A computer-derived graph of a development of deposits of twelve nonferrous metals in geological time is presented. It is based on a file containing over 5000 ore deposits, districts, and metalliferous areas of the world.The sequence of depositional ages based on ore deposits presently outcropping on the earth's surface is, from the oldest to the youngest, Cr, Ni–Au–Cu, Zn–Pb, Ag–Sn, W, Sb, Mo–Hg. Although this sequence parallels several evolutionary trends involved in the formation of the earth's crust, it is believed and semiquantitatively demonstrated that depth of denudation rather than evolution is the more important factor; in other words, the conditions of preservation have had greater influence on the age relationships of ore deposits outcropping on the present earth's surface than have the conditions of formation and their progressive evolution in the earth's history.

You do not currently have access to this article.