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Silvia Volante, William Joseph Collins, Eleanore Blereau, Amaury Pourteau, Christopher Spencer, Noreen Evans, Vito Barrote, A.R. Nordsvan, Zheng-Xiang Li, Jun Li

• Accessory mineral thermometry and thermodynamic modelling are fundamental tools for constraining petrogenetic models of granite magmatism. U–Pb geochronology on zircon and monazite from S-type granites emplaced within a semi-continuous, whole-crust section in the Georgetown Inlier (GTI), NE Australia, indicates synchronous crystallisation at 1550 Ma. Zircon saturation temperature \((T_{zr})\) and titanium-in-zircon thermometry \((T_{(Ti–zr)})\) estimate magma temperatures of ~ 795 \(\pm\) 41 °C \((T_{zr})\) and ~ 845 \(\pm\) 46 °C \((T_{(Ti-zr)})\) in the deep crust, ~ 735 \(\pm\) 30 °C \((T_{zr})\) and ~ 785 \(\pm\) 30 °C \((T_{(Ti-zr)})\) in the middle crust, and ~ 796 \(\pm\) 45 °C \((T_{zr})\) and ~ 850 \(\pm\) 40 °C \((T_{(Ti–zr)})\) in the upper crust. The differing averages reflect ambient temperature conditions \((T_{zr})\) within the magma chamber, whereas the higher \((T_{(Ti–zr)})\) values represent peak conditions of hotter melt injections. Assuming thermal equilibrium through the crust and adiabatic ascent, shallower magmas contained 4 wt% \(H_{2}O\), whereas deeper melts contained 7 wt% \(H_{2}O\). Using these \(H_{2}O\) contents, monazite saturation temperature \((T_{mz})\) estimates agree with \(T_{zr}\) values. Thermodynamic modelling indicates that plagioclase, garnet and biotite were restitic phases, and that compositional variation in the GTI suites resulted from entrainment of these minerals in silicic (74–76 wt% \(SiO_{2}\)) melts. At inferred emplacement \(\textit {P–T}\) conditions of 5 kbar and 730 °C, additional \(H_{2}O\) is required to produce sufficient melt with compositions similar to the GTI granites. Drier and hotter magmas required additional heat to raise adiabatically to upper-crustal levels. S-type granites are low-\(\it T\) mushes of melt and residual phases that stall and equilibrate in the middle crust, suggesting that discussions on the unreliability of zircon-based thermometers should be modulated.