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Continental and Oceanic Core Complexes 1888 2013 Continental and oceanic core complexes 1888 2013 CELEBRATING ADVANCES IN GEOSCIENCE 1,† 1 2 3 Donna L. Whitney , Christian Teyssier , Patrice Rey , and W. Roger Buck Invited Review 1Department of Earth Sciences, University of Minnesota, Minneapolis, Minnesota 55455, USA 2School of Geosciences, University of Sydney, Sydney NSW 2006, Australia 3Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA ABSTRACT rocks ± upper mantle in the footwall of the nor- Core complexes were fi rst recognized in the mal fault(s). The resulting structure is a core continents (e.g., Anderson, 1972; Coney, 1974, Core-complex formation driven by litho- complex, which occurs in both continental and 1980; Crittenden et al., 1980; Lister and Davis, spheric extension is a fi rst-order process of oceanic lithosphere (Figs. 1 and 2). Extension is 1989), and they have been identifi ed in the geo- heat and mass transfer in the Earth. Core- the direct driving force for core-complex devel- logic record from the Precambrian (Holm, 1996) complex structures have been recognized opment, but in continental settings, the far-fi eld to the present (Hill et al., 1992). Core complexes in the continents, at slow- and ultraslow- tectonic regime may be one of convergence, and were later identifi ed at slow- and ultraslow- spreading mid-ocean ridges, and at continen- therefore continental core complexes may occur spreading oceanic divergent zones (e.g., Cannat, tal rifted margins; in each of these settings, in orogenic settings under an overall regime of 1993; Cann et al., 1997; Blackman et al., 1998; extension has driven the exhumation of deep plate convergence. Tucholke et al., 1998; Karson, 1999; Ranero crust and/or upper mantle. The style of ex- As extension proceeds, heat and material are and Reston, 1999; Dick et al., 2000). Continen- tension and the magnitude of core-complex transferred from deep (hot, ductile) to shallow tal and oceanic core complexes have similar di- exhumation are determined fundamentally (cool, brittle) levels, driving vigorous fl uid fl ow mensions, fault geometry, and kinematics (Figs. by rheology: (1) Coupling between brittle and strongly infl uencing the location and mag- 1 and 3), and both involve exhumation of deeper and ductile layers regulates fault patterns nitude of subsequent extension. Interactions levels of the lithosphere to shallow levels (John in the brittle layer; and (2) viscosity of the among minerals, fl uids, and/or magma may pro- and Cheadle, 2010). fl owing layer is controlled dominantly by duce economically important mineral deposits, In this review, we discuss the origin and the synextension geotherm and the presence and young extensional zones may be sources significance of continental core complexes or absence of melt. The pressure-tempera- of hydrothermal activity during and after active and oceanic core complexes. Although the ture-time-fl uid-deformation history of core faulting. term metamorphic core complex is a common complexes, investigated via fi eld- and mod- eling-based studies, reveals the magnitude, rate, and mechanisms of advection of heat A continental detachment system and material from deep to shallow levels, as meteoric Figure 1. Continental (A) and water well as the consequences for the chemical and oceanic (B) core complexes dif- meteoric water σ1 physical evolution of the lithosphere, includ- fer in their primary rock types σ3 ing the role of core-complex development in (granitic and metasedimentary fluid crustal differentiation, global element cycles, rocks in continental core com- brittle flow layer and ore formation. In this review, we provide plexes vs. gabbro and serpenti- a survey of ~40 yr of core-complex literature, nite in oceanic core complexes), brittle-ductile discuss processes and questions relevant to and therefore in the minerals transition: ~300–400°C mylonite the formation and evolution of core com- that infl uence the rheology of (quartz rheology) zone plexes in continental and oceanic settings, fluids derived from crystallization ductile the complexes. Nevertheless, of metamorphic/igneous rocks ~15 km layer highlight the signifi cance of core complexes many fi rst-order processes of for lithosphere dynamics, and propose a few their origin and evolution are B oceanic detachment system possible directions for future research. similar, and therefore there are Oceanic core complex many similarities in their archi- sea water sea INTRODUCTION tecture. In B, the detachment ridge serpentinite water fault roots in gabbro magma at axis When the lithosphere is under extension, the sheared depth (option 1); option 2 con- fluid domi- brittle upper crust breaks and is displaced along gabbro nantly siders a “dry” spreading center flow σ1 brittle normal faults. When extension is concentrated in which the brittle detachment fluid layer σ3 on one or a few faults in a narrow region, ductile transitions to a ductile shear flow ? ? gabbro material ascends from deeper levels of the litho- zone at depth (lithosphere Option 1 ? ? sphere, resulting in exhumation of deep crustal boudinage). brittle-ductile Option 2 ? mylonite transition: ~600°C ductile ~10 km †E-mail: [email protected] (olivine rheology) melt layer GSA Bulletin; March/April 2013; v. 125; no. 3/4; p. 273–298; doi: 10.1130/B30754.1; 13 fi gures. For permission to copy, contact [email protected] 273 © 2013 Geological Society of America Whitney et al. A 120°W0° 120°E PL AMOR Lf No N. American Cordillera 60°N 60°N Fig. 2B MC-Pyr Fig. 2C SB ReVe Aegean Sh BB Po YOHHa To Rh Li AA Ni KS Hh LR Ch Lo SEGKEd Nx GM Xi Ba AD Ho At La SC DI M-Ca Ka DNCV Go 0° Ma 0° Da, Nb Mid- Atlantic AB Ridge Pa Southwest Indian Australian- Ridge Antarctic 60°S Discordance 60°S continental core complex + Antarctica: Fosdick core complex, Marie Byrd Land oceanic core complex continental margin core complex 0° 120°E Figure 2 (on this and following page). (A) Map of the world showing the locations of some Phanerozoic core complexes in the continents and oceans. Key to abbreviations: AA—Alpi Apuane (Italy); AB—Atlantis Bank (SW Indian Ridge); AD—Ama Drime (Nepal); AMOR—Arctic segment of Mid-Atlantic Ridge; At—Atlantis Massif (Mid-Atlantic Ridge); Ba—Baja (Mexico); BB—Bay of Biscay; Ch—Chapedony (Iran); Da—Dayman (Papua New Guinea); DI—Doi Inthanon (Thailand); DNCV—Day Nui Con Voi (Vietnam); Ed—Edough (Algeria); GK—Grand Kabilye (Algeria); GM—Gurla Mandhata (Pamirs); Go—Godzilla; Ha—Harkin (China/Mongolia); Hh—Hohhot (China); Ho—Hongzhen (China); Ka—Kane (Mid-Atlantic Ridge); KS—Kongur Shan (Pamirs); La—Laojunshan (China); Lf—Lofoten (Norway); Li—Liaodong Peninsula (China); Ma—Malino (Indonesia); Lo—Louzidian (China); LR—Lora del Rio (Spain); M-Ca—Mid-Cayman spreading center; MC-Pyr—Massif Central (France–Pyrenees, France, Spain; includes Montagne-Noire); Nb—Normanby Island (Papua New Guinea); Ni—Niğde (Turkey); No—Norway rifted continental margin; Nx—Naxos (Greece); Pa—Paparoa (New Zealand); PL— Payer Land (Greenland); Po—Pohorje Mountains (Slovenia); Re—Rechnitz (Austria); Rh—Rhodope (Greece, Bulgaria); SB—southern Brittany (France); SC—Song Chay (China); Sh—Shaerdelan (China); SE—Sierra de las Estancias (Spain); To—Tormes (Spain); Ve— Veporic (Slovenia); Xi—Xiaoqinling (China); YOH—Yagan-Onch-Hayrhan (China/Mongolia). description of core complexes on the conti- relevant to crustal evolution and seismogenesis DEFINITIONS nents, for the sake of simplicity (and symme- in extending lithosphere, and core complexes try), in this review we use the terms continental have therefore been intensively studied using Herein, we use the following general defi ni- core complex (equivalent to metamorphic a variety of techniques, e.g., fi eld-based stud- tion of a core complex and the processes that core complex) and oceanic core complex. We ies (e.g., Davis and Coney, 1979; Miller et al., drive core-complex formation: do not discuss in any detail the formation of 1983; Bozkurt and Park, 1994; Gessner et al., A core complex is a domal or arched geologic continental margin core complexes, although 2001), numerical modeling (e.g., Buck et al., structure composed of ductilely deformed rocks some locations are highlighted on a world map 1988; Lavier et al., 1999; Tirel et al., 2004, and associated intrusions underlying a ductile- (Fig. 2A). 2008; Rey et al., 2009a, 2009b; Allken et al., to-brittle high-strain zone that experienced tens Over the past ~40 yr, interest in core com- 2011), and analog modeling (e.g., Brun et al., of kilometers of normal-sense displacement in plexes has remained high because these struc- 1994; Tirel et al., 2006). response to lithospheric extension. tures are common in extending orogens and There remain important questions about The lithospheric extension that results in along slow-spreading oceanic divergent zones, core-complex initiation and evolution. In this core-complex formation is commonly driven by and because they record fundamental thermo- review, we integrate knowledge derived from plate divergence, such as at mid-ocean ridges mechanical processes in extending lithosphere. different types of investigations (fi eld, mod- and along rifted continental margins. Extension An understanding of the uplift and exhuma- eling) of continental and oceanic core com- also occurs in plate convergence settings by slab tion of ductile rocks below low-angle normal plexes and discuss some of these unresolved rollback (e.g., the backarc of an oceanic subduc- faults, as well as the dynamics of the faults, is issues. tion zone) or by orogenic collapse
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