New cognition and discovery of rare earth deposits in the Xiaolonghe tin-REE polymetallic orefield of Tengchong in Yunnan Province

By the analogy and contrast of the primary structure, alteration and mineralization in Guyong rock body of Xiaolonghe area in Tengchong city, combining with tectonic geochemistry,geochronology and preliminary investigation, pervasive hydrothermal alteration, intrusive breccia and large REE ore bodies were discovered. And the rare metals (Rb and Nb) and scare metal (Ga) were accompanied. Also the synmagmatic faults were found in the later period. The U-Pb ages for the monazite and zircon of the altered granitic rocks are (75.61±0.47) Ma and (75.68 ± 0.72) Ma, and the U-Pb ages for the cassiterite and zircon of the biotite K-feldspar granites are (76.3 ± 3.2) Ma and (77.29 ± 0.54) Ma. These ages are very close, which reflects that they may be the products of tectonic activities at later period of the magmatic action.