Tectonic analysis of a mining district; Pachuca, Mexico

Abstract

An ore guide is generally a combination of structure, mineral assemblage and host rock which suggests an outer portion, whether top, side, or bottom, of a setting enclosing an ore body.Such a guide is empirical if the reason for its acceptance as a guide lies in the fact that ore has been found elsewhere in settings that look similar to the one in question, and so long as the underlying reasons for the preference shown by known ore for such settings are not understood. Use of empirical ore guides far from known ore is dangerous, for an ore setting in one district may have a meaning quite different from that of a similar-looking setting in another district.Ore settings seen today are inert, but the history of ore formation is one of dynamic events: the ore solutions moved along their channels to the place where they deposited their load, and the walls of the fracture within which the ore body deposited often moved also, at the time the ore body was being deposited within them.Deciphering this dynamic record, dominated as it was in many cases by tectonics, may be called tectonic analysis. The Pachuca silver district is used as an example of the use of this tool in exploration; but while knowledge of Pachuca tectonics has been painfully acquired over many years, an attractive possible application of tectonic analysis lies in the speedy evaluation of virgin districts.