The Application of Electron Microprobe Dating Method on Uranium Minerals in Changjiang Granite, Northern Guangdong

Uraninite is considered to be the main ore source provider of granite-hosted uranium deposits, it plays a significant role in mineralization assessment of granite and constraining the age of digenesis and uranium mineralization.Changjiang granite is a part of the Zhuguang Mountains, and is important U-bearing granite in the north of Guangdong.Uranium minerals in this granite are studied by Electron Microprobe.Results show that uranium minerals mainly fill in the spaces between minerals or are surrounded by pyrite.Uranium minerals are also found in quartz, biotite, chlorite and other minerals.The main types of uranium minerals are uraninite, pitchblende, uranothorite and uranophane.The chemical ages of uraninite and pitchblende dated by Electron Microprobe can be divided into three groups, 155 Ma, 106 Ma and 74 Ma.The first group represents the formation age of Changjiang granite mass, and the second and third groups represent multiple stages of uranium mineralization.From rock formation to about 106 Ma, the composition of uraninite has not changed significantly.Obvious U activation and migration did not happen until 74 Ma, so the main uranium mineralization of Changjiang granite may have occurred at about 74 Ma or later.