Rare metal-enriched granites are typically peraluminous and are formed through fluid-absent mica dehydration melting during prograde metamorphism, followed by magmatic fractionation and later hydrothermal exsolution of magmatic fluids. Metals such as Li, Sn, and W are primarily supplied by the granitic magma, making the concentration of metals in the granitic melt critical for the fertility of these granites.
Our experiments at 300 and 900 MPa and oxygen fugacities of ~FMQ−2 and ~FMQ+3 helped constrain the extent of metal-enrichment in granitic magma produced by mica dehydration melting. Muscovite dehydration melting at 750 °C produces a small amount of peraluminous granitic melt (
This underscores the importance of the source rock composition, as even modest Sn content in the protolith (about twice that of average continental crust) favours the generation of Sn-enriched melts. Fractional crystallisation then further concentrates Sn to the typical levels seen in Sn-specific granites.
Our comparison with Sn(W) granites in South China suggests that rare-metal granites are generated by biotite-dehydration melting combined with melt fractionation, and that favourable sources (lithology and pre-enrichment) play a significant role in enhancing the potential for rare-metal deposit formation on a regional scale.
| Subject : | : | Poster |
| Topics | : | Magma & Ores |
| Keywords | : | dehydration melting ; Sn ; granites ; partitioning |
| PDF version | : |  PDF version |
