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《Chinese Journal of Geophysics》 2005-06
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Detection of mineralogical changes in pyrite using measurements of temperature-dependence susceptibilities

LI Hai-Yan,ZHANG Shi-HongState Key Laboratory of Geological Processes and Mineral Resources & Key Laboratory of Lithosphere Tectonics andLithoprobing Technology of Ministry of Education,China University of Geosciences,Beijing 100083,China  
Detailed measurements of temperature-dependence susceptibilities were employed to detect mineralogical changes of pyrite samples from Song county,Henan Province.The results indicate that pyrite converts into pyrrhotite in either an argon or an air atmosphere through two possible processes.One is that magnetite firstly appears around the powder of pyrite by oxidation caused by oxygen adsorbed on the powder,and then the newly formed magnetite reacts with sulfur atoms which are released from the pyrite lattice and converts into pyrrhotite at higher temperature.The other is that pyrite directly transforms into pyrrhotite by desulphation,and this reaction is the main source of pyrrhotite in our experiments.During heating in an argon atmosphere,magnetite begins to occur at 380℃,while pyrrhotite does not occur until 535℃.When pyrite is heated to 535℃~560℃,the Curie temperature of the newly formed pyrrhotite is not stable,and the Curie temperature of newly formed pyrrhotite may tend to be stable when pyrite is heated to above about 560℃.The type of the newly formed magnetic minerals when pyrite is heated in an argon atmosphere only depends on the maximal temperature,and does not depend on the linger time at the maximal temperature,while the amount of the newly formed magnetic minerals is controlled by both these factors.
【Fund】: 国家自然科学基金(40032010B);; 教育部新世纪优秀人才支持计划(NCET-04-0727)资助
【CateGory Index】: P618.31;
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