Geochronology of the Narenwula W polymetallic deposit in Inner Mongolia and its implications for ore prospecting

The Narenwula quartz -vein type tungsten polymetallic deposit, located in the southwestern Great Hinggan Mountains in Inner Mongolia, Northeast China, is a recently discovered large W-Bi-Ag-Zn-Cu deposit. However, the geochronological and genetical relationship between the deposit and the multiple stages of regional tectonic -magmatic events remains unclear, which severely hinders the understanding of the genesis of the deposits and ore deposits exploration in this area. In this paper, LA-HR-ICP-MS U-Pb ages of zircon and monazite in ore -bearing coarse -grained monzogranite as well as wolframite and cassiterite in quartz -vein type ore are studied to constrain the geochronological framework of the granites and the ore. The zircon and monzonite from the monzogranite yielded U-Pb ages of 146.2 +/- 2.2Ma and 144.2 +/- 0.8Ma, respectively, which are consistent with each other within permitted errors, and thus indicating that the ore -bearing rocks were formed in the Late Jurassic. The wolframite and cassiterite from the quartz -vein type ore yielded U-Pb ages of 136.7 +/- 1.0 Ma and 137. 8 1. 9Ma, respectively, indicating that the W-polymetallic deposit were formed in the Early Cretaceous. Since the formation time gap of the granite and the W-polymetallic ore (similar to 10Myr) is larger than the lifetime of a granitic magmas activity, there is no genetic relationship between the monzogranite and W-polymetallic mineralization. These geochronological data indicate that the ore -causative granite should be buried in the deep in the area and there is a high potential for Wpolymetallic ore exploration in the deep of the ore district. Combined with the regional metallogenic studies, we propose that the formation of the Narenwula deposit is mainly controlled by the extension process after the closure of the Mongolian -Okhotsk Ocean, and may be superimposed by the remote effect of the subduction of paleo-Pacific plate.