Igneous and metamorphic complexes of the Guiana shield in Suriname

Abstract

The crystalline basement of Suriname was formed essentially in the Lower Proterozoic during the Trans-Amazonian orogeny around 2000 to 1870 Ma ago. Two belts of high-grade metamorphic rocks probably developed as intracratonic basins within an older, possibly Archaean continent. A greenstone belt with basic and intermediate volcanics, volcaniclastic greywackes and coarse-clastic (molassic?) sediments is supposed to have formed in an island-arc-back-arc marginal basin environment at the northern margin of the older continent. Deformation and metamorphism took place around 2000 Ma ago. Extensive acid magmatism around 1870 Ma represents a subsequent stage in the Trans-Amazonian Orogenic Cycle, marked by acid ignimbritic volcanism, and next by granitoid and gabbroic intrusions. Most of the older basement was remobilized and reworked during this stage. Cratonization of the region was completed before the deposition of the Roraima Formation sandstones and pyroclastics around 1650 Ma and the intrusion of the Avanavero and Käyser Dolerites. Metamorphism, mylonitization and mica age resetting occurred around 1250 Ma in western Suriname during the Nickerie Metamorphic Episode. The intrusion of the Permo-Triassic Apatoe Dolerite around 230 Ma marks the beginning of the separation of South America and Africa.