U-Pb and 40Ar/39Ar geochronology of the coastal Sonora batholith: New insights on Laramide continental arc magmatism
The coastal Sonora batholith comprises a series of Cretaceous granitoids that intruded a metasedimentary basement of possible Mesozoic age. They are partially covered by Tertiary volcanic flows and pyroclastic rocks. In order to elucidate the crystallization and cooling history of the granitoids, n...
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Universidad Nacional Autónoma de México
2018-01-01
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| Series: | Revista Mexicana de Ciencias Geológicas |
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| Online Access: | https://rmcg.unam.mx/index.php/rmcg/article/view/661 |
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| author | Ernesto Ramos-Velázquez Thierry Calmus Victor Valencia Alexander Iriondo Martín Valencia-Moreno Hervé Bellon |
| author_facet | Ernesto Ramos-Velázquez Thierry Calmus Victor Valencia Alexander Iriondo Martín Valencia-Moreno Hervé Bellon |
| author_sort | Ernesto Ramos-Velázquez |
| collection | DOAJ |
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The coastal Sonora batholith comprises a series of Cretaceous granitoids that intruded a metasedimentary basement of possible Mesozoic age. They are partially covered by Tertiary volcanic flows and pyroclastic rocks. In order to elucidate the crystallization and cooling history of the granitoids, nine rock samples were collected from Bahía Kino to Punta Tepopa. Eight samples dated by U-Pb zircon geochronology show that the Coastal Sonora batholith was emplaced during the Late Cretaceous, between
90.1 ± 1.1 and 69.4 ± 1.2 Ma. The interval of ~20 Ma between the different stages of crystallization indicate that magmatism was relatively static within coastal Sonora, although the magmatic arc recorded an eastward migration as a whole during Cretaceous and Paleogene. In addition, three of these samples were also dated by 40Ar/39Ar in biotite and K-feldspar separates. Ages vary from ~74 to 67 Ma in biotite and from ~68 to 42 Ma in K-feldspar. We interpret these ages as the cooling progression of the batholith, associated with exhumation of the region before the Basin and Range extension. Furthermore, these results show a local trend towards younger ages to the north of the batholith, and they are in good agreement with the model of a general eastward migration of the Cretaceous-Tertiary magmatic arc in northwestern Mexico. In general, the available ages suggest that the arc moved slowly across Baja California between 140 and 105 Ma, and continued its eastward migration across the eastern portion of Baja California and Sonora between 105 and ~60 Ma. According to the isotopic ages, the Coastal Sonora batholith would be the westernmost part of the Laramide magmatic event (~90 – 40 Ma). Thus, on the basis of new and available geochronologic, petrographic, and geochemical data, we propose that the Coastal Sonora batholith and the eastern portion of the Peninsular Ranges batholith belong to a single magmatic arc, which was separated during the continental breakup and rifting of the Gulf of California in the Tertiary.
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| format | Article |
| id | doaj-art-1444b95c7ace46c49436ee7bbcf264b4 |
| institution | OA Journals |
| issn | 1026-8774 2007-2902 |
| language | English |
| publishDate | 2018-01-01 |
| publisher | Universidad Nacional Autónoma de México |
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| series | Revista Mexicana de Ciencias Geológicas |
| spelling | doaj-art-1444b95c7ace46c49436ee7bbcf264b42025-08-20T02:32:41ZengUniversidad Nacional Autónoma de MéxicoRevista Mexicana de Ciencias Geológicas1026-87742007-29022018-01-01252U-Pb and 40Ar/39Ar geochronology of the coastal Sonora batholith: New insights on Laramide continental arc magmatismErnesto Ramos-Velázquez0Thierry Calmus1Victor Valencia2Alexander Iriondo3Martín Valencia-Moreno4Hervé Bellon5Estación Regional del Noroeste, Instituto de Geología, Universidad Nacional Autónoma de México, Apartado Postal 1039, Hermosillo, Sonora, 83000, México. Universidad Autónoma de Baja California Sur, Departamento de Geología, Apartado Postal 19-B, La Paz, B.C.S., 23080, México.Estación Regional del Noroeste, Instituto de Geología, Universidad Nacional Autónoma de México, Apartado Postal 1039, Hermosillo, Sonora, 83000, México.University of Arizona, Department of Geosciences, Tucson, Arizona 85721, USA.Centro de Geociencias, Universidad Nacional Autónoma de México (UNAM), Campus Juriquilla 76230, Juriquilla, Querétaro, México. Department of Geological Sciences, University of Colorado at Boulder, Boulder, Colorado 80309, USA.Estación Regional del Noroeste, Instituto de Geología, Universidad Nacional Autónoma de México, Apartado Postal 1039, Hermosillo, Sonora, 83000, México.UMR 6538, Domaines Océaniques, IUEM, Université de Bretagne Occidentale, 6, Av. Le Gorgeu, BP 809, F-29285, Brest Cedex, France. The coastal Sonora batholith comprises a series of Cretaceous granitoids that intruded a metasedimentary basement of possible Mesozoic age. They are partially covered by Tertiary volcanic flows and pyroclastic rocks. In order to elucidate the crystallization and cooling history of the granitoids, nine rock samples were collected from Bahía Kino to Punta Tepopa. Eight samples dated by U-Pb zircon geochronology show that the Coastal Sonora batholith was emplaced during the Late Cretaceous, between 90.1 ± 1.1 and 69.4 ± 1.2 Ma. The interval of ~20 Ma between the different stages of crystallization indicate that magmatism was relatively static within coastal Sonora, although the magmatic arc recorded an eastward migration as a whole during Cretaceous and Paleogene. In addition, three of these samples were also dated by 40Ar/39Ar in biotite and K-feldspar separates. Ages vary from ~74 to 67 Ma in biotite and from ~68 to 42 Ma in K-feldspar. We interpret these ages as the cooling progression of the batholith, associated with exhumation of the region before the Basin and Range extension. Furthermore, these results show a local trend towards younger ages to the north of the batholith, and they are in good agreement with the model of a general eastward migration of the Cretaceous-Tertiary magmatic arc in northwestern Mexico. In general, the available ages suggest that the arc moved slowly across Baja California between 140 and 105 Ma, and continued its eastward migration across the eastern portion of Baja California and Sonora between 105 and ~60 Ma. According to the isotopic ages, the Coastal Sonora batholith would be the westernmost part of the Laramide magmatic event (~90 – 40 Ma). Thus, on the basis of new and available geochronologic, petrographic, and geochemical data, we propose that the Coastal Sonora batholith and the eastern portion of the Peninsular Ranges batholith belong to a single magmatic arc, which was separated during the continental breakup and rifting of the Gulf of California in the Tertiary. https://rmcg.unam.mx/index.php/rmcg/article/view/661geochronologyU-Pb40Ar/39ArCretaceous-Tertiary magmatic arcLaramideCoastal Sonora batholith |
| spellingShingle | Ernesto Ramos-Velázquez Thierry Calmus Victor Valencia Alexander Iriondo Martín Valencia-Moreno Hervé Bellon U-Pb and 40Ar/39Ar geochronology of the coastal Sonora batholith: New insights on Laramide continental arc magmatism Revista Mexicana de Ciencias Geológicas geochronology U-Pb 40Ar/39Ar Cretaceous-Tertiary magmatic arc Laramide Coastal Sonora batholith |
| title | U-Pb and 40Ar/39Ar geochronology of the coastal Sonora batholith: New insights on Laramide continental arc magmatism |
| title_full | U-Pb and 40Ar/39Ar geochronology of the coastal Sonora batholith: New insights on Laramide continental arc magmatism |
| title_fullStr | U-Pb and 40Ar/39Ar geochronology of the coastal Sonora batholith: New insights on Laramide continental arc magmatism |
| title_full_unstemmed | U-Pb and 40Ar/39Ar geochronology of the coastal Sonora batholith: New insights on Laramide continental arc magmatism |
| title_short | U-Pb and 40Ar/39Ar geochronology of the coastal Sonora batholith: New insights on Laramide continental arc magmatism |
| title_sort | u pb and 40ar 39ar geochronology of the coastal sonora batholith new insights on laramide continental arc magmatism |
| topic | geochronology U-Pb 40Ar/39Ar Cretaceous-Tertiary magmatic arc Laramide Coastal Sonora batholith |
| url | https://rmcg.unam.mx/index.php/rmcg/article/view/661 |
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