Abstract:

The Nui Phao Polymetal Deposit occurring in Dai Tu District, Thai Nguyen Province, Northern Vietnam has a big wolfram reserve in association with other economic minerals and metals such as fluorite, bismuth, copper, gold, etc. The estimated reserve of fluorite in Nui Phao is significant. Scientific research results indicate that the Nui Phao mineralization was formed as the results of different tectonic and magmatism episodes. Hence, the mineralization at Nui Phao is complex with the multi sources of ore components. The research data shows that the Nui Phao ore was accumulated in association with the metasomatism between the Ordovician-Silurian carbonate- terrigenous sedimentary rocks of Phu Ngu Formation with the Da Lien Cretaceous Two-mica Granite of Pia Oac Complex and the Nui Phao Triasic Biotite Granite of Nui Dieng Complex. Despite the most major economic mineral of the Nui Phao Polymetal Deposit is sheelite, the fluorite is an important economic mineral formed in association with the formation of skarn and greisen bodies, which was poorly studied in the previous researches. The new research result of the authors indicates that the hydrothermal alteration as well as metasomatism in the study area is influenced by at least 3 metasomatic episodes including skarnisation, greisenisation and the late hydrothermal alteration medium to low temperature, that is genetically related to the fluorite-polymetallic mineralization.