Appendix 1: Analytical Techniques
Whole-rock elemental analysis
Thirteen samples (Table 1) were analyzed in the laboratory of Actlabs, Ontario, Canada. Powered samples weighing 200 mg along with standards were fused using a lithium metaborate/tetraborate flux and then totally dissolved using 5% HNO3. Major elements, Ba, Sr, Y, Zr, Be, Sc and V were analysed using an ICP (Varian 735 ICPOES) and all other elements by an ICP-MS (ELAN 9000). Loss on ignition was determined by heating powdered samples for 2 hours at 10500 C. A number of international rock standards were analysed simultaneously and the values obtained for them are presented in Appendix 3 to indicate the high quality of analysis. Further details of analytical techniques are given in http://www.actlabs.com/. For rest of the samples major elements were analyzed by wavelength dispersive X-ray fluorescence (WDXRF) spectrometry using a Philips PW2400 instrument. Analyses were carried out on undiluted, plain pressed pellets made from 1 gm of ultrafine (-300 mesh) rock powder using boric acid as packing material. Overall precision is typically better than 3% for the major elements. Trace element compositions were determined by PerkinElmer Sciex ELAN DRC II ICP-MS at National Geophysical Research Institute (NGRI), Hyderabad. Close digestion of 0.05 gram sample was done using Savillex Tefflon vessels using acid mixture (7:3:2 HF-HNO3-HCl). Closed vessels were kept on hot plate at 110 °C for 48 hours. Then the contents were evaporated to dryness. The remaining residues were dissolved by adding 10 ml 1:1 HNO3 and kept on a hot plate for 10 minutes to dissolve all suspended particles. The detail of analytical protocol is same as Roy et al. (2007). Values of international rock standards JG-2 (granite), JR-2 (rhyolite) and JB-2 (basalts) analysed are given in Appendix 3.       
Zircon U-Pb dating and trace element analysis
U-Pb dating and trace element analyses of zircon were conducted synchronously by LA-ICP-MS at the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan. Detailed operating conditions for the laser ablation system and the ICP-MS instrument and data reduction are the same as description by Liu et al. (2008; 2010 a,b). Laser sampling was performed using a GeoLas 2005. An Agilent 7500a ICP-MS instrument was used to acquire ion-signal intensities. Helium was applied as a carrier gas. Argon was used as the make-up gas and mixed with the carrier gas via a T-connector before entering the ICP. Nitrogen was added into the central gas flow (Ar+He) of the Ar plasma to decrease the detection limit and improve precision (Hu et al., 2008). Each analysis incorporated a background acquisition of approximately 20-30 s (gas blank) followed by 50 s data acquisition from the sample. The Agilent Chemstation was utilized for the acquisition of each individual analysis. Off-line selection and integration of background and analyte signals, and time-drift correction and quantitative calibration for trace element analyses and U-Pb dating were performed by ICPMSDataCal (Liu et al., 2010a; Liu et al., 2008). 
Zircon 91500 was used as external standard for U-Pb dating, and was analyzed twice every 5 analyses. Time-dependent drifts of U-Th-Pb isotopic ratios were corrected using a linear interpolation (with time) for every five analyses according to the variations of 91500 (i.e., 2 zircon 91500 + 5 samples + 2 zircon 91500) (Liu et al., 2010a). Preferred U-Th-Pb isotopic ratios used for 91500 are from Wiedenbeck et al. (1995). Uncertainty of preferred values for the external standard 91500 was propagated to the ultimate results of the samples. Concordia diagrams and weighted mean calculations were made using Isoplot/Ex_ver3 (Ludwig, 2003). Trace element compositions of zircons were calibrated against multiple-reference materials (BCR-2G and BIR-1G) combined with internal standardization (Liu et al., 2010a). The preferred values of element concentrations for the USGS reference glasses are from the GeoReM database (http://georem.mpch-mainz.gwdg.de/).
Sm-Nd isotopic analysis
	One hundred mg of powdered rock sample was dissolved in 3ml of HF (48%) and 1ml of HNO3 acid, first at room temperature for about 12-15 hours and then on a hot plate. After dissolution, mixed 149Sm-150Nd spikes were added to the solution and evaporated. Chemical separations were performed using HCl acid eluents, which were prepared by sub-boiling distillation of AR grade acid, purchased from Qualigens. Samples were first eluted with 2N and then with 6N HCl on 3.7ml (in 2N HCl) of Bio-Rad AG 50 X 8, 200-400 mesh H+ form cation exchange resin in 6 mm ID silica glass columns to obtain REE fractions. Sm and Nd were separated from the REE fraction by using LN-Spec (Part No. C-50) resin from Eichrom. The total procedure blank in the laboratory is less than 0.8 ng for Nd at present. Isotopic measurements were performed on a Thermo Electron TRITON T1 fully automatic variable multi-collector mass spectrometer at the National Facility on Geochronology/Isotope Geology, IIT Roorkee. During the period of analysis the Japanese JNdi-1 Nd standard gave a mean 143Nd/144Nd value of 0.512117 ± 15 (N = 22).  The concentrations of Sm and Nd were obtained by isotope dilution technique. Detailed protocol of the procedures followed in this laboratory and instrumental details was published by Choudhary et al. (2004).