Elastic wave velocity in rocks from Dabieshan and its constraints for lithospheric composition and crust-mantle recycling |
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Authors: | ZHAO Zhidan Nicolas ICHRISTENSEN Zhou Wenge Xie Hongsen ZHANG Zeming |
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Institution: | 1. Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;China University of Geosciences, Beijing 100083, China 2. Department of Geology and Geophysics, University of Wisconsin, Madison WI 53706, USA 3. Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China 4. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China |
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Abstract: | P- and S-wave velocities in eclogites and granulites from the Dabie ultrahigh pressures (UHP) meta
morphic belt, China, were measured at room temperature under the hydrostatic pressures up to 1.0 GPa. The ultrahigh
pressure eclogites had the highest densities (3.3 ~ 3.6 g.cm-3) , high velocities and the lowest anisotropy (1.4%c ~
2.6 % ) . The lowest densities (2.8 ~ 3.1 g. cm- 3 ) and the highest Poisson' s ratios (0.28 ~ 0.29) were found in gran
ulites, whereas the strongest anisotropies (6. 1 % ~8.4% ) were found in the high-pressure (HP) eclogites. Compari
son of the velocities in rocks with that observed in the deep seismic sounding profile crossing Dabieshan suggests that e
clogites might exist in the lower crust of Dabieshan, but the quantity might be small. The upper mantle has very similar
velocities as the UHP eclogites and serpentinizated/water-bearing dunite. The formation of eclogite represents the crust
mantle recycling processes. Crustal material is delaminated and sinks into the mantle by way of eclogite, whereas only a
small part of the eclogite could return to the crust. |
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Keywords: | Dabieshan eciogite elastic wave velocity anisotropy Poisson' s ratios |
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