|Author(s)||Vanier and Lafrance, 2020|
|Methodology||Defined from geological survey and geophysical data|
|Geological(s) subdivision(s)||Churchill Province / Ungava Orogen / Narsajuaq Lithotectonic Domain|
|Main movement||Does not apply|
|Deformation style||Regional fabric defined by a foliation and lineation of moderate to strong intensity|
|Metamorphic facies (mean facies related to main deformation)||Granulites|
This record is based on aeromagnetic maps’ interpretation (Intissar et al., 2014) and information collected from geological survey carried out in the summer of 2019 in the Sirmiq Lake area (Vanier and Lafrance, 2020).
The Sanngumaq Structural Domain (DSsan) forms a 2-4 km-wide corridor oriented WSW-ENE. This strip is contained within the Sources Structural Domain (DSsou) in gradual contact with the DSsan, both to the north and south.
The main fabrics affecting the DSsan are a subvertical foliation and subhorizontal lineation. The limited amount of data is due to the small size of this domain. However, measurements are consistent across the domain. The foliation is expressed by the planar alignment of biotite. Also, quartz commonly forms lenses, highlighting both the foliation and stretch lineation.
|Main Fabric||Type of Fabric||Direction (°)||Dip / Plunge (°)||Number of Measurements||Comments|
|Foliation Sn||Tectonometamorphic foliation and gneissosity||254||73||11|
|Lineation Ln||Stretch and mineral lineation||070||05||5||
Does not apply.
Does not apply.
The DSsan displays a deformation of moderate to intense intensity. Structures are clearly marked and correlate from one outcrop to another. Although mylonites are absent, the common presence of stretched quartz is indicative of intense deformation. Parallelism between the structures indicates that the most appropriate structural style for this area is parallel. The structural attribute that distinguishes it from the adjacent Sources Structural Domain is the steep dip of planar structures at ~73°, compared to 48° for the DSsou. Lineations are more shallowly inclined and oriented WSW-ENE, compared to NW for the western part of the DSsou.
Metamorphic characteristics of the DSsan are similar to those of the adjacent DSsou. The main deformation episode took place at high temperature, at the granulite facies.
Two positive ridgess of the residual magnetic field pass through the entire DSsan. These aeromagnetic lineaments run parallel to the main DSsan fabrics, which are oriented WSW-ENE. The area north of these ridges corresponds to a negative anomaly of the residual magnetic field.
No chronological reference is available in the DSsan. It is assumed that the main deformation is contemporanous to that which affected the DSsou. Synkinematic ages derived from metamorphic ages, the latter being interpreted as contemporaneous to the main deformation, are 1806 ±38 Ma (Navvaataaq Suite), 1880 ±9 Ma and 1841 ±24 Ma (Pingasualuit Complex).
INTISSAR, R., BENAHMED, S., D’AMOURS, I. 2014. Levé magnétique et spectrométrique aéroporté de la partie nord de l’Orogène de l’Ungava, Province de Churchill. MRN. DP 2014-03, 10 pages and 410 plans.
VANIER, M.-A., LAFRANCE, I., 2019. Géologie de la région du lac Sirmiq, Orogène de l’Ungava, Nunavik, Québec, Canada. MERN. BG 2020-02, 1 plan.
Ministère de l’Énergie et des Ressources naturelles (MERN). Sanngumaq Structural Domain. Quebec Structural Lexicon. https://gq.mines.gouv.qc.ca/lexique-structural/domaine-structural-de-sanngumaq_en/ [accessed on Day Month Year].
Ghyslain Roy, P. Geo. (coordination); James Moorhead, P. Geo., M.Sc. (critical review); Simon Auclair, P. Geo., M.Sc. (editing); André Tremblay (HTML editing); Céline Dupuis, P. Geo., Ph.D. (English version)