Batholith-hosted polyphase gold mineralization at the Brothers project, eastern Suriname

Abstract

The gold mineralization at the Brothers Project, located in eastern Suriname, is hosted by a large tonalitic batholith, emplaced during the Transamazonian orogenic cycle (2260–1950 Ma) and spatially associated with the Marowijne greenstone belt of the Guiana Shield. A multiscale, field-based approach from district to drill core scale was used to study the deformation history, the geometry and spatial distribution of intrusion-hosted, ENE-striking shear zones and associated gold-bearing quartz veins. At the drill core scale, this orogenic gold deposit recorded a polyphase deformation history dominated by a progressive ductile deformation stage D1BR, associated with both shearing and folding that is locally overprinted by a late brittle deformation stage D2BR. Within this structural framework a complex vein system is preserved with syn-shearing tension-vein arrays, massive-laminated fault-fill veins, and post-shearing extensional veins. Two main gold events are related to syn- and post-shearing pyritization (Py1a and Py2). At the camp scale, multiple ENE-striking steeply dipping strike-slip to reverse oblique-slip shear zones occur within the rigid batholith. These gold-bearing structures contain oblique to subvertical ore shoots. At the district scale, identified gold trend distribution and LiDAR-aeromagnetic-based structural patterns highlight that auriferous target zones are located at the intersection between ENE-striking shear zones and NNW-striking brittle structures, that correspond to zones of enhanced permeability and thus intense hydrothermal activity recorded by different vein systems. Analogies with other Paleoproterozoic intrusion-hosted gold deposits of the Guiana Shield and the West African craton show that the central parts of large intrusive complexes can host significant gold mineralization related to orogenic events.