Complex Zircon Genesis Of Advanced Metamorpic Rocks In Xinjiang Kuruktag Region

The study is based on the field investigation of the Xinditag Region of Xinjiang Province.The Paleo-Proterozoic Xinditag Group exposed at the Kuruktag region was sampled.Multiple analysis were applied to indentify the petrology,date the detrital zircon U-Pb ages,obtain the REE characteristics,discriminate the zircon's origin and its metamorphic grade,providing new evidences for the research of the Paleo-Proterozoic Xinditag Group exposed at the Kuluktag region.It is also important for the zircon U-Pb chronology research of the Tarim Craton.The petrology analysis indicated that the sample was graphitiferous garnet-bearing feldspar quartzite.The metamorphic grade was amphibolites facies.The coupled analysis of 80 zircon U-Pb ages and CL images found out that the oldest zircon was 2666±10Ma,while the youngest was 1838±21Ma.Most of the zircons were metamorphic origined,with none or weak zoning.The cores and rims were recognized.Some zircons were classic amphibolites facies,bearing a magmatic core and a metamorphic rim.The metamorphic event took place at 2100~1800Ma,with a 1910 Ma peak,64 suits of rare earth elements were analyzed.The chondrite-normalized figures showed that all the patterns were characterized by LREE deficit and HREE enrichment,with obvious positive Ce anomalies and negative Eu anomalies.The zircons were rich in REE(260.6ppm-11915.6ppm,3719.7ppm in average)with a wide range and two separate groups: 260.7-996.1ppm and1536.3-11915.6ppm.Some zircons featured HREE deficit.The(Pr/Gd)CN-(Gd/Yb)CN plot also suggested two separate groups.The zircons featuring HREE deficit were granulite facies while the zircons featuring HREE enrichment were amphibolites facies.In general,the zircons beared cores of both granulite facies and amphibolites facies,while their rims were amphibolites facies.