~ ICPMSDataCal (Liu et al., 2008a; Liu et al., 2010a).
(5)U-Pb dating and trace element analyses of zircon by LA-ICP-MS U-Pb dating and trace element analyses of zircon were conducted synchronously by LA-ICP-MS at the State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry Chinese Academy of Sciences. Laser sampling was performed using a GeoLas Pro193 nm ArF excimer laser. An Agilent 7500x ICP-MS instrument was used to acquire ion-signal intensities. Helium was applied as a carrier gas which was mixed with Argon via a T-connector before entering the ICP-MS. Each analysis incorporated
a background acquisition of approximately 30 s (gas blank) followed by
60 s of data acquisition from the sample. 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., 2008a; Liu et al., 2010a). Zircon 91500 was used as external standard for U-Pb dating, and was analyzed twice every 6-8 analyses (i.e., 2 zircon 91500 + 6-8 samples + 2 zircon 91500). 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 (Ludwig, 2003). Trace element compositions of zircons were calibrated against multiple-reference materials (NIST 610，BHVO-2G，BCR-2G，BIR-1G) combined with Si internal standardization.The preferred values of element concentrations for the USGS reference glasses are from the GeoReM database (http://georem.mpch-mainz.gwdg.de/).
(6)Trace element analyses of quartz by LA-ICP-MS
Quartz trace element analyses was conducted at the State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry Chinese Academy of Sciences (IGCAS) by using an Agilent 7900 ICP-MS equipped with a
~
GeoLasPro 193 nm ArF excimer laser. Laser repetition of 10 Hz, energy density of 12J/cm2 and spot size of 44 μm were used during the analyses. For the quantitative calibrations, external standard of NIST SRM610 or GSE-1G was used and analyzed twice every 10 analyses. An internal standard-in-dependent calibration strategy, which is based on the normalization of the sum of all metal oxides to 100 wt%, was applied to the calibrations (Liu et al., 2008). NIST SRM612 and GSD-1G were analyzed to monitor the accuracy of the results, which show that the uncertainties of most elements are less than 10%. A nature quartz standard was also analyzed to monitor the accuracy. This standard has recommended values for Ti (57±4 ppm), Al (154±15 ppm), Li (30±2 ppm), Fe (2.2±0.3 ppm), Mn (0.34±0.04 ppm), Ge (1.7±0.2 ppm) and Ga(0.020±0.002 ppm) (Audétat et al., 2015). The detailed analytical procedures are described in Lan et al. (2017, 2018).
(7)Major and trace element analyses of fluid inclusion by LA-ICP-MS Individual fluid inclusion major and trace element analyses was conducted at the State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry Chinese Academy of Sciences (IGCAS) by using an Agilent 7900 ICP-MS equipped with a GeoLasPro 193 nm ArF excimer laser. The standard ablation cell was optimized with resin mold to get a small volume and to improve the washout efficiency. Laser repetition of 9~10 Hz and energy density of 10-11 J/cm2 were used during the analyses. Laser spot size changed from 24 to 44 μm based on the sizes of the fluid inclusions.
being added to increase Helium was used as the carrier gas with 3 ml/min N
2
the sensitivity. Argon was used as the makeup gas and mixed with the carrier gas via a T-connector before entering the ICP. NIST SRM610 was
wt.% concentrations used as the external standard and the NaCl
equivalent
obtained independently by microthermometry as the internal standard
~
(Heinrich et al., 2003). NIST SRM610 was analyzed twice every 10 analyses. The data collected from the ICP-MS were processed by the SILLS software (Guillong et al., 2008). The charge-balance method was adopted to correct the modeled amounts of Na (from the NaCl eqv. wt%) for salinity contributions of other chloride salts (Allan et al., 2005). To ensure the fluid inclusion signals being processed without the interference from the host crystal, only spectra containing signals coincident with Na and other cations were selected. Synthetic ?uid inclusions containing ?ve elements of Na, K, Ca, Rb and Cs (standard values are Na=K=Ca= 2.05 wt%, Rb=300 ppm, Cs= 200 ppm) were also analyzed to monitor the accuracy, which show the total uncertainties of less than 16%. The detailed analytical procedures are described in Lan et al. (2017, 2018).