Original paper

Pyrrhotite inclusions in dark pigmented apatite from granitic rocks

Gottesmann, Barbel; Wirth, Richard

European Journal of Mineralogy Volume 9 Number 3 (1997), p. 491 - 500

28 references

published: Jun 2, 1997
manuscript accepted: Nov 19, 1996
manuscript received: Feb 8, 1996

DOI: 10.1127/ejm/9/3/0491

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ArtNo. ESP147050903002, Price: 29.00 €

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Abstract

Abstract Combined microprobe, HRTEM, and optical microscopic investigations of the dusky cores of accessory apatite from granitic rocks identified the pigment in these cores as hexagonal pyrrhotite. Pyrrhotite particles are generally below the detection limit of conventional light microscopy, but cause pleochroism of apatite. These inclusions may be very fine-grained (≤ 1 μm) specks or, more rarely, rods. They are rhythmically arranged in layers normal to the c-axis of apatite, separated by nearly inclusion-free zones. Apatite and pyrrhotite are epitactically intergrown, with (1010)apatite 1 1 (0001)pyrrhotite and [0001]apatite 1 1 [2110]pyrrhotite. Apatite host and pyrrhotite inclusions presumably crystallized simultaneously, forming oriented intergrowths which are favored by the similarity in lattice spacings. The pigmented apatites probably represent foreign material within the granitic magma.

Keywords

pigmented pleochroic apatitepyrrhotitegraniteTEMelectron probe microanalysisSaxony/Germany.