Sr-rich minerals in a carbonatite skarn, Fuerteventura, Canary Islands (Spain)

Metamorphosed carbonatites and related skarn deposits, located in Fuerteventura Basal Complex, contain unusual Sr-rich minerals. Maximum SrO concentration in the following minerals are: calcite, 7.23 wt%; apatite, 5.22 wt%; epidote, 11.64 wt%; clinozoisite, 1.25 wt%; allanite, 5.63 wt%; britholite, 4.11 wt% and a Sr–Na aluminosilicate (probably stronalsite), 16.44 wt% SrO. Calcite and apatite are chemically similar to those found in carbonatites and are therefore considered to be of igneous origin. Textural evidence indicates that the first skarn stage garnet+diopside+Sr–Na aluminosilicate formed as the result of chemical interaction between carbonatites and adjacent silicate rocks. The formation of Sr-bearing epidote/clinozoisite, allanite and britholite appears to be related to the release of Sr into the fluid phase from the breakdown of high temperature assemblages during the retrograde skarn stage. During the final evolution stages, further alteration of britholite by bastnasite and tornebohmite took place. The occurrence of REE minerals shows that the fluids responsible for this metasomatism must also have transported significant quantities of REE.