Alkaline sulfide oxidation process for treating refractory sulfide ore particles enriched in a metal to be recovered wherein refractory sulfide ore particles are submitted to at least 3 stages in each of which said refractory sulfide ore particles are oxidized in surface by an oxidizing agent in an alkaline oxidation step (CSTR) in alkaline liquid phase and form an alkaline slurry containing surface oxidized refractory sulfide ore particles and in each of which said alkaline slurry is further submitted to a mechanical activation step for removing from the surface oxidized refractory sulfide ore particles at least partly a surface layer containing oxidized matter, said mechanical activation forming a mechanically activated slurry containing oxidized matter, refractory sulfide ore particles from which oxidized matter has been removed, alkaline liquid phase and liberated metal to be recovered by further processing or returned to a next or a previous alkaline oxidation step, said alkaline liquid phase containing calcium hydroxide as alkaline agent and said refractory ore being gold refractory sulfide ore or concentrate such as gold-containing pyrite ore or concentrate, gold containing arsenopyrite ore or concentrate, copper sulfide ore or concentrate, nickel sulfide ore or concentrate, zinc sulfide ore or concentrate or cobalt sulfide ore or concentrate and combined metal sulfide ore or concentrate such as low grade copper-gold sulfide ores or concentrates, characterized in that said at least 3 stages comprising: • a series of n alkaline oxidation steps in a series of n reactors (CSTR), each n th alkaline oxidation forming a n th alkaline slurry, where n is an integer comprised between 3 and 10, preferably between 4 and 8, more preferably between 5 and 7, • a series of x mechanical activation steps, each mechanical activation step being a mechanical activation of said n th alkaline slurry, where x is an integer, equal or lower than n, and comprised between 3 and 10, preferably between 4 and 8, more preferably between 5 and 7, wherein said series of n alkaline oxidation steps comprises at least: • a first alkaline oxidation step where said refractory ore particles enriched in a metal to be recovered are fed into an agitated reactor and form a first alkaline slurry, • at least one intermediate alkaline oxidation step fed with one alkaline slurry from a previous alkaline oxidation step, • a last alkaline oxidation step being said n th alkaline oxidation step fed with one alkaline slurry from a previous alkaline oxidation step, said series of x mechanical activation steps comprising at least: • a first mechanical activation step of said first alkaline slurry in a first mechanical activation means to form a first mechanically activated slurry, • at least one intermediate mechanical activation step of a n th alkaline slurry with said n th alkaline slurry being comprised between a 2 nd alkaline slurry and a (x-1) th alkaline slurry in a y th mechanical activation means to form a y th mechanically activated slurry, • a last mechanical activation step of said last alkaline slurry being said x th mechanical activation step in a x th mechanical activation means to form a x th mechanically activated slurry. • a series of n alkaline oxidation steps in a series of n reactors (CSTR), each n th alkaline oxidation forming a n th alkaline slurry, where n is an integer comprised between 3 and 10, preferably between 4 and 8, more preferably between 5 and 7, • a series of x mechanical activation steps, each mechanical activation step being a mechanical activation of said n th alkaline slurry, where x is an integer, equal or lower than n, and comprised between 3 and 10, preferably between 4 and 8, more preferably between 5 and 7, • a first alkaline oxidation step where said refractory ore particles enriched in a metal to be recovered are fed into an agitated reactor and form a first alkaline slurry, • at least one intermediate alkaline oxidation step fed with one alkaline slurry from a previous alkaline oxidation step, • a last alkaline oxidation step being said n th alkaline oxidation step fed with one alkaline slurry from a previous alkaline oxidation step, • a first mechanical activation step of said first alkaline slurry in a first mechanical activation means to form a first mechanically activated slurry, • at least one intermediate mechanical activation step of a n th alkaline slurry with said n th alkaline slurry being comprised between a 2 nd alkaline slurry and a (x-1) th alkaline slurry in a y th mechanical activation means to form a y th mechanically activated slurry, • a last mechanical activation step of said last alkaline slurry being said x th mechanical activation step in a x th mechanical activation means to form a x th mechanically activated slurry.