Correlations between oceanic crustal thickness, melt volume, and spreading rate from global gravity observation
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ORIGINAL RESEARCH PAPER
Correlations between oceanic crustal thickness, melt volume, and spreading rate from global gravity observation Duo Zhou1 · Chun‑Feng Li1,2 · Sergio Zlotnik3 · Jian Wang4 Received: 6 February 2020 / Accepted: 8 August 2020 © Springer Nature B.V. 2020
Abstract Oceanic crustal accretion at mid-ocean ridges is a function of spreading rate, mantle temperature, and composition, which are intertwined in affecting melt production and oceanic crustal thickness. Sparse and irregular seismic and geochemical observations on a global scale showed no correlation between crustal thickness and spreading rate along slow to fast-spreading centers. Here, we compile a global oceanic crustal thickness model from gravity data to revisit this issue at a high resolution. Gravity-observed melt volume shows a positive correlation with spreading rate globally, implying that spreading rate is the dominant factor in melt production. However, oceanic crustal thickness is negatively correlated with spreading rate from slow to fast-spreading centers, and this trend is further consolidated by the increase in Curie point depth (a geothermal proxy) and ridge depth with increasing spreading rate. Thus, a decreasing near-ridge temperature probably contributes to crustal thinning from slow to fast-spreading centers. Inferred low melt volume anomalies beneath fast-spreading centers are consistent with a 20 °C temperature drop in the near-ridge mantle, likely caused by efficient hydrothermal cooling. Keywords Oceanic crustal thickness · Gravity inversion · Melt volume · Spreading rate · Mantle temperature · Hydrothermal circulation
Introduction Approximately 60% of the Earth’s crust is formed by mantle decompression melting at mid-ocean ridges (Müller et al. 2008). The processes of oceanic crustal accretion vary with spreading rate (Christeson et al. 2019). At slow-spreading centers, magma supply is episodic (Bach and Fruh-Green 2010), with deep and rarely detectable magma chambers (Purdy et al. 1992; Searle 2013), crustal thickness and seafloor morphology are highly variable (Chen 1992; Lin and * Chun‑Feng Li [email protected] 1
Institute of Marine Geology and Resources, Zhejiang University, Zhoushan, China
2
Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
3
Laboratori de Calcul Numèric, Escola Tècnica Superior d’Enginyers de Camins, Universitat Politècnica de Catalunya, Barcelona, Spain
4
National Institute of Natural Hazards, Ministry of Emergency Management of China, Beijing, China
Morgan 1992). In contrast, at fast-spreading ridges, magma supply is stable (Christeson et al. 2019), with much shallower and more observable magma chambers, crustal thickness and seafloor morphology are relatively uniform (Lin and Morgan 1992). A variety of parameters, such as mantle melting extent (Niu and Hékinian 1997), mantle upwelling rate (Forsyth 1992), and simulated melt volume (Bown and White 1994), correlate well with spreading rate. However, o
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