Gondwana Research 33 (2016) 4–23 Contents lists available at ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr GR Focus Review Geophysical constraints on geodynamic processes at convergent margins: A global perspective I.M. Artemieva a,⁎, H. Thybo a, A. Shulgin b a Geology Section, IGN, University of Copenhagen, Øster Voldgade 10, Copenhagen 1350, Denmark b Centre for Earth Evolution and Dynamics (CEED), University of Oslo, P.O. Box 1028 Blindern, NO-0315 Oslo, Norway article info abstract Article history: Convergent margins, being the boundaries between colliding lithospheric plates, form the most disastrous areas Received 7 April 2015 in the world due to intensive, strong seismicity and volcanism. We review global geophysical data in order to il- Received in revised form 22 June 2015 lustrate the effects of the plate tectonic processes at convergent margins on the crustal and upper mantle struc- Accepted 23 June 2015 ture, seismicity, and geometry of subducting slab. We present global maps of free-air and Bouguer gravity Available online 6 August 2015 anomalies, heat flow, seismicity, seismic Vs anomalies in the upper mantle, and plate convergence rate, as well fi Handling Editor: M. Santosh as 20 pro les across different convergent margins. A global analysis of these data for three types of convergent margins, formed by ocean–ocean, ocean–continent, and continent–continent collisions, allows us to recognize Keywords: the following patterns. (1) Plate convergence rate depends on the type of convergent margins and it is signifi- Plate boundaries cantly larger when, at least, one of the plates is oceanic. However, the oldest oceanic plate in the Pacific ocean Subduction zone has the smallest convergence rate. (2) The presence of an oceanic plate is, in general, required for generation Dip angle of high-magnitude (M N 8.0) earthquakes and for generating intermediate and deep seismicity along the conver- Seismicity gent margins. When oceanic slabs subduct beneath a continent, a gap in the seismogenic zone exists at fl Heat ow depths between ca. 250 km and 500 km. Given that the seismogenic zone terminates at ca. 200 km depth in Gravity case of continent–continent collision, we propose oceanic origin of subducting slabs beneath the Zagros, the Pamir, and the Vrancea zone. (3) Dip angle of the subducting slab in continent–ocean collision does not correlate neither with the age of subducting oceanic slab, nor with the convergence rate. For ocean–ocean subduction, clear trends are recognized: steeply dipping slabs are characteristic of young subducting plates and of oceanic plates with high convergence rate, with slab rotation towards a near-vertical dip angle at depths below ca. 500 km at very high convergence rate. (4) Local isostasy is not satisfied at the convergent margins as evidenced by strong free air gravity anomalies of positive and negative signs. However, near-isostatic equilibrium may exist in broad zones of distributed deformation such as Tibet. (5) No systematic patterns are recognized in heat flow data due to strong heterogeneity of measured values which are strongly affected by hydrothermal circulation, mag- matic activity, crustal faulting, horizontal heat transfer, and also due to low number of heat flow measurements across many margins. (6) Low upper mantle Vs seismic velocities beneath the convergent margins are restricted to the upper 150 km and may be related to mantle wedge melting which is confined to shallow mantle levels. © 2015 Published by Elsevier B.V. on behalf of International Association for Gondwana Research. Contents 1. Introduction............................................................... 7 2. Tectonicandtopographicexpressionofconvergentboundaries........................................1110 3. Convergencerate.............................................................1212 4. Seismicityatconvergentmargins.....................................................1212 5. Dipangleofsubduction..........................................................1413 6. Gravityanomalies............................................................1414 7. Thermalstructureacrosstheconvergentmargins..............................................1515 8. Seismicimagesofconvergentmargins...................................................1515 9. Conclusions...............................................................2019 Acknowledgments...............................................................2020 References..................................................................2020 ⁎ Corresponding author. E-mail addresses: [email protected] (I.M. Artemieva), [email protected] (H. Thybo), [email protected] (A. Shulgin). http://dx.doi.org/10.1016/j.gr.2015.06.010 1342-937X/© 2015 Published by Elsevier B.V. on behalf of International Association for Gondwana Research. I.M. Artemieva et al. / Gondwana Research 33 (2016) 4–23 5 Fig. 1. Global distribution of convergent margins of different types. Topography and bathymetry based on ETOPO1 (Amante and Eakins, 2009). Fig. 2. Sketches of three major types of convergent margins. Fig. 3. Profiles across the convergent margins (illustrated in Fig. 4). See Table 1 for details. 6 Table 1 Major characteristics of convergent margins discussed in text. Profile in Location Tectonic setting Type of conv. Convergence Subduction angle, Subduction Age of subducting Seismicity range Fig. 3 margin rate (cm/y)a sub-Moho (deg)b angle, deep oceanic plate (Ma) (km) (deg)b WNA Western North America The Cascadia subduction zone: the oceanic Juan de Fuca and Gorda Plates OC, PBZ 2.3 ––10 Crustal subduct beneath the continental North American plate; further south it forms the zone of orogeny within the Western USA SA1 South America-Andes The oceanic Nazca Plate subducts beneath the continental South American OC 6.8 13 70 25 b200, 515–650 SA2 Plate along the Peru–Chile Trench 7.2 30 ? 40 b290, 580–610 SA3 7.4 13 ? 35 b200, 575–620 AS South Atlantics-Sandwich The oceanic South American Plate subducts beneath the South OO or OC 5.7 40 ? 70 b170, 270–310 Sandwich Plate (composed of oceanic lithosphere with continental fragments), forming the South Sandwich Trench CA Pacific Central America The oceanic Cocos Plate subducts under the Caribbean Plate and forms the CO 7.8 ? ? 15 b95, 205 Middle America Trench PAE, North Pacific, the Aleutians The oceanic Pacific Plate subducts under the continental segment of the OC 6.6 11 90 55 b230 North American Plate along the Aleutian Trench (PAE); further west, the fi Paci c Plate subducts under the oceanic segment of the North American I.M. Artemieva et al. / Gondwana Research 33 (2016) 4 Plate (PAW) PJ West Pacific (PJ = Japan, The oceanic Pacific plate subducts beneath the continental Amurian and OC 9.4 23 32 130 b230, 310–410 PK PK = Kamchatka) Okhotsk Plates (parts of the Eurasian Plate) at the Japan and Kuril OC 8.1 40 65 100 b190, 310, 490, Trenches 610–660 PR West Pacific, Ryukyu The oceanic Philippine Sea Plate subducts beneath the continental OC 7.9 53 – 50 b250 Eurasian Plate at the Ryukyu Trench PM West Pacific, Mariana The oceanic Pacific Plate subducts under the oceanic Philippine Sea Plate OO 2.7 27 70 160 b260, 310, 410–610 at the Mariana Trench SP West Pacific, Philippines The continental Sunda Plate subducts under the Philippine Mobile Belt at CC or OC 10.0 36 75 50 b160, 220–240, the Negros and the Cotabato Trenches, while the continental Eurasian 525–615 Plate subducts under the Philippine Mobile Belt at the Manila Trench. On the eastern side of the Philippines, the direction of subduction reverses: the oceanic Philippine Sea Plate subducts under the Philippine Mobile Belt at the Philippine and East Luzon Trenches SJ1 Indian ocean, Sunda-Java The oceanic Indo-Australian Plate subducts beneath the continental Sunda OC 4.8 25 ? 50 b235, 585 SJ2 Plate along the Sunda Trench 4.9 25 90 130 b185, 520–640 NZS New Zealand (NZS South-west of New Zealand: the Indo-Australian Plate subducts OC? 3.4 ? ? 65 b50, 100 – NZN = South Island; under the oceanic Pacific Plate (NZS). North-east of New Zealand the OO 7.2 43 74 95 0–650 23 NZN = North Island) direction of subduction reverses: the oceanic Pacific Plate subducts under the Indo-Australian Plate (note that E–W are flipped on profile NSN in Fig. 10). PC Pacific, New Caledonia The oceanic Indo-Australian Plate subducts beneath the oceanic OO 9.2 50 85 20 b340 Pacific Plate EAG Mediterranean Europe Broad band of diffuse deformation caused by the collision of the PBZ 0.5 ––– Crustal, 600 EAH (EAG = Gibraltar arc– continental African and Eurasian Plates, with numerous subduction zones CC 1.0 13 51 200? b180 Pyrenees; EAH = Hellenic and the orogenic belt that extends from the Atlantic coast through the arc–Carpathians) Mediterranean region (Alps, Carpathians, Pyrenees, Apennines, Dinarides, Atlas, Balkans, Caucasus) to Zagros and Anatolia. Profile EAG crosses the Gibraltar arc and the Pyrenees. In some parts of the Mediterranean Sea, oceanic lithosphere subducts under the continental Eurasian Plate (the Hellenic arc, profile EAH, which further crosses the Vrancea zone in the Carpathians). TH Tibet-Himalayas-Central Broad band of diffuse deformation caused by the collision of the PBZ, CC 4.6 ––– Crustal Asia continental Indian and Eurasian Plates, which includes the Himalayas, Tibet (under which the Indian Plate subducts under the Eurasian Plate), the orogenic belts of the Central Asia and the Indonesian Archipelago a Convergence rate is based on MORVEL plate velocity model (DeMets et al., 2010). b Subduction