Structural Geology of the Northern and North-Eastern Zone (N–NE Zone), Leh–Ladakh Region

Abstract

The North–Northeastern zone of the Ladakh batholith, Leh–Ladakh Region is more heterogeneous in style, compared to the adjacent south High Strain Zone. It extends some 40 km NW–SE, and is up to 12 km wide NE–SW. This chapter reports the results of field-based observations and structural readings alongside detailed anlaysis of photographs and photomosaics. The N–NE Zone is characterised by a higher abundance of ductile deformation, which has produced a series of discrete shear zones that vary in scale from cm and metres to km wide. Shear zone-rich regions exhibit discrete zones of highly-sheared rock separated by low and lower strain zones. Other sub-zones are dominated by fold structures, particularly where meta-sediments crop out. More extensive lower strain zones are characterised by thrusts and high angle extensional faults. Shear zones produce strong gnieissic foliation, intense fracture and cleavage, extended xenoliths with long/sort axial ratios up to 20, and S–C fabrics. Brittle structures such as thrust zones have similar kinematic indicators to the High Strain Zone (NNW–NE vergence) reflecting a prevalent ENE–WSW structural grain. Shear zones mostly strike NW–SE to NNW–SSE. Fold axial planes vary in strike between NW–SE and NE–SW with the larger folds displaying a north–south axial planar strike. Structural data from the N–NNE zone support and extend the klippen-fractured basement model derived from structural analysis of the southern High Strain zone.