Seismic properties of peridotite xenoliths as a clue to imagine the lithospheric mantle beneath NE Tasmania, Australia
Seismic properties of peridotite xenoliths as a clue to imagine the lithospheric mantle beneath NE Tasmania, Australia
复制标题
橄榄岩捕虏体的地震特性作为想象澳大利亚塔斯马尼亚东北部岩石圈地幔的线索
DOI：
10.1016/j.tecto.2011.12.002
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发表时间：
2012
期刊：
影响因子：
2.9
通讯作者：
Takako Satsukawa
中科院分区：
文献类型：
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作者：
Katsuyoshi Michibayashi;Takako Satsukawa
澳大利亚塔斯马尼亚州东北部的橄榄岩捕虏体由尖晶石橄榄岩和小粒子石组成，根据塔斯马尼亚州地下的地热梯度，这些橄榄岩捕虏体起源于深度不到40公里的最上层地幔，其中莫霍河的深度为29公里。在收集到的13个样品中，有5个样品（1个橄榄石和4个橄榄石）的晶体偏好取向（CPOs）足够大，可以进行测量。橄榄石型CPOs以（010）[100]滑移为主。对捕虏体进行的地温分析表明，捕虏体温度为950 ~ 1050℃，压力为0.7 ~ 1.1 gpa。利用这些数据，我们计算了在1000°C和1GPa条件下，在三种地球动力学模型（伸展、剪切和上升流）下，具有理想体积分数的橄榄石和辉石岩石在不同方向的结构参考框架下的地震特性变化。水平伸展模型最能解释塔斯马尼亚东北部最上层岩石圈地幔的结构。
Peridotite xenoliths from Northeast Tasmania, Australia, consist of spinel lherzolites and minor dunites that originated from the uppermost mantle at depths of less than 40km, based on the geothermal gradient beneath Tasmania, where the depth of the Moho is 29km. The crystal preferred orientations (CPOs) of olivine and pyroxene were measured in 5 of 13 collected samples (1 dunite and 4 lherzolites) that were large enough to enable measurements. Olivine CPOs indicate the dominance of (010) [100] slip. Geothermobarometric analyses of the xenoliths yield temperatures of 950–1050°C and pressures of 0.7–1.1GPa. Using these data, we calculated changes in the seismic properties of a rock with ideal volume fractions of olivine and pyroxene under conditions of 1000°C and 1GPa, for various orientations of the structural reference frame in the case of three geodynamic models (extension, shear, and upwelling). The model of horizontal extension performs best in explaining the structure of the uppermost lithospheric mantle beneath Northeast Tasmania.