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Nipukatasi Massif
Stratigraphic label: [narc]nip
Map symbol: nAnip

First published: 15 September 2017
Last modified:

 

Translation of original French

 

 

 

 

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
None
 
Author: Brisson et al., 1998
Age: Precambrian / Archean / Neoarchean
Reference section:  
Type area: The Nipukatasi Massif is located east of Rocher Lake, at the southern limit of the Frotet-Evans Volcano-sedimentary Belt and south of the Lucky Strike Shear Corridor (NTS sheets 32K08, 32K09, 32J12). Most outcrops characterizing the unit are located in the area between Rocher and Amisquioumisca lakes.
Geological province: Superior Province
Geological subdivision: Opatica Subprovince
Lithology: Monzodiorite, quartz monzodiorite and biotite ± hornblende granite
Unit type: Lithodemic
Rank: Lithodeme
Status: Formal
Use: Active

 

 

Related unit(s)
  • None
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Background

The Nipukatasi Massif is mentioned for the first time by Brisson et al. (1998) in the Rocher Lake geology report (NTS sheet 32K09). The unit had previously been recognized by Franconi (1974) who mentioned the presence of granites and alaskites, without naming it.

 

Description

The Nipukatasi Massif consists essentially of monzodiorite, quartz monzodiorite, and biotite ± hornblende granite. The rock is medium to coarse-grained, massive and homogeneous in appearance. The color varies from light beige-pink in altered surface to medium gray-pink in fresh exposure. The size of albitized plagioclase crystals commonly exceeds 5 mm, which gives the rock an inequigranular texture. Quartz is scarce in monzodiorites and quartz monzodiorites where it is interstitial to feldspar crystals. Ferromagnesian minerals include biotite (5 to 10%) and hornblende (less than 1%, often in clusters). Muscovite is present in accessory amounts. The egde area of the Nipukatasi Massif includes xenoliths of dioritic gneiss attributed to the Chensagi Suite (nAchg), as well as xenoliths of migmatitized paragneiss (nAroc1) and amphibolite (nAroc2) attributed to the Rocher Complex. 

 

Thickness and distribution

The Nipukatasi Massif extends over a maximum length of 40 km along an ENE-WSW axis and a maximum width of 18 km along an NNW-SSE axis (NTS sheets 32K08, 32K09 and 32J12). The unit covers an area of about 500 km2

Dating

A granite sample from the Nipukatasi Massif did not contain zircon (Bandyayera and Sharma 2001). 

Stratigraphic Relationship(s)

The Nipukatasi Massif is hosted by volcano-sedimentary rocks of the Rocher Complex (nAroc) and dioritic gneisses of the Chensagi Suite (nAchg). On its edge, it includes many xenoliths of these lithologies. East of Rocher Lake, the contact of the Nipukatasi Massif with the Rocher Complex is characterized by two types of discordant intrusions in amphibolite: a) intrusions of leucocratic monzodiorite isoclinally folded and cut by regional foliation, and b) inequigranular granite intrusions affected by hematite alteration that cut regional foliation. Crosscutting relationships between monzodiorite and granite intrusions, host amphibolite and regional foliation suggest a syn-tectonic to late-tectonic emplacement.

Paleontology

Does not apply.

References

Author(s) Title Year of Publication Hyperlink (EXAMINE or Other)
BANDYAYERA, D. – SHARMA, K.N.M. Minéralisations en Ni-Cu±ÉGP dans la bande volcano-sédimentaire de Frotet-Evans (SNRC 32K). Ministère des Ressources naturelles, Québec; MB 2001-06, 74 pages. 2001 MB 2001-06
BRISSON, H. – GOSSELIN, C. – FALLARA, F. – GAULIN, R. – DION, D.-J. Géologie de la région du lac Rocher (SNRC 32K09). Ministère des Ressources naturelles, Québec; RG 98-05, 22 pages. 1998 RG 98-05
FRANCONI, A Géologie de la moitié ouest de la bande volcano-sédimentaire de Frotet-Evans, territoire d’Abitibi, rapport intérimaire. Ministère des Richesses naturelles, Québec; DP-265, 141 pages. 1974 DP 265

 

 

 

 

27 février 2018