Incompatible is a technical term which cannot be considered in geosciences without a chemical, mineralogical, structural or lithological system. Gold is incompatible to the intrusive emplacement of a normal granite, because it cannot be accommodated in any of the major constituents´ crystal lattice. Gold is, however, compatible to a structurebound mineralization made up of quartz, arsenopyrite, and pyrite. There is more than one mineral which being part of the mineral association can either host gold or accommodate it in its lattice and the fluid ascending along the fault has the potential to carry gold in whatever type of chemical compound so as to be concentrated when the physical-chemical regime is suitable for its precipitation.
H.G.Dill
Many thanks Dr/Harald G. Dill
Now! gold may be compatible or incompatible according to the physical-chemical ? but i know: Compatibility is controlled by valence and ionic radius , as well as compatible elements are preferentially partitioned into the solid phases and incompatible elements are preferentially partitioned into the melt. please, can you give me any information about factors and criteria which control these terms ( compatible and incompatible).
I think you may have missed the point made in the previous answer. You can't say compatible/ incompatible without some more context. An element may act in a compatible way in one magma, and incompatible way in another - it's dependent on the P-T-X conditions.
In a very broad sense, Au is generally incompatible in most systems. However, as mentioned in the previous answer, this is dependent on the system, and there are circumstances where it can be compatible.
Is there a particular circumstance that you are asking about? You need to provide more detail to get a specific answer.
Regards,
Ed
Thanks Dr/ James Edward
I didn't miss the point, i know any element has different behavior in different systems that depend on physical-chemical conditions, now i ask about gold when and why it become compatible or incompatible (i ask about about factors and criteria )
best regards
refaey
Hi Rafaey,
There's lots of factors that may influence the compatibility - for instance, what phase is the gold hosted in at the source? What are the oxygen fugacity conditions at the time of melting (this will affect the stability of that host phase)? What ligands are available to transport the Au? What are the P-T conditions?
Gold is quite chalcophile in it's behaviour, and so it is often strongly influenced by the sulfides - if sulfides are stable, it is more likely to be compatible. This is still a generalisation, but maybe points you in the right direction?
Dear Refaey,
I agree with the previous writers that Au can be compatible or incompatible depending on the magma generation conditions. Some research has shown that Au, Cu and Pd behaved incompatibly in basalts and andesitic glasses, whereas they became compatible in low-K dacites. See for example “The Role of Late Sulfide Saturation in the Formation of a Cu- and Au-rich Magma: Insights from the Platinum Group Element Geochemistry of Niuatahi–Motutahi Lavas, Tonga Rear Arc” in Journal of Petrology, 2015, Vol. 56, No. 1, 59–81; doi: 10.1093/petrology/egu071. To decide this the authors examined magmatic minerals, volcanic glass and melt inclusions.
Other research from SE Russia showed that Au is incompaticle in Ca-alkaline granites and concentrated in the latest granite intrusive portions.
Regards,
Irina