The displacement criteria in fibrous crystallized gypsum veins in Southern Hemrin Anticline east of Iraq

الملخص EN

This paper deals with gypsum veins in Mudstone and Siltstone in the South Hemrin area (NE Muqdadia) in the eastern part of Iraq.

The criteria which characterize displacements in fibrous crystallized gypsum veins have been studied and two types recognized: 1-The criteria which appear on the vein surfaces.

These criteria give precisely the direction and type of displacement.

The determination of the chronology of successive displacements along the veins is hindered because the effects of the last displacement usually erase features associated with the first.

The types of displacement features are: cavities and convexities, tectonic tool marks, accretionary growth steps, teeth and sheet structures and wavy structure.

2-The criteria which appear in vein sections.

These criteria give with some difficulty the type and direction of the displacement without precisely determining the age of deformation in relation to the inferior and posterior displacement.

The types of displacement features in this case are: fibers perpendicular to vein walls, fibres oblique to vein walls, bent fibres, secondary wall-parallel fractures, conjugate shear fractures, en- echelon fractures and en- echelon veins