Abstract This paper reports field, petrological and structural data of the peraluminous cordierite-andalusite-bearing Campanario-La Haba granite. Crystallization age is constrained by Rb-Sr whole-rock dating at 309 ± 6 Ma (with ( 87 Sr/ 86 Sr) i = 0.70739 ± 0.00038) and took place during late Hercynian tectonic events. The pluton shows a petrographic zonation, although there are no marked differences in chemical compositions between the margin and the centre of the intrusion. Petrography, mineralogical data and geochemical modelling indicate melt generation by partial melting of a metasedimentary protolith, probably with some mantelic contribution as shown by its low Sr i value, followed by emplacement at P < 3 kbar. The internal structure of the pluton resulted from the lateral spreading in the stretching direction given by an N120–130E dextral strike-slip zone and the external geometry seems to be strongly conditioned by faults (Riedel R type fractures) formed in the host rocks. This emplacement model agrees with that defined for the adjacent Extremadura granitic plutons and for the Los Pedroches batholith suggesting the existence of a dextral regional shear-zone in the South branch of the Central Iberian Zone.

Liquidus phase relationships at H 2 O-saturated and -undersaturated conditions and 2 kbar in the systems Qz–Or–Ab (SiO 2 –KAlSi 3 O s –NaAlSi 3 O s ), Qz–Or–Ab–Al 2 O 3 , and subsystems are compared and discussed. In the peraluminous systems (i.e. when melts are saturated with respect to mullite) the liquidus temperatures are lowered by 40–55°C for compositions in the quartz primary field and by 15–25°C for cotectic compositions. The composition of the Qz–Ab eutectic and of the minimum are slightly shifted towards more Qz-rich compositions (minimum composition at P(H 2 O)=2 kbar in the system Qz–Or–Ab– Al 2 O 3 saturated with respect to mullite: Qz 40 Or 23 Ab 37 ). In melts saturated with sillimanite or mullite, the effect of high Al content may be lower for the Qz–Or than for the Qz–Ab eutectic. The depression of the liquidus temperatures may be partly related to the higher H 2 O solubility in melts saturated with respect to mullite. The solubility of H 2 O in a melt with a composition of Qz 28 Or 34 Ab 3R at 2 kbar and 800°C is 5.77 ± 0.15 wt% H 2 O and 6.36 ± 0.30 wt% H 2 O in a melt with the same Qz/Or/Ab proportions but saturated with respect to mullite. The effect of high Al contents on the Mg and Fe contents of Ca-free granite melts was investigated at 775°C–3 kbar (melts coexisting with phlogopite), and at 820°C–2 kbar (melts coexisting with biotite and spinel), under NNO buffer conditions. Less than 0.15 wt% MgO is incorporated in subaluminous melts coexisting with phlogopite, whereas peraluminous melts (2.9 wt% normative corundum) contain 0.6–0.7 wt% MgO. A similar behaviour of the MgO content is observed for melts coexisting with biotite. In contrast, no significant effect of high Al contents on the FeO content of melt coexisting with biotite was observed. This suggests that the Fe/Mg ratio may be significantly lower in peraluminous than in subaluminous granitic melts.