Bulletin-65—Metallogenic Provinces of the Southwestern United States and Northern Mexico

By C. W. Burnham, 1959, 76 pp, 4 tables, 3 figs., 8 plates, 1 index.

Some of the metallogenic provinces of the southwestern U.S. and northern Mexico are defined by the geographic distribution of sulfophile trace elements in more than 500 samples of chalcopyrite and sphalerite from 172 mining districts.

Maps that show the geographic distribution of tin, silver, and the "combined metal content" in sphalerite, reveal three major belts of high trace-element content in the Southwest. These belts, which are here called the Eastern, Central, and Western metallogenic belts, are consistent in trend and position with a belt-like distribution of the major ore deposits of copper, gold, silver, and other metals. However, the deposits of a given metal tend to be concentrated in certain segments of the metallogenic belts; consequently, the metallogenic provinces, in the ordinary sense, are merely component parts of the larger belt-like features.

The metallogenic belts also are generally consistent in position and trend with the major tectonic features, although they don't appear to be closely related in time. Hence, it is suggested that both the metallogenic belts and the major tectonic features are the effects of a more fundamental cause, which perhaps is a combination of compositional heterogeneities and associated physical discontinuities in the deep-seated source regions of the ores.

This bulletin embodies, in part, the results of an investigation of the geographic distribution of trace or minor elements in two hypogene sulfide minerals, chalcopyrite and sphalerite. The investigation was undertaken mainly in an attempt to define quantitatively some metallogenic provinces in the southwestern US, as a knowledge of these features are of considerable value in the search for new ore deposits and associated geologic features. Especial emphasis is placed on a discussion of the results of the work, and an effort has been made to restrict speculation on the origin of the features that are described, for in the present state of knowledge gross speculation would serve little constructive purpose.