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Navvaataaq Suite
Stratigraphic label: [narc]nav
Map symbol: nAnav

First published: 7 May 2018
Last modified: 2 october 2019

 

 

 

 

 

 

 

 

 

 

 

 

 

Translation of original French

 

 

 

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
 
nAnav1 Opdalite and enderbite containing biotite-hornblende-hypersthene laminae or clusters

 

 
Author:Charette and Beaudette, 2018
Age:Neaoarchean
Reference section:None
Type area:Ivitaarqiap Lake area (NTS sheet 35K06)
Geological province:Churchill Province
Geological subdivision:Ungava Orogen /  Narsajuaq Lithotectonic Domain
Lithology:Hypersthene felsic intrusive rock
Type:Lithodemic
Rank:Suite
Status:Formal
Use:Active

 

 

Background

The Navvaataaq Suite, introduced by Charette and Beaudette (2018), includes orthopyroxene felsic intrusive rocks that intrude into foliated to gneissic banded granulitic rocks of the Narsajuaq Domain. The unit name originates from Navvaataaq Lake, which is located near the largest intrusion of opdalite and enderbite within the domain (NTS sheets 35K05 and 35K06). Previously, lithologies of this suite were assigned to unit pPNAR1 of the Older plutonic suite and unit pPNAR4 of the younger plutonic suite described by St-Onge and Lucas (1992) and St-Onge et al. (1992).

 

 

Description

 

 

Navvaataaq Suite 1 (nAnav1): Opdalite and Enderbite Containing Biotite-Hornblende-Hypersthene Laminae or Clusters

The Navvaataaq Suite (nAnav1) consists of opdalite and enderbite, medium to coarse grained, leucoratic and massive to foliated. A common feature of these rocks is the concentration of ferromagnesian minerals in millimetric to centimetric discontinuous laminae or in clusters, producing a speckled appearance. Within these clusters, brownish orthopyroxene cores are usually observed with the naked eye. Intrusive rocks generally have heterogeneous appearance that is produced at the outcrop scale by variations in size (usually medium to coarse-grained, or locally fine-grained), altered surface colour (beige, beige-green, green, brown-green, brownish, brownish beige, pinkish beige) and proportion of ferromagnesian minerals (5-20%). The petrographic study indicates that these intrusive rocks locally have a homogeneous composition ranging from enderbite to opdalite, locally charnockite, or are formed of two diffuse phases, occurring as undulating bands or clusters, which are difficult to distinguish in outcrop. One of these phases is charnockitic and the other is opdalitic or enderbitic. The charnockitic phase is slightly coarser grained and includes quartz zones or clusters. In outcrop, the heterogeneous appearance is sometimes amplified by the presence of 2-30% of variably assimilated mafic-ultramafic enclaves and by the presence of 5 to 20% pinkish or whitish centimetric bands in diffuse contact in orthopyroxene felsic rocks. These bands are irregular, discontinuous and straight-lined or undulating. They may be conformable to or cut foliation. Locally, small (1-2 cm) phenocrystals of K-feldspar or plagioclase are present.

 

Microscopic photographic study supports the intrusive nature of this suite that is not recrystallized or is only recrystallized locally. Quartz usually occurs as irregular zones, interstitial between subhedral to anhedral crystals of plagioclase and K-feldspar. Plagioclase is anti-perthitic and myrmekites are present in the matrix or are concentrated on the rims of mafic mineral clusters and laminae. The majority of these clusters and laminae are composed of intergrown biotite flakes and hornblende, matted or as poikilitic crystals. Apatite and magnetite are usually associated with ferromagnesian minerals. When present in the mineral assemblage, orthopyroxene is associated with mafic clusters and laminae and is partially to be completely replaced by iddingsite, biotite, chlorite, calcite, or a fine-grained assemblage of these minerals. In some places, orthopyroxene appears to be completely replaced by fibrous amphibole clusters, indicating uralitization of orthopyroxene, or is surrounded by poikilitic anhedral or matted hornblende. Clinopyroxene occurs in some samples as better preserved crystals, or is locally partially replaced by hornblende. Few secondary minerals are present in intrusive rocks of the Navvaataaq Suite. Euhedral zircons and allanite occur as trace minerals.

 

 

Thickness and Distribution

Opdalite and enderbite of the Navvaataaq Suite occur in the central-west and northwest portion of the Narsajuaq Domain as subconformable, folded intrusions within the foliated to gneissic granulitic rocks of the Pingasualuit Complex (nApgs) and the Siurartuuq Suite (nAsir) or as large kilometric masses containing several klippes of these lithologies. 

Dating

A medium-grained, foliated and speckled opdalite, present in a kilometric intrusive mass assigned to unit nAnav1, was sampled by Charette and Beaudette (2018) in the Wolstenholme Lake area. An age around 2560 Ma was obtained and is interpreted as crystallization (Davis and Sutcliffe, 2018). The Paleoproterozoic age around 1806 Ma is the maximum age for the end of metamorphism.

Isotopic SystemMineralMaximum Crystallization Age (Ma)(+)(-)Metamorphic Age (Ma)(+)(-)Reference(s)
U-PbZircon2560262618063838Davis and Sutcliffe, 2018

 

Stratigraphic Relationship(s)

Intrusive rocks of unit nAnav1 usually occur as intrusions forming conformable to subconformable, regular decimetric to metric layers in hypersthene quartz diorite and hypersthene diorite unit of the Pingasualuit Complex (nApgs1). In the larger intrusion masses associated with the Navvaataaq Suite, lithologies of this complex are present in variably assimilated enclaves. Also, enderbite and opdalite of unit nAnav1 are in sharp to diffuse contact and cut granoblastic potassic rocks of the Siurartuuq Suite (nAsir1). Field observations indicate that the Navvaataaq Suite is late with respect to granoblastic charnockite.

Paleontology

Does not apply.

References

Author(s)TitleYear of PublicationHyperlink (EXAMINE or Other)
CHARETTE, B. – BEAUDETTE, M.Géologie de la région du cap Wolstenholme, Orogène de l’Ungava, Province de Churchill, sud-est d’Ivujivik, Québec, Canada. Ministère de l’Énergie et des Ressources naturelles, Québec; BG 2018-03.2018BG 2018-03
DAVIS, D.W. – SUTCLIFFE, C.N.U-Pb Geochronology of Zircon and Monazite by LA-ICPMS in Samples from Northern Quebec. UNIVERSITY OF TORONTO. MB 2019-01, 113 pages2018MB 2019-01
ST-ONGE, M.R. – LUCAS, S.B. – PARRISH, R.R.Terrane accretion in the internal zone of the Ungava orogen, northern Quebec. Part 1: tectonostratigraphic assemblages and their tectonic implications. Canadian Journal of Earth Sciences; volume 29, pages 746-764.1992Source
ST-ONGE., M.R. – LUCAS, S.B.New insight on the crustal structure and tectonic history of the Ungava Orogen, Kovik Bay and Cap Wolstenholme, Quebec. In: Current Research, Part C; Geological Survey of Canada, Paper 92-1 C, pages 31-41.1992Source

 

 

7 novembre 2018