wawasan - Geophysics - # Crustal Accretion at Ultraslow-Spreading Mid-Ocean Ridges

Highly Variable Crustal Thickness Observed at the Ultraslow-Spreading Gakkel Ridge in the Arctic Ocean

Q: How do the active mantle flow processes driving crustal accretion at ultraslow-spreading ridges differ from those at faster-spreading ridges?

At ultraslow-spreading ridges like the Gakkel Ridge, the active mantle flow processes driving crustal accretion differ significantly from those at faster-spreading ridges. In the context of the Gakkel Ridge study, the observed variability in crustal thickness ranging from 3.3 km to 8.9 km along the ridge axis indicates a complex interplay of factors. Unlike faster-spreading ridges where passive mantle upwelling and melting dominate, ultraslow-spreading ridges exhibit buoyant active mantle flow driven by thermal and compositional density changes due to melt extraction. This active mantle upwelling is influenced by mantle temperature and composition, leading to the variable crustal thickness observed. The influence of active upwelling is predicted to increase with decreasing spreading rate, highlighting a fundamental difference in the processes driving crustal accretion at ultraslow-spreading ridges compared to faster-spreading ones.

Q: What are the potential implications of the observed crustal thickness variability for the long-term evolution and structure of the oceanic lithosphere?

The observed crustal thickness variability along the Gakkel Ridge has significant implications for the long-term evolution and structure of the oceanic lithosphere. The increase in crustal thickness from about 4.5 km to about 7.5 km over the past 5 Myr suggests dynamic processes at play in crustal accretion at ultraslow-spreading ridges. This variability challenges the conventional models of passive mantle upwelling and melting, indicating that active mantle flow processes play a crucial role in shaping the oceanic lithosphere. The long-term implications include the potential for diverse crustal structures and compositions along ultraslow-spreading ridges, which can impact seafloor morphology, hydrothermal activity, and the distribution of seismicity in these regions. Understanding the crustal thickness variability is essential for unraveling the complex evolution of the oceanic lithosphere over geological timescales.

Q: How might the findings from this study on the Gakkel Ridge inform our understanding of crustal formation processes at other ultraslow-spreading mid-ocean ridges around the world?

The findings from the study on the Gakkel Ridge provide valuable insights that can inform our understanding of crustal formation processes at other ultraslow-spreading mid-ocean ridges worldwide. By revealing the highly variable crustal thickness and the role of active mantle flow in driving crustal accretion, this study challenges existing models and highlights the need for a more nuanced approach to studying ultraslow-spreading ridges. The observed variability in crustal thickness suggests that similar processes of active mantle upwelling may be at play in other ultraslow-spreading ridges, influencing their crustal structure and evolution. By recognizing the significance of active mantle flow in shaping crustal accretion, researchers can refine models of mid-ocean ridge dynamics and better understand the diversity of crustal formation processes at ultraslow-spreading ridges globally.

Konsep Inti

Crustal thickness at the ultraslow-spreading Gakkel Ridge in the Arctic Ocean varies significantly, ranging from 3.3 km to 8.9 km, and has increased over the past 5 million years, contradicting predictions of passive mantle upwelling models.

Abstrak

The study presents the first high-resolution ocean-bottom seismometer (OBS) experiment conducted at the Gakkel Ridge, the slowest-spreading mid-ocean ridge on Earth. The results show that crustal thickness along the ridge axis is highly variable, ranging from 3.3 km to 8.9 km, and has increased from about 4.5 km to 7.5 km over the past 5 million years in an across-axis profile.

This observed variability in crustal thickness does not align with the predictions of passive mantle upwelling models, which suggest decreased crustal thickness at spreading rates less than 20 mm/year. Instead, the findings can be explained by a model of buoyant active mantle flow driven by thermal and compositional density changes due to melt extraction.

The influence of active versus passive upwelling is predicted to increase with decreasing spreading rate. The process of active mantle upwelling is primarily influenced by mantle temperature and composition. This implies that the observed variability in crustal accretion, including varied crustal thickness, is likely an inherent characteristic of ultraslow-spreading ridges.

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Statistik

Crustal thickness ranges between 3.3 km and 8.9 km along the Gakkel Ridge axis.
Crustal thickness increased from about 4.5 km to about 7.5 km over the past 5 million years in an across-axis profile.

Kutipan

"Unexpectedly, we find that crustal thickness ranges between 3.3 km and 8.9 km along the ridge axis and it increased from about 4.5 km to about 7.5 km over the past 5 Myr in an across-axis profile."
"The highly variable crustal thickness and relatively large average value does not align with the prediction of passive mantle upwelling models."

Wawasan Utama Disaring Dari

Highly variable magmatic accretion at the ultraslow-spreading Gakkel Ridge - Nature

by Tao Zhang,Ji... pada www.nature.com 08-21-2024

https://www.nature.com/articles/s41586-024-07831-0

Highly variable magmatic accretion at the ultraslow-spreading Gakkel Ridge - Nature

Pertanyaan yang Lebih Dalam

How do the active mantle flow processes driving crustal accretion at ultraslow-spreading ridges differ from those at faster-spreading ridges?

At ultraslow-spreading ridges like the Gakkel Ridge, the active mantle flow processes driving crustal accretion differ significantly from those at faster-spreading ridges. In the context of the Gakkel Ridge study, the observed variability in crustal thickness ranging from 3.3 km to 8.9 km along the ridge axis indicates a complex interplay of factors. Unlike faster-spreading ridges where passive mantle upwelling and melting dominate, ultraslow-spreading ridges exhibit buoyant active mantle flow driven by thermal and compositional density changes due to melt extraction. This active mantle upwelling is influenced by mantle temperature and composition, leading to the variable crustal thickness observed. The influence of active upwelling is predicted to increase with decreasing spreading rate, highlighting a fundamental difference in the processes driving crustal accretion at ultraslow-spreading ridges compared to faster-spreading ones.

What are the potential implications of the observed crustal thickness variability for the long-term evolution and structure of the oceanic lithosphere?

The observed crustal thickness variability along the Gakkel Ridge has significant implications for the long-term evolution and structure of the oceanic lithosphere. The increase in crustal thickness from about 4.5 km to about 7.5 km over the past 5 Myr suggests dynamic processes at play in crustal accretion at ultraslow-spreading ridges. This variability challenges the conventional models of passive mantle upwelling and melting, indicating that active mantle flow processes play a crucial role in shaping the oceanic lithosphere. The long-term implications include the potential for diverse crustal structures and compositions along ultraslow-spreading ridges, which can impact seafloor morphology, hydrothermal activity, and the distribution of seismicity in these regions. Understanding the crustal thickness variability is essential for unraveling the complex evolution of the oceanic lithosphere over geological timescales.

How might the findings from this study on the Gakkel Ridge inform our understanding of crustal formation processes at other ultraslow-spreading mid-ocean ridges around the world?

The findings from the study on the Gakkel Ridge provide valuable insights that can inform our understanding of crustal formation processes at other ultraslow-spreading mid-ocean ridges worldwide. By revealing the highly variable crustal thickness and the role of active mantle flow in driving crustal accretion, this study challenges existing models and highlights the need for a more nuanced approach to studying ultraslow-spreading ridges. The observed variability in crustal thickness suggests that similar processes of active mantle upwelling may be at play in other ultraslow-spreading ridges, influencing their crustal structure and evolution. By recognizing the significance of active mantle flow in shaping crustal accretion, researchers can refine models of mid-ocean ridge dynamics and better understand the diversity of crustal formation processes at ultraslow-spreading ridges globally.