Gustavo Marchant Allende
MIT Department: Earth, Atmospheric and Planetary Sciences
Faculty Mentor: Nicole Nie
Research Supervisor: Zhaoqiu Lin
Undergraduate Institution: Macalester College
Hometown: Santiago, Chile
Website: Intern’s Website, LinkedIn
Biography
Gustavo Marchant Allende is a rising senior at Macalester College, majoring in Geology and minoring in Statistics. He conducted research under Dr. Emily First in 2023, investigating the petrogenesis of lunar Ti-rich pyroclastic samples collected by the Apollo 17 mission. Currently, he works with Dr. Nicole Nie at MIT, exploring the geochemical characteristics of spinel lherzolites to understand mid-ocean ridge basalt (MORB) magmatism. He is building a chemical diffusion profile of iron-magnesium exchange to explore the role of diffusion during the ascent history of mantle-derived magmas. Gustavo’s interests lie in the geochemistry and petrology of the Earth’s upper mantle and its relation to the oceanic crust. He hopes to pursue a Ph.D. in Earth and Planetary Sciences, also exploring connections between Earth’s magmatism and other planetary bodies. Originally from Santiago, Chile, Gustavo is a United World College graduate, passionate about bikeable cities and international cuisines.
Abstract
Rock-melt diffusion in the upper mantle via a peridotite xenolith from the Tariat region, Mongolia
Gustavo Marchant Allende¹, Zhaoqiu Lin², Nicole Nie²
¹ Department of Geology, Macalester College
² Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts
Institute of Technology
Partial melting of the mantle to generate mid-ocean ridge basalts (MORBs) is a widely accepted, yet enigmatic, process. The Fe isotopic composition of MORBs indicates enrichment in heavier isotopes, contradicting the predictions of the established equilibrium partial melting model. We explore the role of chemical diffusion as a kinetic process, which might modify melts during their generation and transport. This study explores a peridotite xenolith from Mongolia’s Shavaryn-Tsaram basaltic outcrop (S-11), which could provide insights into this mantle-melt interaction. S-11 contains a contact zone of spinel lherzolite and a pyroxenite vein. Three thin sections of S-11 will be analyzed using a petrographic microscope for petrography and mineral modes. Major olivine, spinel, orthopyroxene, and clinopyroxene element compositions will be examined through scanning electron microscopy (SEM) and electron microprobe analysis (EMPA). A continuous chemical profile of iron-magnesium exchange along the melt-mantle boundary will be acquired to investigate the role of diffusion in the transportation of mantle-derived melts. Preliminary results suggest a redistribution of Al and Ca along the melt-mantle boundary. This points to a kinetic reaction rather than equilibrium crystallization. Continuous work will use diffusivity rates to estimate time scales of kinetic redistribution during melt generation and solidify our understanding of MORBs.
