TECTONIC AND METAMORPHIC EVOLUTION

OF THE CENTRAL HIMALAYAN DOMAIN

IN SOUTHEAST ZANSKAR

by Pierre Dèzes

7. THE ZSZ: AGE AND AMOUNT OF SHEAR

And he told stories, tracing with a finger in the dust, of the immense and sumptuous ritual of avalanche-guarded cathedrals; of processions and devil dances; of the changing of monks and nuns into swine; of holy cities fifteen thousand feet in the air; of intrigue between monastery and monastery; of voices among the Hills, and of that mysterious mirage that dances on dry snow. «Kim» Rudyard Kipling

7.1 Introduction

We have seen in the preceding chapters that the exhumation of the High Himalayan Crystalline Sequence was assisted by extensional movements along the Zanskar Shear Zone. The exhumation of the HHCS had two major effects on the tectonometamorphic history of this unit: (1) The thickness of the Barrovian metamorphic zones has been reduced significantly through ductile shearing along the ZSZ. (2) Vapour-absent anatectic melting occurred in the highest grade Barrovian metamorphic zone, resulting in the production of leucogranitic rocks.

The thermobarometric data and the petrographic evidences we have presented in chapter 5 will be used to quantify the amount of ductile shearing along the ZSZ.

The geochronological data presented in chapter 6 will be used to constrain the age and duration of ductile extensional tectonics at the top of the HHCS.