Abstract

Thirty-eight samples of pyroxene and 5 of amphiboles were obtained from a suite of skarn rocks, pyroxenites, and hybrid rocks collected from various localities of the Grenville of western Quebec and eastern Ontario, and analyzed spectrographically for minor and trace element content. The elements, and their ranges of values were as follows: B, 7-90 p.p.m.; Be, 0-9 p.p.m.; Ga, 0-60 p.p.m.; Cr, trace to 200 p.p.m.; Li, 0-150 p.p.m.; Ti, 200-1,200 p.p.m.; Ni, 1-50 p.p.m.; Mo, none; Co, 5-45 p.p.m.; Cu, 0-50 p.p.m.; V, 8-86 p.p.m.; Zr, 12-117 p.p.m.; Mn, 600-2,800 p.p.m.; Sc, trace-15 p.p.m.; Y, trace-18 p.p.m.; Sn, none; Sr, 17-450 p.p.m.; Pb, trace to 300 p.p.m.; and Ba, 1-44 p.p.m. The location of the minor elements is discussed in terms of the crystal chemistry of the pyroxenes, and in terms of the known behavior patterns of the elements in rocks and minerals. It is concluded that most of the minor components are, generally, in structural sites in the mineral. When compared with pyroxenes of igneous genesis, the minerals are conspicuously poorer in most elements except Be, Ga, Sr, and Ba, which are at about the same level as in igneous pyroxenes; B, however, has a higher concentration. This is explained in terms of the abundances of minor elements in the Grenville sediments. It is concluded that, just as in igneous crystallization the bulk composition of the magma influences the minor element composition of the individual minerals, so in metamorphic reconstitution the composition is governed by the country rock. Calculations show that the total minor element composition of the pyroxenes is less than that of igneous pyroxenes, judging from the literature, and less than that of amphiboles from the same rocks. The method of calculation was devised so that elements were weighted with respect to their natural abundance.

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