The Journal of Petrology, Volume 38, Issue 11: November 1997.

Interlayered eclogites, blueschists and epidote amphibolites from NE Oman: a record of protolith compositional control and limited fluid infiltration

AK El-Shazly^1,2,*, MA Worthing¹ and JG Liou³

¹Department of Earth Sciences, Sultan Qaboos University, PO Box 36, Al-Khod PC 123, Oman, ²Department of Geological Sciences, Southern Methodist University, Dallas, TX 75275, USA, ³Department of Geology and Earth Systems Science, Standford University, Stanford, CA 94305, USA, ^*Corresponding author

Eclogites, blueschists, clinopyroxene-rich rocks and epidote amphibolites occur interlayered on a millimetre to decimetre scale in a mafic unit interbedded with calcareous and quartz mica shists in NE Oman. These rocks constitute part of the continental margin of Oman subducted during the Cretaceous. Petrological data indicate that they evolved through a clockwise P-T path and attained peak conditions at T 560°C, P >12 kbar, where the mineral assemblages of the blueschists, eclogites and clinopyroxene-rich rocks were all stable. Whole-rock major, trace and rare earth element data indicate that the mineralogical differences between these rock types resulted from the metamorphism of interlayered basaltic flows and tuffs of variable compositions possibly reflecting different degrees of magmatic differentiation. The interlayered epidote amphibolites are chemically similar to the blueschists and appear to have formed from the eclogites and blueschists during unroofing aided by fluid infiltration. Oxygen isotope data for minerals and whole rocks indicate low fluid:rock ratios during metamorphism and unroofing. The data also suggest that different layers may have interacted with fluids of different isotopic signatures throughout their history. These results are similar to data reported for other areas of continent-continent collision or continental crust subduction.

Key words: blueschists; eclogites; epidote amphibolites; fluids;stable isotopes

Pages 1461-1487