Silicocarbonatitic Melt Inclusions in Fluorapatite from the Yates Prospect, Otter Lake, QuÉbec: Evidence of Marble Anatexis in the Central Metasedimentary Belt of the Grenville Province.

Schumann, Dirk, Martin, Robert F., Fuchs, Sebastian and de Fourestier, Jeffrey (2019) Silicocarbonatitic Melt Inclusions in Fluorapatite from the Yates Prospect, Otter Lake, QuÉbec: Evidence of Marble Anatexis in the Central Metasedimentary Belt of the Grenville Province. The Canadian Mineralogist, 57 (5). pp. 583-604. DOI 10.3749/canmin.1900015.

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Abstract

We have investigated a locality very well known to mineral collectors, the Yates U-Th prospect near Otter Lake, Québec. There, dikes of orange to pink calcite enclose euhedral prisms of fluorapatite, locally aligned. Early investigators pointed out the importance of micro-inclusions in the prisms. We describe and image the micro-inclusions in two polished sections of fluorapatite prisms, one of them with a millimetric globule of orange calcite similar to that in the matrix. We interpret the globule to have been an inclusion of melt trapped during growth. Micro-globules disseminated in the fluorapatite are interpreted to have crystallized in situ from aliquots of the boundary-layer melt enriched in constituents rejected by the fluorapatite; the micro-globules contain a complex jigsawed assemblage of carbonate, silicate, and sulfate minerals. Early minerals to crystallize are commonly partly dissolved and partly replaced by lower-temperature phases. Such jigsawed assemblages seem to be absent in the carbonate matrix sampled away from the fluorapatite prisms. The pressure and temperature attained at the Rigolet stage of the Grenville collisional orogeny were conducive to the anatexis of marble in the presence of H2O. The carbonate melt is considered to have become silicocarbonatitic by assimilation of the enclosing gneisses, which were also close to their melting point. Degassing was important, and the melt froze quickly. The evidence points to a magmatic origin for the carbonate dikes and the associated clinopyroxenite, rather than a skarn-related association.

Document Type: Article
Keywords: marble, anatexis, silicocarbonatite, melt inclusions, clinopyroxenite, Yates U-Th prospect, Otter Lake, Quebec
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS > Marine Mineralische Rohstoffe
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.3749/canmin.1900015
ISSN: 0008-4476
Date Deposited: 25 Sep 2019 09:45
Last Modified: 06 Feb 2020 09:08
URI: http://oceanrep.geomar.de/id/eprint/47818

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