|
|||||
|
|
Melt inclusions from the deep Slave lithosphere: implications for the origin and evolution of mantle-derived carbonatite and kimberlite |
|
| Authors: | Esm van Achterbergh William L Griffin Chris G Ryan Suzanne Y O'Reilly Norman J Pearson Kevin Kivi Buddy J Doyle |
| Institution: | a GEMOC ARC National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia b CSIRO Exploration and Mining, P.O. Box 136, North Ryde, NSW 1670, Australia c Kennecott Canada Exploration Inc., 1300 Walsh Street, Thunder Bay, Ontario, Canada P7E 4X4 d Kennecott Canada Exploration Inc., 354-200 Granville Street, Vancouver, British Columbia, Canada V6C 154 |
| Abstract: | Melt inclusions in clinopyroxenes from lherzolitic xenoliths from the deep lithospheric mantle beneath the Slave Craton (Lac de Gras area, Canada) reveal multiple origins for carbonatitic melts. One type of inclusions consists of a series of silicate–carbonate–silicate concentric layers, interpreted to have unmixed under disequilibrium conditions during rapid ascent to the surface. Bulk major- and trace-element compositions are typical of Group 1 kimberlites and quantitative nuclear microprobe imaging of the globules reveals fractionation of related elements (e.g. F–Br, Nb–Ta) between the silicate and carbonate components. The globules probably formed by partial melting of carbonated peridotite, consistent with results of melting experiments and some models for the generation of kimberlite magmas. They provide evidence for a genetic relationship between some carbonate-rich magmas and ultramafic silicate magmas, and for the possibility of unmixing processes of these melts during their evolution. The second inclusion type comprises carbonate-rich globules interpreted as samples of Mg-carbonatite melt that quenched on ascent to the surface. Bulk major- and trace-element compositions indicate that the melts were derived from a carbonate-rich source and oxygen, carbon, and strontium isotope data are consistent with the involvement of recycled crustal material and suggest that some mantle-derived carbonatites are unrelated to kimberlites. |
| Keywords: | Kimberlite Carbonatite Immiscible mantle melts Partial melting Mantle metasomatism |
| 本文献已被 ScienceDirect 等数据库收录！ | |