Geochemical and Sr-Nd isotopic characterisation of Higher Himalayan eclogites (and associated metabasites)
Spencer, David A.; Tonarini, Sonia; Pognante, Ugο
published: Feb 8, 1995
manuscript accepted: Sep 20, 1994
manuscript received: May 20, 1994
ArtNo. ESP147050701007, Price: 29.00 €
Abstract Eclogites of the Higher Himalaya were analysed for their bulk rock geochemistry and Sr-Nd isotopic composition. These results are compared to lower grade metamorphic equivalents of rocks of the same age as well as to unmetamorphosed basalt. Major and trace element diagrams indicate tholeiitic to alkalic magma compositions which evolved by fractional crystallisation. 87Sr/86Sr initial values for the eclogite are 0.7053-0.7073 with values increasing for metabasites of lower metamorphic grade. 147Sm/144Nd values range from lower than chondritic to slightly higher. 143Nd/144Nd measured values range from 0.51201 to 0.51283, with εNd(t) from +4.9 to -10. The lowest values occur in the least metamorphosed rocks. Based on their bulk geochemistry and isotope data, the eclogites could be the equivalents of the Permian Panjal Traps. The observed isotopic "trends" are here suggested not to be explained by variations of metamorphic grade, but indicate some protolith contamination with the evolved Higher Himalayan continental crust.