Daliran, F; Stosch, HG; Williams, P; ,
Initial results from the study of three Fe oxide-apatite-REE deposits and the coeval apatite-rich magmatic-metasomatic rocks (apatitites) of Chogart, Lakkeh Siah, and Gasestan in the Bafq district reveal a complex history of multistage metasomatic alteration and mineralization. Distal/regional alteration consists of K-feldspatization, albitization, selective replacement of the host rhyolites by the ore-related metasomatic mineral assemblage, sericitization, late talc and calcite metasomatism. The metasomatic mineral assemblage consists of monazite, F-Cl-REE apatite, magnetite (+/- haematite), allanite, Ca-thorite, zircon, titanite, rutile, xenotime, and synchysite, and Sr-barite. The ore-related metasomatism locally succeeded the broad-scale, multistage actinolitization and includes the following stages: (1) F-Cl-REE-apatite-monazite-magnetite(+/- fluorite +/- anhydrite), pyroxene or actinolite +/- garnet; (2) actinolite, apatite, monazite, xenotime, allanite, Sr-barite; (3) precipitation of considerable amounts of carbonates and quartz; (4) local talc alteration, and minor pyrite +/- chalcopyrite. Broad-scale alteration associated with Fe oxide-apatite-REE mineralization within rhyolitic rocks along the Bafq structural zone and the association with a bimodal volcanism indicate an early Cambrian tectonomagmatic control on the mineralization that was probably related to intraplate rifting.