|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
1 GEOMAR Research Centre for Marine Geosciences, Wischhofstrasse 1-3, 24148 Kiel, Germany
Models of melting accompanying mantle upwelling predict far more melt than is observed at nonvolcanic margins. The discrepancy may be explained if the paradigm of a uniform asthenosphere is incorrect. Work on the velocity structure of the continents has shown that the convecting sublithospheric mantle may have a potential temperature as low as 1200 °C, 
100 °C cooler than that beneath the oceans. The continental geotherm derived from studies on xenoliths brought up by kimberlites is also compatible with a cool sublithospheric mantle except where perturbed by mantle plumes. Upwelling of such cool mantle during rifting leads to little melt production, even for rapid extension rates, explaining the formation of amagmatic margins away from mantle plumes. However, the transition to seafloor spreading and the development of normal-thickness oceanic crust requires the invasion of the amagmatic rift by hotter oceanic asthenosphere and/or plume material. This influx may cause a transient thermal uplift, recorded as a breakup unconformity. Conversely, at volcanic margins, the onset of seafloor spreading is accompanied by the escape of the hot plume puddle along the mid-ocean ridge system away from the volcanic margin, leading to a pulse of rapid subsidence.
Key Words: rifting • breakup • geotherm • melting • mantle • unconformity
This article has been cited by other articles:
|
|
 |
|
  T. J. Reston The extension discrepancy and syn-rift subsidence deficit at rifted margins Petroleum Geoscience, August 1, 2009; 15(3): 217 - 237. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. J. Shillington, C. L. Scott, T. A. Minshull, R. A. Edwards, P. J. Brown, and N. White Abrupt transition from magma-starved to magma-rich rifting in the eastern Black Sea Geology, January 1, 2009; 37(1): 7 - 10. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. G. Fitton The OIB paradox Geological Society of America Special Papers, January 1, 2007; 430(0): 387 - 412. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. E. Tucholke, D. S. Sawyer, and J.-C. Sibuet Breakup of the Newfoundland Iberia rift Geological Society, London, Special Publications, January 1, 2007; 282(1): 9 - 46. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. R. Hopper, T. Funck, and B. E. Tucholke Structure of the Flemish Cap margin, Newfoundland: insights into mantle and crustal processes during continental breakup Geological Society, London, Special Publications, January 1, 2007; 282(1): 47 - 61. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. J. Reston The formation of non-volcanic rifted margins by the progressive extension of the lithosphere: the example of the West Iberian margin Geological Society, London, Special Publications, January 1, 2007; 282(1): 77 - 110. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. L. Harry and S. Grandell A dynamic model of rifting between Galicia Bank and Flemish Cap during the opening of the North Atlantic Ocean Geological Society, London, Special Publications, January 1, 2007; 282(1): 157 - 172. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. J. Reston, T.J. Reston, V. Gaw, J. Pennell, D. Klaeschen, A. Stubenrauch, and I. Walker Extreme crustal thinning in the south Porcupine Basin and the nature of the Porcupine Median High: implications for the formation of non-volcanic rifted margins Journal of the Geological Society, September 1, 2004; 161(5): 783 - 798. [Abstract] [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
