Re: Geology Question (KRS related)

Daryl Krupa wrote: 1138707616.882103.267900@xxxxxxxxxxxxxxxxxxxxxxxxxxxx,

Steve Marcus wrote:
"Daryl Krupa" <icycalmca@xxxxxxxxx> wrote in message 


[...]

Does Wolter say that chlorite is a type of mica? 

Nielsen and Wolter's book, at page 34, discusses
the mineralogy of the KRS and states:
"The elongated grains exhibit a preferred orientation
that is sub-parallel (nearly parallel) with the foliation
composed of various mica minerals (muscovite, chlorite
and biotite) that comprise the matrix."


 Aaarrgghh. How are we supposed to parse this sentence?
 I can't tell what is supposed to be composed of mica.
 It's not the foliation, because that is a physical property of the
rock indicating a significant direction of stress on the rock during
metamorphosis.
 It's not the preferred orientation, because that is also
a physical property of the rock, also indicating
a significant direction of stress on the rock during metamorphosis.
 It might be the elongated grains, but then we have to guess at
what words are missing to connect
"The elongated grains" to "composed of various mica minerals".
 Of course, I assume that there is a connection, rather than
that the writing above should actually have been printed as
two separate sentences.
 As quoted above, the sentence is unclear as to its meaning.
 This would be an example of a style of writing that
is not indicative of scientific thought processes;
it also does not qualify for technical writing standards.

 Did you quote the book word-for-word, i.e. verbatim, above?
 If so, that quotation might be evidence that Wolter's writing
has not been submitted to other geologically-minded types
for commentary, review, or analysis.
 Alternatively, it's just evidence of sloppiness.


[...]

I have pages 34-39 of a Wolter's 2003 paper.
said to be the same as in the book.

p34
   The mineralogy of the stone, a metagreywacke,
   was comprised dominantly of most angular, fine
   grained quartz, orthoclase feldspar, and rock
   fragments. The elongated detrital grains exibited a
   preferred orientation that is sub-parallel with the
   foliation composed of various minerals (muscovite,
   chlorite and biotite) that comprise the matrix.
   The presence of cleavage, a mild foliation and the
   mineral chlorite indicate low-grade metamorphism.
   (personal communication, R.W. Ojakangas, 2003)

p36
   The KRS is fine-grained metasedimentary rock
   called a metagreywacke. The stone exhibits a
   strong preferred orientation of very fine mica
   minerals (biotite, muscovite and chlorite.
   A second, less obvious preferred orientation of
   micas suggests the stone was subjected to two
   different metamorphic events. This two-directional
   foliation of the mica minerals is a unique and
   diagnostic feature of the KRS metagreywacke.


--
º°º°º°º < Peter Alaca > º°º°º°º°º°º°º°º°º°º°º°º°º°º°º°º°º°º°



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  • Re: Geology Question (KRS related)
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