DISCLAIMER: This English version is translated from the original French. In case of any discrepancy, the French version shall prevail.
|Author:||Lafrance et al., 2014|
|Type area:||Saffray lake area (NTS sheet 24G)|
|Geological province:||Churchill Province|
|Geological subdivision:||Baleine Lithotectonic Domain|
|Lithology:||Foliated to gneissic, felsic to intermediate potassic intrusive rocks|
The Saffray Suite was defined by Lafrance et al. (2014) in the Saffray Lake area (sheet 24G) to describe a series of potassic intrusions associated with strong magnetic anomalies oriented E-W to ESE-WNW. It has been extended eastward in the Henrietta Lake area (Lafrance et al., 2015), towards the SE in the Brisson Lake area (Lafrance et al., 2016), and southward in the Jeannin Lake (Charette et al., 2016) and Résolution Lake areas (Lafrance et al., in preparation).
The Saffray Suite is associated with intense magnetic anomalies extending over several kilometres. It has been divided into two informal units by Lafrance et al. (2014): magnetic quartz monzonite (nAsaf1), and magnetic granite (nAsaf2). A magnetic syenite unit (nAsaf3) was also mapped in the Jeannin Lake area (Charette et al., 2016).
Unit nAsaf1 consists mainly of quartz monzonite associated with lower amounts of granodiorite, quartz monzodiorite and monzogranite. It is fine to medium grained, granoblastic and foliated. K-feldspar occurs as lenticular bands and porphyroclasts. The rock is pinkish to yellowish grey and commonly gneissic. It contains 15-30% ferromagnesian minerals that form clusters and discontinuous millimetre to centimetre-wide bands. They consist of brown biotite and green hornblende accompanied locally by altered clinopyroxene. These commonly show intergrowth textures with lower temperature minerals. Accessory minerals are abundant (2-10%) and consist of magnetite, sphene, apatite, epidote, allanite, chlorite and zircon with, more locally, carbonates and muscovite. On outcrops, these rocks are injected with magnetic pink granite similar to that of unit nAsaf2. These millimetric to metric injections are generally discontinuous, boudinaged and conformable to foliation. Unit nAsaf1 rocks also contain centimetric to metric enclaves of fine-grained granoblastic and highly magnetic gabbronorite and gabbro. These mafic rocks locally are the dominant lithology of the outcrop.
Unit nAPsaf2 forms small, slightly deformed granitic masses a few kilometres in diameter within well-foliated potassic rocks of unit nAsaf1. It consists of pink, homogeneous, magnetic and medium to coarse-grained granite. Granite is massive or slightly foliated and contains 1-12% ferromagnesian minerals represented by brown biotite and magnetite. The main accessory minerals are muscovite, apatite, chlorite, sphene, epidote, zircon, allanite and hematite. In thin sections, myrmekitic textures are generally observed.
Saffray Suite 2a (nAsaf2a): Heterogeneous Granite
In the Saffray Lake area (Lafrance et al., 2014), tonalitic gneiss of the Ungava Complex (ApPung2) is injected with >50% magnetic granite similar to that of unit nAsaf2. These heterogeneous zones have been assigned to subunit nAsaf2a. Within it, granite occurs as centimetre to decimetre-wide injections parallel to gneissosity, accentuating banding.
Syenite of unit nAsaf3 forms intrusions <1 km wide spatially associated with potassic rocks of unit nAsaf1. It is dark pink, medium to coarse grained and massive to slightly foliated. It is also cut by unit nAsaf2 granite. Syenite contains 5-12% ferromagnesian minerals, mostly magnetite and epidote with, locally, smaller amounts of brown biotite or green hornblende. These tend to form clusters with accessory minerals, which consist of muscovite, sphene, allanite, chlorite, apatite, sulphides and zircon. Locally, syenite also contains fractured clinopyroxene, surrounded by hornblende and sphene.
The Saffray Suite is an important unit within the Baleine lithotectonic domain, with an area of ~3151 km2, particularly in the Saffray Lake (Lafrance et al., 2014) and Jeannin Lake (Charette et al., 2016) areas. It is observed in a wide corridor oriented NW-SE to N-S directly west of the De Pas Supersuite. Informal unit nAsaf1 (2694 km2) is by far the most important, with units nAsaf2 (158 km2), nAsaf2a (293 km2) and nAsaf3 (6 km2) covering much smaller areas.
Crystallization ages of the Saffray Suite are similar to those of large, highly magnetic, late tectonic Archean potassic intrusions located in the Superior Province (Simard et al., 2008), west of the Labrador Trough. Compositional, geochronological and structural similarities between intrusions of the Saffray Suite and those west of the Labrador Trough support the hypothesis that the Baleine Lithotectonic Domain had separated from the Superior Province (Wardle et al., 2002). In addition, intrusions of the Saffray Suite have a well-visible E-W structural grain on the regional aeromagnetic map, which is interpreted as an Archean heritage similar to that of potassic intrusions of the Superior (Lafrance et al., 2014).
The presence of migmatitic rocks of the False and Winnie suites between intrusions of the Saffray Suite within the Baleine Domain could indicate that the sedimentary cover overlaid the Saffray Suite before Paleoproterozoic deformation. Much of this coverage was eroded after this domain was thrusted to the west. Rocks of the Saffray Suite occur as enclaves in and are intruded by the majority of Paleoproterozoic intrusive units present in the Baleine Domain, especially those of the De Pas Supersuite and whitish intrusions of the Aveneau Suite. In the southern part of the Jeannin Lake area (Charette et al., 2016), potassic rocks of unit nAsaf1 are locally similar to some of the rocks assigned to the Champdoré Suite. However, the absence of a significant magnetic anomaly in this area and the respective dating in the two units indicate that they are indeed two distinct suites.
Does not apply.