• 责任者：Men Qingbo (State Key Laboratory for Mineral Deposits Research ; School of Earth Sciences and Engineering ; Nanjing University ; Nanjing 210093 ; China) ; Wang Qin
• 刊名：Acta Petrologica et Mineralogica
• 出版年：2013
• 卷期：32(5)
• 关键词：石榴子石辉石岩 ; garnet pyroxenite ; 电导率 ; electrical conductivity ; 底侵作用 ; underplating
• 页码：p.652-662
• 图表：5 illus., 2 tables, 56 refs.
• 分类号：0801
• issnNo：ISSN1000-6524
• isbnNo：CN11-1966/P

     Garnet pyroxenite xenoliths from the Hannuoba Cenozoic basalt were formed by magmatic underplat- ing in the uppermost mantle hansi-font-family: ’times new roman’">（40--45 kinhansi-font-family: ’times new roman’">）, and represent the crust-mantle transition zone. The electrical con- ductivity of sintered garnet pyroxenite WD958 was measured at 1.2 GPa and 380 -- 900hansi-font-family: ’times new roman’">℃, using a Solartron 1260 Phase-Gain Analyzer. The temperature dependence of electrical conductivity hansi-font-family: ’times new roman’">（ahansi-font-family: ’times new roman’">） can be fitted by an Arrhe- nius equationhansi-font-family: ’times new roman’">： a - o0 exphansi-font-family: ’times new roman’">（ - AH/kThansi-font-family: ’times new roman’">）, where T is in Kelvin and k is the Dohzmann constant. Values of the pre- exponential factor hansi-font-family: ’times new roman’">（a0hansi-font-family: ’times new roman’">） and activation enthalpy of electric conductivity hansi-font-family: ’times new roman’">（AHhansi-font-family: ’times new roman’">） of sample WD958 are 97.5 S/m and 1.27 eV, respectively. The water contents of minerals were analyzed using the Fourier transform infrared spectrometry. The average water content in clinopyroxene is 117 hansi-font-family: ’times new roman’">×10-6 H2O, whereas olivine is very dry hansi-font-family: ’times new roman’">（〈 1 hansi-font-family: ’times new roman’">×10-6H20hansi-font-family: ’times new roman’">） and the water content in garnet cannot be determined due to alteration. The laboratory-derived electrical conductivity of mantle minerals shows that the calculated conductivity using the Hashin-Shtrikman av- erage can match the measured values by assuming a mixture of hydrogen-bearing clinopyroxene, dry garnet and dry olivine. This demonstrates the contribution of both small polaron conduction and proton conduction mecha- nisms to the bulk conductivity of garnet pyroxenite, and the sample can be regarded as a resistive matrix with non-interconnected conductive inclusions. If the water partition equilibrium between minerals is preserved at the in situ depth hansi-font-family: ’times new roman’">（40--45 kmhansi-font-family: ’times new roman’">）, the electrical conductivity of garnet pyroxenite will be enhanced by 1 order magni- tude and the proton conduction mechanism becomes predominant. For the lithosphere with a high geothermal gradient, the temperature at the Moho depth could reach 1 000 hansi-font-family: ’times new roman’">℃ and garnet pyroxenite is characterized by high conductivity. In contrast, under normal geothermal gradients, garnet pyroxenite shows conductivity as low as spinel lherzolite. During magmatic underplating, therefore, the electrical crust-mantle boundary will vary with temperature and water concentration.