Interplay of deformation and magmatism in the Pangong Transpression Zone, eastern Ladakh, India: Implications for remobilization of the trans-Himalayan magmatic arc and initiation of the Karakoram Fault

Abstract

In the eastern part of Ladakh, the right-lateral Karakoram Fault Zone (KFZ) bifurcates into two strands called the Pangong Strand and the Tangtse Strand. These two strands bound a region called the Pangong Transpression Zone (PTZ), which consists of migmatitic dioritic gneiss, calc-silicates and the Durbuk Pluton; a pluton of two-mica leucogranite. Outcrop scale observations suggest pervasive migration of leucogranitic melt through the existing tectonic structures of the gneiss. Magnetic fabric from both the tectonized and undeformed parts of the Durbuk Pluton show parallelism with the tectonic fabric of the host gneiss, which, along with pervasive melt migration, indicates syn-kinematic relationship between deformation along the KFZ, leucogranite magmatism and emplacement of the Durbuk Pluton. U–Pb geochronology of zircons from the dioritic gneiss yields a crystallization age of 63.6 ± 1.5 Ma and also shows younger zircon growth down to ∼13 Ma, which suggest arc magmatism at ∼65 Ma followed by partial melting and leucogranite magmatism in the KFZ till ∼13 Ma. One two-mica leucogranite sample from the Durbuk Pluton gives a crystallization age of 22.7 ± 0.5 Ma. As the Durbuk Pluton is syn-tectonic with deformation along KFZ, it is inferred that the KFZ initiated at least ∼23 Ma ago.