Petrography of the Ambela Granitic Complex, NW Pakistan
Abstract
The Ambela granitic complex occupies the southeastern part of the Buner subdivision of Swat. It is a composite batholith consisting of a variety of oversaturated (70%), saturated (2O %), and undersaturated rocks (50%). The batholith may have formed over a considerable length of time, spanning from middle to late Paleozoic. Petrographic studies (800 thin sections) allow a threefold grouping of the rocks. Group I includes granites, alkali granites and microporphyrites; these appear to represent the early magmatic episode of the complex. Group II includes quartz syenites, alkali quartz syenites, syenites, feldspathoidal syenites, carbonatite, ijolite, lamprophyre, and associated pegmatites and fenites. Considerable metasomatic changes were associated with successive alkali rich intrusive phases of this group of rocks. Basic dykes (Group III), intruding both Group I and II rocks, represent the last magmatic episode and constitute about 5% of the complex. This paper presents petrographic details of the various types of rocks in the complex.
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