2025 Undergraduate Research Showcase
Testing the Use of Zircon Chemistry to Infer Crustal Thickness in the Gangdese Arc, Southern Tibet
Document Type
Student Presentation
Presentation Date
4-15-2025
Faculty Sponsor
Dr. Matthew Kohn
Abstract
The Gangdese Arc spans the ~2000 km-long southern margin of the Tibetan Plateau and was formed between ~50 and 150 million years ago (Ma), when the Indian plate subducted beneath the Asian plate. Recent work (Tang et al., 2021; Geology) near Lhasa, Tibet, in the East-central part of the arc has used rare-earth element chemistry of zircon crystals in modern sediments to infer crustal thickness changes through time. They infer major pulses of magmatism at ~45-50 and ~65-90 Ma, and increases in crustal thickness between ~75-100 Ma and ~30-55 Ma. We tested Tang et al.’s interpretations by measuring zircon age and chemistry in sands collected near Lhasa and in an area ~1000 km to the west. All data show a major pulse of magmatism at ~45-50 Ma, but the older 75-100 Ma pulse is absent in the west. We find no consistent trends in zircon rare-earth element chemistry through time, rather (a) different magmatic centers have different zircon compositions, and (b) some zircon compositions correlate with Ti content, which is temperature-sensitive. Evidently, zircon chemistry depends on factors other than crustal thickness, including temperature.
Recommended Citation
Lopez, Armando and Kohn, Matthew, "Testing the Use of Zircon Chemistry to Infer Crustal Thickness in the Gangdese Arc, Southern Tibet" (2025). 2025 Undergraduate Research Showcase. 185.
https://scholarworks.boisestate.edu/under_showcase_2025/185