Hypersolvus
Encyclopedia
In hypersolvus granites, as used by Tuttle and Bowen in 1958, crystallization at relatively low water pressures results in the formation of a single feldspar
as opposed to subsolvus
granites in which two distinct types of feldspar are present.
The distinctive character of feldspar in hypersolvus granite is to present exsolution textures. That is because the high temperature feldspar was ternary (i.e. contained comparable parts of the Ca, Na, K components) and was later dissociated during the cooling phase into K-rich parts and Na-Ca-rich parts, within the initial crystal. The resulting texture is referred to as perthitic
.
Feldspar
Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....
as opposed to subsolvus
Subsolvus
In subsolvus or two feldspar granites crystallisation occurs at high water pressures resulting in the formation of two types of feldspar as opposed to hypersolvus granites in which crystallization at relatively low water pressures results in the formation of a single feldspar variety.Quoting Tuttle...
granites in which two distinct types of feldspar are present.
The distinctive character of feldspar in hypersolvus granite is to present exsolution textures. That is because the high temperature feldspar was ternary (i.e. contained comparable parts of the Ca, Na, K components) and was later dissociated during the cooling phase into K-rich parts and Na-Ca-rich parts, within the initial crystal. The resulting texture is referred to as perthitic
Perthite
Perthite is used to describe an intergrowth of two feldspars: a host grain of potassium-rich alkali feldspar includes exsolved lamellae or irregular intergrowths of sodic alkali feldspar . Typically the host grain is orthoclase or microcline, and the lamellae are albite...
.