Metallogenic Provinces of the Southwestern United States and Northern Mexico

metallogenic provinces, chalcopyrite, sphalerite, molybdenum, silver deposits, lead deposits, gold deposits, copper deposits, zinc deposits, tungsten deposits

Burnham, C. Wayne ; Noble, James A. (advisor)

University:California Institute of Technology

Department:Geological and Planetary Sciences

关键词: metallogenic provinces, chalcopyrite, sphalerite, molybdenum, silver deposits, lead deposits, gold deposits, copper deposits, zinc deposits, tungsten deposits;   

Others  :  https://thesis.library.caltech.edu/9332/1/Burnham_cw_1955.pdf

美国|英语

来源: Caltech THESIS

【 摘 要 】

Some of the metallogenic provinces of the southwestern UnitedStates and northern Mexico are defined by the geographic distributionof trace elements in the primary sulfide minerals chalcopyrite andsphalerite. The elements investigated include antimony, arsenic,bismuth, cadmium, cobalt, gallium, germanium, indium, manganese,molybdenum, nickel, silver, tellurium, thallium, and tin. Of theseelements, cobalt, gallium, germanium, indium, nickel, silver, and tinexhibit the best defined geographic distribution.

The data indicate that chalcopyrite is the preferred host for tinand perhaps molybdenum; sphalerite is the preferred host for cadmium,gallium, germanium, indium, and manganese; galena is the preferred hostfor antimony, bismuth, silver, tellurium, and thallium; and pyrite isthe preferred host for cobalt, nickel, and perhaps arsenic. With respectto the two minerals chalcopyrite and sphalerite, antimony, arsenic,molybdenum, nickel, silver, and tin prefer chalcopyrite; and bismuth,cadmium, cobalt, gallium, germanium, indium, manganese, and thalliumprefer sphalerite. This distribution probably is the result of the interactionof several factors, among which are these: the various radii ofthe elements, the association due to chemical similarities of the majorand trace elements, and the degree of ionic versus covalent and metalliccharacter of the metal-sulfur bonds in chalcopyrite and sphalerite. Thetype of deposit, according to a temperature classification, appears tobe of minor importance in determining the trace element content ofchalcopyrite and sphalerite.

A preliminary investigation of large single crystals of sphaleriteand chalcopyrite indicates that the distribution within a single crystalof some elements such as cadmium in sphalerite and indium and silver inchalcopyrite is relatively uniform, whereas the distribution of someother elements such as cobalt and manganese in sphalerite is somewhatless uniform and the distribution of tin in sphalerite is extremelyerratic. The variations in trace element content probably are duelargely to variations in the composition of the fluids during the growthof the crystals, but the erratic behavior of tin in sphalerite perhaps isrelated to the presence of numerous cavities and inclusions in the crystalstudied.

Maps of the geographic distribution of trace elements in chalcopyriteand sphalerite exhibit three main belts of greater than average traceelement content, which are called the Eastern, Central, and Western belts.These belts are consistent in trend and position with a beltlike distributionof copper, gold, lead, zinc, silver, and tungsten deposits and withmost of the major tectonic features. However, there appear to be nodefinite time relationships, for as many as four metallogenic epochs,from Precambrian to late Tertiary, are represented by ore deposits withinthe Central belt.

The evidence suggests that the beltlike features have a deep seatedorigin, perhaps in the sub-crust or outer parts of the mantle, and thatthe deposits within each belt might be genetically related through abeltlike compositional heterogeneity in the source regions of the ores.Hence, the belts are regarded as metallogenic provinces.