Fig. 2: 147Sm–143Nd and 146Sm–142Nd isotope evolution of the Singhbhum mantle source and petrogenesis.
From: Direct evidence for crust-mantle differentiation in the late Hadean
The tiles illustrate two possible petrogenetic scenarios for the formation of mafic rocks from the IOG greenstone belt and TTGs from the Singhbhum Craton. Panels a and b consider only the isotope composition of the source melts such that the vertical spread defined by TTGs in Nd isotope vs. time space reflects mixing of melts derived from both depleted and primitive mantle (PM) domains. Panels c and d also consider the petrogenesis of TTGs which were likely produced by re-melting of a mafic protolith, here represented by the 3.51 Ga supracrustal rocks from the eastern IOG belt. In this scenario, the most radiogenic Nd isotope compositions require a so-far elusive mafic precursor extracted from the depleted mantle shortly before formation of the granitoids. The distinct evolution of the Isua depleted mantle reservoir is shown for comparison.
