Detrital zircon U-Pb dating and whole-rock geochemical analysis
Description
Detrital zircon U-Pb dating of Nanduan Formation (Quartz sandstone and Phyllite) in the western Yunnan, China. U-Pb dating and trace element analysis of zircon (22CYY0823-01a, 22CYY0823-01b and 22MLY0828-04) were simultaneously conducted by LA-ICP-MS at the Wuhan SampleSolution Analytical Technology Co., Ltd., Wuhan, China. Detailed operating conditions for the laser ablation system and the ICP-MS instrument and data reduction are the same as description by Zong et al. (2017). Laser sampling was performed using a GeolasPro laser ablation system that consists of a COMPexPro 102 ArF excimer laser (wavelength of 193 nm and maximum energy of 200 mJ) and a MicroLas optical system. An Agilent 7900 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. A “wire” signal smoothing device is included in this laser ablation system (Hu et al., 2015). Zircon 91500 and glass NIST610 were used as external standards for U-Pb dating and trace element calibration, respectively. Each analysis incorporated a background acquisition of approximately 20-30 s followed by 50 s of data acquisition from the sample. An Excel-based software ICPMSDataCal was used to perform off-line selection and integration of background and analyzed signals, time-drift correction and quantitative calibration for trace element analysis and U-Pb dating (Liu et al., 2008; Liu et al., 2010). Concordia diagrams and weighted mean calculations were made using Isoplot/Ex_ver3 (Ludwig, 2003). U-Pb dating analysis of zircon (YN16007) were analyzed using an Aglient-7500a quadrupole inductively coupled plasma mass spectrometry coupled with a New Wave SS UP193 laser sampler (LA-ICP-MS) for U-Pb isotope at the Elemental Geochemistry Lab of Institute of Earth Sciences, China University of Geosciences, Beijing. Trace element analysis of whole rock was conducted on Agilent 7700e ICP-MS at the Wuhan SampleSolution Analytical Technology Co., Ltd., Wuhan, China. The detailed sample-digesting procedure was as follows: (1) Sample powder (200 mesh) were placed in an oven at 105 ℃ for drying of 12 hours; (2) 50 mg sample powder was accurately weighed and placed in a Teflon bomb; (3) 1 ml HNO3 and 1 ml HF were slowly added into the Teflon bomb; (4) Teflon bomb was putted in a stainless steel pressure jacket and heated to 190 ℃ in an oven for >24 hours; (5) After cooling, the Teflon bomb was opened and placed on a hotplate at 140 ℃ and evaporated to incipient dryness, and then 1 ml HNO3 was added and evaporated to dryness again; (6) 1 ml of HNO3, 1 ml of MQ water and 1 ml internal standard solution of 1ppm In were added, and the Teflon bomb was resealed and placed in the oven at 190 ℃ for >12 hours; (7) The final solution was transferred to a polyethylene bottle and diluted to 100 g by the addition of 2% HNO3.