Study of the permeability in melting zone of South China Sea based on percolation theory
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ORIGINAL RESEARCH PAPER
Study of the permeability in melting zone of South China Sea based on percolation theory Ju-ying Wan • He-hua Xu • Yan-zhen Li Wei-bing Shu
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Received: 29 March 2014 / Accepted: 12 November 2014 Ó Springer Science+Business Media Dordrecht 2015
Abstract Oceanic crust is formed at mid-ocean ridges. The melting zone extends up to several hundreds of km laterally, the upwelling area at the spreading axis is confined to a narrow belt of only 2–3 km width. Whereas the parameter of permeability that magma ascending from the mantle beneath mid-ocean ridges is still poorly understood, despite the important role of the process for the formation of crust. Based on continuum percolation, we build the random fracture network as magma migration channels of South China Sea; with momentum equation, we deduced the dynamic pressure distribution with passive corner flow. After which, the permeability of melting zone is calculated with finite element method. Numerical simulation results indicate that there exists a power law relationship between the permeability and magma migration channels. The simulated result is consistent with that calculated by fractal method. The discovery of the ruler provides sound theoretical basis for the formation and evolution of oceanic crust, and may help us better understanding the formation and evolution of South China Sea. Keywords Magma migration Oceanic crust Rising divergent mantle flow Percolation method Permeability
J. Wan H. Xu (&) Y. Li W. Shu Key Laboratory of Marginal Sea Geology of Chinese Academy of Sciences, South China Sea Institute of Oceanology, University of Chinese Academy of Sciences, Guangzhou 510301, China e-mail: [email protected] J. Wan e-mail: [email protected] J. Wan Y. Li W. Shu University of Chinese Academy of Sciences, Beijing 100049, China
Introduction The general mechanism of the formation of oceanic crust is well known and is related to the separation of plates at midocean ridges. Deep mantle material ascends and partial melting occurs due to adiabatic decompression of the mantle rock. Magma may be stored temporarily in highlevel magma chambers beneath the ridge axis, thereby intruding into the rift between the plates and solidifying. Sea-floor volcanism takes place at few distinct regions on the ridge axis itself, and the bulk of melt magma transport in fractal fracture or stochastic fractures at greater depth in the crust (Valentini et al. 2007; Batanova and Savelieva 2009; Kelemen et al. 1995; Huppert and Worster 1991; Stanley and Hart 1993). Researchers also uses geochemical method to study the generation and evolution of magma (Zhang et al. 2010, 2012). So the prediction of permeability in the melting zone has been one of the hot spot of attention at home and aboard. The roles of fractures at mantle depth for predicting the thick of ocean crust is still unclear. Observations are not possible; fracture propagation generates no seismic signal during the ascent in the mantle and fracture emplacement is too small to produce
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