The Lianshanguan uranium deposit, Northeast China

The Lianshanguan uranium deposits are located in the Lianoning Province of northeastern China. The deposits occur in a transitional zone lying between an Archaean craton and Lower Proterozoic miogeosynclinal sequences. Three types of uranium mineralisation are present in the area; syngenetic mineralisation occurs in the basal psammitic units of the Lower Proterozoic rocks which, during metamorphism in the period 1900 to 1800 Ma, was partly mobilised and concentrated in the metasediments. Late-orogenic granite emplacement in the Lower Proterozoic saw the development of uranium-bearing alkali solutions that initially produced metasomatic white migmatite in fracture zones marginal to the granites. Ore grades are relatively rich in these alkali hypo-meso metasomatic uranium deposits. With precipitation of potassium and sodium from the metasomatising solutions uranium became further enriched in the evolved fluids. Precipitation of uranium from these fluids produced meso-epithermal mineralisation of the fissure filling type. All three types of uranium mineralisation have been overprinted by tectonic movements associated with activation of the platform cover in the period 90 to 220 Ma. (author)