Ph.D. Thesis Proposal Presentation
Speaker: Maryam Shahabi Far
Title: Mineralogical and isotopic studies of the Marathon PGE-Cu deposit, Ontario
The unique physical and chemical behavior of platinum group elements (PGEs) makes them important for a wide variety of industrial and emerging technologies, including fuel production, engine emission control, catalysts, and communications. Economic concentrations of PGE in the extremely depleted silicate Earth are, however, rare. The largest and most significant PGE deposits around the world are associated with mafic or ultramafic intrusions. The Proterozoic Coldwell alkaline igneous complex, northwestern Ontario is a large intrusive body and hosts PGE-Cu deposits. The Marathon deposit, on the eastern margin of the complex, is hosted within the Two Duck Lake gabbro (TDLG) and comprises three principal zones of mineralization: 1. Footwall Zone, 2. Main Zone, and 3. W-Horizon. The Geordie Lake deposit is located in the north central part of the complex and is hosted by the Geordie Lake gabbro. The genesis of the Marathon and the Geordie Lake PGE-Cu deposits, as well as other contact-style, low sulfide PGE deposits remains a debatable subject. The PGE mineralization at both deposits has been previously suggested to be a result of both magmatic and hydrothermal processes. Elucidating a genetic model for the Marathon mineralization, and thus proposing exploration strategies for this type of deposition, is the focus of this study.
The following fundamental questions will be addressed: 1. How important was the relative proportion of magmatic versus fluid/volatile- related processes for PGE mineralization at the Marathon deposit? 2. What, if any, is the relationship between country rocks and metal precipitation? 3. What, if any, was the role of fluid-rock or fluid-melt interaction in PGE-Cu transportation and deposition? 4. What was the source(s) of fluid(s)/volatile(s) that have affected the deposition? 5. What, if any, is the petrogenetic link among the three mineralized zones, which are characterized by important geochemical and textural differences? 6. Although several similarities between the Marathon and Geordie Lake deposits have been reported, there are also some significant differences. What are the petrogenetic relationships between these two deposits, if any? High precision radiogenic isotopic studies using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS), in combination with a number of other analytical techniques, including quadrupole LA-ICP-MS, scanning electron microscopy (SEM), electron probe micro analysis (EPMA), and also optical microscopy, will be used to address the above-mentioned questions.