Speaker
Dr
Jun LIN
(Shanghai Institute of Applied Physics, Chinese Academy of Sciences)
Description
Pitchblende as the micro/cryptocrystalline uraninite, normally UO2+x, is common U4+ mineral species, and is the main ore mineral in the hydrothermal U deposits. Pitchblende always contains certain amount U6+ in the formula of UO2+x, where x reaches the maximum value as 0.25. The investigation shows that the mineral composition varies as the lodes formed at different stages and changes outwards from the center of the lode. It also indicates that sulfur/H2S and the ferrous minerals may play an important role as a reducer in the deposition of the pitchblende from uraniferrous solution where the uranium migrates mainly in the form of various U6+ compounds. So, the pitchblende deposition is considered to be a reduction – oxidation process between U6+-bearing solution and the rock as diabase is enriched in ferrous minerals.
In general, the iron-bearing minerals with different valence charge are macroscopically distinguished by their colors. However, it is quite different when the iron-bearing minerals are in small amount and highly dispersed, such as the wall rock alteration. In such a circumstance, Mossbauer spectroscopy is of great advantages compared to other methods because of its sensitivity for the iron containing minerals.
Samples were collected from different zones (the pitchblende lode, the chloritized alteration zone and the weakly altered diabase) at a uranium deposit (Fig. 1). Fig. 2 shows the spectra of these samples. Based on the Mossbauer spectroscopy, the main iron mineral in the lode is pyrite, and in the altered zone there is less pyrite relative to that in the lode. There are more original minerals in weakly altered diabase zone. The difference among these three zones originates from the difference of rock alteration. The alteration decreases according to the increase of distance to the center of the lode, from pyritization to chloritzation gradually. The ratio of pyrite decreases with increasing distance to the lode center, while altered ripidolite is most abundant in the altered zone of chloritization.
Primary author
Dr
Jun LIN
(Shanghai Institute of Applied Physics, Chinese Academy of Sciences)
Co-authors
Prof.
Ya-xin Yang
(East China Institute of Technology)
Prof.
Yuan-fu Hsia
(Nanjing University)
