Research Journal of Applied Sciences
ISSN: Online 1993-6079ISSN: Print 1815-932x
Abstract
Uwet granodiorite, a syn-tectonic granitoid of Pan-African
age in South Eastern Nigeria is partly porphyritic, containing megacrysts of
K-feldspars, xenoliths and ellipsoidal bodies. The preferred orientations of
the feldspar phenocrysts are in the NE-SW, NW-SE and N-S, the strongest being
the NW-SE trend. The E-W sectors show minimum grain orientation. Calculated
values of strain-arithmetic mean 
, geometric mean G and harmonic mean H show minimum strain for grains in E-W
orientation and maximum strain for grains in N-S orientation. Phenocrysts in
NE-SW and NW-SE orientations showed intermediate values of strain with the latter
axis having higher values than the former. Generally, irrespective of orientation
or axis, the relationship >
G>H was found to hold. The analysis favours the interpretation that when
two simple shears and a pure shear operate simultaneously in a viscous/ductile
matrix at high temperature under a non-hydrostatic stress state, dimensional
preferred orientation and strain are partitioned unequally along those axes.
The paucity of phenocryst orientation and low strain values in the E-W axis
are an indication that maximum compressive stress (
)
was oriented in this direction, during the Orogeny.
How to cite this article:
Michael I. Oden. Strain Partitioning and Dimensional Preferred Orientation in a syn-Tectonic Granitoid, S.E. Nigeria.
DOI: https://doi.org/10.36478/rjasci.2012.158.164
URL: https://www.makhillpublications.co/view-article/1815-932x/rjasci.2012.158.164