Late Hercynian dyke magmatism of Sarrabus (SE Sardinia)

The late-Hercynian dyke magmatism of Sarrabus reflects the bimodal distribution observed in the other areas of Sardinia, the suite being represented by prevalent basaltic andesites and peraluminous rhyolites. Calcalkaline basalts and andesites are scarce, while dacites are extremely rare. The hypabyssal activity is closed by basaltic dykes with tholeiitic affinity. The chemical composition points out the 'medium-K' and 'high-K' character of the calcalkaline series. Fractionation links are lacking between calcalkaline and the majority of rhyolitic rocks. In comparison with dyke rocks of the other areas of Sardinia, many of the Sarrabus type show a more marked subalkaline character. The compositional variation of calcalkaline rocks can be partly explained by crystal-liquid fractionation processes. Among the rhyolitic rocks, two groups with different peraluminous characters have been recognized.