28-2 Petro-tectonic evolution along the eastern margin of the Gulf of California in Sonora: Linking magmatic plumbing systems and oblique rift tectonics

Session: Recent Advances in the Gulf of California Oblique Rift: Offshore and Onshore Studies // Avances Recientes en el Rift Oblicuo del Golfo de California: Estudios Marinos y Terrestres (Part I)

Presenting Author:

Jesus VIDAL-SOLANO

Authors:

VIDAL-SOLANO, Jesus Roberto¹, Velderrain-Rojas, Luis Alonso², Gomez-Valencia, Alejandra Marisela³, Piña, Adriana⁴, Stock, Joann M.⁵, Paz-Moreno, Francisco A.⁶

(1) Departamento de Geología, Universidad de Sonora, HERMOSILLO, Sonora, Mexico, (2) Departamento de Geología, Universidad de Sonora, Hermosillo, Sonora, Mexico; Departamento de Ingeniería Civil y Minas, Universidad de Sonora, Hermosillo, Sonora, Mexico, (3) Departamento de Ingeniería Civil y Minas, Universidad de Sonora, Hermosillo, Sonora, Mexico, (4) CalTech University, Pasadena, CA, USA, (5) California Institute of Technology, Pasadena, CA, USA, (6) Universidad de Sonora, Departamento de Geología, Hermosillo, Sonora, Mexico,

Abstract:

The eastern margin of the Gulf of California in coastal Sonora (NW Mexico) preserves silicic-to-mafic volcanic and subvolcanic plumbing systems that developed in the Late Miocene during the onset of the oblique-divergent Pacific–North America plate boundary. Here we integrate geological constraints with petrographic, geochemical, and geochronological datasets compiled over ~25 years of onshore studies to evaluate the distribution, petrogenesis, and tectonic significance of volcanic complexes emplaced during transtensional faulting prior to full Gulf opening. Volcanic and subvolcanic suites show a broadly co-magmatic relationship, with magmas sourced from a heterogeneous mantle previously modified by Farallon subduction and subsequently diversified by differentiation. Compositions span tholeiitic and calc-alkaline suites (locally with an adakitic component; Herrera-Acosta et al., this meeting), ultrapotassic (Gómez-Valencia et al., this meeting), and alkaline to transitional terms, including peralkaline manifestations; these features are consistent with AFC processes and variable crustal interaction. We show that episodic transtensional stress controlled magma evolution, ascent, and emplacement between ~12 and 9 Ma. In the southern sector, the sequence begins with evolved magmas producing ignimbrites and lavas, followed by shallow subvolcanic granophyres and interconnected dike-sill networks intruding earlier volcanic deposits. Progressive deformation promoted exhumation of silicic suites and the extrusion of less evolved magmas. Ultimately, westward migration of strike-slip fault systems linked to the Pacific-North America boundary, commonly associated with vertical-axis rotations in igneous complexes (Velderrain-Rojas et al., this meeting), terminated these onshore plumbing systems and shifted magmatism farther west. Beyond its regional relevance, this record illustrates how oblique rift tectonics shape plumbing-system architecture and helps contextualize the occurrence of young plutonic bodies in the Gulf of California within the broader transtensional evolution.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3, 2026

doi: 10.1130/abs/2026CD-13835

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