Influences on the development of volcanic and magma-poor morphologies during passive continental rifting

Abstract

Numerical experiments of passive continental extension with decompressive mantle melting have been conducted to investigate controls on the development of end-member, volcanic and magma-poor, rifted margins. A prediction of end-member margin morphology is made by comparing the relative timing of continental breakup and start of magmatic emplacement. Volcanic margins are interpreted to form when magmatic emplacement begins prior to the full thinning of the continental crust, while magma-poor margins are predicted to form when continental breakup precedes any magmatic emplacement. Systematic investigations of potential influencing variables demonstrate that a variety of factors may influence this relative timing, with model results producing a spectrum of magmatic character. Of the investigated factors, the initial lithosphere geotherm and crustal thickness appear to be the most significant influences on margin morphology. Independent variation of either variable is capable of altering the predicted end-member morphology between volcanic and magma poor. Variations in mantle potential temperature, extension rate, and crustal rheology demonstrate an ability to influence passive margin magmatic character, but are unable to independently induce development of a magma-poor margin. In aggregate, model results suggest that mantle exhumation and formation of a magma-poor margin are encouraged by: a depressed lithosphere geotherm, thin continental crust, rapid extension rates, low mantle potential temperature, and a strong crustal rheology. Relatively early magmatic emplacement and formation of a volcanic margin is predicted for the majority of modeled conditions, and appears bolstered by: an elevated geotherm, thick continental crust, slow extension, high potential temperature, and a weak crustal rheology. PASSIVE MARGIN MORPHOLOGIC VARIATIONS Volcanic passive margins are characterized by significant magmatic emplacement preceding and/or synchronous with the start of continental rifting (e.g., Geoffroy, 2005; Holbrook and Kelemen, 1993; Mutter et al., 1982). This pre-breakup volcanism indicates the relatively early development of mature magmatic systems that are capable of generating and emplacing significant volumes of melt. These magmatic systems may manifest as onshore igneous emplacements, subaerial seaward-dipping reflector sequences, and/or magmatic underplating of the continental crust (

Numerical modelling of Cretaceous Pyrenean Rifting: The interaction between mantle exhumation and syn‐rift salt tectonics

“…Extensional patterns with specific tectonic implications have been explored in detail: 1) wide versus narrow rifts (Buck 1991;Brun, 1999;Gueydan et al, 2008;Tirel et al 2008), 2) oblique extension (Tron and Brun, 1991;McClay and White, 1995;Zwaan et al, 2016). The same occurred about thermal and magmatic aspects of rifting: 1) thermal regimes (Huet et al, 2011;Tirel et al, 2004), 2) melting (Bialas et al, 2010;Schmeling and Wallner, 2012;Davis and Lavier, 2017) or 3) hot versus cold margins (Corti et al, 2003). Of particular interest for the study of passive margins, are modeling works dedicated to: 1) the effects of stretching rate variations (Brun, 1999;Brune et al, 2016;Rey et al, 2009;Nestola et al, 2015;Tetreault and Buiter, 2018), 2) symmetry versus asymmetry of margins (Nagel and Buck, 2004 ;Huismans and Beaumont, 2007), 3) surface processes (Burov and Poliakov, 2001;Bialas and Buck, 2009) , 4) multiple phases of extension (Braun, 1992;…”

Controls on the Thermomechanical Evolution of Hyperextended Lithosphere at Magma‐Poor Rifted Margins: The Example of Espirito Santo and the Kwanza Basins

“…Numerical models can simulate the evolution of magma‐poor hyperextended margins for first‐order features and be used as experimental tools to test mechanisms by which crustal and mantle deformation becomes coupled or decoupled (e.g., Brune et al, ; Chenin et al, ; Davis & Lavier, ; Huismans & Beaumont, , , ; Lavier & Manatschal, ; Naliboff et al, ; Pérez‐Gussinyé & Reston, ; Ranéro & Pérez‐Gussinyé, ; Ros et al, ; Svartman Dias et al, , ; Van Avendonk et al, ). These models did verify that rifting can be polyphase (Lavier & Manatschal, ) and involves the thinning of the continental lithosphere by brittle faulting and ductile shearing eventually leading to embrittlement of the whole lithosphere and the coupling of crustal and mantle deformation.…”

Breakup Without Borders: How Continents Speed Up and Slow Down During Rifting

“…Rift velocity is thought to be one of the key parameters controlling fault evolution and rift symmetry Huismans & Beaumont, 2003;Tetreault & Buiter, 2018), while the rate of extension also governs melt production and affects the volcanic or magma-poor nature of rifted margins (Davis & Lavier, 2017;Lundin et al, 2018;Pérez-Gussinyé et al, 2006). Rift velocity is thought to be one of the key parameters controlling fault evolution and rift symmetry Huismans & Beaumont, 2003;Tetreault & Buiter, 2018), while the rate of extension also governs melt production and affects the volcanic or magma-poor nature of rifted margins (Davis & Lavier, 2017;Lundin et al, 2018;Pérez-Gussinyé et al, 2006).…”