gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/002646198547684 Tungsten-bearing Rutile from the Kori Kollo Gold Mine, Bolivia Rice C. M. Darke K. E. Still J. W. Department of Geology and Petroleum Geology, University of Aberdeen, Aberdeen, Scotland Lachowski E. E. Department of Chemistry, University of Aberdeen, Aberdeen, Scotland 6 1998 62 3 421 429 5 8 1996 28 11 1997 Copyright © 1998, The Mineralogical Society 1998 Abstract

W-bearing rutile formed during alteration ofjarosite 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.

 Keywords tungsten rutile jarosite gold deposits Bolivia