Falk has made the most valid point yet!
The facies models should be based on PT conditions exclusively. In the
interests of clarity, the formation conditions should be in addition to and
NOT part of any rock name, "contact" and "regional" are after all
DESCRIPTIVE terms where as "regional contact" seems more like a split
infinitive.
Eg 1:
"The metapelites in this area clearly belong to the Greenschist facies and
were produced by regional metamorphism"
Eg 2:
" These rock are Mypetnamelites" and just to be helpfull a protracted
discussion on vthem can be found in the journal of pointless new scientific
terms which is regularly released every blue moon in a month of Sundays.
So:
The first example is easily decipherable and in itself contains a large
amount of description. The second example, though at first appears to be
more concise, contains no description and is entirely meaningless without
having read the appropriate articles, and, more to the point carries no
actual information of its own.
Remember....KISS and make up
Keep It Simple Stupid
Daryl Soar
-----Original Message-----
From: Falk H. Koenemann <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 19 May 1999 23:30
Subject: Re: aureoles and facies
Hey guys, how long is the British coast?
What you are doing is the fractal approach to working terms. Contact and
regional metamorphism were clearly defined in areas where they could not be
mixed up. If, invariably, things become more complicated upon closer
inspection,
these terms may loose their originally sharp contours. But since we have all
the
tools to work out the P/T conditions, I cannot really see where the problem
is.
Try to draw a line between continental and oceanic crust along a passive
margin.
At the 100 km scale it works just fine, but at the 1 km scale? The answer
is, if
you work there you have too many other problems to worry about than care
about
fine lines that don't mean much at that scale.
> As usual, Eric has produced some stimulating and pithy discussion points,
> too many to comment on. Returning to the issue of 'facies of contact
> metamorphism' or 'this-or-that hornfels facies', with their heavy genetic
> or textural connotations which are irrelevant to the facies concept, I
> worry about the phenomenon of 'tradition unimpeded by progress'. Is it not
> somewhat misleading, or at least confusing , to refer to a schistose,
> coarse grained, And+Crd metapelitic rock collected from a regional setting
> as belonging to the 'facies of contact metamorphism'? (think of the poor
> students who have to learn this stuff).
>
Falk H. Koenemann
Aachen, Germany [log in to unmask]
http://home.t-online.de/home/hp-fkoe.htm
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|