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Oriented monazite inclusions in apatite porphyroblasts from the Hemlo gold deposit, Ontario, Canada

Published online by Cambridge University Press:  05 July 2018

Yuanming Pan ,
Michael E. Fleet  and
Neil D. Macrae
Yuanming Pan
Affiliation:
Department of Geology University of Western Ontario London, Ontario N6A 5B7, Canada
Michael E. Fleet
Affiliation:
Department of Geology University of Western Ontario London, Ontario N6A 5B7, Canada
Neil D. Macrae
Affiliation:
Department of Geology University of Western Ontario London, Ontario N6A 5B7, Canada
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Abstract

Oriented inclusions of monazite occur in the dark core of apatite porphyroblasts in a muscovite schist from the Archaean Hemlo gold deposit, Ontario, Canada. The monazite inclusions are elongated along the b-axis and parallel to the c-axis of the apatite host; the complete orientation relationship of the monazite/apatite intergrowth is bMnz//cAp, cMnz//aAp. From analysis by SIMS and EMP, the dark core of the apatite porphyroblasts is depleted in LREE (LaN/YbN = 0.56). The monazite inclusions are correspondingly enriched in LREE, but markedly depleted in HREE, compared with monazite grains in the rock matrix and cross-cutting veins. The monazite inclusions precipitated by oriented reaction through rock-fluid interactions during a late hydrothermal alteration. Their unusual REE composition is probably related to both a preferential leaching of LREE from the dark core and a selective transfer of HREE out of the apatite porphyroblasts.

Keywords

apatite porphyroblastsmonaziteoriented intergrowthrare earth elements
Type
Mineralogy
Information
Mineralogical Magazine , Volume 57 , Issue 389 , December 1993 , pp. 697 - 707
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1993

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