Petrology, geochemistry and U-Pb zircon and baddeleyite ages of the alkaline rocks from the central-southern Guyana Shield, northern Amazonian Craton

The Apiau Alkaline Complex (AAC) represents a rift-related intracontinental magmatism and occurs as intrusions within the Precambrian basement of the central-southern portion of the Guyana Shield, Amazonian Craton. The complex extends for over 200 km and comprises monzonites, syenites, nepheline syenites, nepheline-bearing syenites, trachytes and phonolites. It differs from other alkaline rocks of the craton both in age and tectonic setting....