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河北汉诺坝新生代玄武岩携带的石榴辉石岩为岩浆底侵于上地幔顶部40~45 km形成的堆晶岩,是壳-幔过渡带的典型样品。本文使用Solartron 1260阻抗分析仪,测量112 GPa和380~900 e下石榴辉石岩WD958的电阻率。样品电导率(R)与温度的关系遵守Arr henius方程:R=R0ex p(-$H/kT),其中T是样品的绝对温度,k是Boltzmann常数,指前因子R0为9715 S/m,活化焓$H为1127 eV。使用傅立叶红外光谱仪测定样品中单斜辉石的平均含水量为117@10-6H2O,橄榄石无水,石榴子石的含水量因蚀变无法测定。使用Hashin-Shtrikman平均方法计算样品WD958的电导率,发现样品可看作由含水单斜辉石、无水石榴子石和无水橄榄石组成的高阻集合体,电导率同时受小极化子导电和质子导电的影响。如果原位的石榴辉石岩的矿物含水量保持平衡,其电导率将提高1个数量级,质子导电成为主控导电机制。石榴辉石岩在高温的壳-幔过渡带(~1000e)表现为高导层,而在正常地温梯度下,与尖晶石二辉橄榄岩的电导率近似,为高阻层。因此,在岩浆底侵作用下,电性上的壳-幔边界将随着温度和含水量的变化而改变。
The garnet pyroxene from the Cenozoic basalts of Hannoba Dam, Hebei Province is a typical magmatic crust that formed at the bottom of the upper mantle by 40-45 km. It is a typical sample of the crust-mantle transition zone. This paper uses the Solartron 1260 impedance analyzer to measure the resistivity of garnet pyroxene WD958 at 112 GPa and 380-900 e. The relationship between the conductivity of the sample (R) and the temperature follows the Arrhenius equation: R = R0ex p (- $ H / kT) where T is the absolute temperature of the sample, k is the Boltzmann constant, R0 is 9715 S / m, The activation enthalpy $ H is 1127 eV. The average water content of clinopyroxene in the sample was determined by Fourier transform infrared spectroscopy (FTIR) of 117 @ 10-6H2O. The olivine was anhydrous and the water content of garnet could not be determined by the alteration. Using the Hashin-Shtrikman average method to calculate the conductivity of sample WD958, the sample was found to be a high resistance aggregate consisting of hydrous clinopyroxene, anhydrous garnet and anhydrous olivine, with conductivity being simultaneously impressed by the small polaron And proton conductivity. If the mineral content of in-situ garnet pyroxene remains balanced, its conductivity will increase by one order of magnitude, and proton conductivity becomes the dominant conducting mechanism. Garnet pyroxenes are high-conductivity layers in high-temperature crust-mantle transitional zone (~ 1000e), and are similar to spinel lherzolites at high normal temperature gradients. Therefore, under the magmatic underplating, the electrical crust-mantle boundary will change with the change of temperature and water content.