Hi All,
first, thank to understand this mail data-base like me.
Now, talking about shear zones. I found two important constraint when trait
to study major shear zones that juxtapose domains of different rocks (some
time different terranes but not allways). Usually this kind of structure
occur in lower and midle crustal rocks, where deformation progress by
mechanismes like intracrystalline plasticity and mass transfer diffusion
(and other subordinates...). The point are that this mechanismes are very
suitables for the chemical changes in rocks, more in high grade of
metamorphism. So different P-T-t mind different terranes or Clasical
Thermobarometry is a insutable tool, because their equations are based in
balance and not in misbalance conditions with strong links with other
factors like strain mechanism, fluid pressure,.... (together with T, H,
....). The other thing is how we can evaluate all the strain (translation
an internal strain) of this rocks. Textural analysis together with good
mapping works at different scales can be allow our one good aproximation,
but textural analys must be full (CPO´s plus geometric strain analyses plus
petrographical modal analys) and fabrics must be full interpretates, that
mind integrate the L or S or L-S mylonite at the out crop scale and finaly
at the map scale in orther to understand if the lineations are normal or
paralel with the transport direction.
..... defenetly a good topic for a phT fellow
Francisco J. Fernández
Dpto de Geología
Área de Geodinámica
Universidad de Oviedo
C/Arias de Velasco SN
33005 Oviedo. Spain
E-mail [log in to unmask]
http://www.geol.uniovi.es/Users/brojos.html
phone: 34-985103150
FAX 34-985103103
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