Magmatism associated with Gondwanaland rifting and Neo-Tethyan oceanic basin development: evidence from the Mamonia Complex, SW Cyprus

摘要

Volcanic and intrusive rocks of the Dhiarizos Group, occurring within the Mamonia Complex of SW Cyprus, comprise mainly tholeiitic basalts, ocean island tholeiites (OIT) and other alkalic varieties, with minor alkaline lamprophyre intrusive rocks. These rocks were highly tectonized and dismembered during the collision with the Troodos oceanic lithosphere. Trace element data for the most primitive mafic igneous rock samples suggest that the tholeiitic basalts are derived from a depleted mantle source whereas the OIT and the alkalic basalts originated from variable degrees of partial melting of a spinel peridotite mantle. Alkaline lamprophyres are products of a small degree of partial melting of a deep-seated garnet lherzolite. The bulk of the tholeiites and alkalic varieties are Late Triassic in age and are interpreted as having formed during Neo-Tethyan sea-floor spreading and associated seamount volcanism. Amphibole separates from a lamprophyre intrusion have 40Ar–39Ar ages of 140.7 ± 0.4 Ma. In this paper, we report for the first time an Early Cretaceous alkaline lamprophyric magmatism, which is probably associated with a renewed episode of Gondwanaland rifting. These results show that the development of the Neo-Tethyan oceanic basin in the Eastern Mediterranean was largely controlled by a two-phase rifting–drifting process.