Chapter 3 Perthites, Mesoperthites, Antiperthites and Peristerites
1966; Elsevier BV; Linguagem: Inglês
10.1016/s0070-4571(08)70637-x
ISSN2352-2844
ResumoPublisher SummaryA special type of perthites, the so-called mesoperthites, seems to be restricted to special rock types. The proportion of albite and microcline is about 1:1. This type seems to occur exclusively in the deep-seated, highly metamorphic rocks in regions such as southern Norway, Saxony, etc. The presence of such perthites in sedimentary rocks is an important indication in determining their provenance. The lamellar aggregate, composed of a large amount of alkali feldspar and a subordinate amount of albite, is called a perthite. It is the common experience of petrographers that a comparatively large number of alkali feldspars studied are “intergrown” with this kind of albite lamellae. In addition to the two types of unmixed aggregates, another type of lamellar aggregate exists in nature, in which the amount of the potassium-rich phase is rather subordinate in importance to the amount of albite. These aggregates are called antiperthites. According to some authors, these antiperthites are the result of unmixing; others advocate a different genesis. Lamellar aggregates composed of lamellae with an albite composition occurring next to lamellae with a composition of An26 are called peristerites.
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