Rare earth elements in carbonatite and cogenetic alkaline rocks: Examples from Seabrook Lake and Callander Bay, Ontario
- Cite this article as:
- Cullers, R.L. & Medaris, G. Contr. Mineral. and Petrol. (1977) 65: 143. doi:10.1007/BF00371054
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Associated rocks from the Seabrook Lake, carbonatite complex in Ontario show an increase in total REE (rare earth element) content and in light REE enrichment in the following order: fenite ≦quartz monzohite <ijolite <mafic breccia <carbonatite (sövite). Ijolite and carbonatite, which may be comagmatic on the basis of their low and similar initial strontium isotopic ratios, may have originated in the following manner: (1) A small degree of partial melting of the upper mantle could have formed a primary, basic magma, probably having a lower REE content than ijolite. (2) The presumed primary magma could have undergone extensive fractional crystallization of phases such as clinopyroxene, olivine, and ≦1% garnet, to produce residual melts with the REE contents of the ijolite. (3) The carbonatite may represent an immiscible carbonate-rich liquid which separated from the “parent” ijolite liquid, as suggested by REE distribution coefficients between carbonatite and ijolite at Seabrook Lake similar to those obtained for carbonate-rich ocelli and associated lamprophyre at Callander Bay.
The similar REE contents of the fenites and country rock, and the much lower REE contents of the fenites than the associated ijolite, mafic breccia, and carbonatite, suggest that the fenites may be country rock altered by CO2 and H2O-rich fluids.