Michael Di Maio, PhD
M. Di Maio1, L. Godfrey1, R. Mathur2
1Department of Earth and Planetary Sciences, Rutgers University,New Brunswick, New Jersey, USA
2Geology Department, Juniate, Pennsylvania, USA
The Medicine Bow and Sierra Madre ranges in Southern Wyoming host numerous historical copper and precious metal deposits. Mineralization across both ranges shares many geochemical and geophysical characteristics including structural controls, mineral associations, and, importantly, are located within the Mullen Creek Nash Fork (MCNF) shear zone, a boundary flanked by the Wyoming craton to the North and Early to Mid-Proterozoic lithologies to the south. Here we leverage copper isotope composition of stream and spring waters and geophysical surveys to identify promising areas for copper mineralization within the MCNF shear zone. Observations through mapping of one area in the Sierra Madre range revealed a zone of pervasive Fe rich metasomatism, secondary copper mineralization, and an alteration footprint consistent with multiple facies of metasomatic iron alkali-calcic (MIAC) systems. Further investigation of polished sections of samples via SEM-EDS revealed Cu sulfides, uraninite inclusions hosted in bladed hematite, and apatite hosted in magnetite-hematite matrices consistent with an IOA-IOCG group in the MIAC umbrella of deposits. Pb isotopes are utilized to evaluate metal source reservoirs and identify relationships with host rocks and magmatic suites within the region. Carbon and oxygen isotopes in vein hosted carbonate and secondary carbonate are employed to investigate the similarity to other deposits with analogous alteration footprints and help constrain the fluid source within this shear zone. Overall, these results highlight the importance of the MCNF shear zone as a conduit for metasomatic fluids and mineralization in the space created by brittle fractures. This study highlights the potential for mineral exploration and understanding of historical mining in this region and similar tectonic systems.