Subduction history of the Tethyan region derived from seismictomography and tectonic reconstructions

Subduction history of the Tethyan region derived from seismictomography and tectonic reconstructions 

E. Hafkenscheid,1,2 

M. J. R. Wortel,1

and W. Spakman1 

1- Vening Meinesz Research School of Geodynamics, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands. 

2- Now at Shell International Exploration & Production, Rijswijk, Netherlands.

20 April 2005; revised 16 February 2006; accepted 29 March 2006; published 8 August 2006.

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, 111, B08401, doi:10.1029/2005JB003791, 2006

Citation: Hafkenscheid, E., M. J. R. Wortel, and W. Spakman (2006), Subduction history of the Tethyan region derived from seismic tomography and tectonic reconstructions, J. Geophys. Res., 111, B08401, doi:10.1029/2005JB003791.

[1] In the mantle underneath the Tethyan suture zone, large volumes of positive velocityanomalies have been imaged by seismic tomography and interpreted as the present-daysignature of subducted Tethyan lithosphere. We investigate the Mesozoic-Cenozoicsubduction history of the region by integrating independent information from mantletomography and tectonic reconstructions. Three different subduction scenarios for theTethyan oceanic lithosphere, representative for the available tectonic reconstructions, areused to predict the present thermally anomalous volumes associated with the lithosphericsurface subducted since the late Mesozoic. Next, these predicted thermal volumes andtheir expected positions are compared to the relevant anomalous volumes derived fromseismic tomographic images. In this analysis we include, among others, the possibleeffects of ridge subduction and slab detachment after the Cenozoic continental collisions,absolute plate motion, and slab thickening in the mantle. Our preferred subductionmodel comprises the opening of large back-arc oceanic basins within the Eurasian margin.The model points to slab thickening by a factor of 3 in the mantle, in which case theestimated volumes allow for active oceanic spreading (~1–2.5 cm/yr) in the Tethyanlithosphere during convergence. Our results further indicate the occurrence of earlyOligocene slab detachment underneath the northern Zagros suture zone, followed by bothwestward and eastward propagation of the slab tear and diachronous Eocene to Mioceneslab detachment below the eastern to western Himalayas. Free sinking rates of thedetached material of ~2 cm/yr in the lower mantle provide the best fit between thetomographic mantle structure and our Tethyan subduction model

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