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. The liddicoatite contains substantial proportions of the elbaite and rossmanite components; the most calcic composition analyzed corresponds to (Ca(0.498)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 spessartine Sps(89)Grs(9)Alm(2) containing less than or equal to 0.30 wt.% F, and with 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 crystallization in the pegmatite, and its Ca-enriched members have no analogs, individually or collectively, in other Li-tourmaline-bearing pegmatites of the parent pegmatite field or elsewhere. Our observations support neither mobilization of Ca from pre existing pegmatite minerals, nor influx of Ca from host rocks. Preservation of some Ca throughout the crystallization of the apatite- and microlite-poor pegmatite seems to be probable, although the specific mechanism of such process remains to be identified.
Stranger in paradise: liddicoatite from the high grade dike pegmatite, southeastern Manitoba, Canada
Ottolini L
1999
Abstract
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. The liddicoatite contains substantial proportions of the elbaite and rossmanite components; the most calcic composition analyzed corresponds to (Ca(0.498)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 spessartine Sps(89)Grs(9)Alm(2) containing less than or equal to 0.30 wt.% F, and with 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 crystallization in the pegmatite, and its Ca-enriched members have no analogs, individually or collectively, in other Li-tourmaline-bearing pegmatites of the parent pegmatite field or elsewhere. Our observations support neither mobilization of Ca from pre existing pegmatite minerals, nor influx of Ca from host rocks. Preservation of some Ca throughout the crystallization of the apatite- and microlite-poor pegmatite seems to be probable, although the specific mechanism of such process remains to be identified.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
