W-bearing rutile formed during alteration of jarosite by resurgent hydrothermal fluids in the oxide zone of the Kori Kollo gold deposit. The rutile shows sector zoning in basal sections and well developed multiple growth zones, both defined in backscatter electron images by variations in the W content. The maximum WO3 content is 5.3 wt.% and W substitutes for Ti with double substitution of Fe to maintain charge balance. The causes of multiple growth bands are considered to be changes in externally controlled variables occurring in a shallow hydrothermal system. Whereas Ti is probably leached from biotite in dacitic rocks, the W is introduced by hydrothermal fluids.
Rice, C. M., Darke, K. E., Still, J. W., & Lachowski, E. (1998). Tungsten-bearing rutile from the Kori Kollo gold mine, Bolivia. Mineralogical Magazine, 62(3), 421-429. https://doi.org/10.1180/002646198547684