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5.3.4 The metamorphic transition between the TH and the HHCS across the ZSZ

All along the NW-SE trending Kurgiakh valley, the transition between the TH and the HHCS occurs within the 1 km-thick mylonitic Zanskar Shear Zone. The low-grade metasediments of the Karsha Formation at the base of the TH form the hanging wall of this structure. Within the narrow zone defined by the ZSZ, the metasediments of the Phe Formation. show, from top to bottom, a reduced but complete succession of biotite to kyanite zones, indicating a rapid downward increase in metamorphic conditions. The footwall of the ZSZ is then formed by the high-grade metamorphic rocks and leucogranitic plutons of the HHCS. (see cross section). The Biotite Zone The Garnet Zone The Staurolite Zone The Kyanite Zone The Intrusion Zone The Migmatitic Zone


High-grade metamorphism along the Kamirup valley the Biotite Zone next


©Pierre Dèzes