Gondwana Research 83 (2020) 49–62 Contents lists available at ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr Craton destruction links to the interaction between subduction and mid- lithospheric discontinuity: Implications for the eastern North China Craton Ya-Nan Shi a,b, Fenglin Niu a,b, Zhong-Hai Li c,⁎, Pengpeng Huangfu c a State Key Laboratory of Petroleum Resources and Prospecting, Unconventional Petroleum Research Institute, China University of Petroleum at Beijing, Beijing, China b Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX, USA c Key Laboratory of Computational Geodynamics, College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China article info abstract Article history: The continental craton is generally considered to be stable, due to its low-density and high viscosity; however, Received 17 July 2019 the thinning and destruction of cratonic lithosphere have been observed at various parts of the globe, for exam- Received in revised form 16 January 2020 ple, the eastern North China Craton (NCC). Although a large number of geological and geophysical data have been Accepted 16 January 2020 collected to study the NCC, the mechanisms and dynamic processes are still widely debated. In this study, using 2- Available online 28 February 2020 D high-resolution thermo-mechanical models, we systematically explore the key constraints on the destruction fl Handling Editor: T. Gerya of cratonic lithosphere. The model results indicate that the craton destruction processes can be strongly in u- enced by the presence of the so-called mid-lithosphere discontinuity (MLD), and its interaction with subduction. Keywords: The properties of the MLD layer and the density contrast between the lithospheric mantle and asthenosphere Craton destruction play significant roles in the destruction processes. Specifically, the presence of a deep and low-viscosity MLD Mid-lithosphere discontinuity layer within the cratonic lithosphere tends to enhance instability of the craton, making it easier for lithosphere Oceanic plate subduction destruction. In addition, a relatively thick oceanic crust, high convergence rate, and large initial subduction angles North China Craton favor the craton destruction. Finally, we compare the model results with the observations of NCC, which indicate Numerical modeling that the interaction between the Paleo-Pacific subduction and the MLD layer in the cratonic lithosphere has played an important role in the observed large-scale lithospheric removal of the eastern North China Craton. © 2020 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. 1. Introduction South American cratons are estimated to be thinned by ~120 km (Rao et al., 2001, 2013; Dessai et al., 2004; Kumar et al., 2007; Karmalkar Craton is a stable continental lithosphere with a thickness of around et al., 2009; Wu et al., 2014), ~50 km (Griffin et al., 1999b; Howarth 200–300 km that exists for billions of years on the Earth's surface et al., 2014), and ~75 km (Read et al., 2004), respectively. (Jordan, 1988; Griffin et al., 1998; Sleep, 2003; Menzies et al., 2007). Based on the systematic geological and geophysical observations, Their low density and high viscosity retain them above the weak as- many mechanisms have been proposed to explain the thinning and de- thenosphere without destruction by long-term geological processes struction of cratonic lithosphere (Liu and Li, 2018; and references (Schubert et al., 2001; Lee et al., 2011; Wu et al., 2014). However, therein). For the NCC, it is generally proposed that the destruction in many studies revealed that several cratons have experienced significant Mesozoic is controlled by the Paleo-Pacific subduction (Zhu et al., lithospheric thinning, partial or complete removal after the initial build- 2012; and references therein), in which the subduction-induced partial ing and stabilization stage (e.g., Wu et al., 2014; Liu and Li, 2018). For melting may weaken the overriding lithosphere and gradually lead to example, the lithosphere beneath the eastern part of the North China the alteration of mantle lithosphere. Windley et al. (2010) suggested Craton (NCC) is ~100 km thinner than that of the western part that the destruction of NCC was closely related to the hydration process (Fig. 1). The lithospheric thinning is speculated to have occurred in during the Paleo-Pacific subduction, which significantly decreased the the Mesozoic, together with large-scale magmatic activities (Lu et al., viscosity of the cratonic keel. Wang et al. (2016) found two series of 1991; Menzies et al., 1998; Carlson et al., 2005; Zhu et al., 2012; Wu magmatism during the destruction of NCC, which are, respectively, re- et al., 2019). The mantle lithospheres beneath the Indian, Siberian and lated to (i) the perturbation of hydrous mantle transition zone by the subducted Izanagi plate in the period of ~135–115 Ma, and (ii) the as- ⁎ Corresponding author. thenospheric partial melting and lithospheric extension by the rollback E-mail address: [email protected] (Z.-H. Li). of Pacific plate at ~80 Ma in Cenozoic. In addition, the viscosity of the big https://doi.org/10.1016/j.gr.2020.01.016 1342-937X/© 2020 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. 50 Y.-N. Shi et al. / Gondwana Research 83 (2020) 49–62 100˚ 105˚ 110˚ 115˚ 120˚ 125˚ 130˚ 45˚ 45˚ Central Asian Orogenic Belt 80 90 110 110 90 120 100 100 80 Tanlu Fault 40˚ 110 40˚ West NCC 70 200 Bo Sea Qilian Orogen 130 180 160 140 120 90 Central China Orogen 190 Erdos 180 Yellow Sea 35˚ East NCC 35˚ Central Orogenic Belt Qinling-Dabie Belt Songpan-Ganzi Terrane Sulu Belt 30˚ Pacific Ocean 30˚ Yangtze Craton 100 Lithospheric Thickness 100˚ 105˚ 110˚ 115˚ 120˚ 125˚ 130˚ -5 -4 -3 -2 -1 0 1 2 3 4 5 Topography (km) Fig. 1. Tectonic map of the North China Craton (NCC), which is modified from Zhu et al. (2012),andLiu and Li (2018). Different colors represent the topography. Values of lithospheric thicknesses are from the open-sourced dataset (http://www.craton.cn/data)(Chen, 2009, 2010; Chen et al., 2008, Chen L et al., 2009, Chen et al., 2014; Zheng et al., 2017). mantle wedge could be decreased due to the dehydration of the and Gerya, 2014). A rapid delamination of the lower lithospheric mantle subducting plate, which thereby contributes to the vigorous mantle could be also caused by the contact of MLD with a hot asthenosphere convection and an increase in heat flow at the base of the lithosphere (Wang et al., 2018; Liu et al., 2018a, 2018b). (He, 2014). Based on the above discussion, both subduction and MLD may play Recent seismic studies, on the other hand, found a single or multiple certain roles in the craton destruction; however, their effects are gener- velocity discontinuities in the middle of the cratonic lithosphere ally isolated in the previous modeling. Here we present a series of nu- (e.g., Chen, 2017 and references therein), which is known as the mid- merical experiments based on a two-dimensional (2-D) high- lithosphere discontinuity (MLD) or discontinuities (MLDs). The MLDs resolution thermo-mechanical model, in which we have tested the sen- are mostly observed at ~80–100 km depth with a thickness of sitivities of various MLD properties and subduction conditions on the ~20–40 km (Abt et al., 2010; Yuan and Romanowicz, 2010; Chen et al., craton thinning and destruction. 2014; Hopper et al., 2014; Selway et al., 2015; Nita et al., 2016; Aulbach et al., 2017; Kennett and Sippl, 2018; Sun et al., 2018). The 2. Numerical methodology thickness, depth, potential origins and rheological properties of the MLD are still not well constrained (Karato et al., 2015; Selway et al., 2.1. Governing equations 2015; Aulbach et al., 2017; Wang and Kusky, 2019). Various mecha- nisms have been proposed for the nature of the MLDs (Thybo and For the numerical modeling we used a finite-difference numerical Perchuć,1997; Yuan and Romanowicz, 2010; Xu, 2001; Wölbern et al., code (I2VIS) with a marker-in-cell technique (Gerya and Yuen, 2012; Karato et al., 2015; Wang and Kusky, 2019), such as (1) metaso- 2003a). The momentum, continuity and heat conservation equations matism, i.e., through the enrichment of pyroxene, phlogopite, amphi- for a 2D creeping flow including thermal and chemical buoyant forces bole, carbonatite, infiltrated frozen melts (Thybo and Perchuć, 1997; were solved within this code. Xu, 2001; Abt et al., 2010; Wölbern et al., 2012; Sodoudi et al., 2013; Rader et al., 2015; Selway et al., 2015; Wang Z et al., 2016; Aulbach (1) 2D stokes equations: et al., 2017); (2) elastically-accommodated grain boundary sliding (Karato et al., 2015); and (3) change in azimuthal anisotropy (minerals with distinct orientation) (Tommasi et al., 2009; Yuan and Romanowicz, ∂σ 0 ∂σ 0 ∂ xx þ xz ¼ P 2010; Hansen et al., 2012). Regardless of nature, the MLD layer is gener- ∂ ∂ ∂ x z x ð1Þ ally considered to be rheologically weaker than the upper and lower ∂σ 0 ∂σ 0 ∂P zx þ zz ¼ −gρðÞC; M; P; T parts of the lithosphere (Wang and Kusky, 2019). Further numerical ∂x ∂z ∂z studies have demonstrated that a weak MLD layer can significantly pro- mote deformation and destruction of cratonic lithosphere under differ- where x and z are respectively horizontal and vertical coordinates; g is ent tectonic settings (Wang and Kusky, 2019). Under extension and gravitational acceleration; σ'ij are components of deviatoric stress ten- rifting setting, the existence of a weak MLD could accelerate the defor- sor; and the density ρ depends on composition (C), melt fraction (M), mation of the overlying mantle and the crust (Liao et al., 2013; Liao temperature (T) and pressure (P).