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Isotope geochemistry and petrogenesis of peralkaline middle Miocene ignimbrites from central Sonora; relationship with continental break-up and the birth of the Gulf of California

Jesus R. Vidal Solano, Henriette Lapierre, Joann M. Stock, Alain Demant, Francisco A. Paz Moreno, Delphine Bosch, Pierre Brunet and Andrea Amortegui
Isotope geochemistry and petrogenesis of peralkaline middle Miocene ignimbrites from central Sonora; relationship with continental break-up and the birth of the Gulf of California
Bulletin de la Societe Geologique de France (September 2008) 179 (5): 453-464

Abstract

Middle Miocene peralkaline ignimbrites constitute a specific geodynamic marker of the early stage of opening of the Gulf of California, preserved either in central Sonora or the Puertecitos area, in Baja California. Very uniform ages (12-12.5 Ma) obtained on these rocks show that this volcanic episode corresponds to a specific stage in the tectonic evolution of the proto-gulf area. Field observations and slightly different Sr and Nd isotopic signatures support eruptions from several small volume magma batches rather than from a large-volume caldera forming event. Isotopic ratios help to constrain the petrogenesis of the peralkaline liquids by fractional crystallization of transitional basalts in a shallow reservoir, with slight contamination by Precambrian upper crustal material. Less differentiated glomeroporphyritic icelandites erupted at about 11 Ma, mark an increase in the magma production rate and highlight an easier access to the surface, illustrating an advanced stage in the weakening of the continental crust. The tilting of the Middle Tertiary sequences results from a major change in the tectonic regime, from E-W extension giving rise to N-S grabens, to NNW-SSE strike-slip motion that can be related to the transfer of Baja California from North America to the Pacific plate. The location of peralkaline volcanism coincides with the southern edge of the Precambrian crust and the southernmost extension of the California slab window at 12.5 Ma.


ISSN: 0037-9409
EISSN: 1777-5817
Coden: BSGFAE
Serial Title: Bulletin de la Societe Geologique de France
Serial Volume: 179
Serial Issue: 5
Title: Isotope geochemistry and petrogenesis of peralkaline middle Miocene ignimbrites from central Sonora; relationship with continental break-up and the birth of the Gulf of California
Affiliation: Universidad de Sonora, Departamento de Geologia, Sonora, Mexico
Pages: 453-464
Published: 200809
Text Language: English
Summary Language: French
Publisher: Societe Geologique de France, Paris, France
References: 89
Accession Number: 2008-130672
Categories: Igneous and metamorphic petrologyIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. cols., 2 tables, geol. sketch maps
N26°30'00" - N32°30'00", W115°04'60" - W108°30'00"
Secondary Affiliation: Universite Joseph Fourier-Grenoble I, FRA, FranceCalifornia Institute of Technology, USA, United StatesUniversite de Montpellier II, FRA, FranceUniversite Paul Sabatier-Toulouse II, FRA, France
Country of Publication: France
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Societe Geologique de France. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200851
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