Zircon LA-ICP-MS U-Pb Dating of Volcanics in Hala'alate Formation of Western Junggar

Hala'alate formation is widely distributed in Hala'alate Mountain. Few researches have been conducted on this formation and there is great disparity in its age identification. The proportion of volcanic rocks in the area is the highest of all the group-level strata, and the position is relatively new marine volcano and sedimentary formation. LA-ICP-MS dating was used to determine the zircons from pyroxene andesite and rhyolite of the Hala'alate formation by 1:50000 regional geological survey, which yielded zircon U-Pb age of (306.9±5.5) Ma(MSWD=0.39) and (304.5±3.1) Ma(MSWD=0.63) respectively, both were consistent within the error range. Combining with the CL image features of zircons, the formation age of Hala'alate formation was signified. In view of predecessors' fossil information, which confirmed that the forming age of Hala'alate formation was late Carboniferous, the authors considered that the age of lower strata was no earlier than 306.9 Ma. The findings accurately constrained the period of marine volcanic strata in this area, and provided new chronological evidence for volcanic magmatism and tectonic evolution of western Junggar tectonic belt.