High temperature microthermometry and Scanning Electron Microprobe (SEM) analyses were used to study natural magmatic remnants in quartz crystals in granitoids from the Timna Igneous Complex, southern Israel, and to constrain physicochemical parameters during their crystallization. For the porphyritic granite, alkali granite and quartz monzodiorite, liquidus temperatures are 710–770, 770–830 and 770–840°C, respectively; solidus temperatures are 690–770, 710–790 and 770°C, respectively. Pressures during crystallization and water content in the magmas were determined using the phase diagram of the modal granite system. The determined P-T-conditions are typical for water-saturated granitoid magmas (>4–8 wt.%) generated and crystallized at a shallow crustal level.

SEM data on melt inclusions support conclusions of previous investigations on two types of granitoid magmas exposed in the Timna Igneous Complex: the porphyritic and alkali granites. Different trends of crystallization are proposed for these granites. Crystallization of the porphyritic granite started with cotectic crystallization of plagioclase and terminated in residual K-feldspar-rich crystallization; crystallization of the alkali granite took place at higher temperatures, starting with K-rich alkali-feldspar crystallization and terminating in residual Na-rich eutectic crystallization.

Parameters not available from other sources — temperature and pressure of the liquidus and solidus stages, water content, trends of crystallization — were obtained for the porphyritic and alkali granites.

The thermal and compositional conditions of magma chambers constrain the type and complexity of their metasomatic aureoles. Fragments of these aureoles, disrupted during explosive eruptions of Vesuvius, provide quenched snapshots of interactions between potassic magmas and carbonate country rocks. Near the highly crystallized peripheral portions of the chambers, represented by magmatic xenoliths (fergusites, syenites and pyroxenites), skarn aureoles form. Open conduit reservoirs and the lower portions of plinian and subplinian eruption magma chambers develop aureoles controlled by diffusive metasomatism by high-T-modified silicate melts, generating magmatic skarn. In contrast, infiltrative metasomatism by magmatic fluids exsolved from crystallizing margins is responsible for endoskarn (magmatic protolith) and exoskarn (carbonate protolith) formation in the upper portions of plinian and subplinian eruption magma chambers.