Miocene faulting at plate tectonic velocity in the Himalaya of central Nepal

Combination of geochemical zoning in metamorphic garnet and monazite plus in situ Th-Pb isotopic dating of monazite yields P-T conditions, ages and convergence rates for the Main Central Thrust (MCT) and affiliated faults in central Nepal. Inferred rates were 1.5+/-0.9 cm/yr (Langtang Thrust, similar to19 Ma), 2.2+/-0.7 cm/yr (Main Central Thrust, similar to15 Ma) and 7+/-3 cm/yr (Ramgarh Thrust, similar to10 Ma). The lower values are similar to modern convergence rates across the Himalaya, but the Ramgarh Thrust may have briefly absorbed all Indo-Asian convergence at similar to10 Ma. when foreland and marine sedimentation rates markedly increased, and at least one major strike slip fault in Tibet experienced a hiatus in movement. Variable rates of convergence across the Himalaya on Myr timescales imply Myr variations in strain rates throughout all components of the Indo-Asian orogen. (C) 2004 Elsevier B.V. All rights reserved.