Peculiarities of internal structure of feldspars in granites of Salma massif
- Postgraduate student G.V. Plekhanov Saint Petersburg State Mining Institute
Abstract
Some samples of rapakivi granites from Salmi massif (Karelia) were investigated. The inner structure and the composition of feldspars in granites are necessary for understanding of the crystallization paths of this rock. X-ray diffractometry, cathode luminescence (CL) and microprobe analyzes were used in this study. It was found, that alkali feldspar from rapakivi granites is mixture of monoclinic and triclinic phases, and the ratio of these phases is various for different types of granites. A mirmektite zone corresponding of quartz-feldspar eutectic composition is typical for large ovoid crystals. CL and microprobe detected a compositional zoning and two types of albitization in plagioclases.
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