Origin of layering in cumulate gabbros in the Oman ophiolite: Insights from magnetic susceptibility measurements in the Wadi Sadm area
Version of Record online: 21 DEC 2005
Volume 14, Issue 4, pages 564–570, December 2005
How to Cite
Kawamura, K., Hosono, T., Allawati, H. M., Ogawa, Y. and Taniguchi, H. (2005), Origin of layering in cumulate gabbros in the Oman ophiolite: Insights from magnetic susceptibility measurements in the Wadi Sadm area. Island Arc, 14: 564–570. doi: 10.1111/j.1440-1738.2005.00484.x
- Issue online: 21 DEC 2005
- Version of Record online: 21 DEC 2005
- Received 27 April 2005; accepted for publication 5 September 2005.
- anisotropy of magnetic susceptibility;
- cumulate gabbro;
- grain fabric;
- magnetic susceptibility;
- simple shear
Abstract Magnetic susceptibility and the anisotropy of magnetic susceptibility were measured on an 800-cm-thick succession of cumulate gabbro in the Sadm area of the Oman ophiolite. The section contained three distinct cumulate units. The susceptibility tends to decrease upward in each from a melanocratic layer (several tens of centimeters thick) to a leucocratic layer (a few meters thick). The susceptibility decreases in accordance with the decreasing number of magnetite grains, which are the alteration product mainly of olivine minerals. This suggests the cyclic downward accumulation of olivine in the cumulate gabbro. The apparent strain deduced from the patterns of magnetic and grain fabrics was the result mostly of simple shear, so that the layering of gabbro is understood to be formed primarily by a crystal cumulus process followed by simple shear deformation.