Ka. Connors et Gs. Lister, POLYPHASE DEFORMATION IN THE WESTERN MOUNT ISA-INLIER, AUSTRALIA - EPISODIC OR CONTINUOUS DEFORMATION, Journal of structural geology, 17(3), 1995, pp. 305
The polyphase deformation history of the Mount Novit Ranges, western M
ount Isa Inlier, Australia, involved the development of four generatio
ns of N-S to NW-plunging folds, development of which alternated with m
ovement on similar to N-S striking faults/shear zones with west-over-e
ast displacement. The spatial relationships between successive structu
res and the distinct similarities in the kinematics, style, and asymme
try, are all consistent with continuous deformation during E-W to NE-S
W shortening. Additional support for this hypothesis is based on the d
evelopment of the three major fold generations, and the intervening fa
ults and shear zones, during low-P, high-T metamorphism. Although the
duration of this metamorphic event cannot be constrained, recent studi
es have linked low-P metamorphism to heat advection by migrating melts
. Thermal modelling indicates that such metamorphic events will be sho
rt-lived in comparison to those associated with thermal relaxation of
over-thickened crust. Low-P metamorphism is unlikely to persist throug
h two or more separate tectonic events; therefore syn-metamorphic, pol
yphase deformation in the Mount Novit Ranges apparently formed during
a single, continuous tectonic episode. This structural history differs
from both the regional scheme and that of previous workers in this ar
ea. The main differences are: (i) no evidence was found for early thru
st faulting prior to N-S folding; (ii) there are four generations of N
-S to NW-SE folds, as opposed to two; and (iii) this study favors a si
ngle, consistent tectonic regime, in contrast to the interpretation of
three discrete, isolated tectonic events.