Zircon U-Pb Ages and Geochemical Characteristics of the Laoyaquan A-type Granites in East Junggar,North Xinjiang,China

Laoyaquan granitic pluton is the largest pluton containing tin deposit in the Beilekuduk tin metallogenic belt.It is mainly composed of biotite alkali-feldspar granites.LA-ICP-MS U-Pb dating for zircons from two samples yielded the 206Pb/238U ages of 301±2 Ma(2σ,MSWD=1.03) and 300±5 Ma(2σ,MSWD=5.90),suggesting that the emplacement of the pluton occurred at the end of Late Carboniferous.The Laoyaquan alkali-feldspar granite is enriched in silica,alkalis,REE,Rb,K,Th,U,Nd,Hf and depleted in Ba,Sr,P,and Ti,with a strong Eu negative anomaly,showing the features of A-type granites.Both the geochemical characteristics and the zircon U-Pb ages indicate that the formation of the pluton is related to the post-collision and the magmatic activity during Late Carboniferous in northern Xinjiang.