Trace elements in solflde minerals from the Central district, New Mexico and the Bingham district, Utah

Abstract

Chalcopyrite and sphalerite (373 samples) from a variety of ore types in the Central district and the Bingham district have been analyzed spectrographically for trace element content. Both districts exhibit classic examples of hydrothermal deposits zonally related to intrusives. The following conclusions are reached: 1. (1) Solid diffusion at temperatures of 300–500°C is not effective in attaining a homogeneous distribution of trace elements, even over distances of a millimeter, as shown by variability of trace element content within single crystals and polished sections. 2. (2) Correlations of trace element content with textural and structural features, plus zoning within single crystals, show that the trace element content of the Sulfides being deposited changed with time. 3. (3) Several factors besides temperature are necessary to explain the lack of correlation between different trace elements. 4. (4) In both districts, the samples can be divided into two or more groups defined by trace element content, geographic location and geologic occurrence. The groups appear to result from deposition by separate surges of ore fluid differing in trace element content. The separate surges (analogous to the polyascendent ores of Kutina) may have been derived from the same source (magma?) at different stages of differentiation, or from separate sources. 5. (5) Within some groups, lateral and vertical zoning can be distinguished, although considerable variability of unknown origin is superimposed on the zoning, and numerous samples are necessary to confirm it. 6. (6) The partition of elements between sulfides shows no correlation with inferred temperature or with geologic features. It appears that the trace element content in coexisting sulfides in the two districts is generally not in equilibrium.