Tomkins,A.G., Pattison,D.R.M. and Frost,B.R.(2007): On the initiation of metamorphic sulfide anatexis. Journal of Petrology, 48(3), 511-535.

『変成作用による硫化鉱物のアナテクシス（再溶融）の開始について』

『Abstract
　Mineral assemblages in common sulfide ore deposits are examined together with phase relations to (I) investigate the pressure-temperature conditions required for the onset of metamorphically induced partial melting involving economic minerals, and (2) place constraints on the amount of melt produced. Deposits that contain sulfosalt or telluride minerals may start to melt at conditions ranging from lowest greenschist facies to amphibolite facies. Deposits lacking sulfosalt and/or telluride minerals may begin to melt once P-T conditions reach the upper amphibolite facies, if galena is present, or well into the granulite facies if galena is absent. The result is two broad melting domains: a low- to medium-temperature, low melt volume domain involving melting of volumetrically minor sulfosalt and/or telluride minerals; and a high-temperature, potentially higher melt volume domain involving partial melting of the major sulfide minerals. Epithermal gold deposits, which are especially rich in sulfosalt minerals, are predicted to commence melting at the lowest temperatures of all sulfide deposit types. Massive Pb-Zn (-Cu) deposits may start to melt in the lower to middle amphibolite facies if pyrite and arsenopyrite coexist at these conditions, and in the upper amphibolite facies if they do not. Excepting sulfosalt-bearing occurrences, massive Ni-Cu-PGE (platinum group element) deposits will show little to no melting under common crustal metamorphic conditions, whereas disseminated Cu deposits are typically incapable of generating melt until the granulite facies is reached, when partial melting commences in bornite-bearing rocks. The volume of polymetallic melt that can be generated in most deposit types is therefore largely a function of the abundance of sulfosalt minerals. Even at granulite-facies conditions, this volume is usually less than 0.5％. The exception is massive Pb-Zn deposits, where melt volumes significantly exceeding 0.5 vol.％ may be segregated into sulfide magma dykes, allowing mobilization over large distances.

Keywords: sulfide melt; ore deposits; melt migration; metamorphism』

Introduction
Overview of conditions required for sulfide melting
　The temperature of sulfide melting
　Factors affecting the temperature of sulfide melting
　　Pressure
　　Sulfur and oxygen fugacity
　　Water and other hydrothermal phases
　Comparison with silicate metamorphism
　Mineral communication and mobilization-assisted melting
Ealiest melting in sulfide ore deposits
　Massive Pb-Zn±Cu deposits
　　Observations
　　An experimental test of sulfide melting at the Montauban deposit
　　Mineralogical constraints on initial melting
　　Volume of melt generated during initial melting
　　Mobilization-assisted melting in massive Pb-Zn±Cu deposits
　　Evidence for preferential metal accumulation in melts
　Gold deposits - the influence of sulfosalts
　　Observation
　　Mineralogical constraints on initial melting
　　Volume of melt generated
　Initial metamorphic melting in magmatic Ni-Cu-PGE deposits
　　Highly metamorphosed deposits
　　Constraints on initial melting
　Disseminated Cu deposits (porphyry/IOCG/redbed/skarn)
　　Examples of amphibolite- and granulite-hosted Cu deposits
　　Constraints on melting
Mobilization of polymetallic melt at low melt fractions
Discussion and conclusions
Acknowledgements
References

Fig. 3. The temperature-pressure range over which sulfosalts, tellurides, native minerals and sulfides melt. Continuous black lines indicate that pressure constraints are known; dashed black lines indicate that the effect of pressure is unknown. Wide grey lines separate the metamorphic facies [the amphibolite to granulite transition is from Pattison et al. (2003) and the other facies boundaries are from Spear (1993)]. The wide band separating minor from major melting represents the variation caused by differences in the natural environment in the amount of H2O present (Wykes & Mavrogenes, 2005), and in the amount of trace metals present, on an assemblage containing galena+chalcopyrite+pyrrhotite+sphalerite. There will be widespread melting of the major sulfides at lower temperatures in wet, trace metal-rich rocks. The melting curve of galena+troilite (stoichiometric FeS)+sphalerite plots in the same position as that for bornite+ISS and bornite+pyrrhotite (Fe1-xS).

〔Tomkins,A.G., Pattison,D.R.M. and Frost,B.R.(2007): On the initiation of metamorphic sulfide anatexis. Journal of Petrology, 48(3), 511-535.から〕

戻る