Rapakivi granites are defined as A-type granites characterized by the presence, at least in the larger batholiths, of granite varieties showing rapakivi texture (Haapala & Rama 1992).
These stones are coarse-grained rocks with a typical rapakivi texture of large round K-feldspar ovoids, with or without a plagioclase rim.
Sederholm (1891) noted that the typical rapakivi texture is more prone to breakdown of mineral grains than, e.g.
Typical shallow-crustal granites with rapakivi texture are found in the central part (Bogatikov & Birkis 1973), while subvolcanic granophyres occupy large areas in its northern part--on the basement of Ruhnu Island in the Gulf of Riga and in the southwestern part of Saaremaa Island (Kuuspalu 1975; Puura et al.
Plagioclase-mantled alkali feldspar ovoids (the rapakivi texture) are lacking; this texture is found only in the granites of the Riga batholith.
The MWG contains feldspars of various textures and composition, including abundant plagioclase-mantled K-feldspar (rapakivi texture), boxy and spongy cellular plagioclase, and plagioclase that show An spikes and/or central cures of higher Ca content.
The pressure quench formation of rapakivi texture. Contributions to Mineralogy and Petrology, 68, pp.
In addition to the K-feldspar (which includes minor amounts of microcline) + plagioclase assemblage there is a range of disequilibrium feldspar textures, including plagioclase mantles on K-feldspar (rapakivi textures), boxy and spongy cellular plagioclase, complexly zoned plagioclase grains commonly displaying an An "spike", and plagioclase displaying central cored zones.