Deformation Structures in Pegmatite, Aplite and Quartz Veins in Delhi Group Rocks

Abstract

Pegmatite. aplite and quartz veins of varying dimensions occur in association with pelitic schists, calcareous rocks, quartzites, amphibolites belonging to Ajabgarh Formation, Delhi Group in the Narnaul area and act as important structural markers.

The polyphase nature of deformation of the rocks with which these veins occur, is shown by rotation of boudins, presence of overturned tight isoclinal folds resembling F₁, presence of F₂ folds and refolded folds shown by quartz veins, refolding of limbs of folded pegmatites by folds resembling F₃. Features like boudins, pinch and swell structures shown by quartz veins and pegmatites at the limbs and along the axial planes of F₁ folds with S₁ development in the host rock and attenuation and disruption of limbs of tight folds resembling F₁ shown by these veins also point to significant amount of flattening during F₁ folding phase and longitudinal stretching in the late stage of their development. Slippage in the later stages of deformation phase (F₃) is also distinctly borne dy displaced aplite veins.