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- - T-4518 76 <br />Macroscopically, MSPC alteration appears as a bleached, clay-rich, white to pale <br />green envelope around veins (Fig. 46a). It consists of an inner zone of the assembla,;e <br />muscovite, sericite, phengite, and chlorite and an outer zone of chlorite with minor <br />muscovite, sericite, and phengite. The sericite, chlorite and phengite occur together as <br />fine (<100 µm) euhedra] grains replacing plagioclase, orthoclase, and mafic minerals <br />(except biotite). Muscovite, chlorite, or a combination of sericite and phengite replac:e <br />biotite. Muscovite is medium-grained towards the outer edge of the muscovite-dominant <br />zone and in the chlorite zone. Chlorite is medium-grained only in the chlorite zone. <br />Phengite is the predominant mineral in altered monzonite while fine- to medium-grained <br />muscovite is the predominant mineral in altered mica schist unit. <br />Adularia alteration is associated with speculaz hematite and typically overprints <br />MSPC alteration with adularia and secondary quartz. Macroscopically, this alteration is <br />distinguished by fine-grained adularia which gives the sample a pink tint (Fig. 46b). <br />Adularia was identified in thin section by its pseudo-orthorhombic habit and by staining for <br />potassium. Euhedral adularia (20 to 100 µm) is common adjacent to the vein in a zone <br />containing secondary quartz. Less abundant subhedral to anhedral adularia (QO µm) <br />occurs beyond the zone containing secondary quartz. Speculaz hematite and the ~ - <br />associated adularia alteration were too limited in extent to show at the mine map scale <br />Because this alteration type is not widespread and is associated only with speculaz <br />hematite, it has no economic significance. <br /> <br />