Dear Dirk,
Apart from possible variations in the initial crack width and crack
roughness, it is the physical mechanism of crack closure that
eventually will determine the size and distribution of the fluid
inclusions. This depend on parameters like the fluid viscosity, the
elastic properties of the mineral hosting the crack and possibly even
the solubility of the solid in the crack filling fluid. Perhaps - as
you pointed out - even external (tectonic) stresses may play a role.
The good news is that we are working on it and already have made
considerable progress. Basically, we know how it happen from
experimental work. However, we do not yet fully understand why, and
what parameters that determine the final geometry of the captured
fluid volumes. Thus, the process is not yet understood on a
fundamental level and therefore there is no fully adequate answer to
your question.
I advice you to contact Francois Renard in Grenoble
([log in to unmask]) - who was a PostDoc with us in
Oslo until recently and who carried out a number of experiments on
fracture healing to determine the mechanism of fracture healing -
which is exactly what your after.
Best regards
Bjorn jamtveit
>Dear Collegues,
>working in a shear zone setting with a large amount of hydration recorded
>in the shear zone assemblages (Dent Blanche nappe, western Alps), I was
>hoping to apply microthermometry on secondary fluid-inclusions in quartz.
>This quest unfortunately was stopped by the small inclusion size (3-5µm)
>which is below the resolution of our analytical setup (40mag on the
>microscope). This brought up my question: What originally determines the
>size of secondary fluid inclusions? Is it the volume of fluid present in
>the rock while fracturing of the minerals take place? This seems to be
>unlikely for the above mentioned "wet" shear zone setting. Is it the stress
>regime active and leading to fracturing (constrictional vs extensional)? I
>invite your comments and ideas, if there might be recent papers dealing
>with this question, please let me know.
>Cheers
>Dirk
>***************************************************
>Dirk Hellwig
>Department of Geosciences
>Philipps-University Marburg
>Hans-Meerwein-Strasse
>35032 Marburg/Germany
>[log in to unmask]
>phone: +49-6421-2823055
>fax: +49-6421-2828919
>http://staff-www.uni-marburg.de/~hellwig/
>***************************************************
--
*************************
Professor Bjorn Jamtveit
Dept of Geology
University of Oslo
PO Box 1047 Bllindern
N-0316 Oslo
Norway
Phone: +47 22856612 / +47 90730358
FAX: +47 22854215
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