/or gneiss, but failed to significantly disperse and adequately
mix the 87Sr with ambient concentrations of 86Sr. Wasserburg
et al. (1964, p. 4395) even found excess 87Sr in Rb-poor plagioclases and apatites, which
indicates strontium disequilibrium in these rocks. The
metamorphosed 'diabase' would contain areas with poorly mixed 87Sr and low concentrations
of Rb and K. These samples would then yield
badly scattered analyses, including some values with high 87Sr/86Sr and low 87Rb/86Sr
values (that is, absurd ages of '34 billion years,'), on a 87Sr/86Sr vs. 87Rb/86Sr
diagram.
Abundant 87Sr cannot naturally form in 10,000
years or less. Therefore, to explain the
existence of 87Sr, YECs must invoke miracles and unrealistic and groundless accelerations
in radiometric decay rates (Vardiman et al., 2000; also see
Rats in RATE'S
'Research'
While Woodmorappe (1999, p. 16, 21-22, 51-54, 82, 85, 95,
etc.) frequently makes baseless and economically absurd accusations about scientists
arbitrarily 'picking and choosing' the dates that they want, the selective misuse of data
from the Pahrump Rb-Sr diagram by Woodmorappe (1979, p. 122) proves that hypocritical YECs
are not above using this form of data manipulation. By arbitrarily ignoring certain data
points on a graph with badly scattered results and then using the values that are left,
careless individuals can obtain almost ANY line that they want, including 'isochrons' that
represent ridiculously old 'dates' of 34 billion years or even negative 'ages'. Three of
the eight points for the 'Pahrump Diabase' do APPEAR to approximately plot on a false
isochron of '34 billion years' as Dr. Plaisted states, but these data are age meaningless
because the line does NOT fit the other five points, which Woodmorappe (1979, p. 122) and
Dr. Plaisted want to ignore. The presence of excess 87Sr in Rb-poor plagioclases and
apatites (Wasserburg et al., 1964, p. 4395) is a further indication that anomalously old
Rb-Sr dates would be expected with these samples and that it would be unwise to assign
time significance to the Rb-Sr data.
Rather than admitting his mistake in his 1979
article, Woodmorappe (1999, p. 2) again claims that the Rb-Sr diagram of the Pahrump Group
'Diabase' provides an anomalously old date. Now,
however, Woodmorappe (1999, p. 2) claims that the Pahrump Group 'Diabase' was erroneously
dated at 3.2 billion years instead of 34 billion years.
How Woodmorappe (1999, p. 2) derived this new date is unknown. Perhaps he simply has a faulty memory and
remembers the 34 billion year old reference isochron as being 3.2 billion years. Nevertheless, Woodmorappe (1999, p. 2) attempts to
justify his misuse of reference isochrons by claiming that scientists will arbitrarily
assign time meaning to reference isochrons if the 'isochrons' suit their agenda. To
support his accusations, Woodmorappe (1999, p. 2) misrepresents the following quotation
from Ziegler and Stoessel (1993, p. 48):
'As the reference age A is within
the known age range for members of the Gamsberg Granite suite (see above), it POSSIBLY
represents a reset age induced by the intrusion of Gamsberg magmas in the area.' [my
emphasis]
Ziegler and Stoessel (1993, p. 48) are
discussing a 87Sr/86Sr vs. 87Rb/86Sr diagram for the Opetjie Pluton of Namibia.
Woodmorappe (1999, p. 2) claims that this is an example of scientists arbitrarily
assigning time meaning to a reference isochron, supposedly because it suits their desires.
If Ziegler and Stoessel (1993, p. 48) can assign time meaning to a reference isochron for
the Opetjie Pluton, Woodmorappe (1979, p. 122) then argues that he should be able to
derive a Rb-Sr 'date' from a reference isochron for the Pahrump Group 'Diabase'.
Unlike the various reference isochrons for
the Pahrump Group 'Diabase', 'reference line A' for the Opetjie Pluton passes DIRECTLY
THROUGH A VERY LINEAR distribution containing ALL of the data points. The distribution has a correlation coefficient of
0.994 (1.000 is perfectly linear) with a date of 1163.6 +/- 61.4 Ma and a
87Sr/86Sr intercept of 0.7056 +/- 0.00097 (Ziegler and Stoessel, 1993, p.
48). Any quick visual comparison of the Rb-Sr
diagrams for the Pahrump Group 'Diabase' (Faure and Powell, 1972, p. 101) and the Opetjie
Pluton (Figure 8.10, Ziegler and Stoessel, 1993, p. 48) demonstrates that the Pahrump data
as a whole do not fall on any isochron, whereas the Opetjie Pluton may. Clearly, geochronologists are not being arbitrary
and Woodmorappe's (1999, p. 2) claims and accusations are inconsistent and groundless.
Woodmorappe (1999, p. 2) also cites Barovich
and Patchett (1992, Figure 6 on p. 390) as another example of scientists using a reference
isochron. In Figure 6, Barovich and Patchett
(1992, p. 390) draw in a 1.4 billion year old reference isochron for some very scattered
data on a Rb-Sr isochron plot of the Harquahala granite of western Arizona. Barovich and Patchett (1992) studied the isotopic
behavior of Hf, Nd, and Sr in this frequently deformed (mylonitized) granite. However, the caption of Figure 6 in Barovich
and Patchett (1992, p. 390) clearly warns the reader that the data are very scattered and
that the 'isochron' is ONLY for reference purposes:
'Rb-Sr isochron
plot of Harquahala granite samples. Symbols
as in Fig. 3. The 1.4 Ga isochron is for reference only.
Note the scatter of the data points.'
That is, Barovich and Patchett (1992, Figure
6, p. 390) DO NOT consider the reference isochron to be a legitimate Rb-Sr date. Barovich
and Patchett (1992, p. 386) conclude:
'The Rb-Sr
iostopic data show considerable scatter on an isochron plot, exhibiting both gains and
loses of Rb and Sr from the whole-rock systems. In contrast, the Sm-Nd and Lu-Hf isotopic
diagrams, plotting mostly in tight clusters or along 1.4 Ga isochrons. The results show
that while the Sr isotopic system in crustal rocks is quite susceptible to later tectonic
disturbance, both Hf and Nd isotopic systems can provide RELIABLE model age information in
continental crustal terranes even when the rocks have been subjected to low to medium
grades of deformation and metamorphism.' [my emphasis]
Like Ziegler and Stoessel (1993, p. 48), the
discussions in Barovich and Patchett (1992) do not support Woodmorappe's (1999, p. 2)
accusations that scientists arbitrarily assign dates to reference isochrons if these
'isochrons' suit their agenda. Clearly, even
a cursory review of the scattered points on Pahrump Group 'Diabase' isochron (Faure and
Powell, 1972, p. 101-102) and Figure 6 in Barovich and Patchett (1992, p. 390) demonstrate
that these diagrams provide no valid radiometric dates.
Wasserburg et al. (1964, p. 4397) and Faure and Powell (1972, p. 101-102) even
state that the Pahrump diagram is too scattered to provide any radiometric date. So, what justification does Woodmorappe (1979,
1999) have to erect a strawperson argument by claiming that the Pahrump diagram provides a
radiometric date? Despite his irrational
twisting of the data and further misquoting of the literature, Woodmorappe (1999, p. 2;
1979, p. 122) has NO justification for claiming that the data points on this terribly
scattered Pahrump diagram provide a date of either 34 or 3.2 billion years.
Finally, Faure and Powell (1972, p. 102)
state the following conclusions that should be important lessons to anyone that is
interested in reliable radiometric dates:
'In summary,
meaningful dates can be derived from altered rocks under the following conditions: (1) if
isotopic homogenization has occurred among the minerals of a rock, the mineral isochron
indicates the time elapsed since re-equilibration (2) if total-rock samples remained
closed systems during the re-equilibration of the minerals, the total-rock isochron gives
the time elapsed since crystallization and thus the "age" of the rocks; (3) if
the total rocks were open to rubidium and strontium, but the minerals were isotopically
homogenized, the mineral isochron indicates the time of last closure of the minerals, but
the age of the rocks cannot be determined by the Rb-Sr method.'
Clearly, the Pahrump diagram fails to meet
these requirements and Woodmorappe (1979, p. 122; 1999, p. 2) has no basis for slandering
Rb-Sr dating by trying to derive a date from the Pahrump data.
REFERENCES
Barovich, K.M. and P.J. Patchett, 1992,
"Behavior of Isotopic Systematics during Deformation and Metamorphism: A Hf, Nd and
Sr Isotopic Study of Mylonitized Granite," Contrib. Mineral Petrol., v. 109,
p. 386-393.
Dalrymple,
G. B., 1984, "How Old is the Earth?: A Reply to `Scientific' Creationism," in Proceedings
of the 63rd Annual Meeting of the Pacific Division, American Association for the
Advancement of Science, v. 1, pt. 3, Frank Awbrey and William Thwaites (Eds).
Faure,
G. and J. L. Powell, 1972, Strontium
Isotope Geology, Springer-Verlag, New York.
Vardiman, L., A.A. Snelling and E.F. Chaffin
(eds.), 2000, Radioisotopes and the Age of the Earth, Institute for Creation
Research, El Cajon, CA and Creation Research Society, St. Joseph, Mo.
Wasserburg,
G.J., A.L. Albee, and M.A. Lamphere, 1964, "Migration of Radiogenic Strontium during
Metamorphism," J. Geophys. Res., v. 69, n. 20, p. 4395-4401.
Woodmorappe,
J., 1979, "Radiometric Geochronology Reappraised," Creation Research Society
Quarterly, v. 16, September, p. 102f.
Woodmorappe, J., 1999, The Mythology of Modern
Dating Methods, Institute for Creation Research, El Cajon, CA.
Ziegler, U.R.F. and G.F.U. Stoessel, 1993, Age
Determinations in the Rehoboth Basement Inlier, Namibia, Geological Survey of Namibia,
Memoir 14, P.O. Box 2168, Windhoek, Namibia.
