Fig. 3: Evolution of melt compositions during isobaric batch and fractional crystallization of a primitive CLG bulk composition, shown in total alkali–silica space.
From: A mid-crustal tipping point between silica-undersaturated and silica-oversaturated magmas
Whole-rock geochemistry12,14,28 for BLIC shown in coloured symbols following Fig. 1: orange shades for eastern lobe of the NLS (circle), Thor Lake syenite (diamond), Grace Lake granite (cross); blue shades for western lobe of Hearne Channel/Mad Lake granite (upward triangle), Whiteman Lake syenite (pentagon) and CLG (inverted triangle). Grey squares show the composition of selected phase endmembers; see text for discussion. a, Main axes show fractional crystallization; inset shows batch crystallization. Crosses mark the first 50, 75 and 90 vol% of crystallization. b, Crystallization continues from 95% fractionation in a (dotted lines showing evolution up to that point) at 4.0 and 5.0 kbar, with additional calculations at 0.5 kbar intervals; 3.5 kbar included as lower limit of reported BLIC pressures14. aeg, aegirine; ab, albite; cpx, clinopyroxene; di, diopside; fsp, feldspar; Fo, forsterite; hd, hedenbergite; ol, olivine.
