Experimental determination of elastic properties of talc to 800°C, 0.5 GPa; calculations of the effect on hydrated peridotite, and implications for cold subduction zones
Experimental determination of elastic properties of talc to 800°C, 0.5 GPa; calculations of the effect on hydrated peridotite, and implications for cold subduction zones
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DOI：
10.1016/s0012-821x(00)00288-0
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发表时间：
2000-12
影响因子：
5.3
通讯作者：
E. Bailey;J. Holloway
中科院分区：
文献类型：
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作者：
E. Bailey;J. Holloway
我们测量了滑石的纵波速度（VP）作为0.5 GPa温度的函数。在25°C时，vps从5.27±0.23 km s−1下降到800°C时的4.35±0.15 km s−1。将这些结果与先前公布的体积模量(K)和δK/δP相结合，得出大气条件下泊松比（ν）为0.268，剪切模量(G)为22.6 GPa。假设ν与温度无关，则δK/δT值为- 19.3±0.64 MPa K−1at 0.5 GPa。我们利用实验数据，结合已发表的数据，计算了在冷俯冲岩石圈上方与滑石水合的橄榄岩的弹性模量界限。我们发现，在700°C时，仅含0.9 wt% H2O的组合的弹性波速（根据voight - reuss - hill平均值计算）比无水岩石的VP平均低7.6%，剪切波（Vs）平均低9.7%。这些结果与在冷俯冲板块表面附近观察到的转换相行为一致，并且可能将观察到的低速层放置在最底部的地幔楔中，而不是像以前所建议的那样放置在最上面的板块中。
We have measured compressional wave velocity (VP) in talc as a function of temperature at 0.5 GPa. VPfalls from 5.27±0.23 km s−1at 25°C to 4.35±0.15 km s−1at 800°C. Combining these results with a previously published bulk modulus (K) and δK/δP, gives a Poisson’s ratio (ν) of 0.268 and a shear modulus (G) of 22.6 GPa under atmospheric conditions. Assuming that ν is independent of temperature gives a δK/δT value of −19.3±0.64 MPa K−1at 0.5 GPa. We used the experimental data, in combination with published data, to calculate bounds on the elastic moduli of a peridotite hydrated with talc just above cold subducting lithosphere. We find that an assemblage hydrated by only 0.9 wt% H2O has elastic wave velocities (calculated from the Voigt–Reuss–Hill average) lower than the anhydrous rock by an average of 7.6% for VP, and 9.7% for shear waves (Vs) at 700°C. These results are consistent with observations of converted phase behavior in the vicinity of the surface of a cold subducting slab, and may place the low-velocity layer observed in the lowermost mantle wedge, not the uppermost slab as has previously been suggested.