Shear zones: Chemical and textural study of mylonites
Mylonites in ductile shear zones represent the deeper levels
within the continental crust and their petrogenesis provides
insight into the strength and behavior of the crust at depth.
Earlier studies indicated that retrograde mylonites in the
Appalachians were infiltrated by large volumes of fluid,
and subsequent studies have confirmed the importance of
volume loss during mylonitization. The mechanisms of
fluid infiltration and volume loss however still remain
unclear, and much additional work in this area needs to be
undertaken.
References
Yang, X-Y, O’Hara, K. D. and Moecher, D. P., 1998,
Distinction between tectonic mixing and mass transfer
processes in a ductile shear zone, J. Structural Geology,
v. 20, p. 1089-1103
O’Hara, K. D., Sharp, Z. D., Moecher, D. P. and Jenkin,
GRT, 1997, The effect of deformation on oxygen
isotope exchange in quartz and feldspar and
significance of isotopic temperatures in mylonites. J.
Geology 105, 193-204.
O’Hara, K. D., Kirschner, DL and Moecher, DP, 1995,
Petrological constraints on the source of fluid during
mylonitization in the Blue Ridge province, N.
Carolina and Virginia: J. Geodynamics 19, 271-287.
O’Hara, K. D., 1990. Brittle-plastic deformation in
mylonites: The Meadow Fork thrust, an example from
the southern Appalachians. Geol. Soc. Am. Bull., 102,
1706-1713.
O’Hara, K. D., 1990, State of strain in mylonites from the
southern Appalachians, western Blue Ridge province:
the role of volume loss, J. Struct. Geology, 12, 419-430.
O’Hara, KD, 1994, Fluid-rock interaction in crustal shear
zones: A directed percolation approach: Geology 22,
843-846.
O’Hara, K. D., and L. P. Gromet, 1983, Textural and Rb-Sr
isotopic evidence for Late Paleozoic mylonitization
within the Honey Hill fault, SE Connecticut. Amer. J.
Sci., 283, 762-779.