Petrography of Quartz Diorites to The South of Kalam, Swat
Abstract
The quartz diorites of Swat Kohistan appear to be partial melting products of more mafic rocks during the collision of Asian-Indian·landmasses and the Himalayan orogenic-metamorphic episodes. On the basis of texture and type of principal mafic mineral(s), at least four types of quartz diorites can be recognized in the area to the south of Kalam. One of these, with strongly pleochroic hypersthene relics, appears to be a retrograde type after pyroxene granulites. It is not clear whether or not the other types are a product of differentiation from a single parent magma; however, it is likely that they represent independent pulses of diorite (andesite) magma produced over a considerable length of time (Late Cretaceous to late Middle Tartiary), the earlier ones having been metamorphosed.
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