Slightly peraluminous to metaluminous leucogranites are common as dyke swarms in the Burguillos del Cerro Plutonic Complex. They show superimposed hydrothermal alterations consisting of quartzrich albitites and Au-bearing quartz veins. Several types of fluid Inclusions have been distinguished in the alteration. They belong to the system H20-NaCI-KCI-MgCI2-CaCI2 and range from high salinity to low salinity types. In any type, a trend of decreasing salinity concomitant to a decrease of minimum P and T trapping conditions is found. An evolutive model is proposed consisting in the repetitive mixing of hot saline waters, initially of probable magmatic derivation, with a cold low salinity meteoric fluid, in several discrete episodes of hydrofractunng, under declining regional temperature conditions. Albitites and quartz veins seem to be temporally and genetically related