Detrital zircon geochronology of modern rivers in the eastern Pamir syntaxis and its implications on formation of the Pamir accompanying growth of the Tibetan Plateau
Description
We have collected three new sand samples from Taxkorgan River in eastern Pamir syntaxis . Zircon separation was carried out from ~10 kg samples using conventional magnetic and density techniques to concentrate the non-magnetic, heavy fractions. Representative selections of zircons were then extracted by handpicking under a binocular microscope. Then, ~300 zircon grains were randomly selected and then cast into an epoxy mount and polished to obtain an even surface. And the mount was sanded down, polished and cleaned prior to isotopic analysis. U‐Pb geochronology of zircons was conducted by laser ablation multicollector inductively coupled plasma mass spectrometry (LA–MC–ICPMS) at the State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration. The analyses involve ablation of zircon with Resolution M50-LR ArF excimer laser ablation system using a spot diameter of 28 microns, and it is necessary to set the integration time of isotopes to be measured, including 15 ms for 204Pb, 206Pb and 208Pb, 30 ms for 207Pb, 10 ms for 232Th and 238U, and 6 ms for other trace elements using Agilent 7900 quadrupole inductively coupled plasma mass spectrometer (Li et al., 2019). Every set of ten samples analyses was followed by analysis of two zircons standard 91,500 and one zircon standard GJ-1, and the glass standard (Jackson et al., 2004). Common Pb was corrected using the method proposed by Andersen (2002). The experimental results were tuned by the standard program Glitter 4.0, and U‐Pb geochronology with concordance less than 90% were excluded. U‐Pb geochronology were output used by 206Pb/238U and 1σ if less than 1.2 Ga, unless use 207Pb/206Pb and 1σ (Nemchin and Cawood, 2005).