Age and thermal history of the east ore section, Bayan Obo Deposit—a fission track study

Considerable attention has been paid in recent years to the study of geothermal history by using spontaneous fission tracks of238U recorded in minerals. Apatite and zircon were used for fission track study in this paper because apatite has been widely used as a natural geothermometer (Wang Shicheng et al., 1994) to reveal the thermal evolution of sedimentary rocks based on its low annealing temperature of fission tracks and zircon is characterized by a closing temperature above 700°C. The samples were collected from ferruginous, siliceous slate wall rock at the upper levels of the orebody and Nb-REE-Fe ores from deep tunnels. The age and thermal evolution of the orebody were discussed in terms of fission track characters and their length variations observed in the coexisting apatite and zircon in the same specimen.