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.

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Apr 10th, 10:00 AM Apr 10th, 11:30 AM

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