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Report on Rougemont Mountain Area, Rouville and St-Hyacinthe Counties

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Report on Rougemont Mountain Area, Rouville and St-Hyacinthe Counties GM 03503 REPORT ON ROUGEMONT MOUNTAIN AREA, ROUVILLE AND ST-HYACINTHE COUNTIES • ST-HYACINTHE Seig. GASPE M,LSLTD. on ROUGEMONT MOUNTAIN AREA ROUVILLE and ST HYACINTHE COUNTIES QUEBEC Location and Access The area herein described covers 5530 acres; it includes lots 410 to 455 inclusive, 488 to 620 inclusive of the Parish of St-Damase, St-Hyacinthe County, lots 481 to 600 inclusive of the Parish of St-Jean-Baptiste, Rouville County, 550A, 554 to 560 inclusive, 616 to 655 inclusive, 705, 706, 711 to 719 inclusive, 722 to 740 inclusive and 71+6 to 757 inclusive of the Parish of St-Césaire, Rouville County. i It includes about two-thirds of the igneous mass of Rougemont Mountain and a rim of the surrounding sediments. Rougemont Mountain is one of the Monteregian Hills and is located about 25 miles east of Montreal. The Mountain is formed of a series of hills separated from each other by valleys, some of which have very steep slopes. The highest hill to the southwest is over 1200 feet above sea-level. The center of the area is lacking with means of access; no roads go across the hill like on the larger similar hills of Yamaska, Brome and Shefford. There are a few trails leading to the lakes and sugar houses around the hill and one leading to the cross, top of the highest hill to the southwest of the Mountain. GEOLOGY The rocks of the area include first the slaty sediments of the surroundings which enclose the igneous mass made of one main type call cbtieffeleepAiFirAkEthopesitim ion gave several varieties, one MINERAL DEPOSITS BRANCH lighter coloured named Rougemontite and the other darker named Pyroxenite. Through these, dykes occur; they are all narrow (few inches) and may be of several ages since, in places, they cut each other. Sedimentary Rocks The sediments surrounding the igneous mass are all black slate in which the bedding is recognized by the occurrence of thin white beds of limy material. This slate is more metamorphosed as we get closer to the igneous mass and becomes a hornstone in which the fracture is conchoidal and in which the bedding is hardly or not recognizable. Around most of the hill, these sediments are flat lying and have not been upwarped by the igneous mass. The only exception is to the east where we can trace some open folding at least to half a mile away from the contact. Jointing is characteristic in the slate and is usual- ly of two directions at right angles to each other and vertical. Two dykes were seen in these joints: one to the northwest near the Canadian Pacific Television tower, the other to the east, in lot 621. Both were found close to the igneous contact and strike parallel to the prominent jointing, i.e. approximately perpendicular to the Bedding. Their composition is that of the igneous rock nearby and will be discussed later. Essexite The name essexite was given to a rock which is holocrystalline, varying in grain size from medium to coarse and in which the dark minerals make about two-thirds of the rock, the rest being mostly feldspars. The dark minerals in some areas are, besides iron oxide, mostly pyroxenes, but there may as well be some amphibole and biotite. The iron oxide is strongly magnetic and varies in quantity with places; it is very irregularly distributed. The weathering of the rock varies from a brown colour to almost black. It may be thin, like in the variety richer in pyroxene, or almost a foot deep, like in the variety richer in biotite. The iron oxide seems to be more common in the former variety. The feldspar is a plagioclase which cannot be iden- tified to the naked eye, but has been identified by J.J. O'Neill who mapped this area in 1912, as anorthite. This feldspar is alter- ed and in some places has given place to a green epidote. Olivine is also present in some places. The different varieties of essexite may be seen on a single exposure; the rock passes gradually from coarse to finer grained and also from a variety rich is pyroxene to one richer in biotite; these seem to be the result of moving solutions during crystallization. The same explanation could apply to a fluidal arrangement of the minerals which may be observed in some places, as shown by foliation. Roug emontite The name Rougemontite has been given by O'Neill to a rock type similar to the essexite, but richer in feldspathic minerals. The feldspars vary in proportion from one third to two- thirds of the rock. They are again mostly anorthite. The dark constituents are mostly pyroxenes and iron oxides. The latter is strongly magnetic. • 4 - The weathered surface present a mottled appearance; the mass is grey with black spots. It is easily recognized from the other rock types. It is found in small areas, like on the highest summit at the cross; these acreas are mostly on the west side of the whole intrusive. Pvroxenite This rock name was given to an essexite lacking feldspars. It is rich in pyroxene and iron oxide; the feldspar is accessory. The rock is black in colour with a similar wea- thered surface. It is often richer in iron oxide and acts readily on the compass. Jointing is prominent in this kind of rock and may be in two directions at right angles and mostly vertical. The pyroxenite seems to be only a segregation of the one essexite mass as shown in some exposures where we could observe a small mass of pyroxene rich essexite into the normal essexite. Dyke s Several dykes were observed in the area; most of them are within the igneous mass, only a few were found within the sediments and.close to the igneous rocks. They vary in width from few inches to about three feet in thickness: they go in all directions, except those in the sediments which follow jointing. Their composition is that of the igneous rocks: i.e. essexite, pyroxenite and rougemontite. Some are porphyritic towards the center; most are medium grained. The narrow- est are more fine grained. They do not all go in straight line: some were found to give the rock a pillow-like appearance. Two of these dykes were found to carry some disse- minated pyrite. ECONOMIC GEOLOGY Pyrite with some ch alcopyrite was observed in a trench made on the north side of Lake St-Damase. Its extent has not been traced. These minerals are in a mafic essexite, almost pyroxenite. Pyrite was also observed in small quantities on a few exposures and in a couple of dykes. Magnetite or titaniferous magnetite is relatively abundant in several areas of the mountain; as previously mentioned,, the compass needle was often attracted by these during the mapping. CONCLUSION The study of this area shows that there is only one main type of intrusive rock, the essexite: the other types are segregation of the essexite. This rock-type has some alkalinity, and though it is much less alkaline than that of Oka Mountain, it might be interesting to study in greater detail. Reo ectfully submitted, (s) Marcel Tiphane, Marcel Tiphane, Montreal, Quebec. P.Eng., M.Sc. September lys 1955 4,, 6- CONCLUSION The study of this area shows that there is only one main type of intrusive rock, the essexite: the ether types are segregation of the essexite. This rock-type has some alkalinity, and though it is mt.eh less alkaline than that of Oka Mountain, it might be interesting to study in greater detail. Respectfully submitted, (s) Marcel Tiphane Marcel Tiphanei P. Eng., M.Sc. CERTIFICATE I, undersigned, hereby certify that: 1. I am a Canadian born citizen, and reside at 6584, 12th Avenue, Rosemount, Montreal 36, Quebec. 2. I am a regular member of the Corporation of Pro- fessional Engineers of Quebec. 3. I have taken my degree in Mining Engineering at Laval University, and my degree of Master of Science (Geology) at McGill University. 4. I am teaching geology at the Faculty of Sciences; University of Montreal, and also at Ecole Polytech- nique of the same University. 5. I have no interest either directly or indirectly nor do I expect to receive any interest either directly or indirectly in the group of claims involved in the accompanying report on Rougemont Mountain. (s) Marcel Tiphane Marcel Tiphane, P.Eng., M.Sc. .
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