The mineralogical characterstics of scheelite of Nannihu Mo-W deposit in Henan

Nannihu Mo-W deposit is located in the middle part of the East Qinling metallogenic belt.Scheelite is the main tungsten mineral found in the deposit.The research on scheelite in Nannihu Mo-W deposit was carried out by means of the Electron Probe Micro Analysis(EPMA).Two kinds of different scheelite were discovered by observing back scatter electron(BSE) images of scheelite.Base on the different contents of molybdenum elements in scheelite it can be divided into two categories: light scheelite and dark scheelite.The former is formed in skarn and quartz-sulfide vein.The later is found only in quartz-sulfide vein.Chemical component analysis in scheelite shows that,Mo ions has replaced W ions in two kinds of scheelite,but the dark scheelite has relatively more Mo than the light one.Gradually,the contents of Mo decrease while W increases from core to edge,MoO3 and WO3 are negatively correlated in scheelite.In the meanwhile,isomorphism could be seen in these images of the element scaning.