Original paper

REE-bearing sector-zoned lawsonite in the Sanbagawa pelitic schists of the eastern Kii Peninsula, central Japan

Ueno, Takashi

European Journal of Mineralogy Volume 11 Number 6 (1999), p. 993 - 998

15 references

published: Nov 29, 1999
manuscript accepted: Jun 2, 1999
manuscript received: Aug 28, 1998

DOI: 10.1127/ejm/11/6/0993

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Abstract Rare-earth elements (REE)-bearing sector-zoned lawsonite was found in Sanbagawa pelitic schists in the Ise area of the eastern Kii Peninsula, central Japan. The pelitic schists consist mainly of lawsonite, chlorite, phengite, titanite, albite, quartz, calcite and weakly-ordered graphite. Metamorphic conditions are estimated at P = 3-8 kbar and T < 350°C based on stability of the lawsonite-albite-quartz-calcite assemblage. Lawsonite occurs as prismatic and euhedral crystals (up to 500 μm long). Three sectors are well developed in the lawsonite grains. The {100} sector is more enriched in REE (La2O3 up to 0.55, Ce2O3 up to 1.18, and Nd2O3 up to 0.58 wt%) and depleted in Ca than the {010} and {001} sectors. The {001} sector is more enriched in Ti and depleted in Al than the {100} and {010} sectors. Compositional variations in lawsonite grains suggest [6]REE[4] AlCa-1Si-1 and [6]Ti[4]Al(Al, Fe3+)-1Si-1 substitutions. Lawsonite can preferentially concentrate REE, and constitutes a most important REE reservoir at high P-T metamorphic conditions, at which epidote group minerals are unstable.


lawsoniterare-earth elements (REE)sector zoningSanbagawa metamorphic beltpelitic schistJapan.