GOLD DISTRIBUTION IN THE MOBRUN VOLCANIC-ASSOCIATED MASSIVE SULFIDE DEPOSIT, NORANDA, QUEBEC - A PRELIMINARY EVALUATION OF THE ROLE OF METAMORPHIC REMOBILIZATION

The Mobrun Zn-Cu-Au-Ag orebodies show metal zonation typical of volcan ic-associated massive sulfide deposits, although some metamorphic remo bilization of metals has occurred. The nature and distribution of prim ary facies are the result of synvolcanic deposition and reworking of s ulfides by hydrothermal fluids. Secondary facies resulting from metamo rphism and deformation locally overprint primary facies and include tr ansgressive veins which contain remobilized Au as electrum. The distri bution of secondary facies was controlled by the mechanical properties of the mineralization as well as of the surrounding rocks; the mechan ical response of different facies to deformation influenced the develo pment and distribution of zones containing easily recoverable gold. Pr eservation of primary textures is best in the Main and Satellite lense s. The 1100 lens also shows significant preservation of primary facies ; however, development of secondary facies is pronounced. Textural, st ructural, and chemical evidence indicates that the 1100 lens was subje cted to more extreme metamorphic recrystallization and deformation tha n the other lenses. Metamorphic remobilization was important in releas ing refractory Au from sulfides and locally concentrating it in a reco verable form (electrum)