rapakivi texture

rapakivi texture

[¦rä·pə′kē·vē ′teks·chər]
(petrology)
An igneous and metamorphic rock texture in which spherical potassium feldspar crystals are surrounded by a rim of sodium feldspar, both within a finer-grained matrix.
References in periodicals archive ?
The Churio granite is pinkish, apparently fresh, leucocratic with rapakivi texture.
The origin of rapakivi texture by sub-isothermal decom-pression.
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.
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.
It contains abundant large K-feldspar crystals (up to 6 cm) many of which, but not all, are mantled with plagioclase to form rapakivi texture.