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Highly variable magmatic accretion at the ultraslow-spreading Gakkel Ridge.
Tao Zhang1, Jiabiao Li2, Xiongwei Niu1
1Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, China.
Nature
|August 21, 2024
Summary
Crustal thickness at ultraslow-spreading ridges is surprisingly variable and thicker than predicted. Active mantle upwelling, not passive, likely explains this oceanic crustal accretion.
Area of Science:
- Geophysics
- Oceanography
- Tectonics
Background:
- Crustal accretion at mid-ocean ridges shapes oceanic lithosphere.
- Passive mantle upwelling models predict thin crust at spreading rates < 20 mm/year.
Purpose of the Study:
- To image the crustal structure of the ultraslow-spreading Gakkel Ridge.
- To test existing models of crustal accretion at slow-spreading rates.
Main Methods:
- High-resolution ocean-bottom seismometer (OBS) experiment.
- Seismic imaging of crustal structure.
Main Results:
- Observed crustal thickness ranges from 3.3 to 8.9 km along the Gakkel Ridge axis.
- Crustal thickness increased over the past 5 Myr in an across-axis profile.
- Results contradict predictions of passive mantle upwelling models.
Conclusions:
- Buoyant active mantle flow, driven by melt extraction, explains the observed crustal thickness.
- Active mantle upwelling is more influential at slower spreading rates.
- Variability in crustal thickness is likely inherent to ultraslow-spreading ridges.
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