Overview of current understanding, outstanding problems, future research, and exploration significance: Open symbols represent conditions at which all mantle sulphides are consumed during melting, which are the minimum concentrations needed in the sub-arc mantle to explain sulphur and copper abundances in the melt inclusions.
Australian Journal of Earth Sciences, v.
Crystallization of the immiscible monosulphide solid solution Mss segregates from the silicate melt a to form pyrrhotite popyrite pyand intermediate solid solution Iss band then chalcopyrite cp and po c.
Late-stage hydrothermal fluids with low pH and a relatively high oxidation state may leach gold that was incorporated into sulphide minerals, during a sulphide saturation event occurring early in the evolution of a granitoid magma.
Sulphur has to be enriched in the sub-arc mantle, whereas copper may be close to the PM value under some conditions. Sulphide ore in core close up Magmatic sulphide deposits are of course important from an exploration and mining perspective because they host economic quantities of copper, nickel, and the platinum group elements PGE.
A fluid inclusion study: Wallace and Edmonds This is consistent with observations that felsic melts dissolve lower quantities of sulphur than mafic to ultramafic melts Sulphide solubility in magma and Ohmoto ; Carroll and Webster ; Holzheid and Grove ; Li and Ripleysuggesting that the solubility of sulphide minerals in magmas would decrease with fractionation in a granitoid suite.
Pyrrhotite is subsequently oxidized to pyrite and Fe oxide d. These data are useful in defining the limits of sulphur solubility in hydrous, sulphur-saturated magmas at crustal pressures.
These intrusions were saturated in sulphide during magma evolution and gold is dominantly hosted in the sulphide minerals; however, the magmatic suphide minerals are unstable, and ready to be dissolved and decomposed upon reaction with chloride- or bisulphide-bearing circulating hydrothermal fluids, either derived from sequential release of cooling magmas at depth, or from the circulation of local groundwater driven by the cooling intrusion above the brittle-ductile transition.
However, temperature has a variable effect on sulphur solubility, depending on redox conditions. Evidence for multiple fluid reservoirs: Type 2 deposits appear to exhibit more structural control, and exploration models and techniques employed in searching for these deposits should take this, and the mode of gold transport, into account.
Newberry and McCoy ; McCoy et al. With magmatic—hydrothermal evolution, these metals could be partitioned into exsolving magmatic fluids that subsequently form magmatic hydrothermal deposits e. Sulphur is a minor component of this region and occurs at around ppm.
The proportions of these species in a given melt are controlled by the following equilibrium equations: Gold and associated mineralizing elements in intrusion-related gold deposits may therefore be directly derived from the intrusion, although minor amounts could be incorporated from country rocks by selective assimilation and subsequent fractional crystallization.
The Lake George deposit exhibits early tungsten—molybdenum— gold stockwork mineralization superimposed by later gold—antimony quartz vein mineralization associated with a magmatic pyrrhotite-bearing granodiorite intrusion that is contiguous with a large pluton at depth Seal et al.
This contrasts with sulphide-bearing melts NNO; Fig. H2S differentially exsolves with H2O from the melt. Sulphur solubility and the state of sulphide saturation in magmas are two of the most important controlling factors for the formation of intrusion-related gold deposits, such as those in the western Yukon Territory and southwestern New Brunswick Canadaeastern Alaska USAand elsewhere e.
This is demonstrated in Figure 3, which shows how sulphur solubility in the El Chichon trachyandesite varies with temperature at constant pressure in Fe3O4—Fe2O3 magnetite—hematite, or MH.
Sulphur concentrations in the melt inclusions have been assumed to be and ppm minimum and maximum estimate of primary sulphur content in high-CaO melt inclusions, respectivelyand ppm maximum sulphur content of basaltic inclusions.Our solubility data, together with experimental mineralmelt D values and measured concentrations of Cu in silicate minerals of the Duluth Complex, suggest that although Cu is a strongly chalcophile element, appreciable univalent non-Sbonded Cu may be dissolved in a mafic melt, Hence, the addition of externally derived S to a S-poor, Cat.
Request PDF on ResearchGate | Sulfide Saturation in Mafic Magmas: Is External Sulfur Required for Magmatic Ni-Cu-(PGE) Ore Genesis? | The importance of externally derived sulfur in the genesis of. Box 2: Magmatic sulphide saturation (trigger 2).
There is an increasing awareness of the potential importance of magmatic sulphur in controlling metal enrichment or depletion in porphyry systems. Sulphur Solubility in Felsic Magmas: Implications for Genesis of Intrusion-related Gold Mineralization Sulphur solubility and the state of sulphide/sulphate saturation in felsic magmas play an important role in the formation of intrusion-related gold systems.
Oct 20, · One of the most central principles in the formation of a sulphide deposit is the consequent change in solubility of sulphur in a mafic-ultramafic magma as the temperature of the magma changes (cooling after and during emplacement).
This essay aims to define the controls on sulphide solubility in magma, such as pressure, temperature and element activity.Download