Climax-type stockwork molybdenum mineralization records a pervasive, outward-directed movement of ore fluids from a central stock. Recently obtained lead, oxygen, and sulfur isotope data document this phenomenon. Both metals and sulfur are derived in toto from within the stock. Meteoric water and host rocks at upper crustal levels play no role in the ore-forming process. Rather, wallrocks have been chemically overwhelmed by material evolving from the stock complex.