Crystallization depth beneath an oceanic detachment fault (ODP Hole 923A, Mid-Atlantic Ridge)
Oceanic detachment faults are increasingly recognized as playing an integral role in the seafloor spreading process at slow and ultraslow spreading mid-ocean ridges, with significant consequences for the architecture of the oceanic lithosphere. Although melt supply is considered to play a critical c...
| Main Authors: | , , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
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American Geophysical Union (AGU)
2017
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| Online Access: | http://hdl.handle.net/1721.1/106330 https://orcid.org/0000-0001-9722-469X |
| _version_ | 1826192007428571136 |
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| author | Lissenberg, C. Johan Rioux, Matthew MacLeod, Christopher J. Shimizu, Nobumichi Bowring, Samuel A. |
| author2 | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences |
| author_facet | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Lissenberg, C. Johan Rioux, Matthew MacLeod, Christopher J. Shimizu, Nobumichi Bowring, Samuel A. |
| author_sort | Lissenberg, C. Johan |
| collection | MIT |
| description | Oceanic detachment faults are increasingly recognized as playing an integral role in the seafloor spreading process at slow and ultraslow spreading mid-ocean ridges, with significant consequences for the architecture of the oceanic lithosphere. Although melt supply is considered to play a critical control on the formation and evolution of oceanic detachments, much less well understood is how melts and faults interact and influence each other. Few direct constraints on the locus and depth of melt emplacement in the vicinity of detachments are available. Gabbros drilled in ODP Hole 923A near the intersection of the Mid-Atlantic Ridge and the Kane transform fault (23°N; the MARK area) represent magmas emplaced into the footwall of such a detachment fault and unroofed by it. We here present U-Pb zircon dates for these gabbros and associated diorite veins which, when combined with a tectonic reconstruction of the area, allow us to calculate the depths at which the melts crystallized. Th-corrected single zircon U-Pb dates from three samples range from 1.138 ± 0.062 to 1.213 ± 0.021 Ma. We find a crystallization depth of 6.4 +1.7/−1.3 km, and estimate that the melts parental to the gabbros were initially emplaced up to 1.5 km deeper, at <8 km below the seafloor. The tectonic reconstruction implies that the detachment fault responsible for the exposure of the sampled sequence likely crossed the ridge axis at depth, suggesting that melt emplacement into the footwall of oceanic detachment faults is an important process. The deep emplacement depth we find associated with “detachment mode” spreading at ∼1.2 Ma appears to be significantly greater than the depth of magma reservoirs during the current “magmatic mode” of spreading in the area, suggesting that the northern MARK segment preserves a recent switch between two temporally distinct modes of spreading with fundamentally different lithospheric architecture. |
| first_indexed | 2024-09-23T09:04:45Z |
| format | Article |
| id | mit-1721.1/106330 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T09:04:45Z |
| publishDate | 2017 |
| publisher | American Geophysical Union (AGU) |
| record_format | dspace |
| spelling | mit-1721.1/1063302024-05-15T03:19:18Z Crystallization depth beneath an oceanic detachment fault (ODP Hole 923A, Mid-Atlantic Ridge) Lissenberg, C. Johan Rioux, Matthew MacLeod, Christopher J. Shimizu, Nobumichi Bowring, Samuel A. Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Bowring, Samuel A Oceanic detachment faults are increasingly recognized as playing an integral role in the seafloor spreading process at slow and ultraslow spreading mid-ocean ridges, with significant consequences for the architecture of the oceanic lithosphere. Although melt supply is considered to play a critical control on the formation and evolution of oceanic detachments, much less well understood is how melts and faults interact and influence each other. Few direct constraints on the locus and depth of melt emplacement in the vicinity of detachments are available. Gabbros drilled in ODP Hole 923A near the intersection of the Mid-Atlantic Ridge and the Kane transform fault (23°N; the MARK area) represent magmas emplaced into the footwall of such a detachment fault and unroofed by it. We here present U-Pb zircon dates for these gabbros and associated diorite veins which, when combined with a tectonic reconstruction of the area, allow us to calculate the depths at which the melts crystallized. Th-corrected single zircon U-Pb dates from three samples range from 1.138 ± 0.062 to 1.213 ± 0.021 Ma. We find a crystallization depth of 6.4 +1.7/−1.3 km, and estimate that the melts parental to the gabbros were initially emplaced up to 1.5 km deeper, at <8 km below the seafloor. The tectonic reconstruction implies that the detachment fault responsible for the exposure of the sampled sequence likely crossed the ridge axis at depth, suggesting that melt emplacement into the footwall of oceanic detachment faults is an important process. The deep emplacement depth we find associated with “detachment mode” spreading at ∼1.2 Ma appears to be significantly greater than the depth of magma reservoirs during the current “magmatic mode” of spreading in the area, suggesting that the northern MARK segment preserves a recent switch between two temporally distinct modes of spreading with fundamentally different lithospheric architecture. 2017-01-10T19:19:49Z 2017-01-10T19:19:49Z 2015-12 2015-07 Article http://purl.org/eprint/type/JournalArticle 1525-2027 http://hdl.handle.net/1721.1/106330 Lissenberg, C. Johan et al. “Crystallization Depth beneath an Oceanic Detachment Fault (ODP Hole 923A, Mid-Atlantic Ridge): CRYSTALLIZATION DEPTH.” Geochemistry, Geophysics, Geosystems 17.1 (2016): 162–180. https://orcid.org/0000-0001-9722-469X en_US http://dx.doi.org/10.1002/2015gc006027 Geochemistry, Geophysics, Geosystems Creative Commons Attribution 4.0 International License http://creativecommons.org/licenses/by/4.0/ application/pdf American Geophysical Union (AGU) American Geophysical Union |
| spellingShingle | Lissenberg, C. Johan Rioux, Matthew MacLeod, Christopher J. Shimizu, Nobumichi Bowring, Samuel A. Crystallization depth beneath an oceanic detachment fault (ODP Hole 923A, Mid-Atlantic Ridge) |
| title | Crystallization depth beneath an oceanic detachment fault (ODP Hole 923A, Mid-Atlantic Ridge) |
| title_full | Crystallization depth beneath an oceanic detachment fault (ODP Hole 923A, Mid-Atlantic Ridge) |
| title_fullStr | Crystallization depth beneath an oceanic detachment fault (ODP Hole 923A, Mid-Atlantic Ridge) |
| title_full_unstemmed | Crystallization depth beneath an oceanic detachment fault (ODP Hole 923A, Mid-Atlantic Ridge) |
| title_short | Crystallization depth beneath an oceanic detachment fault (ODP Hole 923A, Mid-Atlantic Ridge) |
| title_sort | crystallization depth beneath an oceanic detachment fault odp hole 923a mid atlantic ridge |
| url | http://hdl.handle.net/1721.1/106330 https://orcid.org/0000-0001-9722-469X |
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