In-situ U-Pb dating of pitchblende and the REE characteristics using LA-ICP-MS in Xiangyangping uranium deposit

Abstract

The Xiangyangping uranium deposit is a newly discovered granite-type uranium deposit, which is one of the representative granite-hosted uranium deposits in the Miaoershan uranium ore field.The Xiangyangping uranium deposit has developed a large number of primary pitchblende veins, but the chronology characteristics of uranium minerals are obscure, especially the application of in-situ analysis technique is lacking.In order to further clarify the uranium mineralization age of the uranium deposits, in-situ U-Pb isotopic dating of pitchblende veins exposed in the borehole was studied by using LA-ICP-MS.The U-Pb age dating of the pitchblende obtained ages of 51.59 Ma and 41.10 Ma, suggesting that there are two phases of uranium mineralization in the Xiangyangping area, which are consistent with the main mineralization periods of 65-50 Ma and 45-40 Ma for the Shazijiang uranium deposit.The former is the main metallogenic age of Xiangyangping uranium ore deposit, while the latter is the thermal event time of late fluid activity leading to pitchblende alteration, indicating that there is a major uranium metallogenic event of about 52 Ma in the Miaoershan uranium ore field.The chondrite-normalized patterns of rare earth elements are rich in light-REE, with obvious negative Eu anomalies.The distribution curve of rare earth elements in pitchblende is characterized by in seagull pattern, which is similar to low-high grade uranium ore, and different from the "right-dipping type" of fresh granite and altered granitic cataclastic rock.The migration of REE and pitchblende was synchronous, which is the product of crystallization and precipitation at a low-temperature hydrothermal environment.

Keywords

• pitchblende
• la-icp-ms
• rare earth element
• xiangyangping