Coherent solvus

Figure 3.16 Solvus and spinodal decomposition fields as a function of elastic strain, (a) Strain-free or chemical solvus (b) strain-free spinodal (c) coherent solvus (d) coherent spinodal. From Ganguly and Saxena (1992). Reprinted with permission of Springer-Verlag, New York.

Sipling R J. and Yund R. A. (1976). Experimental determination of the coherent solvus for sanidine-high albite. Amer. Mineral, 61 897-906. 

The compositional relations of the sodic and potassic phases in perthites depend on whether the phases are coherent or not. If the perthitic phases are non-coherent (or if the rock consists of separate grains of sodic and potassic feldspar) their equihbrium compositions are given by the strain-free solvus. This is the solvus which has been studied extensively in the past. These sentences. 

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