Geologic and Structural Evolution of the NE Lau Basin, Tonga: Morphotectonic Analysis and Classification of Structures Using Shallow Seismicity
The transition from subduction to transform motion along horizontal terminations of trenches is associated with tearing of the subducting slab and strike-slip tectonics in the overriding plate. One prominent example is the northern Tonga subduction zone, where abundant strike-slip faulting in the NE...
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Frontiers Media S.A.
2021-06-01
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| Series: | Frontiers in Earth Science |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/feart.2021.665185/full |
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| author | Melissa O. Anderson Chantal Norris-Julseth Kenneth H. Rubin Karsten Haase Mark D. Hannington Mark D. Hannington Alan T. Baxter Margaret S. Stewart |
| author_facet | Melissa O. Anderson Chantal Norris-Julseth Kenneth H. Rubin Karsten Haase Mark D. Hannington Mark D. Hannington Alan T. Baxter Margaret S. Stewart |
| author_sort | Melissa O. Anderson |
| collection | DOAJ |
| description | The transition from subduction to transform motion along horizontal terminations of trenches is associated with tearing of the subducting slab and strike-slip tectonics in the overriding plate. One prominent example is the northern Tonga subduction zone, where abundant strike-slip faulting in the NE Lau back-arc basin is associated with transform motion along the northern plate boundary and asymmetric slab rollback. Here, we address the fundamental question: how does this subduction-transform motion influence the structural and magmatic evolution of the back-arc region? To answer this, we undertake the first comprehensive study of the geology and geodynamics of this region through analyses of morphotectonics (remote-predictive geologic mapping) and fault kinematics interpreted from ship-based multibeam bathymetry and Centroid-Moment Tensor data. Our results highlight two notable features of the NE Lau Basin: 1) the occurrence of widely distributed off-axis volcanism, in contrast to typical ridge-centered back-arc volcanism, and 2) fault kinematics dominated by shallow-crustal strike slip-faulting (rather than normal faulting) extending over ∼120 km from the transform boundary. The orientations of these strike-slip faults are consistent with reactivation of earlier-formed normal faults in a sinistral megashear zone. Notably, two distinct sets of Riedel megashears are identified, indicating a recent counter-clockwise rotation of part of the stress field in the back-arc region closest to the arc. Importantly, the Riedel structures identified in this study directly control the development of complex volcanic-compositional provinces, which are characterized by variably-oriented spreading centers, off-axis volcanic ridges, extensive lava flows, and point-source rear-arc volcanoes. This study adds to our understanding of the geologic and structural evolution of modern backarc systems, including the association between subduction-transform motions and the siting and style of seafloor volcanism. |
| first_indexed | 2024-12-16T23:27:23Z |
| format | Article |
| id | doaj.art-a0883ddd797347388133e89bee5ffa2a |
| institution | Directory Open Access Journal |
| issn | 2296-6463 |
| language | English |
| last_indexed | 2024-12-16T23:27:23Z |
| publishDate | 2021-06-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Earth Science |
| spelling | doaj.art-a0883ddd797347388133e89bee5ffa2a2022-12-21T22:11:58ZengFrontiers Media S.A.Frontiers in Earth Science2296-64632021-06-01910.3389/feart.2021.665185665185Geologic and Structural Evolution of the NE Lau Basin, Tonga: Morphotectonic Analysis and Classification of Structures Using Shallow SeismicityMelissa O. Anderson0Chantal Norris-Julseth1Kenneth H. Rubin2Karsten Haase3Mark D. Hannington4Mark D. Hannington5Alan T. Baxter6Margaret S. Stewart7Department of Earth Sciences, University of Toronto, Toronto, ON, CanadaDepartment of Earth Sciences, University of Toronto, Toronto, ON, CanadaDepartment of Geology and Geophysics, SOEST, University of Hawaii, Honolulu, HI, United StatesGeoZentrum Nordbayern, Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen, GermanyDepartment of Earth Sciences, University of Ottawa, Ottawa, ON, CanadaGEOMAR, Helmholtz Centre for Ocean Research Kiel, Kiel, GermanyDepartment of Earth Sciences, University of Ottawa, Ottawa, ON, CanadaDepartment of Earth and Environmental Sciences, Mount Royal University, Calgary, AB, CanadaThe transition from subduction to transform motion along horizontal terminations of trenches is associated with tearing of the subducting slab and strike-slip tectonics in the overriding plate. One prominent example is the northern Tonga subduction zone, where abundant strike-slip faulting in the NE Lau back-arc basin is associated with transform motion along the northern plate boundary and asymmetric slab rollback. Here, we address the fundamental question: how does this subduction-transform motion influence the structural and magmatic evolution of the back-arc region? To answer this, we undertake the first comprehensive study of the geology and geodynamics of this region through analyses of morphotectonics (remote-predictive geologic mapping) and fault kinematics interpreted from ship-based multibeam bathymetry and Centroid-Moment Tensor data. Our results highlight two notable features of the NE Lau Basin: 1) the occurrence of widely distributed off-axis volcanism, in contrast to typical ridge-centered back-arc volcanism, and 2) fault kinematics dominated by shallow-crustal strike slip-faulting (rather than normal faulting) extending over ∼120 km from the transform boundary. The orientations of these strike-slip faults are consistent with reactivation of earlier-formed normal faults in a sinistral megashear zone. Notably, two distinct sets of Riedel megashears are identified, indicating a recent counter-clockwise rotation of part of the stress field in the back-arc region closest to the arc. Importantly, the Riedel structures identified in this study directly control the development of complex volcanic-compositional provinces, which are characterized by variably-oriented spreading centers, off-axis volcanic ridges, extensive lava flows, and point-source rear-arc volcanoes. This study adds to our understanding of the geologic and structural evolution of modern backarc systems, including the association between subduction-transform motions and the siting and style of seafloor volcanism.https://www.frontiersin.org/articles/10.3389/feart.2021.665185/fullNE lau basinback-arcgeologic mappingsubmarine volcanismmegashearmorphotectonic analysis |
| spellingShingle | Melissa O. Anderson Chantal Norris-Julseth Kenneth H. Rubin Karsten Haase Mark D. Hannington Mark D. Hannington Alan T. Baxter Margaret S. Stewart Geologic and Structural Evolution of the NE Lau Basin, Tonga: Morphotectonic Analysis and Classification of Structures Using Shallow Seismicity Frontiers in Earth Science NE lau basin back-arc geologic mapping submarine volcanism megashear morphotectonic analysis |
| title | Geologic and Structural Evolution of the NE Lau Basin, Tonga: Morphotectonic Analysis and Classification of Structures Using Shallow Seismicity |
| title_full | Geologic and Structural Evolution of the NE Lau Basin, Tonga: Morphotectonic Analysis and Classification of Structures Using Shallow Seismicity |
| title_fullStr | Geologic and Structural Evolution of the NE Lau Basin, Tonga: Morphotectonic Analysis and Classification of Structures Using Shallow Seismicity |
| title_full_unstemmed | Geologic and Structural Evolution of the NE Lau Basin, Tonga: Morphotectonic Analysis and Classification of Structures Using Shallow Seismicity |
| title_short | Geologic and Structural Evolution of the NE Lau Basin, Tonga: Morphotectonic Analysis and Classification of Structures Using Shallow Seismicity |
| title_sort | geologic and structural evolution of the ne lau basin tonga morphotectonic analysis and classification of structures using shallow seismicity |
| topic | NE lau basin back-arc geologic mapping submarine volcanism megashear morphotectonic analysis |
| url | https://www.frontiersin.org/articles/10.3389/feart.2021.665185/full |
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