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An optimised and improved process is presented for the sequential separation of Pb, Sr, and light rare earth elements (LREEs) from a single aliquot of digested silicate sample.Cation exchange resin, Sr resin, and Ln resin columns are used to achieve 80-90% recovery yield of each element with high purity. Pb and Sr are recovered using a miniaturised Sr column after the separation of the Pb-Sr fraction from the digested silicate sample using cation exchange resin (AG50W-X8). The rare earth elements (REE) fraction recovered from the same step is used to separate Nd using Ln resin. We have used dilute HNO3 to elute a Ce and Sm free Nd fraction (Ce/Nd < 10 -5 ). The REE fraction was oxidised with > 5 mM NaBrO3 solution prior to loading on the Ln resin. The required concentration of NaBrO3 was tested using reference rock JB-2 and 5 mM was found to be sufficient for REE from 20 mg rock powder. The separation process also yields highly pure Ba, La, Ce, and Sm as by-products which can be used for isotopic analyses. The activity of the NaBrO3 solution degrades rapidly, and therefore should be used within 2-3 days of preparation. Pb-Sr-Nd Isotopic ratios of nine reference rocks and sediments from GSJ and USGS were measured using TIMS and are found to be accurate and reproducible. We also report the first Pb-Sr-Nd isotopic ratios for JSL-1 (slate from GSJ) and Pb isotopic ratio of SDO-1 (shale from USGS).

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The Khammam Schist Belt (KSB), southeastern India, represents a part of the collision zone that is sandwiched between the Eastern Dharwar Craton to the west and the Eastern Ghats Mobile Belt (EGMB) to the east. Quartzofeldspathic gneisses of the EGMB and garnet-kyanite metapelites of the KSB have been investigated to characterize P-T-t evolution of the Khammam region. Pseudosection modeling reveals that the melt-bearing quartzofeldspathic gneiss experienced peak and post-peak metamorphism at P-T conditions of 7.9-8.1 kbar/790-810 °C and ~ 7.0 kbar/740-750 °C, respectively. In contrast, metapelite witnessed peak metamorphism at 7.4-7.8 kbar/600-640 °C, followed by post-peak retrogression at 6.1-6.6 kbar/590-625 °C. U-Th-(total) Pb monazite ages from the gneiss constrain the peak and retrograde metamorphic episodes at 1.63-1.53 Ga and 1.48-1.38 Ga, while those in the metapelites were determined at 1.25-1.20 Ga and 1.18-1.10 Ga, respectively. These P-T-t estimates indicate that the KSB, Vinjamuru, and Ongole domains evolved distinctly during Late Paleoproterozoic-Late Mesoproterozoic. The younger ages (0.90-0.81 Ga) were ascribed to the formation of the Eastern Indian Tectonic Zone, implying its extension beyond the western margin of the EGMB. Besides, the distinct Neoarchean ages (2.79-2.45 Ga) are related to the Archean protolith of the quartzofeldspathic gneisses, which were likely derived from the Archean crust of the Napier-Rayner Complex. This tectonothermal restoration is new and characterizes the Khammam region as the hot and composite collision zone with protracted geological history.