37 Cordilleran Margin Evolution and Supercontinent Tectonics: From Pangea Assembly to North American Orogenesis (Posters)

This session integrates tectonics, petrology, geochronology, stratigraphy, and paleontology to illuminate how Paleo-Pacific plates drove subduction dynamics, crustal evolution, and paleogeographic reconstructions across the complex geological architecture of the American Cordilleras.

Friday, 24 April 2026
8:00 AM - 5:30 PM
LMH, 5th Floor Chapel

Titanite ID-TIMS U-Pb Geochronology in Mylonites: A Direct Dating Approach for Ductile Deformation in the Chiapas Massif Complex, SE Mexico.

Paper number: 37-8
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The breakup of the Pangea supercontinent during the Mesozoic led to a reorganization of global tectonics. In eastern Mexico, this process was expressed by the motion of the Maya Block, which translated and rotated counterclockwise from a position adjacent to North America to its present position in southern Mexico during the Jurassic. This displacement was accommodated primarily by the East Mexico Transform Fault, a right-lateral structure that trends NNW from the Tamaulipas Coastal Plain to Chiapas. The Chiapas Massif Complex (CMC), located along the southern margin of the Maya Block, is closely linked to this tectonic episode and preserves evidence of ductile deformation associated with Maya Block translation and rotation. Recently, Jurassic ages were reported from monazite and zircon rims in mylonitized granites of the CMC, interpreted as reflecting the time of deformation in these bodies. However, the kinematics of these deformations and the direct linkage of the age to deformation remain unconstrained by an integrated structural and geochronologic approach.

Titanite, a common accessory mineral in CMC rocks, is a particularly suitable geochronometer for addressing this problem. It is notable for its ability to incorporate U and for its high closure temperature, which allows it to retain radiogenic Pb at temperatures below ~750 °C, thereby preserving the U-Pb isotopic system closed at medium-grade metamorphism. In addition, its sensitivity to variations in pressure–temperature conditions and differential stress promote key processes such as growth from precursor phases (ilmenite or rutile) and dynamic recrystallization, which in turn links the time of titanite crystallization with the time of deformation

In this contribution, we present preliminary results from structural geological mapping in the central–southern CMC, highlighting the discovery of significant ductile shear zones. We also present our progress in overcoming analytical challenges encountered during the implementation of U–Pb titanite geochronology by isotope dilution–thermal ionization mass spectrometry (ID-TIMS) in our laboratory (LEMITE) at the Departamento de Geología, CICESE. Finally, we present the first U–Pb titanite ages obtained from crystals separated from CMC mylonitic rocks.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3

doi: 10.1130/abs/2026CD-410864

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