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At 03:35 PM 8/2/01 +0200, you wrote: >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/ >>*************************************************** > > Dirk, Bjorn, P, T and strain rate should be considered. Crack nucleation and healing in the brittle regime produces FI-textures different from those in dynamically recrystallized quartz. In my limited experience from greenschist and amphibolite facies shear zones, ductile deformation apparently sweeps quartz free of FI's. Resulting fabrics have only tiny inclusions, decorating (sub)grain boundaries. cheers, Frank ------------------------------------- Frank F. Beunk Institute of Earth Sciences, Dept. of Petrology, Vrije Universiteit De Boelelaan 1085, 1081 HV Amsterdam, the Netherlands phone +31-20-4447371 FAX +31-20-6462457 e-mail: [log in to unmask]