Grain-scale and deposit-scale heterogeneity of Re distribution in molybdenite at the Bagdad porphyry Cu-Mo deposit, Arizona

Based on our current understanding of trace element incorporation during hydrothermal molybdenite growth, this evidently heterogeneous distribution of Re in molybdenite precludes the use of microprobe spot measurements of Re as a vector to mineralization, which was the original focus of this study. A follow-up analysis by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) using spot diameters of 150 μm reduced the observed intra-grain variability from 1.67 to 1 order of magnitude, but still failed to yield data that correlated with any known geological features. This suggests that any further work toward using molybdenite Re content as a vector to mineralization should either focus on whole-grain methods of analysis or else should use detailed microprobe mapping of molybdenite growth zones to guide point analyses, and then correlate the growth zones in molybdenite samples taken over distance through the deposit. This approach could help shed light on how the development of heterogeneous Re concentrations on the micro-scale relates to the processes of molybdenite precipitation and alteration.