Rob,
If there are any sulfides and the rocks are old, Re/Os may give
some constraints. Otherwise, not much would be possible from
chronology. Maybe rock magnetism could be useful.
eric
On Feb 2, 2005, at 2:05 PM, Robert Twiss wrote:
> While this topic of dating shear zone deformation is on people's
> minds, I'd like to ask if anyone knows of any way of dating serpentine
> slickenfibers in shear zones. The Coast Range of California and the
> Sierra Nevada have many serpentinized ultramafic rocks in which shear
> zones have developed. The shear zones characteristically have
> abundant serpentine slickenfibers that have grown on shear fractures.
> The fibers are presumably mixed with fine-grained magnetite, because
> they carry a magnetic signature. Being able to date the shearing
> would go a long way toward helping sort out the deformation history of
> these rocks, but I don't know if it is even possible.
>
> Rob Twiss
>
>
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> Robert J. Twiss, Prof. Emeritus email:
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