Episodic kinematics in continental rifts modulated by changes in mantle melt fraction
Oceanic crust is created by the extraction of molten rock from underlying mantle at the seafloor ‘spreading centres’ found between diverging tectonic plates. Modelling studies have suggested that mantle melting can occur through decompression as the mantle flows upwards beneath spreading centres1, b...
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sg-ntu-dr.10356-868842020-09-26T21:28:41Z Episodic kinematics in continental rifts modulated by changes in mantle melt fraction Moore, James Daniel Paul Smith, Euan Stern, Tim Lamb, Simon Earth Observatory of Singapore Geodynamics Geophysics Oceanic crust is created by the extraction of molten rock from underlying mantle at the seafloor ‘spreading centres’ found between diverging tectonic plates. Modelling studies have suggested that mantle melting can occur through decompression as the mantle flows upwards beneath spreading centres1, but direct observation of this process is difficult beneath the oceans. Continental rifts, however—which are also associated with mantle melt production—are amenable to detailed measurements of their short-term kinematics using geodetic techniques. Here we show that such data can provide evidence for an upwelling mantle flow, as well as information on the dimensions and timescale of mantle melting. For North Island, New Zealand, around ten years of campaign and continuous GPS measurements in the continental rift system known as the Taupo volcanic zone reveal that it is extending at a rate of 6–15 millimetres per year. However, a roughly 70-kilometre-long segment of the rift axis is associated with strong horizontal contraction and rapid subsidence, and is flanked by regions of extension and uplift. These features fit a simple model that involves flexure of an elastic upper crust, which is pulled downwards or pushed upwards along the rift axis by a driving force located at a depth greater than 15 kilometres. We propose that flexure is caused by melt-induced episodic changes in the vertical flow forces that are generated by upwelling mantle beneath the rift axis, triggering a transient lower-crustal flow. A drop in the melt fraction owing to melt extraction raises the mantle flow viscosity and drives subsidence, whereas melt accumulation reduces viscosity and allows uplift—processes that are also likely to occur in oceanic spreading centres. NRF (Natl Research Foundation, S’pore) Accepted version 2017-12-28T05:01:17Z 2019-12-06T16:30:54Z 2017-12-28T05:01:17Z 2019-12-06T16:30:54Z 2017 Journal Article Lamb, S., Moore, J. D. P., Smith, E., & Stern, T. (2017). Episodic kinematics in continental rifts modulated by changes in mantle melt fraction. Nature, 547, 84-88. 0028-0836 https://hdl.handle.net/10356/86884 http://hdl.handle.net/10220/44212 10.1038/nature22962 en Nature © 2017 Macmillan Publishers Limited, part of Springer Nature. This is the author created version of a work that has been peer reviewed and accepted for publication by Nature, Macmillan Publishers Limited, part of Springer Nature. It incorporates referee’s comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document. The published version is available at: [http://dx.doi.org/10.1038/nature22962]. 36 p. application/pdf |
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Geodynamics Geophysics Moore, James Daniel Paul Smith, Euan Stern, Tim Lamb, Simon Episodic kinematics in continental rifts modulated by changes in mantle melt fraction |
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Oceanic crust is created by the extraction of molten rock from underlying mantle at the seafloor ‘spreading centres’ found between diverging tectonic plates. Modelling studies have suggested that mantle melting can occur through decompression as the mantle flows upwards beneath spreading centres1, but direct observation of this process is difficult beneath the oceans. Continental rifts, however—which are also associated with mantle melt production—are amenable to detailed measurements of their short-term kinematics using geodetic techniques. Here we show that such data can provide evidence for an upwelling mantle flow, as well as information on the dimensions and timescale of mantle melting. For North Island, New Zealand, around ten years of campaign and continuous GPS measurements in the continental rift system known as the Taupo volcanic zone reveal that it is extending at a rate of 6–15 millimetres per year. However, a roughly 70-kilometre-long segment of the rift axis is associated with strong horizontal contraction and rapid subsidence, and is flanked by regions of extension and uplift. These features fit a simple model that involves flexure of an elastic upper crust, which is pulled downwards or pushed upwards along the rift axis by a driving force located at a depth greater than 15 kilometres. We propose that flexure is caused by melt-induced episodic changes in the vertical flow forces that are generated by upwelling mantle beneath the rift axis, triggering a transient lower-crustal flow. A drop in the melt fraction owing to melt extraction raises the mantle flow viscosity and drives subsidence, whereas melt accumulation reduces viscosity and allows uplift—processes that are also likely to occur in oceanic spreading centres. |
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Earth Observatory of Singapore |
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Earth Observatory of Singapore Moore, James Daniel Paul Smith, Euan Stern, Tim Lamb, Simon |
format |
Article |
author |
Moore, James Daniel Paul Smith, Euan Stern, Tim Lamb, Simon |
author_sort |
Moore, James Daniel Paul |
title |
Episodic kinematics in continental rifts modulated by changes in mantle melt fraction |
title_short |
Episodic kinematics in continental rifts modulated by changes in mantle melt fraction |
title_full |
Episodic kinematics in continental rifts modulated by changes in mantle melt fraction |
title_fullStr |
Episodic kinematics in continental rifts modulated by changes in mantle melt fraction |
title_full_unstemmed |
Episodic kinematics in continental rifts modulated by changes in mantle melt fraction |
title_sort |
episodic kinematics in continental rifts modulated by changes in mantle melt fraction |
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2017 |
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https://hdl.handle.net/10356/86884 http://hdl.handle.net/10220/44212 |
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1681057232867819520 |