282 Crustal Petrology, Part II

This session explores various igneous and metamorphic processes that have shaped Earth’s crust. We welcome contributions from the micro- to macroscale, from the deep to shallow crust, and from field- to laboratory- to modeling-based.

Wednesday, 22 October 2025
1:30 PM - 5:30 PM
HBGCC, 216AB

Understanding Subduction Zone Rocks from Baja California, Mexico Using U-Pb Dating, QuiG, and ZiR

Paper number: 282-3
Program: Technical Sessions
Time: 2:10 PM – 2:25 PM

Authors

Abstract

Cedros Island contains a Mesozoic-aged subduction mélange containing rock of varying metamorphic grades, within which high-pressure, low-temperature samples were collected. We present temperatures of metamorphism determined by zirconium-in-rutile thermometry (ZiR), pressures at which garnet in our samples reached, determined by quartz-in-garnet barometry (QuiG), and U-Pb dates of rutile and titanite using LA-ICP-MS to assess when the metamorphic conditions that formed these rocks occurred. The ZiR measurements found temperatures ranging from  ~480 - ~630 °C, and the QuiG measurements resulted in pressures ranging from ~0.7 GPa to ~1.5 GPa.  The U-Pb dates for titanite range from 140 ± 15 Ma to 165 ± 17 Ma, while the rutile U-Pb analysis resulted in one date at 154.7 ± 6.1 Ma. These results can help us better constrain our current models of subduction with actual temperatures and pressures of subduction rocks and provide a snapshot of the tectonic regime of North America’s western margin during the Mesozoic.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-411967

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