|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
1 Laboratoire GTS, UMR 5573, Université Montpellier II, F-34095 Montpellier, France
2 IUEM/Université Bretagne Occidentale, Place Nicolas Copernic, F-29280 Plouzané, France
3 IRD Centre de Bretagne, B.P. 70, F-29280 Plouzané, France
Slab melting has been suggested as a likely source of adakitic arc magmas (i.e., andesitic and dacitic magmas strongly depleted in Y and heavy rare earth elements). Existing numerical and petrologic models, however, restrict partial melting to very young (
5 Ma) oceanic crust (typically at 60–80 km depth). Paradoxically, most of the known Pliocene-Quaternary adakite occurrences are related to subduction of 10–45 Ma lithosphere, which should not be able to melt under normal subduction-zone thermal gradients. We propose an unusual mode of subduction known as flat subduction, occurring in 
10% of the world's convergent margins, that can produce the temperature and pressure conditions necessary for fusion of moderately old oceanic crust. Of the 10 known flat subduction regions worldwide, eight are linked to present or recent (<6 Ma) occurrences of adakitic magmas. Observations from Chile, Ecuador, and Costa Rica suggest a three-stage evolution: (1) steep subduction produces a narrow calc-alkaline arc, typically 300 km from the trench, above the asthenospheric wedge; (2) once flat subduction begins, the lower plate travels several hundred kilometers at nearly the same depth, thus remaining in a pressure-temperature window allowing slab melting over this broad distance; and (3) once flat subduction continues for several million years, the asthenospheric wedge disappears, and a volcanic gap results, as in modern-day central Chile or Peru. The proposed hypothesis, which reconciles thermal models with geochemical observations, has broad implications for the study of arc magmatism and for the thermal evolution of convergent margins.
Key Words: flat subduction • thermal structure • slab melting • adakites
This article has been cited by other articles:
|
|
 |
|
  R. Baumgartner, L. Fontbote, R. Spikings, M. Ovtcharova, U. Schaltegger, J. Schneider, L. Page, and M. Gutjahr Bracketing the Age of Magmatic-Hydrothermal Activity at the Cerro de Pasco Epithermal Polymetallic Deposit, Central Peru: A U-Pb and 40Ar/39Ar Study Economic Geology, July 1, 2009; 104(4): 479 - 504. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M.-X. Ling, F.-Y. Wang, X. Ding, Y.-H. Hu, J.-B. Zhou, R. E. Zartman, X.-Y. Yang, and W. Sun CRETACEOUS RIDGE SUBDUCTION ALONG THE LOWER YANGTZE RIVER BELT, EASTERN CHINA Economic Geology, March 1, 2009; 104(2): 303 - 321. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. RodrIguez, D. Selles, M. Dungan, C. Langmuir, and W. Leeman Adakitic Dacites Formed by Intracrustal Crystal Fractionation of Water-rich Parent Magmas at Nevado de Longavi Volcano (36{middle dot}2{degrees}S; Andean Southern Volcanic Zone, Central Chile) J. Petrology, November 1, 2007; 48(11): 2033 - 2061. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. P. Richards and R. Kerrich Special Paper: Adakite-Like Rocks: Their Diverse Origins and Questionable Role in Metallogenesis Economic Geology, June 1, 2007; 102(4): 537 - 576. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X.-L. Xiong Trace element evidence for growth of early continental crust by melting of rutile-bearing hydrous eclogite Geology, November 1, 2006; 34(11): 945 - 948. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. A. BRYANT, G. M. YOGODZINSKI, M. L. HALL, J. L. LEWICKI, and D. G. BAILEY Geochemical Constraints on the Origin of Volcanic Rocks from the Andean Northern Volcanic Zone, Ecuador J. Petrology, June 1, 2006; 47(6): 1147 - 1175. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. M. Kay, O. Mancilla, and P. Copeland Evolution of the late Miocene Chachahuen volcanic complex at 37{degrees}S over a transient shallow subduction zone under the Neuquen Andes Geological Society of America Special Papers, January 1, 2006; 407(0): 215 - 246. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. GUO, W. FAN, and C. LI Geochemistry of late Mesozoic adakites from the Sulu belt, eastern China: magma genesis and implications for crustal recycling beneath continental collisional orogens Geological Magazine, January 1, 2006; 143(1): 1 - 13. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Q. WANG, J.-F. XU, P. JIAN, Z.-W. BAO, Z.-H. ZHAO, C.-F. LI, X.-L. XIONG, and J.-L. MA Petrogenesis of Adakitic Porphyries in an Extensional Tectonic Setting, Dexing, South China: Implications for the Genesis of Porphyry Copper Mineralization J. Petrology, January 1, 2006; 47(1): 119 - 144. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. SAMANIEGO, H. MARTIN, M. MONZIER, C. ROBIN, M. FORNARI, J.-P. EISSEN, and J. COTTEN Temporal Evolution of Magmatism in the Northern Volcanic Zone of the Andes: The Geology and Petrology of Cayambe Volcanic Complex (Ecuador) J. Petrology, November 1, 2005; 46(11): 2225 - 2252. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. R. Cooke, P. Hollings, and J. L. Walshe Giant Porphyry Deposits: Characteristics, Distribution, and Tectonic Controls Economic Geology, August 1, 2005; 100(5): 801 - 818. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. M. Jacques The influence of intraplate structural accommodation zones on delineating petroleum provinces of the Sub-Andean foreland basins Petroleum Geoscience, January 1, 2004; 10(1): 1 - 19. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. M. Jacques and JohnM. Jacques A tectonostratigraphic synthesis of the Sub-Andean basins: implications for the geotectonic segmentation of the Andean Belt Journal of the Geological Society, September 1, 2003; 160(5): 687 - 701. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. M. Garrison and J. P. Davidson Dubious case for slab melting in the Northern volcanic zone of the Andes Geology, June 1, 2003; 31(6): 565 - 568. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. S. Marshall, B. D. Idleman, T. W. Gardner, and D. M. Fisher Landscape evolution within a retreating volcanic arc, Costa Rica, Central America Geology, May 1, 2003; 31(5): 419 - 422. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J.-F. Xu, R. Shinjo, M. J. Defant, Q. Wang, and R. P. Rapp Origin of Mesozoic adakitic intrusive rocks in the Ningzhen area of east China: Partial melting of delaminated lower continental crust? Geology, December 1, 2002; 30(12): 1111 - 1114. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Samaniego, H. Martin, C. Robin, and M. Monzier Transition from calc-alkalic to adakitic magmatism at Cayambe volcano, Ecuador: Insights into slab melts and mantle wedge interactions Geology, November 1, 2002; 30(11): 967 - 970. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. E. Mungall Roasting the mantle: Slab melting and the genesis of major Au and Au-rich Cu deposits Geology, October 1, 2002; 30(10): 915 - 918. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Hollings and K. Ansdell Paleoproterozoic arc magmatism imposed on an older backarc basin: Implications for the tectonic evolution of the Trans-Hudson orogen, Canada Geological Society of America Bulletin, February 1, 2002; 114(2): 153 - 168. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. G. Macpherson and R. Hall Timing and tectonic controls in the evolving orogen of SE Asia and the western Pacific and some implications for ore generation Geological Society, London, Special Publications, January 1, 2002; 204(1): 49 - 67. [Abstract] [PDF]
|
|
|
|
|
|
A. Aguillon-Robles, T. Calmus, M. Benoit, H. Bellon, R. C. Maury, J. Cotten, J. Bourgois, and F. Michaud Late Miocene adakites and Nb-enriched basalts from Vizcaino Peninsula, Mexico: Indicators of East Pacific Rise subduction below southern Baja California? Geology, June 1, 2001; 29(6): 531 - 534. [Abstract] [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
