Deformation pattern and vein development in Delhi Supergroup rocks, northeastern part of Delhi-Aravalli belt: Implication of late stage dilation

The Delhi Supergroup rocks of Mesoproterozoic age in the north-eastern part of Delhi-Aravalli belt are polydeformed. These rocks show meso and micro-scale stretched quartzo-feldspathic veins in the gneissic rocks in association with marble and amphibolites in contrast to those commonly described from the low grade metamorphic rocks in the northeastern part of the Delhi-Aravalli belt. The textural features of the veins which show stretched crystals in gneisses indicate that these developed in phases episodically in the direction of mineral lineation. The veins occupy tensional cracks without shear component and developed when the fluid pressure was high enough as they form in amphibolite facies of metamorphism.