Research Mentor(s): Jackie Kleinsasser, PhD Candidate
Research Mentor School/College/Department: Earth and Environmental Sciences, College of Literature, Science, and the Arts
Presentation Date: Thursday, April 22, 2021
Session: Session 2 (11am – 11:50am)
Breakout Room: Room 15
The Duluth Complex is a series of rock formations in northeastern Minnesota that formed 1.1 billion years ago. On the southwestern side of the Complex, there are 14 different igneous intrusions containing minerals rich in iron and titanium, known as oxide-bearing ultramafic intrusions (OUIs). Although little is known about the genesis of these OUIs, there are many minerals present which can act as proxies to gain insight as to how they formed, such as olivine, a silicate mineral. Since olivine can have a range of compositions with varying amounts of iron and magnesium (from Mg2SiO4 to Fe2SiO4) and it is one of the first minerals to crystallize out of magma as it cools, we can discover a lot about the formation and emplacement these OUIs from its composition alone. Rock samples containing olivine were analyzed with microscopic techniques to find shapes and textures of formation. This analysis indicated that olivine forms in many shapes, such as tubular and trapezoidal in the Titac and ropy and striated in the Longnose. Chemical analysis indicated that the Longnose intrusion had more magnesium rich olivine, and the magnesium content increased with depth (from ~60-~70% Mg), while the Titac had higher amounts of magnesium at the top, but iron dominated lower in the intrusion (from ~60% Mg at the top; ~30% Mg at the bottom). These compositional differences give insight into the magma composition of the OUIs, and help us understand how they formed.