Mississippi Valley-type lead-fluorite-barite deposits of the Hansonburg mining district, New Mexico
— Putnam, Borden R., III, David I. Norman, and Robert W. Smith

Genetic models for Mississippi Valley-type deposits have long been discussed. A wide variety of models have been hotly debated (Brown, 1967); examples are the early-diagenetic model of Davis (1977) and ideas postulating ore deposition from two fluids (Ohle, 1980).The pioneering work by White (1958) and others suggests the active involvement of basinal, connate brines in the transport of metals. An enigma concerning Mississippi Valley-type deposits is the size of the districts and the uniform style of mineralization within the district. In this, the Hansonburg district is no different. It is 5 km long with virtually identical mineralization over the entire district. Similar mineralization (galena, fluorite, and barite) occurs sporadically along the entire Rio Grande rift in New Mexico.

The mineralization of the Hansonburg deposit was studied in detail in order to obtain sufficient data to form a coherent genetic model for a Mississippi Valley-type deposit. The study consisted of microther-mometry and microanalysis of fluid inclusions from minerals in paragenetic sequence from several deposits in the Hansonburg district. Thermodynamic calculations based upon the analyses yielded pH, foe, and fs, of the mineralizing solutions. These, coupled with field