Re: KRS - artificial weathering

From: Eric Stevens (eric.stevens_at_sum.co.nz)
Date: 09/28/04 

Date: Tue, 28 Sep 2004 21:21:08 +1200

On 27 Sep 2004 15:49:03 -0700, icycalmca@yahoo.com (Daryl Krupa)
wrote:

>Eric Stevens <eric.stevens@sum.co.nz> wrote in message news:<l1tel0ldkmn2qf6uetj44ufvleppnb0671@4ax.com>...
>> On 26 Sep 2004 13:25:38 -0700, icycalmca@yahoo.com (Daryl Krupa)
>> wrote:
>
><snip>
>> > Not necessarily; they refer to the "highly problematic nature" of
>> >Ankara greywacke, which might possibly mean that tests do not measure
>> >porosity.
>>
>> That logic is bothy shaky and, by your own description, attended by a
>> significant degree of uncertainty.
>
> I left out a word.
> It should have read:
>> > Not necessarily; they refer to the "highly problematic nature"
>> >of Ankara greywacke, which might possibly mean that tests do not
>> >measure
>any
>> >porosity.
>
> I.e., the porosity test might have given a null value.
> Absent a description of their results, we don't know one way
>or the other.
>
>> http://egi-geothermal.org/Publications/ALLIS_1999.PDF
>>
>> "Gunderson, R. 1992. Porosity of reservoir
>> greywacke at The Geysers. In: C, Stone, ed.
>> Monograph on The Geysers Geothermal Field
>> , Spec.Rep. 17, GRC, 89-96."
>>
>>
>> There is plenty more like that if you look for them.
>>
>> --- snip ---
>
> I don't have access to Gunderson (1992), but I will
>have access to Moore and Gunderson (1995), which was ref'd
>by several papers on The Geysers, later.
> Abstract here:
>
>http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995GeCoA..59.3887M
>
> From the other papers, it seems that porosity in the greywacke
>there is along dissolved calcite veins after contact metamorphism
>by a felsite intrusion.
> Not exactly the situation on Runestone Hill.

I've now got to the bottom of the refrence to 'apparent porosity'.

First, there is the actual porosity through the solid matrix of the
greywacke. This is basically the one to which I have been referring.

The second is the 'apparent porosity' which arises from the fact that
the rock is full of micro cracks, fissures, cavities etc, all of which
provide paths for liquid flow through alternate to the flow through
the solid matrix.

If a reagent is diffusing through the rock it will experience two
broad types of reactoins. First there are surface reactions which will
occur on the exposed surface and on the surface of the micro cracks
and fissures. Then there are the reactions within the solid matrix
which can only take place as a result of diffusion of the reagent
through the solid matrix. The rate of this relies upon the actual
porosity. This is the one which I believe a forger would have a very
hard job to work around.

Eric Stevens

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