Dave, 21 May '99
Inasmuch as you are clearly the "man" -- or should I be more
politically correct, and say the "one" on matters of low P
metamorphism, I totally defer to your opinion on the point you make
below. By my age I've had lots of time to accumulate ignorance and
misconceptions. Unfortunately, it is often painfully obvious
to those who are in the know on a given matter.
Cheers, Chuck
> Date: Fri, 21 May 1999 13:56:04 -0600
> Subject: Re: aureoles and facies
> From: David Pattison <[log in to unmask]>
> To: [log in to unmask]
> Reply-to: [log in to unmask]
> Chuck - with reference to your comments below.....
>
> >Maybe Bowen left
> >metamorphic petrologists with a bad legacy when in (1940, J. Geol.) he
> >stated that the goal of Met. Pet. was to establish a petrogenetic grid! At
> >least it's a legacy that may have out lived it's usefulness in terms of
> >being a still pressing goal. To a very considerable extent, we have the
> >required grids.
>
> ...... I disagree, at least for thermodynamically calculated grids for low
> pressure metapelites (which have special relevance to this debate on
> 'regional contact metamorphism'!). Bowen's legacy still pertains. Currently
> existing thermodynamic data sets do a moderate to poor job of handling
> natural low pressure mineral assemblage sequences. Rectification of this
> deficiency is a worthwhile goal, because variations in mineral assemblages
> are far more useful in providing information on subtle P-T variations in
> low-P (And-Sil type) settings than geothermobarometry - see my chapter on
> metapelites in the Am Min 'Contact metamorphism' volume (v. 26, 1991) to
> see why.
>
> Dave
>
> David R.M. Pattison, Department of Geology and Geophysics,
> University of Calgary, Calgary, Alberta, T2N 1N4, Canada.
> Phone: 403-220-3263 (my office); 403-220-5841 (dept. office)
> Fax: 403-284-0074 email: [log in to unmask]
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