41 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 III)

This session highlights recent research on the Gulf of California–Salton Trough plate boundary from ~12 Ma to today. We welcome terrestrial and marine studies involving tectonics, basin analysis, volcanology, sedimentology, and more. English or Spanish.

Friday, 24 April 2026
1:30 PM - 5:30 PM
LMH, Fiesta Terrace Salon

Deciphering the origin of fumarolic fluids associated with the Pescadores fault, Sierra Cucapah, Baja California (Mexico)

Paper number: 41-5
Program: Technical Sessions
Time: 2:55 PM – 3:15 PM

Authors

  • Ivan Barea-Perez Presenting Author
    Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California (CICESE), Ensenada, Baja California
  • Claudio Inguaggiato
    Departamento de Geología, Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California (CICESE), Ensenada, Baja California
  • Loic Peiffer
    Departamento de Geología, Unidad La Paz, Centro de Investigación Científica y Educación Superior de Ensenada, Baja California (CICESE), La Paz, Baja California
  • John Fletcher
    Departamento de Geología, Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California (CICESE), Ensenada, Baja California, Mexico
  • Franco Tassi
    Dipartimento Scienze della Terra Università di Firenze, Firenze, Italy. , Firenze
  • Agnes Mazot
    GNS Science, Natural Hazards/Volcanology, Taupo

Abstract

A fumarole activated by the 7.2 El Mayor-Cucapah seismic event along a segment of the Pescadores fault in the Sierra Cucapha (Mexicali, Baja California), was investigated during two field surveys conducted in November 2022 and 2023. Temperature was measured inside the main vent, and sample fluids were collected to analyze the chemical and isotopic composition of gases and to identify their origin and relative influences of mantle and crust on their geochemistry. Moreover, we compare the results of the chemical and isotopic composition with other thermal fluids reported in Baja California, including Cerro Prieto and Salton Sea geothermal plants.

The fumarole fluids have a temperature of 99.7 ˚C and are predominantly composed of steam (~99 Vol.%), with CO2 as the main dry gas. Helium isotopes coupled with 4He/20Ne indicates a dominantly crustal radiogenic source (93.6%) with a minor mantle contribution up to 6.4%. Based on the δ13CCO2 values coupled to the CO2/3He ratios, the main source of the CO2 is the limestone, with a lesser contribution from organic-rich sediments. The δ13CCH4 and δDCH4 values indicate a thermogenic signature for the fumarole fluids, similar to the those reported in the Cerro Prieto and Salton Sea geothermal fields.

A comparison of Moho depths and mantle-derived helium proportion in Baja California show a close relationship between shallower Moho depths and higher proportions of mantle-derived helium, a relation best demonstrated in the Gulf Extensional Province (GEP). In contrast along the Baja California Microplate (BCM), where a deepest Moho had been reported, crustal derived radiogenic helium is the dominant source.

Based on the regional structural context and the magma aging model of the Pescadores fumarole, we support the hypothesis that mantle-derived helium in the fumarole may ascend through the intersection of the Pescadores fault and the Unnamed keystone fault.

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

doi: 10.1130/abs/2026CD-411016

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