Occurrence of Paired-Metamorphic Belts in the Himalaya

The Indus Suture Zone in Eastern Ladakh shows two metamorphic belts, a northern low pressure belt and the southern high pressure belt. The two belts to be referred to as Pongong and Zildat-Sumdo metamorphic belts respectively are now separated by the Ladakh batholith and post-batholith Indus flyschoidal sediments. Postmetamorphic thrusting has narrowed the width of the two belts though they can be traced for over 100km in the Indian territory before they extend into Tibet. The Pongong belt shows andalusite-kyanite-sillimanite type metamorphism accompanied by andesitic and rhyolitic volcanism and granitic activity. The Zildat-Sumdo belt is characterized by glaucophanitic metamorphism accompanied by abundant basites and ultra-basites. The two belts do not differ much in age though the high-pressure belt may be slightly younger. They have developed due to subduction and accompanying regional metamorphism.