The Vancouver miner says it has finalized the transaction, paying US$4.5 million for the Cerro Prieto project in Sonora state as planned.
But the two companies have also agreed on an amended and restated debt assignment and share purchase agreement, which includes a quarterly production royalty payment made to Oroco.
Goldgroup also says it will begin small-scale trial mining and leaching in the fourth quarter to determine the ideal parameters to put the project into production in 2014.
Cerro Prieto is located in northern Sonora state, with mineral concessions in an area of about 7,000 hectares.
Goldgroup is a miner active in Mexico with a portfolio that includes its 100 per cent owned advanced stage gold development project Caballo Blanco in Veracruz state and a 50 per cent interest in DynaResource de Mexico, S.A. de C.V., which owns 100 per cent of the San Jose de Gracia gold exploration project in Sinaloa state. The company also owns and operates the Cerro Colorado gold mine in Sonora.
Besides Cerro Prieto, Vancouver-based Oroco has the 193-hectare Xochipala property in Mexico's Guerrero state.