The Geology of the Rolwaling-Lapchi Kang Himalayas, East-Central Nepal: preliminary findings

Abstract

Between the Tethyan sediments to the north and the Main Boundary Thrust to the south ten lithotectonic units have been identified in the Rolwaling-Lapchi Kang Himalayas and the Tamba Kosi region of east-central Nepal. These are (1) the Rolwaling Granites, (2) the Rolwaling Paragneisses, (3) the Rolwaling Migmatites, (4) the Alampu Schists, (5) the Khare Phyllites , (6) The Chagu-ChilangkaAugen Gneisses; (7) The Laduk Phyllites, (8) the Suri Dhoban Augen Gneisses, (9) the Rarnechap Group, and (10) the Mahabharat Crystallines. The Main Central Thrust (MCT) is a major lithologic, metamorphic and structural discontinuity separating the overthrust Higher Himalayan crystallines from the underthrust Lesser Himalayan metasediments. The Mahabharat Crystallines are an outlying klippe of Higher Himalayan rocks, underlain by the MCT, that has been thrust a minimum of 80 kilometers over the underlying Lesser Himalayan metasediments. Extending approximately 5 km below the MCT and 15 km above the MCT the Himalayas are a shear-thrust zone exhibiting ductile, brittle-ductile and brittle deformation as well as an inverted metamorphic sequence.