Cobalt in sphalerite – Central mining district, New Mexico: Supplement 11 from 'Trace elements in sulfide minerals from the Central Mining District, New Mexico and the Bingham Mining District, Utah' (Thesis)

A total of 143 samples of chalcopyrite, 230 samples of sphalerite, and a few samples of other hydrothermal minerals from the Central and Pinos Altos mining districts of New Mexico, and the Bingham mining district of Utah, have been analyzed spectrographically for trace element content. Most of the sphalerites have also been analyzed for iron content by an x-ray fluorescence method. For many elements, variations within single crystals and within mines show no correlation with variations of other elements in the sulfides, indicating that several factors, not temperature alone, are of importance in determining the trace element content of sulfides. Changes in the composition of the hydrothermal fluid with time and position are believed to be the most important causes of variations in the sulfides, but temperature and lack of equilibrium are also believed to be significant. In the chalcopyrite and sphalerite from both districts the trace element contents are found to fall readily into two or more groups as defined by trace element content. The groups can generally be distinguished geographically and also show geologic and mineralogic differences, although enough similarities exist among groups in the Central mining district to conclude that temperature and other environmental factors are not the primary cause for the grouping, but that the differences probably existed in the hydrothermal fluids before they reached the site of deposition. The trace element content of sphalerite from the Central mining district shows a poorly developed but distinct lateral zoning away from the Hanover-Fierro and Santa Rita stocks. This zoning in trace element content is accompanied by an increase in the Pb/Zn ratio and an increase in the average silver content of the ores. A similar zoning may exist in the trace element content of chalcopyrite from this district and in the trace element content of sphalerite from the Bingham mining district. In addition, a poorly developed vertical zoning in the trace element content of sphalerite ...