Zircon U-Pb age and geochemical characteristics of meta-andesite in Qiongzuerkai area of Harlik Mountain, Xinjiang

The studied volcanic rocks are mainly distributed in Qiongzuerkai area of Harlik Mountain. There are no accurate ages and geochemical data for these rocks, The genesis and the geodynamical background of these volcanic rocks have been controversial for a long time. In order to tackle this problem, the authors chose layered volcanic rocks in Qiongzuerkai area of Harlik Mountain as the study object. LA-ICP-MS zircon U-Pb ages of 309.9±4.6Ma(MSWD=2.6,n=9)and 304.6±1.8Ma(MSWD=0.84,n=11)from two meta-andesites suggest that these volcanic rocks erupted in Late Carboniferous. The meta-andesite is characterized by SiO₂ content from 49.96%~62.22%, low TiO₂(0.94%~1.7%)and high Al₂O₃(14.76%~16.25%). The meta-andesite forms a LREE-enriched distribution pattern with a strong contrast between LREE and HREE and the existence of negative Eu anomalies(δEu=0.88~0.94). Geochemical characteristics of meta-andesite suggest that this rock shows island-arc volcanic characteristics, being enriched in LILE such as Th, U, Ce, Rb and Ba and depleted in HFSE such as Nb, Ta and Ti. The mantle source was made up of crust melt, subducted ocean crust melt and so on, with the addition of crustal material during plate subduction. Combined with regional data, the authors consider that the evolution of the Carboniferous volcanic activity might have been associated with the Kanggurtag basin.