Geological setting of the Paleoproterozoic Rosebel gold district, Guiana Shield, Suriname

Abstract

Abstract The Rosebel gold district is hosted in a Paleoproterozoic greenstone belt of the Guiana Shield and has many characteristics that enable classification of the ores as an orogenic gold deposit. Host rocks have undergone several phases of deformation. However, gold deposition occurred late in the structural history of the belt, and is considered part of a late regional metallogenic event with respect to the geotectonic evolution of the Guiana Shield. Economic gold mineralization is hosted in felsic to mafic volcanic rocks and two sedimentary successions that are differentiated into turbiditic and arenitic depositional packages. The detailed lithostratigraphic characterization and the geochemistry enable the correlation of the local rock types with the Paramaka, the Armina, and the Rosebel formations respectively. The Rosebel district comprises eight discrete gold deposits distributed along two major structures. The northernmost structure is a sub-vertical WNW–ESE shear zone that preserves evidence of dextral strike–slip followed by normal faulting. The southern structure is an east–west reverse fault along which gold deposits are mainly hosted in the footwall. Gold mineralization is associated with quartz vein arrays developed along pre-existing structural heterogeneities, such as stratigraphic contacts and fold hinges. Four main sets of veins are recognized in the district: shear veins, north–south tension veins, stacks of north-dipping tension veins, and anticline-hosted tension veins. Mineralized quartz veins are typically associated with a wallrock alteration assemblage comprising sericite, chlorite, carbonate, tourmaline, pyrite, pyrrhotite, and plagioclase. The presence of a WNW–ESE dextral strike–slip structure, an east–west reverse fault, and north–south tension veins are consistent with the formation of a Riedel system during a simple shear event. All vein sets cut deformed sedimentary rocks that were deposited in a pull-apart basin, which together with their planar geometries, indicates a late-Transamazonian orogen timing for gold mineralization. Extensive dating of other orogenic gold deposits in the Guiana Shield has revealed ages between 2.023 and 1.955 Ga for gold mineralization, which is broadly coeval with the onset of late-Transamazonian calc-alkaline volcanism and plutonism (2.05–1.88 Ga) south of the Guiana Shield.