Differences in isotopic signature of Neoproterozoic crust of NW India - evidence for a lithospheric boundary?

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The Neoproterozoic crust of NW India is mostly composed of two felsic magmatic suites, the Erinpura granites and the Malani Igneous Suite (MIS). Timing of the two events fall into the time period of worldwide rifting, related to Rodinia break-up, whereby India was situated at the periphery of the supercontinent. Different tectono-magmatic models have been proposed (arc, back-arc setting, plume activity) in order to explain the Neoproterozoic evolution of the NW Indian terrane and its relationship to neighboring terranes in South China (Yangtze and Cataysia blocks). However, these models are not consistent with the results from our previous project. Our results in combination with literature data show a spatial discrimination of the NW Indian into regions with positive and negative eNd values and suggest that the inferred lineament separate two different lithospheric blocks. There is indication that this lithospheric boundary formed already during the earlier magmatic episode (Erinpura granites, ca. 890 to 820 Ma) and we suspect pre-Malani crustal extension and rifting along a continental margin as a more appropriate scenario We anticipate that the isotopic ratios of the Malani type rocks just mimic a preexisting crustal configuration which would have important implications for interpretation of the tectonic setting for this younger (770 to 750 Ma) magmatic activity. In order to verify this hypothesis we would like to analyse Sr and Nd isotopes of samples from transects from the craton to the rifted margin, to get better constrains on the transition from negative to positive eNd values. Moreover, we would like to measure Sr, Nd and Pb isotopes from Malani mafic dykes that appear in the same region and which can give insights into the underlying mantle.