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Barlow Pluton
Stratigraphic label: [narc]bar
Map symbol: nAbar

First published: 21 March 2018
Last modified:

 

 

 

 

 

 

 

 

 

 

 

Translation of original French

 

 

 

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
 
None
 
Author: Caty, 1975
Age: Neoarchean
Stratotype: Reference outcrop 14-YD-5042 located on a logging road connecting on the Nord Road (UTM NAD83, zone 18: 553326 mE, 5561568 mN)
Type area: Lake Waconichi area (NTS sheet 32J01)
Geological province: Superior Province
Geological subdivision: Abitibi and Opatica Subprovinces
Lithology: Quartz monzodiorite and tonalite
Type: Lithodemic
Rank: Lithodeme
Status: Formal
Use: Active

 

 

Background

The intrusion was first described as the Barlow River Complex by Caty (1975) and Boudreault (1977), and later as the Barlow Pluton in subsequent publications (Racicot, 1979; Racicot et al., 1984).

 

 

Description

 

According to Racicot et al. (1984, p. 189): “The Barlow Pluton is composed of two series of rocks, an outer shell of quartz monzodiorite and a core of leucotonalite. The transition between the two is relatively abrupt, but with the mutual dyking relationship typical of coeval intrusions. Structurally, the mass is surrounded by a relatively narrow envelope with a mylonitic texture which fades out into a more typically igneous foliation in the interior of the batholith. Structures are dominantly E-W, parallel to the elongation of the batholith and the regional structural trend. The outer quartz monzodiorite shell is variable in composition, showing primary banding, shown by a variation in the content of mafic minerals, and a variety of early or synchronous mafic dykes which are deformed or partly digested by the principal phases. The principal mineral components are plagioclase, An24 (50-60%), quartz (10-15%), clinopyroxene and/or green hornblende (15%) with varying amounts of interstitial microcline (10-15%). The resulting rock is quite distinctive, and seems to occur only in masses in a similar structural position in the region. The leucotonalite core is a relatively monotonous rock, light grey, coarse-grained and composed of tabular crystals of plagioclase, An24 (55-60%), with amoeboid quartz grains (25-30%) and biotite (0-5%). Late aplite dykes cutting the main phases are granodioritic in composition.” 

 

 

Thickness and Distribution

The Barlow Pluton is an ovoid intrusion. Its E-W-oriented long axis is parallel to regional foliation over a distance of ~39 km. The short axis is oriented N-S and measures ~8.5 km in length. The Barlow Pluton occupies the northern portion of NTS sheet 32J01 and northwestern portion of sheet 32I04.

 

Dating

Sample Number Isotopic System Mineral Crystallization Age (Ma) (+) (-) Reference(s)
Barlow GC-10 U-Pb Zircon 2697 3 3 Gariépy and Allègre, 1985

Stratigraphic Relationship(s)

At its southern edge, the Barlow Pluton cuts mafic volcanic rocks of the Obatogamau Formation in the Abitibi Subprovince. At its northern limit, it cuts gneiss, tonalite, mafic gneiss, garnet amphibolite and pegmatite which characterize the Opatica Subprovince. In the southeast, Paleoproterozoic sedimentary rocks of the Chibougamau Formation unconformably lie on the pluton. 

Paleontology

Does not apply.

References

Author(s) Title Year de Publication Hyperlink (EXAMINE or Other)
BOUDREAULT, A.P. Géologie de la demie est du canton de Blaiklock (comté d’Abitibi-Est). Ministère des Richesses naturelles, Québec; DPV-541, 10 pages, 1 plan. 1977 DPV 541
CATY, J.L. Géologie de la demie-ouest du canton de Richardson (comté d’Abitibi-Est). Ministère des Richesses naturelles, Québec; DP-342, 14 pages, 2 plans. 1975 DP 342
GARIÉPY, C. – ALLÈGRE, C. The lead isotope geochemistry and geochronology of late-kinematic intrusives from the Abitibi greenstone belt, and the implications for late Archaean crustal evolution. Geochimica et Cosmochimica Acta; volume 49, pages 2371–2383. 1985 Source
RACICOT, D Pétrographie et géochimie du pluton de la rivière Barlow, Chibougamau, Québec. Université du Québec à Chicoutimi; master’s thesis, 115 pages. 1979 Source
RACICOT, D. – CHOWN, E.H. – HANEL, T. Plutons of the Chibougamau-Desmaraisville belt: A preliminary survey. In Chibougamau, Stratigraphy and Mineralization: proceedings of the Chibougamau Symposium and Field Trip, sponsored by the Geology Division of CIM, and held in Chibougamau, Quebec, (Editors: J. Guha, et E.H. Chown). Canadian Institute of Mining and Metallurgy; Special Volume 34, pages 178–197. 1984

 

 

13 septembre 2019