38 Plate Boundary Evolution and Lithospheric Dynamics of Western North America (Posters)

We invite presentations on Cenozoic tectonics, volcanism, sedimentation, and geohazards offshore and along the margin of western North America. Example topics include crustal structure, mantle processes, triple-junction migration, paleomagnetism, active faulting, marine stratigraphy, and seismicity.

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

Internal Structure and Magma Interaction in a Syn-Extensional Miocene Plutonic Suite: Field and Magnetic Constraints from Puerta del Sol, Central Sonora, Mexico

Paper number: 38-1
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Syn-extensional Miocene intrusive rocks are widely exposed in the Puerta del Sol area, central Sonora. These Miocene intrusions are composed mainly of gabbroic bodies, with subordinate felsic intrusive rocks. The intrusive suite displays pronounced internal heterogeneity at the outcrop scale. Although the main intrusive body can be broadly classified as a gabbro based on its plagioclase-rich mineralogy, field observations reveal significant spatial variations in texture, structure, and magmatic fabrics. Distinct domains within the intrusive body include zones characterized by magmatic foliation, areas rich in mafic enclaves of variable textures and mineralogy, and sectors showing evidence of magma mingling and interaction. Mafic enclaves vary in shape and distribution, ranging from angular bodies with sharp, planar contacts to abundant globular or cuspate enclaves with irregular, lobate margins. In several localities, mafic material occurs as schlieren-like structures or elongated lenses that define flow strucures. These features suggest interaction between compositionally distinct magmas that were coevally in a plastic state but did not fully homogenize. The gabbroic intrusion is locally cut by mafic dikes, as well as by aplitic dikes, indicating multiple intrusive pulses. Structural measurements of magmatic foliation and associated field fabrics document internal organization within the pluton. Bulk magnetic susceptibility values range from ~1.8 × 10⁻⁴ to 2.3 × 10⁻³, indicating variable magnetic mineral content across the intrusive body and showing its heterogeneous character. Finally, a study of anisotropy of magnetic susceptibility (AMS) aims to constrain magma flow patterns and emplacement mechanisms. Together, field relationships, structural data, and magnetic properties highlight the Puerta del Sol intrusion as a key example of syn-extensional Miocene plutonism in central Sonora and provide a framework for understanding magma dynamics during continental extension.

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

doi: 10.1130/abs/2026CD-410915

© Copyright 2026 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.