Genesis of the Magenta Zone, Northmet Copper-Nickel-PGE Deposit, Minnesota
Location
CSU Ballroom
Start Date
10-4-2018 10:00 AM
End Date
10-4-2018 11:30 AM
Student's Major
Chemistry and Geology
Student's College
Science, Engineering and Technology
Mentor's Name
Steven Losh
Mentor's Department
Chemistry and Geology
Mentor's College
Science, Engineering and Technology
Description
The Magenta Zone is part of a large Cu-Ni-Platinum Group element deposit located in Northern Minnesota. The sulfide mineralization of the Magenta Zone cuts through existing igneous rock layering (e.g., Units 3, 4, 5, and 6). Previous research concluded the Magenta Zone did not form due to hydrothermal fluids reprecipitating sulfides in a discordant zone nor is it related to a dike that cuts across existing layers. We tested the hypothesis that the mineralization was caused by late magma that was injected into a partly-crystallized “mush” of mineral grains. If this magma were compositionally different from that which crystallized the older “mush”, we might expect to find compositional zoning in minerals, such as olivine, crystallized from that magma. Preliminary line-scan SEM data shows that there is little to no zoning of olivine grains, with might mean that the injected magma had the same composition as that associated with the “mush.” Because injection of sulfide-bearing magma might also produce variations in the ratio of Pd to Cu in sulfides that crystallized along its flow path (because Pd and Cu separate differently between magma and crystals), we examined numerous maps and cross sections through a 3D geochemical model of the deposit. These images show varying patterns of Pd/Cu ratios relative to faults that might have acted as conduits for the magma. We are continuing to obtain data that bear on the origin of this intriguing feature known as the Magenta Zone.
Genesis of the Magenta Zone, Northmet Copper-Nickel-PGE Deposit, Minnesota
CSU Ballroom
The Magenta Zone is part of a large Cu-Ni-Platinum Group element deposit located in Northern Minnesota. The sulfide mineralization of the Magenta Zone cuts through existing igneous rock layering (e.g., Units 3, 4, 5, and 6). Previous research concluded the Magenta Zone did not form due to hydrothermal fluids reprecipitating sulfides in a discordant zone nor is it related to a dike that cuts across existing layers. We tested the hypothesis that the mineralization was caused by late magma that was injected into a partly-crystallized “mush” of mineral grains. If this magma were compositionally different from that which crystallized the older “mush”, we might expect to find compositional zoning in minerals, such as olivine, crystallized from that magma. Preliminary line-scan SEM data shows that there is little to no zoning of olivine grains, with might mean that the injected magma had the same composition as that associated with the “mush.” Because injection of sulfide-bearing magma might also produce variations in the ratio of Pd to Cu in sulfides that crystallized along its flow path (because Pd and Cu separate differently between magma and crystals), we examined numerous maps and cross sections through a 3D geochemical model of the deposit. These images show varying patterns of Pd/Cu ratios relative to faults that might have acted as conduits for the magma. We are continuing to obtain data that bear on the origin of this intriguing feature known as the Magenta Zone.
Recommended Citation
Qualls, William. "Genesis of the Magenta Zone, Northmet Copper-Nickel-PGE Deposit, Minnesota." Undergraduate Research Symposium, Mankato, MN, April 10, 2018.
https://cornerstone.lib.mnsu.edu/urs/2018/poster-session-A/37
