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Anomalous Cr-rich zones in sector-zoned clinopyroxene macrocrysts in gabbro, Mont Royal, Montreal, Quebec, Canada

Andrei Y. Barkov and Robert F. Martin
Anomalous Cr-rich zones in sector-zoned clinopyroxene macrocrysts in gabbro, Mont Royal, Montreal, Quebec, Canada (in A tribute to John Leslie Jambor, Robert F. Martin (prefacer))
The Canadian Mineralogist (September 2015) 53 (5): 895-910

Abstract

We document unusual zones of Cr enrichment (up to 0.9 wt.% Cr (sub 2) O (sub 3) ) in sector-zoned clinopyroxene crystals from gabbro sampled near the outer contact of the Mont Royal intrusive complex, of Early Cretaceous age, located in the city of Montreal. Mont Royal is one of the Monteregian Hills, but by no means the best-known mineralogically. We describe the compositional variation in macrocrysts of Ti-rich clinopyroxene by means of element-distribution maps and a detailed 0.37 mm traverse across the contact between a relatively homogeneous core and a mantle showing sector and oscillatory zoning. A Cr- and Mg-enriched zone appears in that interval and is also recorded in the coeval ferri-kaersutite. Both elements, being highly compatible, are not expected to build up in a boundary layer. After a period of slow growth in a hotter part of the reservoir, the macrocrysts seem to have migrated near the outer contact, where more rapid loss of heat and degassing contributed to the development of sector and oscillatory zoning. Such zoning was accompanied by an overall rise in f(O (sub 2) ). The anomalous Cr-Mg-enriched zones seem more likely attributable to local cooling and oxidation of the magma than to an episode of replenishment in the magma reservoir.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 53
Serial Issue: 5
Title: Anomalous Cr-rich zones in sector-zoned clinopyroxene macrocrysts in gabbro, Mont Royal, Montreal, Quebec, Canada
Title: A tribute to John Leslie Jambor
Author(s): Barkov, Andrei Y.Martin, Robert F.
Author(s): Martin, Robert F.prefacer
Affiliation: Cherepovets State University, Research Laboratory of Industrial and Ore Mineralogy, Cherepovets, Russian Federation
Affiliation: McGill University, Montreal, QC, Canada
Pages: 895-910
Published: 201509
Text Language: English
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 26
Accession Number: 2016-094384
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
N45°19'60" - N45°45'00", W74°00'00" - W73°30'00"
Secondary Affiliation: McGill University, CAN, Canada
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Association of Canada. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201646
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