P. Geoffrey Feiss
Reconnaissance of the Tetrahedrite-Tennantite/Enargite-Famatinite Phase Relations as a Possible Geothermometer
Economic Geology and the Bulletin of the Society of Economic Geologists (May 1974), 69(3):383-390

Abstract:
The equilibrium distribution of arsenic and antimony between coexisting tetrahedrite-tennantite and enargite or famatinite is a function of temperature. Preliminary calibration suggests that this distribution may provide a useful geothermometer.Experimental syntheses of coexisting tetrahedrite-tennantite and enargite or famatinite were carried out at 500 degrees C and 400 degrees C. At 500 degrees C the tie lines between tetrahedrite-tennantite and enargite or famatinite are very nearly colinear with sulfur in the system Cu ₃ As-Cu ₃ Sb-S. With decreasing temperature, a given enargite coexists with increasingly more antimonian tetrahedrite-tennantite. The composition of the tetrahedrite-tennantite in equilibrium with both enargite and famatinite migrates from approximately tn ₇₀ at 500 degrees C to tn ₅₆ at 400 degrees C. Attempts to synthesize coexisting phases below 400 degrees C are continuing.Enargite appears to coexist with tetrahedrite (tn ₀ -tn ₅₀ ) immediately below 400 degrees C suggesting that the common association of arsenian Cu ₃ (As,Sb)S ₄ and antimonian Cu ₁₂ (As,Sb) ₄ S ₁₃ in the same deposits is a function of partitioning of arsenic and antimony under mesothermal conditions.