Abstract: The Deerni large Co-Cu deposit was mainly formed by submarine exhalative-sedimentation and also enriched by late-stage super imposed mineral ization.The superim posed mineralization is indicated by occurrence of Co orebodies in the shape of overshoes and pyrrhotite thin shell.Also, it is characterized by alteration, disappearance or purification of spar sely disseminated magnetite and participation of Ni in the contact sites of ore-bearing ultrabasic rocks and industrial or ebodies, with the criteria of Co overshoes and, All these pheno mena indicate that the ultrabasic rocks have made certain contribution to the mineralization of the Deerni deposit.