Research Journal of Applied Sciences

Year: 2012
Volume: 7
Issue: 3
Page No. 158 - 164

Strain Partitioning and Dimensional Preferred Orientation in a syn-Tectonic Granitoid, S.E. Nigeria

Authors : Michael I. Oden

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 , 2012. Strain Partitioning and Dimensional Preferred Orientation in a syn-Tectonic Granitoid, S.E. Nigeria. Research Journal of Applied Sciences, 7: 158-164.

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