1985 Volume 35 Issue 193 Pages 317-329
In the double side-polished thin sections, the details of the internal structure in wolframite can be observed in transmitted light. The microscopic study of wolframite is effective to reveal the history of the wolframite mineralization. The internal structures in wolframite can be divided into four categories. There are the homogeneous structure (Zone A), the oscillatory zoned structure (Zone B), the irregular structure (Zone C) and the banded structure (Zone D) from the core to the margin of the crystal. This zonal sequence can be interpreted as the formational sequence.
Quantitative chemical analyses of wolframite show that its composition varies considerably within a single crystal. This compositional heterogeneity in wolframite interferes with the accurate evaluation of the compositional variation of wolframite throughout the deposits by bulk analysis. Taking observations of the internal structures into consideration, the compositional variation of wolframite throughout the deposits is revealed. Wolframites, in the up-per and the western parts of the No. 7 Vein which is the champion vein in the Takatori deposits, are dominantly composed of Zone A and rich in Mn WO4 contents. In contrast to this, wolframites in the lower and the eastern parts are dominantly composed of Zone B and rather poor in Mn WO4 contents.
The internal structure and the composition preserved within each wolframite crystal, and their distribution pattern in the No. 7 Vein are reasonably explained by the interpretation that the crystallization of wolframite in the upper and the western parts of the No. 7 Vein is ealier than that in the lower and the eastern parts.
