Fig. 4: Comparison of the mineral and fluid compositions as well as the related products’ texture during sanidine albitisation predicted by thermodynamic modelling with those observed experimentally.

Modelling results from (A) pure water; (B) NaCl and NaF solutions. C describes the extrapolated evolution of solids and fluids chemistry and the related zonation texture observed in our study. Different stages are highlighted by different background colours: orange = sanidine dissolution; grey = albite and K-feldspar co-precipitation at the peritectic point; pink = albite precipitation via replacement of sanidine; green = K-feldspar precipitation via replacement of albite (locally sanidine where albite is fully consumed). The green dashed lines represent the ions composition in solution and the red and orange solid lines represent the solid composition. (B3) shows the modelled reaction products intergrowth texture as an albite-enriched phase and a K-feldspar enriched phase co-exist with each other, which was observed in the experiment using sanidine (Ab₆₀Or₄₀) reacted with H₂O/HCl at 500 °C, 1000 Mpa¹⁸. The compositions of albite and K-feldspar (red solid lines from C1) are from electron probe analysis results (Supplementary Fig. 2). The composition of ions (green dashed line from C1) from solution is extrapolated from the Lippmann diagram in equilibrium with a given solid solution composition. The horizontal axis of (C1) shows relative increasing sanidine/water ratio from left to right. Mineral abbreviations⁵²: Ab = Albite, Bt = Biotite, Fl = Fluorite, Kfs = K-feldspar, Qtz = Quartz, Sa = Sanidine.