Dear Professor Tavarnelli,
During the Geological Congress in Florence I presented a poster about
reactivation of faulting in the Okanagan core complex in British Columbia.
During the congress you asked me about a possibility that we will submit a
manuscript for publication in the “Tectonic Inversion and Structural
Inheritance in Mountain Belts” volume and I said we will try. Unfortunately
we could not complete the paper before the dead line and only now we
have completed it. I am writing to inquire whether, despite the delay, there is
still a possibility to submit our manuscript to the “Tectonic inversion…”
volume? I’m aware that the official deadline has passed long ago, but
decided to give it a try, in case that there is any delay (which in practical life
sometimes happen). I attach the abstract of the manuscript to present its
essence.
Please let me know if it is still be possible to submit the manuscript. I’ll be
glad if it is still possible, and of course will understand if it isn’t.
Sincerely,
Yehuda Eyal
Evidence for, and implications of the reactivation of Eocene joints and pre-
existing structural fabric in the Okanagan core-complex, B.C. Canada
Abstract
We studied the brittle deformational history of the Okanagan metamorphic
core complex, and its hanging wall carapace, in the Canadian Cordillera, in
southern British Columbia by an extensive mesostructural study. In this
region macro-structures are rarely exposed, although their existence can be
deduced from field relationships. Observed closely-spaced faults that are
either perpendicular to bedding, or which were sub-vertical to inferred
paleohorizontal and with very small dispersion of strike are interpreted to
have originated as joints that were reactivated, as faulted joints, by
subsequent shear due to a relative change in stress orientation. The
faulted joints are similar to observed open-mode fracture system (joints) that
exhibits no evidence for subsequent reactivation. The deformational history
reveals that the transition from ductile to brittle deformation occurred during
the early-middle Eocene and was associated with tectonic unroofing or
extensive erosion and exhumation of the Okanagan core complex. The first
brittle deformation was a pervasive open-mode fracturing in the hanging
wall carapace of sedimentary rocks and plutons characterized by a N-S
trend, with a very small dispersion, which formed either perpendicular to
bedding or was sub-vertical with respect to the inferred paleohorizontal.
These fractures are of similar trend with a middle Eocene dyke swarm in
part of the study area and beyond. Okanagan core complex metamorphic
rocks exhibit brittle fractures with the characteristics of, and interpreted to
be, a reactivation of the metamorphic foliation in response to the same E-W
extension recorded by the joints and dykes. Subsequently, a few
deformation phases reactivated the pervasive open-mode fractures. The
first, a shear deformation, associated with normal dip-slip motion along the
open-mode fractures, is explained by either regional tilting, accompanying
continued extension, of the area under a steady orientation of the stress
field or a small change of the stress field. The later deformations, indicated
by strike-slip or reverse motions indicate a significant change in the stress
field orientation. We suggest that similar fault sets of consistent attitude,
typically with very small dispersion can be interpreted as faulted joints
using only their stereographic projection pattern relative to the inferred
paleohorizontal.
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