Lithostratigraphic correlations in the western Himalaya - An isotopic approach

We present the results of a whole-rock Nd isotopic study of two contrasting regions of the western Himalaya, using the neodymium model age approach on the scale of a single orogen. High-grade metasedimentary reeks from Zanska r yield model ages (T-DM) that are similar to those of the High Himalayan C rystalline Series (T-DM = 1.2-2.0 Ga; epsilon(Nd) = -6 to -16) and distinct from values from the Lesser Himalaya (T-DM = 2.3-3.4 Ga; epsilon(Nd) = -18 to -27), Hence these tno Lithological sequences can be recognized for 2000 km along the strike of the orogen. Data for the basement of the Nanga Parb at massif at the western extremity of the Himalaya (T-DM = 2.3-2.8 Ga; epsi lon(Nd) = -18 to -30) suggest that these rocks are not equivalent to the Hi gh Himalaya, as previously supposed, but have affinities with the Lesser Hi malaya, A thin metasedimentary cover sequence on the margins of the Nanga P arbat massif is isotopically indistinguishable from the High Himalaya (T-DM = 1.6-1.8 Ga; epsilon(Nd) = -10 to -14). The prior misidentification of th e provenance of the massif stems from its high metamorphic grade, character istic of the High Himalaya, but in this case related to the unique Neogene history of the Nanga Parbat massif, which has exhumed a higher-grade equiva lent of the Lesser Himalaya that is not seen elsewhere.