Road Log and Stop Descriptions
This excursion is expected to last a full day. The location of the different stops is shown on the geological map of the Preissac-Lacorne batholith shown in figure 1. We will commence our tour by examining typical occurrences of Be- and Ta-bearing granitic pegmatite dykes intruded within the Lacorne pluton (STOP 1). This will be followed by a visit to an unusual spodumene-lepidolite-beryl-bearing pegmatite body (STOP 2). We will then proceed westward across the batholith to look at a spodumene-albite pegmatite showing cropping out south of the Lamotte pluton (STOP 3). We will then proceed northward along highway 109 to study the northern contact of the Lacorne pluton with its metasedimentary host (STOPS 4, 5 and 6). Finally, we will complete our tour by moving south to the Moly Hill pluton, a small muscovite-garnet granitic body hosting a stockwork Mo-deposit (STOP 7).
Figures & Tables
Geology and Gold, Rare Element, and Base Metal Mineralization of the Val D'or Area, Quebec
The Val d’Or mining district, located in the southern part of the Abitibi belt in the Superior Province, consists of a typical Archean supracrustal volcanosedimentary sequence, obliquely cut by narrow northeast-trending Proterozoi’c diabase dykes.
The geology of the Val d’Or area is shown in figure 1. It was initially described by Gunning and Ambrose (1940) and Norman (1946, 1947), and was subsequently revised by Latulippe (1976), Imreh (1984) and more recently by Robert (1989).
The northernmost volcanic unit in the Val d’Or area is an extensive ultramafic lava plain known as the Malartic Group. The Lower Malartic is mainly composed of komatiitic ultramafic lava and subordinate basaltic flows. The Upper Malartic, comprised of basaltic lava with horizons of ultramafic and felsic volcaniclastic rocks (lmreh, 1984), is dominated by two main schistosities, S1 and S2 S1, oriented northwest, is related to the principal flattening plane. S1 is reoriented by an east-west fabric (S2) which is related to asymmetrical Z-folds found over most of the Val d’Or area. The Kiena Mine, one of the mines we will visit during the second day of our tour, is hosted by the Upper Malartic Group.
The Kewagama Group, located to the south of the Malartic Group, contains beds of metawacke and metapelite which have undergone two distinct folding events.axial planes related to the first folding event, oriented northwest, have been reoriented during a second phase of deformation that generated folds whose axial traces are oriented at 278° (Tourigny, 1984).
The Blake River Group, dominating the Rouyn-Noranda district 100 km to the west of Val d’Or, pinches out between the metasedimentary Kewagama and Cadillac groups near the town of Malartic. Here, the Blake River Group is composed of brecciated basaltic lavas with a main schistosity oriented at 275°.
The Cadillac Group, occurring to the south of the Blake River and Kewagama groups, is composed of metawacke and metapelite. Axial plane traces oriented at 284° terminate against the contact of the Blake River Group.
The Piché Group is found only within the Cadillac tectonic zone in the Val d’Or area. It consists mainly of ultramafic lava. Where the deformation is intense, the lava is completely transformed to talc-carbonate schist. Where the deformation is less intense, spinifex textures are still visible.
The Cadillac tectonic zone, generally oriented east-west, has been traced from Vauquelin township (east of Val d’Or) west to the border of Ontario and beyond.