APPENDIX A
1. Whole-rock geochemical analysis
Whole rock samples were crushed in a corundum jaw crusher (to 60 mesh). About 60 g was powdered in an agate ring mill to less than 200 mesh. Major element analysis was performed at the State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Wuhan) on a XRF-1800 spectrometer. Total Fe content is reported as Fe2O3. Loss on ignition (LOI) was measured by weighing before and after 30 min. of calcination at 950 ℃. Analytical error is usually <1% and detection limit is <0.05 for most major elements. For trace elements (including rare earth elements), the rock powders were first digested by HF + HNO3 in Teflon bombs and then analyzed on an Agilent 7500a ICP-MS at the State Key Laboratory of Geological Processes and Mineral Resources (GPMR), China University of Geosciences (Wuhan). The analytical precision is generally better than 5% for most elements. The detailed sample-digesting procedure for ICP-MS analyses and analytical precision and accuracy for trace elements are described by (Liu et al., 2008).
2. LA-ICPMS zircon U-Pb age and trace element analysis
Zircons were separated from sedimentary samples by conventional procedure and purified by hand-picking under a binocular microscope, then mounted in epoxy and polished. The BSE and CL images were conducted on a JEOL JXA-8100 electron microprobe. The representative CL images for the analyzed zircons were shown in Supplementary Figure 2. Prior to LA-ICPMS analysis, zircons were subject to aggressive washing with dilute HNO3 and ultrasonication to eliminate the outer parts. For the LA-ICPMS analysis, laser sampling was performed using a Geolas 2005, and ion-signal intensities were acquired by an Agilent 7500a ICP-MS instrument. The diameter of the laser spot was 32 μm for all samples except sample Luz8 with 24 μm. 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. Detailed operating conditions for the laser ablation system and the ICP-MS instrument and data reduction are described by (Liu et al., 2010). Zircon 91500 (206Pb/238U age = 1062.4 ± 0.4Ma, Wiedenbeck et al., 1995) was used as external standard for U-Pb dating, and was analyzed twice every 5 analyses. Off-line selection and integration of background and signals, and time-drift correction and quantitative calibration for trace element analyses and U-Pb dating were performed by ICPMSDataCal (Liu et al., 2010; Liu et al., 2008). Concordia diagrams and weighted mean calculations were made using Isoplt/Ex_ver3 (Ludwig, 2003). Zircon standards Gj-1 was analyzed as unknown and the obtained mean 206Pb/238U age is 599.8±3.1 Ma (2σ) in line with the recommended age [599.8±1.7 Ma (2σ), Jackson et al., 2004]. 
For the trace element signals, the depth-related fractionation of time-resolved spectra acquired by LA-ICPMS analysis was inspected during data reduction to remove the possibility of obvious accidental analysis of zircon-hosted inclusions such as apatite or monazite. Trace element compositions of zircons were calibrated against multiple-reference materials combined with the NIST 610 glass as internal standardization (Liu et al., 2010). The trace element concentrations in zircon standard 91500 are calibrated by Si-in NIST 610 glass as internal standards. Except La and Pr, all the trace element concentrations have uncertainties within 10 % (Liu et al., 2010; Yang et al., 2012). Detection limits for reported trace elements can be found in Yang et al. (2012).
References
Jackson SE, Pearson NJ, Griffin WL, Belousova EA. 2004. The application of laser ablation-inductively coupled plasma-mass spectrometry to in situ U-Pb zircon geochronology. Chemical Geology 211:47-69.
Liu Y, Gao S, Hu Z, Gao C, Zong K. 2010. Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-North China Orogen: U-Pb dating, Hf isotopes and trace elements in zircons of mantle xenoliths. Journal of Petrology 51(1-2):537-571.
Liu Y, Zong K, Kelemen PB, Gao S. 2008. Geochemistry and magmatic history of eclogites and ultramafic rocks from the Chinese continental scientific drill hole: subduction and ultrahigh-pressure metamorphism of lower crustal cumulates. Chemical Geology 247:133-153.
Ludwig kR. 2003. User`s manual for Isoplot 3.00: a geochronological toolkit for microsoft Excel: Berkeley Geochronology Center Special Publication No. 4.
Wiedenbeck, M., Allé, P., Corfu, F., Griffin, W.L., Meier, M., Oberli, F., von Quadt, A., Roddick, J.C, Spiegel, W., 1995. Three natural zircon standards fro U-Th-Pb, Lu-Hf, trace element and REE analyses. Geostand. Newsl. 19: 1-23.
Wiedenbeck M, Hanchar JM, Peck WH, Sylvester P, Valley J, Whitehouse M, Kronz A, Morishita Y, Nasdala L, Fiebig J, Franchi I, Girard JP, Greenwood RC, Hinton R, Kita N, Mason PRD, Norman M, Ogasawara M, Piccoli PM, Rhede D, Satoh H, Schulz-Dobrick B, Skår Ø, Spicuzza MJ, Terada K, Tindle A, Togashi S, Vennemann T, Xie Q, Zheng YF. 2004. Further characterisation of the 91500 zircon crystal. Geostandards and Geoanalytical Research 28(1):9-39.
Yang, J., Cawood, P.A., Du, Y., Huang, H., Huang, H., Tao, P., 2012. Large Igneous Province and magmatic arc sourced Permian-Triassic volcanogenic sediments in China. Sedimentary Geology, 261-262: 120-131.

Figure Caption:
Supplementary Figure 1. (A) SiO2-TiO2 and (B) SiO2-CaO plots for the Late Permian-Middle Triassic samples from the Youjiang Basin.

Supplementary Figure 2. Representative cathodoluminescence images for detrital zircons from (A) Sample Sdz28, (B) Sample Pyz80, (C) Sample Nhg1, (D) Sample Pnt59, (E) Sample Bdg1, (F) Sample Luz8 and (G) Sample Lz01.

Supplementary Figure 3. Chondrite normalized rare earth element distribution patters for detrital zircons from (A) Sample Luz8, (B) Sample Lz01, (C) Sample Pyz80, (D) Sample Bdg1, (E) Samples Pnt59 and Sdz28, and (F) Sample Nhg1.