磁铁矿热电效应:地震地电异常的新模式
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摘要
采用BHTE-06新型热电测量仪,选择地壳内广泛分布的磁铁矿进行热电性测量,结果表明:磁铁矿的热电导型均为N型,其热电系数σ(单位温差下热电势增量)近似恒值,为-0.05mV/℃,标准偏差1.15,这说明磁铁矿为电子型半导体并具有稳定的热电转换效能。通过不同成因磁铁矿对比测量,以及固定和不固定结晶学方向的对比测量还可知,磁铁矿的热电性不受其成因和结晶学方向的制约,说明磁铁矿聚集体能够将热电效应叠加放大。因此认为,地壳中的磁铁矿聚集体可能是地震过程中将热能转换为电能的热-电转换器,热电效应可能是导致地震地电场异常的原因之一,即地震地电异常存在热电机制。依据测试所得的热电系数σ值,按照热电和地电基本理论进行的电场模拟计算表明:由磁铁矿热电效应引起的热电场强度能够达到-n×10-6V/m～-n×10-4V/m,该电场强度足以引起地表电场的显著异常,因而是地震地电异常的重要模式之一。
The magnetite,exist widely in crust,was tested on thermoelectricity by new equipment of BHET-06.The results showed that the electric-conduction of all magnetite samples are N-type(also called electron type),and thermoelectric coefficient σ(thermal voltage was divided by temperature difference)is a constant value of-0.05 mV/℃ approximately,with the standard deviation is 1.15.It means that the thermal energy can be converted steady into electric energy by magnetite.Furthermore,results by compared test for different genetic magnetite under fixed and unfixed position showed that the thermoelectricity of magnetite is not controlled by genesis and crystallography direction.This implied that the thermoelectric effect of the magnetite can be piled up and made much stronger.For this reason,a new viewpoint is proposed that the magnetite aggregate in the crust is maybe a converter from thermal into electric during process of earthquake occurrence,namely,thermoelectric effect may be one of reasons on abnormal geo-electricity during earthquake,or abnormal geo-electricity in earthquake is caused by thermoelectric mechanism.Based on the thermoelectric coefficient value tested in the experiments,and on the thermoelectric and geo-electric theories,the thermoelectric field was computed.It was showed that the field intensity can reach-n×10-6 V/m～-n×10-4 V/m.Obviously,the field values are large enough to lead to the geo-electric abnormity.So it is considered that thermoelectric effect is a new model for the abnormal geo-electricity during the earthquake process.
The magnetite,exist widely in crust,was tested on thermoelectricity by new equipment of BHET-06.The results showed that the electric-conduction of all magnetite samples are N-type(also called electron type),and thermoelectric coefficient σ(thermal voltage was divided by temperature difference)is a constant value of-0.05 mV/℃ approximately,with the standard deviation is 1.15.It means that the thermal energy can be converted steady into electric energy by magnetite.Furthermore,results by compared test for different genetic magnetite under fixed and unfixed position showed that the thermoelectricity of magnetite is not controlled by genesis and crystallography direction.This implied that the thermoelectric effect of the magnetite can be piled up and made much stronger.For this reason,a new viewpoint is proposed that the magnetite aggregate in the crust is maybe a converter from thermal into electric during process of earthquake occurrence,namely,thermoelectric effect may be one of reasons on abnormal geo-electricity during earthquake,or abnormal geo-electricity in earthquake is caused by thermoelectric mechanism.Based on the thermoelectric coefficient value tested in the experiments,and on the thermoelectric and geo-electric theories,the thermoelectric field was computed.It was showed that the field intensity can reach-n×10-6 V/m～-n×10-4 V/m.Obviously,the field values are large enough to lead to the geo-electric abnormity.So it is considered that thermoelectric effect is a new model for the abnormal geo-electricity during the earthquake process.
引文
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[13]Kapicka A,Petrovsky E,Hrouda F,Pohl J.Change in magnetic parameters of rocks under stress conditions of the earth′s crust:relation-ship to magnetic mineralogy[J].Rev Pressure Sci Technol,1998,7:69-71.
[14]钱复业,赵玉林.地电场短临预报方法研究[J].地震,2005,25(2):33-40.
[2]强祖基,姚清林,魏乐军,等.震前卫星热红外环形应力场特征[J].地球学报,2008,29(4):486-494.
[3]李家驹.矿物的热电效应及其应用[J].地质论评,1965,23(4):316-317.
[4]曹显光,梁秉强.地震带与矿产密集区的相关性分析[J].西南矿产地质,1997,(3,4):88-94.
[5]邓明德,耿乃光,崔承禹.岩石应力状态改变引起岩石热状态改变的研究[J].中国地震,1997,13(2):17-185.
[6]张永仙,尹祥础.热物质运移与震前地表垂直形变异常关系研究[A].陈云泰主编.中国地震学会第八次学术大会论文摘要集[C].北京:地震出版社,2000,111.
[7]刘恩科,朱秉升,罗晋生.半导体物理学[M].北京:电子工业出版社,2008,350-364.
[8]Pecheraky D M,Genshaft YS.Petromagnetismof the continental crust:a summary of21th century research[J].Physics of the Solid Earth,2002,38(1):2-32.
[9]任留东,牛宝贵,吴春明,等.大别山霓辉花岗岩中磁铁矿的形成[J].矿物岩石,2008,28(4):36-42.
[10]张海东,刘建超,刘淑文,等.太行山南段平顺地区矽卡岩铁矿地质特征及成矿模式[J].矿物岩石,2009,29(3):53-59.
[11]Rudnick R L,Taylor S R.The composition and petrogenesis of the lower crust:a xenolith study[J].J Geophys Res,1987,92:13981-14005.
[12]张昌达.由卫星和航空磁测成果推断中国岩石圈的磁性特征[J].地球物理学进展,2003,18(1):103-110.
[13]Kapicka A,Petrovsky E,Hrouda F,Pohl J.Change in magnetic parameters of rocks under stress conditions of the earth′s crust:relation-ship to magnetic mineralogy[J].Rev Pressure Sci Technol,1998,7:69-71.
[14]钱复业,赵玉林.地电场短临预报方法研究[J].地震,2005,25(2):33-40.
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