The Guano-Guayes property, in the St Cyr Range of the Pelly Mountains, covers a skarn about 300 m wide, 70 m thick and 1100 m long. Contact metasomatism of Silurian to Devonian carbonate rocks formed the skarn adjacent to a mafic rich syenite stock coeval with the Seagull Creek volcanic rocks of probably Mississippian age.
Forty Guano-Guayes property rock samples were analysed for rare earth elements (REE) by neutron activation. REE values from syenite, normalized to chondritic values, have a pattern comparable to, but slightly higher than, those from standard crustal rocks. Dikes, cogenetic with syenite, intrude sedimentary rocks within and near the contact metamorphic aureole. These dikes are dark-coloured and originally contained up to 25% zircon, which is now partly altered. The zircon is enriched in total REE and relatively enriched in light REE compared to the syenite, probably by selective partitioning of REE during crystallization of zircon. REE patterns in the skarn and sedimentary rocks suggest that fluids circulated through the syenite and carried trace amounts of REE from the dikes into either skarn or sedimentary rocks.
