Lithogeochemistry of Geological Units of the Commissaires Lake Area
The majority of these samples were analyzed for major oxides, trace elements and base metals. A few selected samples of mafic to ultramafic rocks were also analyzed for platinum, palladium and gold. Analyses were performed by various element-specific techniques such as inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and instrumental neutron activation analysis (INAA).
The CIPW norm including biotite and hornblende was calculated for the diagram classification of intrusive and intermediate rocks according to Hutchison (1974, 1975), as described by Janoušek et al. (2006) in the Geochemical Data Toolkit (GCDkit) software. The latter has been used to make all geochemical diagrams listed in the tables below.
Felsic and Intermediate Intrusive Rocks
Stratigraphic Unit | Classification | Affinity | Rare Earth Element (REE) Diagram | Setting |
|---|---|---|---|---|
Rhéaume Intrusive Suite (mPrhe2) | Syenogranite, quartz syenite and mangerite (Diagram) | K-rich units (shoshonitic series type) (Diagram)
| Negative slope diagram (light REE enrichment vs. heavy REE) Negative to slightly positive Eu anomaly (Diagram) | Anorogenic (Diagram) |
Jobber Mangerite (mPjob) (1 sample) | Mangerite-syenite (Diagram) | Shoshonitic series type (Diagram) | Negative slope diagram and positive Eu anomaly (Diagram) | Mostly anorogenic (Diagram) |
Leda Intrusive Suite (mPled) | Quartz monzonite, granite, syenite, monzonite, mangerite, hypersthene quartz diorite and alkali feldspar granite (Diagram) | Units more enriched in K (shoshonitic series type) and calc-alkaline facies (Diagram) | Negative slope diagram and generally positive Eu anomaly, except for alkali feldspar granite which has a strong positive Eu anomaly (Diagram) | |
Léo Plutonic Suite (mPleo) (1 sample) | Hypersthene granite (charnockite) (Diagram) | K-rich calc-alkaline unit (Diagram) | Light REE enrichment vs. heavy REE, slight positive Eu anomaly (Diagram) | |
Lachance Mangerite (mPlhc) | Quartz monzonite (mangerite), quartz syenite and granite (syenogranite) (Diagram) | K-rich calc-alkaline to shoshonitic series type (Diagram) | For the three units: – generally negative slope diagram (light REE enrichment vs. heavy REE); – Eu anomalies varying from positive to negative. (Diagram) | Mostly anorogenic (Diagram) |
Bonhomme Plutonic Suite (mPboh) | Quartz ± hypersthene diorite, quartz monzonite (mangerite) and granite (adamellite) (Diagram) | Calc-alkaline to mostly shoshonitic series type (Diagram) | ||
Bardeau Plutonic Suite (mPbad) | Granite, alkali feldspar granite, quartz diorite, granodiorite, mangerite (plot in the monzogabbro field since it is rich in ferromagnesian minerals), tonalitic mobilisate migmatitic mangerite (Diagram) | K-rich calc-alkaline unit (Diagram) | ||
Thaddé Plutonic Suite (mPthd) | Granite (charnockite), alkali feldspar granite, quartz monzodiorite, quartz syenite and quartz monzonite (mangerite) (Diagram) | K-rich calc-alkaline to shoshonitic series type series (Diagram) | Generally, for the three suites: – negative slope diagram (light REE enrichment vs. heavy REE); – Eu anomalies varying from positive to negative; – syenite and alkali feldspar granite more enriched in light REE. (Diagram) | Mostly anorogenic for the alkaline facies of the three suites (Diagram) |
Mimosa Plutonic Suite (mPmim) | Granite, granodiorite (opdalite, charnockite), monzonite, monzodiorite and diorite. All these lithologies can contain quartz and hypersthene. (Diagram) | Mostly calc-alkaline series to shoshonitic series type (Diagram) | ||
Marianne Plutonic Suite (mPmae) | Granite (charnockite), alkali feldspar granite, syenite, quartz ± hypersthene syenite, quartz diorite (Diagram) | Mostly shoshonitic series type (Diagram) | ||
Travers Suite (mPtra) | Syenite ± quartz ± hypersthene, granite (syenogranite), alkali feldspar granite, monzonite, quartz monzonite and mangerite (plot in the field of quartz monzodiorites since mangerite contains >20% ferromagnesian minerals) (Diagram) | K-rich calc-alkaline series to shoshonitic series type (Diagram) |
Generally, all lithologies of the suite show these characteristics: – negative slope diagram (light REE enrichment vs. heavy REE); – Eu anomalies varying from positive to negative; Outcrop 18-AM-2019 shows a less pronounced negative slope diagram and a strong positive Eu anomaly. (Diagram) | Mostly anorogenic (Diagram) |
Sainte-Hedwidge Intrusive Suite (mPshe) | Granite, quartz monzonite and quartz monzodiorite (Diagram) | Generally, both suites are of shoshonitic series type (Diagram) | Generally, both suites show these characteristics: – negative slope diagram (light REE enrichment vs. heavy REE); – Eu anomalies varying from positive to negative.
(Diagram) | Anorogenic for both suites (Diagram) |
Rodez Plutonic Suite (mPrdz1) | Granite (adamellite), syenite, quartz monzonite, quartz syenite, quartz diorite, all lithologies ± hypersthene (Diagram) |
Mafic and Ultramafic Intrusive Rocks
Stratigraphic Unit | Lithology | Affinity | Tectonic Setting |
|---|---|---|---|
Claire Gabbronorite (mPclr) | Gabronorite ± Fe-Ti ± P ± V oxides and ultramafic rock |
Tholeiitic to calc-alkaline (Diagram)
| Mafic rocks mostly plot in the field of intraplate basalts. (Diagram) |
Roc Suite (mPsro2) | Gabronorite ± Fe-Ti ± P ± V oxides |
Mafic rocks are mainly divided between the fields of intraplate basalts and mid-oceanic ridge basalts. (Diagram) | |
Rodez Plutonic Suite (mPrdz2) | Anorthosite, leuconorite, gabbronorite ± rich in Fe-Ti ± P ± V | Tholeiitic (Diagram) |
|
Gabbronorite belonging to the: Thaddé Plutonic Suite (mPthd) Sainte-Hedwidge Intrusive Suite (mPshe) Marianne Plutonic Suite (mPmae) Léo Intrusive Suite (mPleo) (1 sample) Travers Suite (mPtra) | Gabbro, gabbronorite and ultramafic rock (Diagram) | Mainly calc-alkaline (Diagram) |
Mafic rocks of the Thaddé Plutonic Suite, Sainte-Hedwidge Intrusive Suite and Marianne Plutonic Suite plot in the field for intraplate “basalts”, while rocks of the Travers Suite correspond to those defined for the intraplate, mid-oceanic ridges and island arc “basalts”. Other samples of the Léo Plutonic Suite and Travers Suite are out of scope in the diagram. (Diagram) |
Sedimentary Rocks | |||
| Stratigraphic Unit | Lithology | Protolith and Alteration | |
Barrois Complex (mPboi4) | Biotite paragneiss, quartzite, calcosilicate rocks and granite | Weakly altered metasedimentary rocks, likely derived from tonalite and granite (Diagram) |
|
Wabash Complex (mPwab1, mPwab2) | Biotite ± sillimanite ± graphite ± garnet paragneiss, migmatitic paragneiss, quartzite, calcosilicate rocks, marble, migmatite derived from sedimentary rock | Biotite ± sillimanite ± graphite ± garnet paragneiss showing a trend towards the illite pole More altered paragneiss than those of the Barrois Complex Paragneiss derived from a felsic protolith (tonalite, granodiorite, granite) (Diagram) | |
References
Other publications
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