Abstract

Lithium minerals, especially spodumene, are typical of many of the pegmatites along the margins of a granitic stock in LaCorne Township, north of Val D'Or, Quebec. Recent diamond drilling has shown some interesting features in the structure and composition of these dikes.The majority of the dikes strike nearly parallel to the nearest part of the granite contact and dip toward the center of the stock. They occur both within the granite and just outside it in basic lavas or sediments.The unusual feature of their composition is the uniformity in texture and average percentage of the spodumene in individual dikes. One series of such dikes on the north side of the stock shows an average spodumene content of about 25 percent. The crystals are arranged in a parallel pattern normal to the walls and are accompanied by feldspars, quartz, and minor amounts of beryl and tantalite. The texture of the more consistent dikes is finer than is usually seen in pegmatites. These finer-grained, uniform dikes are usually close to the granite contact, while those closer to the center of the stock are more variable in texture and spodumene content and contain more beryl.No evidence has been seen that the present minerals were formed by replacement of earlier minerals in the dikes.

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