From: bobb@tekig1.PEN.TEK.COM (Robert W Bales)
Newsgroups: talk.origins
Subject: Response to Bill Jefferys, part 1
Date: 17 Dec 92 20:33:54 GMT


This is a response to one of Bill Jefferys' articles which he has posted
several times.  Since it was a detailed article, it requires a detailed
response.  When it was initially posted, I did not get a response completed
before I thought that the discussion had moved on.  Some time ago, I completed
a response, but did not post it because other articles I posted were taking
up all the time I could spare, and I did not need another subject.  This is
that response, slightly revised and updated to include information I've
found since I first wrote it.

As I've said, I think Bill's article is the best summary I've seen of the
evidence for isochron accuracy.  But it is still not good enough to show that
isocrons are always accurate, that the earth is billions of years old, or
that the young-earth theory is not viable.

To hold down the length, I'll post the response in pieces.  All reference
sources will be given in the last piece.

The first section deals with objections I raised to radioactive isotope
dating based on what a geology textbook said regarding processes other than
the passage of time which can affect isotope ratios.

#># me
#>  Bill
#   me

>I read what you wrote very carefully. I intended (perhaps unclearly) to
>dispute your claim that Durrance's 11 points are relevant to isochron
>dates. They are not, despite the following attempt of yours to revive
>Durrance:

There is the theme here, and in other postings, that isochron methods are
different than non-isochron radioactive methods.  What is different is not
the basic types of measurements made, but  the method of correlating data
from multiple isotope measurements.  Before you can construct an isocron,
you must measure isotope amounts and ratios.  And those measurements are
affected by the same factors that affect other isotopic measurements,  Since
the quote from Durrance, part of which is reproduced below, lists factors
which can keep isotopic measurement from being true reflections of age, the
factors do, *by the definitiion of the subject* apply to isochrons.  The
question, which I'll discuss below, is whether or not the techniques used for
isochrons permit us always to detect when the measurements have been affected.

#Most, but not all, of the points from Durrance are specifically about
#Potassium-Argon dating.  Since isochrons do not use this method, the specific
#points do not apply. However, before listing specifics, Durrance makes a
#general statement:

#    "Thirdly, to obtain the age of formation of a rock or mineral, the
#    material must have remained a close chemical system since its
#    formation, with neither gain nor loss of radioactive parent or
#    daughter atoms. . . . Unfortunately, geologic materials and
#    environments do not often meet this requirement." [1]

#Since isochron methods deal with geologic materials and environments, they
#fall within the scope of what Durrance talks about.

>They do not. Dalrymple flatly contradicts you. He writes:

>   Note that the Rb-Sr isochron method requires no knowledge or 
>   assumptions about either the isotopic composition or the 
>   amount of the initial daughter--in fact, that is something 
>   learned from the method. [2, page 32,34]

Most people would consider that Dalyrmple is an expert source on geology, not
simply because he is a geologist, but because of the evidence that he
presumably knows.  Thus, it is any evidence behind the words that would give
them athority, and not the fact that Dalrymple said them.

So, what are the facts?  We have a theory that a certain method will give
the initial isotope concentrations.  The scientific way to verify the claim is
to take rock samples for which we *independently* of the isochron method know
the initial concentrations, apply the method to the samples, and compare the
outcome with the known values.  Dalyrymple does not list the results of any
such tests.  Neither does Bill.  Neither have other people in this newsgroup
during our long discussions on isochrons.  Without scientific verification,
the only scientific statement is that it is unknown if the theory is correct.

In evaluating the theory given by Dalyrmple, consider also his statement:

     "When a rock is first formed, say from a magma, the Sr(87)/Sr(86)
     ratios in all of the minerals willl be the same, regardless of
     the rubidium or strontium contents of the minerals, so all of
     the samples will plot on a horizontal line."  (page 32) [2]

Reference [3] shows this to be untrue in some cases.  Thus, being contradicted
by Dalyrmple does not automatically mean I am wrong.

>  The rocks or minerals must have remained closed systems to rubidium and
>  strontium since formation, BUT IF THIS CONDITION IS NOT TRUE, THEN THE
>  DATA WILL NOT PLOT ON AN ISOCHRON.

The experimental observation of data which DO plot on an isochron, but give
ages wrong by 70 million to 3 billion years shows that the above is not so.

When I first wrote a respose (which I did not post) prior to the curren
update.

    If the system is closed, the data will plot on an isochron.  If the system
    is not closed, how the data will plot depends on what has happened to the
    system.  And what has happened to the system? *We don't know*  How would
    an unknown event cause the data to plot. *We don't know*.

I wrote this on the theoretical basis that something not shown to be
impossible should not be ruled out even if it disagrees with a particular
theory.  And I was widely said to be either stupid, dishonest, or bigoted for
holding this position.  But now we see:

    "One serious consequence of the mantle isochron model is that
    crystallization ages determined on basic igneous rocks by the
    Rb-Sr whole rock technique can be greater than the true age by
    many hundreds of millions of years.  This problem of inheirited
    age is more serious for younger rocks , and there are well-
    documented instances of conflicts between stratigraphic age and
    Rb-Sr age in the literature." (page 1093) [3]

and

     "The occurrence of uranium-neodymium and rubidium-strontium
     'psuedoisochrons' of different ages in these contaminated
     continental volcanos indicates that they are artifacts of the
     contamination processes and have no temporal significance with
     respect to mantle fractionation events." (page 743 -- abstract
     of paper) [4]

What was said to be impossible has been observed.  It seems Bales knows more
science than he is given credit for.

   Bob Bales
   Tektronix, Inc.

I help Tektronix make their instruments. They don't help me make my opinions.