Stranger in paradise: liddicoatite from the high grade dike pegmatite, southeastern Manitoba, Canada

Liddicoatite, locally with cores of highly X-vacant elbaite, occurs in the High Grade Dike pegmatite of the Cat Lake - Winnipeg River pegmatite field, in the southwestern margin of Superior Province of the Canadian Shield. Th e liddicoatite contains substantial proportions of the elbaite and rossmani te components; the most calcic composition analyzed corresponds to (Ca(0.49 8)Na(0.395)square(0.107))(Li1.396Al1.122Mn0.414Fe0.065)Al-6(Si5.888Al0.112) O-30(F-0.484). Liddicoatite is closely associated with Ca-enriched spessart ine Sps(89)Grs(9)Alm(2) containing less than or equal to 0.30 wt.% F, and w ith pollucite, which is the only one with detectable Ca (0.26 to 0.44 wt.% CaO) among pollucite samples from similar to 70 worldwide localities. This mineral assemblage was the last product of primary, near-solidus crystalliz ation in the pegmatite, and its Ca-enriched members have no analogs, indivi dually or collectively, in other Li-tourmaline-bearing pegmatites of the pa rent pegmatite field or elsewhere. Our observations support neither mobiliz ation of Ca from pre existing pegmatite minerals, nor influx of Ca from hos t rocks. Preservation of some Ca throughout the crystallization of the apat ite- and microlite-poor pegmatite seems to be probable, although the specif ic mechanism of such process remains to be identified.