Sainte-Véronique Structure – Quebec, Canada
- Type: Syenite/Pluton
- Diameter: 9 Kilometres
- Location: N 46° 32.2’ W 74° 59.9’, Quebec, Canada
- Sainte-Véronique is a potassic pluton* in the southwestern Grenville Province
*Pluton: A large igneous intrusion formed at great depth in the crust. Any body of igneous rock that solidified below the earth’s surface.
Since publishing my crater explorations with the RASC Ottawa website, I have received input from interested people in many countries suggesting circular features that appear “interesting”. This circular feature near the Quebec town of Sainte-Véronique was suggested to me. Eric and I did a short exploration flight over the site in 2011.
This image illustrates a possible eroded rim at the north east edge of the structure, it was very obvious from the air. From this documentation we were about to expedite a ground exploration of the site in search of shatter cones (proof of an impact event).
But first we received a consultation from a geologist. The structure was revealed to us to be a natural geological circular pluton (syenite). This saved us a tromp through the bush, like we did at Alsever Lake.
Elzevir Terrane SYENITES**
The alkalic rocks of the Elzevir Terrane typically occur as large (10 to 40 km2), round plutonic bodies. A northeast trending group of syenites, the Gawley Creek Syenite in the south, followed by the Mount Moriah and Skootamatta Syenites are situated to the east and northeast of the Blue Mountain Syenite.
The Gawley Creek, Mount Moriah, Skootamatta and Mount St. Patrick Syenites may be part of a approximately 1085 Ma suite of syenite intrusions that stretch from Madoc in Ontario to Mount Laurier in Quebec*** (Easton, personal communication). The equivalent plutons have recently been studied in detail by Corriveau (personal communication). These bodies are younger than the peak of Grenville metamorphism, having distinct pluton shapes and little affected by Grenville tectonism (Easton, personal communication) unlike the syenites of the Bancroft Terrane. These bodies are therefore attractive targets since they are relatively uniform, massive, coarse grained homogeneous bodies.
**SYENITE: is a plutonic rock defined as an igneous, intrusive rock composed of at least 65% alkali feldspar, and less than 5% quartz. Plagioclase and mafic minerals make up the remaining mineralogy. A leucocratic syenite can contain up to 30% mafic minerals, and a mesocratic syenite will contain more than 30% mafic minerals (e.g., mesocratic nepheline syenite of the Callander Bay Complex). The term alkali syenite is often used to describe a rock where alkali feldspars constitute 90% or more of the rock, and plagioclase compositions are Ano-40, where plagioclase is present. Syenites such as the Otto Stock, Lebel Stock, McElroy Stock of the Superior Province and the Gawley Creek, Mount Moriah, Skootamatta, Burns Lake and Mount St. Patrick Syenites of the Grenville Province containing neither quartz nor nepheline is considered saturated. Oversaturated rocks contain modal quartz, incompatible with the presence of nepheline and therefore representing less attractive targets since AhOa content is limited. Undersaturated rocks contain modal nepheline, and these bodies, where they contain less than 10% mafic minerals, represent more prospective A12O3 and CaO+NazO+KzO targets (Dolan et al, 1991).
Sainte-Véronique is a circular, layered body of silica-undersaturated mica pyroxenite and shonkinite dipping moderately toward the center, rimmed by an arcuate unit of silica-undersaturated syenite, with an outer margin of miaskitic nepheline syenite and a hybrid unit (Rive 1976). Sainte-Véronique, all magmas belong to the potassic alkaline series. Proportions of the intrusive units are 17% mica pyroxenite, 2% shonkinite, 7% nepheline syenite, 66% syenite, and 8% hybrid syenite (Andrews 1996).
Plutons of the ultrapotassic Kensington–Skootamatta suite are alkalic, shoshonitic to ultrapotassic, and generally have low to moderate silica contents (45 to 60 weight %). They are characterized by TiO2 >0.8 and P2O5 >0.21 (Corriveau 1990). They are typically associated with intense aeromagnetic highs, and generally have low to moderate eU and eTh contents on detailed airborne gamma ray spectrometric maps of the area. Monzonite to syenite plutons of the Kensington–Skootamatta suite in Ontario have U/Pb zircon age determinations ranging from 1077 to 1090 Ma, but most ages cluster around 1088 Ma (Easton et al, 2009).
Andrews, Oluf E.G., Apatite in the Kensington and Sainte-Véronique Plutons: An Indicator of Magmatic and Hydrothermal Processes. Department of Earth and Planetary Sciences, Mcgill University, December 1996.
Corriveau, L. 1990. Proterozoic subduction and terrane amalgamation in the southwestern Grenville Province, Canada:evidence from ultrapotassic to shoshonitic plutonism; Geology, v.18, p.614-617.
Davidson, A., van Breemen, O., Late Grenvillian granit plutons in the Central metasedimentary belt, grenville Province, southeastern Ontario. Radiogenic age and isotopic studies: report 13, Geological Survey of Canada, 2000.
M.L. Dolan, D.H. Hains and D.R. Ash, High-Alumina Rocks in Ontario: Resources and Process Technology. Mines and Minerals Division, Ministry of Northern Development and Mines, 1991.
Easton, M., Sangster, P., LeBaron, P., Rössing-style (Granite-Hosted) Uranium Mineralization in the Central Metasedimentary Belt of the Grenville Province, 2009.
Rive, M., Region of Sainte-Véronique: Minister of Natural Resources, Quebec. 1976.