| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Journal of Petrology 45(7) © Oxford University Press 2004; all rights reserved
The Problem of Dating High-pressure Metamorphism: a U–Pb Isotope and Geochemical Study on Eclogites and Related Rocks of the Mariánské Lázn
Complex, Czech Republic
T
DRÁ3
1 NERC ISOTOPE GEOSCIENCES LABORATORY, KEYWORTH, NOTTINGHAM NG12 5GG, UK
2 IGL, JUSTUS LIEBIG UNIVERSITÄT, SENCKENBERGSTR. 3, D-35390 GIESSEN, GERMANY
3 CZECH GEOLOGICAL SURVEY, PRAGUE, CZECH REPUBLIC
4 DEPARTMENT OF GEOLOGY, UNIVERSITY OF LEICESTER, UNIVERSITY ROAD, LEICESTER LE1 7RH, UK
* Corresponding author. Telephone: +49 (0641) 9936016. Fax: +49 (0641) 9936019. E-mail: Hilke.Timmermann{at}geolo.uni-giessen.de
This study presents new geochemical (major and trace element, Nd–Sr isotope) and U–Pb zircon, monazite, titanite and rutile data for various rock types (eclogite, high-pressure granulite, amphibolite, orthogneiss, leucosome) of the high-grade metamorphic Mariánské Lázn
Complex in the western Bohemian Massif. Concordant U–Pb zircon analyses from the mafic to intermediate samples disclose the Mariánské Lázn Complex as a mixture of c. 540 Ma oceanic rocks juxtaposed at depth with lower-crustal rocks of the structurally overlying Teplá–Barrandian Unit. This interpretation refutes earlier models in which the Mariánské Lázn Complex was interpreted as a dismembered Cambro-Ordovician ophiolite complex affected by Variscan subduction. Metamorphic zircon in mafic rocks of the Mariánské Lázn Complex, as well as monazite from orthogneiss, and titanite in leucosome yield ages around 380 Ma. On the basis of detailed petrography and cathodoluminescence imaging we conclude that the c. 380 Ma age reflects the timing of Variscan exhumation and associated decompression melting under upper amphibolite-facies to granulite-facies conditions. Thereby, the data derived from metamorphic zircon of eclogites and high-pressure granulite, unexpectedly, do not date the timing of eclogitization, which could have happened just before Variscan exhumation, or even shortly after Late Cadomian protolith formation.
KEY WORDS: Bohemian Massif; eclogites; geochemistry; U–Pb geochronology; zircon
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  T.S. Rohr, H. Austrheim, and M. Erambert Stress-induced redistribution of yttrium and heavy rare-earth elements (HREE) in garnet during high-grade polymetamorphism American Mineralogist, August 1, 2007; 92(8-9): 1276 - 1287. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. S. Martinez, R. Arenas, P. Andonaegui, J. R. M. Catalan, and J. A. Pearce Geochemistry of two associated ophiolites from the Cabo Ortegal Complex (Variscan belt of NW Spain) Geological Society of America Memoirs, January 1, 2007; 200(0): 445 - 467. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Fernandez-Suarez, R. Arenas, J. Abati, J.R. M. Catalan, M.J. Whitehouse, and T.E. Jeffries U-Pb chronometry of polymetamorphic high-pressure granulites: An example from the allochthonous terranes of the NW Iberian Variscan belt Geological Society of America Memoirs, January 1, 2007; 200(0): 469 - 488. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Gomez Barreiro, J. R. Wijbrans, P. Castineiras, J. R. Martinez Catalan, R. Arenas, F. Diaz Garcia, and J. Abati 40Ar/39Ar laserprobe dating of mylonitic fabrics in a polyorogenic terrane of NW Iberia Journal of the Geological Society, January 1, 2006; 163(1): 61 - 73. [Abstract] [Full Text] [PDF]
|
|