Crustal stacking and expulsion tectonics during continental subduction: P-T deformation constraints from Oman

Agard, Philippe and Searle, Michael P. and Alsop, G. Ian and Dubacq, B. (2010) Crustal stacking and expulsion tectonics during continental subduction: P-T deformation constraints from Oman. Tectonics, 29. 19 PP.. DOI 10.1029/2010TC002669

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Abstract

The northeastern continental margin of Oman in the Saih Hatat region is characterized by high-pressure (HP) chloritoid- or carpholite-bearing metasediments and highly deformed mafic eclogites and blueschists in a series of tectonic units bounded by high-strain ductile shear zones. New data on the upper cover units of this HP nappe stack indicate that all of them underwent similar P conditions to the underlying Hulw structural unit (with a cooler exhumation pressure-temperature path). Early SSW directed crustal thickening during ophiolite emplacement created recumbent folds and strong schistose fabrics in these Permian-Mesozoic shelf carbonates and was followed by later NNE dipping normal sense shear zones and normal faults. The Mayh unit shows high strain in a 15–25 km long sheath fold that likely formed at carpholite grade pressures of 8–10 kbar. We show that there are no significant P differences across the Hulw shear zone (upper plate–lower plate discontinuity) or between the overlying Mayh, Yenkit-Yiti, and Ruwi units. Postpeak metamorphic exhumation of the HP rocks was therefore accomplished by bottom-to-SSW (rather than top-to-NNE) active footwall extrusion beneath a fixed, static, passive hanging wall. Footwall uplift beneath these passive roof faults resulted in progressive expulsion of the HP rocks from depths of ∼80–90 km (eclogites) and mainly 30–35 km (blueschists and chloritoid-/carpholite-bearing units) during the Campanian–Early Maastrichtian. Oman thus provides a detailed record of how continental material (thick platform shelf carbonates) progressively jammed a subduction zone and emphasizes the contrasting behavior between cover units and their underlying basement.

Item Type:	Article
Uncontrolled Keywords:	2010AREP; IA62;
Subjects:	02 - Geodynamics, Geophysics and Tectonics
Divisions:	02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title:	Tectonics
Volume:	29
Page Range:	19 PP.
Identification Number:	10.1029/2010TC002669
Depositing User:	Sarah Humbert
Date Deposited:	04 Jun 2011 14:50
Last Modified:	23 Jul 2013 10:02
URI:	http://eprints.esc.cam.ac.uk/id/eprint/2072

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