stripes
A mountain rising some 600-700 m above the surrounding plain is underlain by a central biotite granite around which, on the northern side, is an arcuate intrusion of gabbro/diorite around which again is a separate circular intrusion of syenite. The gabbro/diorite rocks comprise poikilitic kaersutite, plagioclase (An83-20), titanaugite, biotite and magnetite. The syenites are made of perthite, aegirine, augite and fayalite which may be rimmed by green amphibole. Up to 10% quartz is present with accessory apatite, sphene, allanite and zircon. Plagioclase- biotite lamprophyre dykes occur around the intrusion as well as feldspar-free analcime melteigites. Analyses for major and trace elements, including REE and Sr isotopes, and some mineral data will be found in Eby (1985a) and Pb isotopes in Eby (1985b).
CURRIE, K.L. 1976a. The alkaline rocks of Canada. Bulletin, Geological Survey of Canada, 239: 1-228.
EBY, G.N. 1984b. Geochronology of the Monteregian Hills alkaline igneous province, Quebec. Geology, 12: 468-70.
EBY, G.N. 1985a. Monteregian Hills II. Petrography, major and trace element geochemistry, and strontium isotopic chemistry of the eastern intrusions: Mounts Shefford, Brome, and Megantic. Journal of Petrology, 26: 418-48.
EBY, G.N. 1985b. Sr and Pb isotopes, U and Th chemistry of the alkaline Monteregian and White Mountain igneous provinces, eastern North America. Geochimica et Cosmochimica Acta, 49: 1143-53.
SEGUIN, M.K.- and ST-HILAIRE, B. 1985. Magnetochronologie des formations rocheuses du Mont Megantic et des environs, Quebec meridionel. Canadian Journal of Earth Sciences, 22: 487-97.
