72-2 Garnet Diffusion Chronometry Reveals Ultrafast Exhumation of the Subduction Mélange of Cedros Island, Baja California, Mexico
Session: Toe to Toe: Cordilleran Systems from Trench to Retroarc Domains (Posters)
Poster Booth No.: 262
Presenting Author:
Yiruo XuAuthors:
Xu, Yiruo1, Holder, Robert M.2, Neumann, Sam R.3, Connop, Charlotte4(1) Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA, (2) Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA, (3) Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA, (4) Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA,
Abstract:
Subduction mélanges, mixed fragments of subducted blocks in a fine-grained matrix, provide valuable constraints on how crustal and mantle materials move at the interface between the subducting slab and the overlying mantle wedge. The mechanism and timescale of their exhumation from great depths remain controversial. Cedros Island, Baja California, Mexico is composed of a late Jurassic–Cretaceous subduction mélange of various metamorphic grades tectonically emplaced beneath an ophiolite. Garnet grains in the garnet amphibolite blocks exhibit complex, sharply defined compositional zoning, requiring metamorphism and exhumation over a very short time scale. Using phase equilibria modeling and garnet diffusion chronometry, we show that garnet growth happened as discrete pulses during rapid compression and decompression by ~8 kbar, possibly due to local fluid overpressure. After peak metamorphism, the mélange cooled at approximately 10 °C/kyr, far exceeding the rates predicted by geodynamic models. Based on structural observations in the field, a possible explanation for such rapid cooling is exhumation by normal faulting and tectonic extrusion.
Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025
doi: 10.1130/abs/2025AM-7571
© Copyright 2025 The Geological Society of America (GSA), all rights reserved.
Garnet Diffusion Chronometry Reveals Ultrafast Exhumation of the Subduction Mélange of Cedros Island, Baja California, Mexico
Category
Topical Sessions
Description
Session Format: Poster
Presentation Date: 10/19/2025
Presentation Room: HBGCC, Hall 1
Poster Booth No.: 262
Author Availability: 3:30–5:30 p.m.
Back to Session