Sm-Nd and Zircon U-Pb ages from garnet-bearing eclogites, NE Oman: constraints on High-P metamorphism

Details Sm-Nd and Zircon U-Pb ages from garnet-bearing eclogites, NE Oman: constraints on High-P metamorphism Sm-Nd and Zircon U-Pb ages from garnet-bearing eclogites, NE Oman: constraints on High-P metamorphism

May 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004e%26psl.222..407g&link_type=abstract

Earth and Planetary Science Letters, Volume 222, Issue 2, p. 407-422.

Computer Science

11

Subduction, Eclogite Facies, Oman, Sm-Nd Dating, U-Pb Shrimp Zircon Dating

Scientific paper

Poly-deformed and poly-metamorphosed glaucophane-eclogite mega-boudins beneath the Samail Ophiolite, Oman record an early subduction-related high-P metamorphism as well as subsequent overprinting deformation and metamorphism related to exhumation. Previously published Rb/Sr ages of 78 Ma and 40Ar/39Ar ages of 82-79 Ma record the major NE-directed shearing event that partially exhumed the eclogites to a shallower crustal level. New Sm/Nd garnet-garnet leachate-whole rock isochron data from garnet-bearing eclogite assemblages in the As Sifah subwindow in NE Oman are 110+/-9 Ma (DG02-87D); 5-point isochron) and 109+/-13 Ma (DG02-86E; 3-point isochron). On the basis of microfabric and field structural relationships these ages are interpreted to reflect the timing of prograde, peak high-P metamorphism in the rocks structurally beneath the Samail Ophiolite. This metamorphism clearly predates the age of formation of the obducted Samail oceanic lithosphere (97-94 Ma) as well as the subsequent obduction onto the margin (80-70 Ma). A U-Pb SHRIMP zircon age from small (<200 μm in length) zircons with herring-bone textured zoning from DG02-87D indicate that rapid zircon growth associated with high-Si phengites occurred at 82+/-1 Ma. Zircon growth is possibly related to liberation of Zr on garnet breakdown during decompression metamorphism under high-P conditions with exhumation. These data require that crustal stacking models attendant with ophiolite obduction are inappropriate to explain the Oman high-P metamorphism.

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