Résumé
The Yaou deposit, located in French Guiana within the Guiana Shield, is hosted by the Paramaca Paleoproterozoic greenstone belt. The deposit displays multiple intrusive bodies aligned along a shear zone. The local deformation stages show a progressive evolution from the ductile regime to the brittle one. The D-1/2 event is responsible for the main penetrative foliation with associated ductile veining while the D-3 phase is related to a sinistral shearing. An intrusive event affects the district and is identified as being syn-D-3. The following phase D-4 represents a transitional to brittle veining set located preferentially within intrusive bodies and along the shear zone. A local D-5 brecciation event is offsetting the D-4 veins and is overprinted by late D-5 veinlets. A multi-stage model for the formation of the gold mineralization is presented focusing on gold-bearing pyrite. At the macroscopic scale, the gold mineralization is polyphased with the D-3 shearing and the D-4 brittle events being auriferous. A total of 6 generations of pyrite are defined. Results of in situ analyses using LA-ICP-MS on pyrite show that pyrite Py-3 exhibits an Au-As correlation with a cobalt and arsenic rhythmic zonation. Diagenetic pyrite Py-0 are a potential primary source of submicroscopic gold having a low contribution to the total budget. Pyrite Py-3 shows some gold content due to remobilization of Au-D0. Gold in pyrite Py-4 is found as submicroscopic gold, as micro-inclusions and as infilling fractures in association with other elements such as Te, Ag and Bi. Most contribution to the Au system is from micro-inclusions and relatively few from both free gold and submicroscopic. Pyrite Py-5 shows some late remobilization.