Systematics of tetrahedrite-series compositional variations
Tetrahedrite occurs as a common but important minor phase in many base metal sulfide ore deposits where it is often the most important source of silver. Examination of published analyses of 1290 natural and 275 synthetic tetrahedrites indicates that compositional substitutions are controlled by multiple factors. Complete solid solution exists between pure Sb (tetrahedrite) and pure As (tennantite) end members. Compositional limits of base and precious metal in natural tetrahedrites appear to be: Cu - 4-10, Ag - 0-6, Fe, Zn, Hg - 0-2 atoms per formula unit. Silver substitution for copper is most strongly dependent upon Sb content, but also correlates with Fe content. Unit cell dimensions of natural and synthetic tetrahedrites, except for natural silver-rich samples, vary linearly with composition and permit the development of a regression equation that predicts values +/- .05 A. Unit cell dimensions of Ag-rich natural samples increase to a maximum at 4 atoms per formula unit, then decreases. Calculations of net ionic charge and of valence electrons per unit cell for these analyses indicates that a simple Brillouin zone model of bonding is superior to an ionic model in explaining compositional variations in tetrahedrite.
- Research Organization:
- Virginia Polytechnic Institute and State Univ., Blacksburg (USA)
- OSTI ID:
- 6459337
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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