Submarine Deep‐Water Lava Flows at the Base of the Western Galápagos Platform
Abstract To investigate the initial phases of magmatism at the leading edge of the upwelling mantle plume, we mapped, photographed, and collected samples from two long, deep‐water lava flows located at the western base of the Galápagos Platform using the remotely operated vehicle Hercules. Lavas wer...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Wiley
2018-10-01
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| Series: | Geochemistry, Geophysics, Geosystems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2018GC007632 |
| _version_ | 1797685928364343296 |
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| author | Molly Anderson V. Dorsey Wanless Darin M. Schwartz Emma McCully Daniel J. Fornari Max P. Jones S. Adam Soule |
| author_facet | Molly Anderson V. Dorsey Wanless Darin M. Schwartz Emma McCully Daniel J. Fornari Max P. Jones S. Adam Soule |
| author_sort | Molly Anderson |
| collection | DOAJ |
| description | Abstract To investigate the initial phases of magmatism at the leading edge of the upwelling mantle plume, we mapped, photographed, and collected samples from two long, deep‐water lava flows located at the western base of the Galápagos Platform using the remotely operated vehicle Hercules. Lavas were recovered from four areas on the seafloor west of Fernandina volcano, including the western flow fronts of two deep‐water flows, heavily sedimented terrain between the two flows, and the eastern, shallower end of one flow. The sediment cover and morphologies are distinct between the western flow fronts and the eastern region based on seafloor imagery, suggesting that the long lava flows are not a single eruptive unit. Major and trace element concentrations reveal both tholeiitic and alkalic compositions and support the interpretation that multiple eruptive units comprise the deep‐water flows. Alkalic lavas have higher [La/Sm]N ratios (2.05–2.12) and total alkali contents (5.18–5.40) compared to tholeiitic lavas, which have [La/Sm]N ratios ranging from 1.64 to 1.68 and total alkali contents ranging from 3.07 to 4.08 wt%. Radiogenic isotope ratios are relatively homogeneous, suggesting a similar mantle source. We use petrologic models to assess three alternative mechanisms for the formation of the alkalic magmas: (1) high‐pressure crystallization of clinopyroxene, (2) mixing of high silica and mafic magmas, and (3) variable extents of melting of the same mantle source. Our modeling indicates that the alkalic samples form from lower extents of melting compared to the tholeiitic lavas and suggests that the deep‐water alkalic lavas are analogous to the initial, preshield building phase observed south of Hawaii and at the base of Loihi Seamount. |
| first_indexed | 2024-03-12T00:58:18Z |
| format | Article |
| id | doaj.art-99a336b0d8064142af4263778157a859 |
| institution | Directory Open Access Journal |
| issn | 1525-2027 |
| language | English |
| last_indexed | 2024-03-12T00:58:18Z |
| publishDate | 2018-10-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj.art-99a336b0d8064142af4263778157a8592023-09-14T11:39:59ZengWileyGeochemistry, Geophysics, Geosystems1525-20272018-10-0119103945396110.1029/2018GC007632Submarine Deep‐Water Lava Flows at the Base of the Western Galápagos PlatformMolly Anderson0V. Dorsey Wanless1Darin M. Schwartz2Emma McCully3Daniel J. Fornari4Max P. Jones5S. Adam Soule6Department of Geosciences Boise State University Boise ID USADepartment of Geosciences Boise State University Boise ID USADepartment of Geosciences Boise State University Boise ID USADepartment of Geosciences Boise State University Boise ID USAGeology and Geophysics Department Woods Hole Oceanographic Institution Woods Hole MA USAGeology and Geophysics Department Woods Hole Oceanographic Institution Woods Hole MA USAGeology and Geophysics Department Woods Hole Oceanographic Institution Woods Hole MA USAAbstract To investigate the initial phases of magmatism at the leading edge of the upwelling mantle plume, we mapped, photographed, and collected samples from two long, deep‐water lava flows located at the western base of the Galápagos Platform using the remotely operated vehicle Hercules. Lavas were recovered from four areas on the seafloor west of Fernandina volcano, including the western flow fronts of two deep‐water flows, heavily sedimented terrain between the two flows, and the eastern, shallower end of one flow. The sediment cover and morphologies are distinct between the western flow fronts and the eastern region based on seafloor imagery, suggesting that the long lava flows are not a single eruptive unit. Major and trace element concentrations reveal both tholeiitic and alkalic compositions and support the interpretation that multiple eruptive units comprise the deep‐water flows. Alkalic lavas have higher [La/Sm]N ratios (2.05–2.12) and total alkali contents (5.18–5.40) compared to tholeiitic lavas, which have [La/Sm]N ratios ranging from 1.64 to 1.68 and total alkali contents ranging from 3.07 to 4.08 wt%. Radiogenic isotope ratios are relatively homogeneous, suggesting a similar mantle source. We use petrologic models to assess three alternative mechanisms for the formation of the alkalic magmas: (1) high‐pressure crystallization of clinopyroxene, (2) mixing of high silica and mafic magmas, and (3) variable extents of melting of the same mantle source. Our modeling indicates that the alkalic samples form from lower extents of melting compared to the tholeiitic lavas and suggests that the deep‐water alkalic lavas are analogous to the initial, preshield building phase observed south of Hawaii and at the base of Loihi Seamount.https://doi.org/10.1029/2018GC007632submarine volcanismGalápagosalkalic magmatismmantle plumemantle melting, radiogenic isotopes |
| spellingShingle | Molly Anderson V. Dorsey Wanless Darin M. Schwartz Emma McCully Daniel J. Fornari Max P. Jones S. Adam Soule Submarine Deep‐Water Lava Flows at the Base of the Western Galápagos Platform Geochemistry, Geophysics, Geosystems submarine volcanism Galápagos alkalic magmatism mantle plume mantle melting, radiogenic isotopes |
| title | Submarine Deep‐Water Lava Flows at the Base of the Western Galápagos Platform |
| title_full | Submarine Deep‐Water Lava Flows at the Base of the Western Galápagos Platform |
| title_fullStr | Submarine Deep‐Water Lava Flows at the Base of the Western Galápagos Platform |
| title_full_unstemmed | Submarine Deep‐Water Lava Flows at the Base of the Western Galápagos Platform |
| title_short | Submarine Deep‐Water Lava Flows at the Base of the Western Galápagos Platform |
| title_sort | submarine deep water lava flows at the base of the western galapagos platform |
| topic | submarine volcanism Galápagos alkalic magmatism mantle plume mantle melting, radiogenic isotopes |
| url | https://doi.org/10.1029/2018GC007632 |
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