LA-ICP-MS detrital zircon U-Pb ages of interbedded quartzite from the metamorphic belt of the Chinese Altay: Constraint on depositional time and provenance

Progressive metamorphic belts occur extensively in Chinese Altay. The depositional time and provenance of the metasediments in the metamorphic belts are critical for understanding the rock-forming process and the evolution of the orogen. Based on petrological analysis, the authors conducted LA-ICP-MS U-Pb analysis of detrital zircons from the quartzite narrowly interbedded in the metamorphic belt and yielded 100 concordant or nearly concordant ages with a range from (443±5) Ma to (2682± 19) Ma. Most of the detrital zircons have Cambrian ages of 486~540 Ma with the peaks between 527 and 535 Ma. One fourth of the zircon grains show Neoproterozoic ages. A few detrital zircon grains formed in the Meso-Paleoproterozoic period and even in the Archean period. Combining the youngest detrital zircon age with the emplacement time of the tonalite which directly intruded in the metamorphic belt, it could be inferred that the protolith of the quartzite deposited between the Early Silurian and the Early Devonian and later experienced metamorphism. The Cambrian and even younger detrital zircons were possibly derived from the contemporaneous igneous rocks in the region. Since the lack of Precambrian rocks in the Chinese Altay, the Precambrian detrital zircons may imply a hidden ancient basement in the region or could be ascribed to a faraway source from the neighboring block.