|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
1 Mineralogisch-Petrographisches Institut, Universität Kiel, 24098 Kiel, Germany
2 Max-Planck-Institut für Chemie, Postfach 3060, 55020 Mainz, Germany
U-Pb geochronology on metamorphic minerals from a 35-km-long belt of eclogite-facies rocks in central Tanzania yields a Paleoproterozoic age of 2 Ga for the time of metamorphism. Peak metamorphic conditions found in eclogites (± kyanite) and metapelites reached about 750 °C and 18 kbar. A clockwise pressure-temperature path is deduced from mineral zonations, inclusion relations, and retrograde reaction textures. Near-isothermal decompression can be explained by erosion or tectonically controlled exhumation that followed tectonic thickening of the crust during subduction. Trace and rare earth element geochemistry indicates a mid-ocean ridge basaltlike mantle source for the precursors of the mafic members of the eclogite-facies rock suite. All the observations combined indicate that these high-pressure rocks are the oldest-known large-scale outcrops of eclogites formed during subduction of oceanic lithosphere. Linking eclogite formation to a Paleoproterozoic subduction event adds credibility to models of crust dynamics that advocate the operation of plate-tectonic processes early in Earth's history. The paucity of Precambrian eclogites may then be addressed as a problem of preservation rather than lack of formation.
This article has been cited by other articles:
|
|
 |
|
  G.C. Begg, W.L. Griffin, L.M. Natapov, S. Y. O'Reilly, S.P. Grand, C.J. O'Neill, J.M.A. Hronsky, Y. P. Djomani, C.J. Swain, T. Deen, et al. The lithospheric architecture of Africa: Seismic tomography, mantle petrology, and tectonic evolution Geosphere, February 1, 2009; 5(1): 23 - 50. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X. Zhou, G. Zhao, C. Wei, Y. Geng, and M. Sun EPMA U-Th-Pb monazite and SHRIMP U-Pb zircon geochronology of high-pressure pelitic granulites in the Jiaobei massif of the North China Craton Am J Sci, March 1, 2008; 308(3): 328 - 350. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. B. Dawson Chapter 3 Regional geology Geological Society, London, Memoirs, January 1, 2008; 33(1): 9 - 12. [Full Text] [PDF]
|
|
|
|
 |
|
 R. Bousquet, R. El Mamoun, O. Saddiqi, B. Goffe, A. Moller, and A. Madi Melanges and ophiolites during the Pan-African orogeny: the case of the Bou-Azzer ophiolite suite (Morocco) Geological Society, London, Special Publications, January 1, 2008; 297(1): 233 - 247. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. F. Dewey The secular evolution of plate tectonics and the continental crust: An outline Geological Society of America Memoirs, January 1, 2007; 200(0): 1 - 7. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. ULIANOV and A. KALT Mg-Al Sapphirine- and Ca-Al Hibonite-bearing Granulite Xenoliths from the Chyulu Hills Volcanic Field, Kenya J. Petrology, May 1, 2006; 47(5): 901 - 927. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Sommer, A. Kroner, S. Muhongo, and C. Hauzenberger SHRIMP zircon ages for post-Usagaran granitoid and rhyolitic rocks from the Palaeoproterozoic terrain of southwestern Tanzania South African Journal of Geology, September 1, 2005; 108(2): 247 - 256. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M.G. Bjornerud and H. Austrheim Inhibited eclogite formation: The key to the rapid growth of strong and buoyant Archean continental crust Geology, September 1, 2004; 32(9): 765 - 768. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. S. Brewer, T.S. Brewer, C.D. Storey, R.R. Parrish, S. Temperley, and B.F. Windley Grenvillian age decompression of eclogites in the Glenelg-Attadale Inlier, NW Scotland Journal of the Geological Society, July 1, 2003; 160(4): 565 - 574. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. H. Grantham, M. Maboko, and B. M. Eglington A review of the evolution of the Mozambique Belt and implications for the amalgamation and dispersal of Rodinia and Gondwana Geological Society, London, Special Publications, January 1, 2003; 206(1): 401 - 425. [Abstract] [PDF]
|
|
|
|
|
|
R. E. Hanson Proterozoic geochronology and tectonic evolution of southern Africa Geological Society, London, Special Publications, January 1, 2003; 206(1): 427 - 463. [Abstract] [PDF]
|
|
|
|
|
|
J. B. DAWSON Metasomatism and Partial Melting in Upper-Mantle Peridotite Xenoliths from the Lashaine Volcano, Northern Tanzania J. Petrology, September 1, 2002; 43(9): 1749 - 1777. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. HERMS Fluids in a 2 Ga old subduction zone -- deduced from eclogite-facies rocks of the Usagaran belt, Tanzania European Journal of Mineralogy, April 1, 2002; 14(2): 361 - 373. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. B. M. Mapeo, R. B. M. MAPEO, R. A. ARMSTRONG, and A. B. KAMPUNZU SHRIMP U-Pb zircon geochronology of gneisses from the Gweta borehole, northeast Botswana: implications for the Palaeoproterozoic Magondi Belt in southern Africa Geological Magazine, May 1, 2001; 138(3): 299 - 308. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Moller, K. Mezger, and V. Schenk Crustal Age Domains and the Evolution of the Continental Crust in the Mozambique Belt of Tanzania: Combined Sm-Nd, Rb-Sr, and Pb-Pb Isotopic Evidence J. Petrology, April 1, 1998; 39(4): 749 - 783. [Abstract] [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
