• 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

     <font size="3"><font face="Times New Roman">Garnet pyroxenite xenoliths from the Hannuoba Cenozoic basalt were formed by magmatic underplat- ing in the uppermost mantle font>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">（<font face="Times New Roman">40--45 kinfont>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">）<font face="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 -- 900font>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">℃<font face="Times New Roman">, using a Solartron 1260 Phase-Gain Analyzer. The temperature dependence of electrical conductivity font>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">（<font face="Times New Roman">afont>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">）<font face="Times New Roman"> can be fitted by an Arrhe- nius equationfont>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">：<font face="Times New Roman"> a - o0 expfont>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">（<font face="Times New Roman"> - AH/kTfont>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">）<font face="Times New Roman">, where T is in Kelvin and k is the Dohzmann constant. Values of the pre- exponential factor font>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">（<font face="Times New Roman">a0font>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">）<font face="Times New Roman"> and activation enthalpy of electric conductivity font>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">（<font face="Times New Roman">AHfont>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">）<font face="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 font>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">×<font face="Times New Roman">10-6 H2O, whereas olivine is very dry font>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">（〈<font face="Times New Roman"> 1 font>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">×<font face="Times New Roman">10-6H20font>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">）<font face="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 font>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">（<font face="Times New Roman">40--45 kmfont>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">）<font face="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 font>font-family: 宋体; mso-ascii-font-family: ’times new roman’; mso-hansi-font-family: ’times new roman’">℃<font face="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.font>font>