文献类型：期刊文献

英文题名：Mechanism and kinetics of pseudomorphic mineral replacement reactions: A case study of the replacement of pentlandite by violarite

作者：Xia, Fang[2];Brugger, Joel[1,3];Chen, Guorong[4];Ngothai, Yung[2];O'Neill, Brian[2];Putnis, Andrew[5];Pring, Allan[1,3]

机构：[1]S Australian Museum, Dept Mineral, Adelaide, SA 5000, Australia;[2]Univ Adelaide, Sch Chem Engn, Adelaide, SA 5005, Australia;[3]S Australian Museum, Sch Earth & Environm Sci, Adelaide, SA 5000, Australia;[4]E China Univ Sci & Technol, Key Lab Ultrafine Mat, Minist Educ, Sch Mat Sci & Engn, Shanghai 200237, Peoples R China;[5]Univ Munster, Inst Mineral, D-48149 Munster, Germany

年份：2009

卷号：73

期号：7

起止页码：1945

外文期刊名：GEOCHIMICA ET COSMOCHIMICA ACTA

收录：;WOS:【SCI-EXPANDED(收录号:WOS:000264518500011)】；

基金：The authors are indebted to Dr. Peter Self, Mr. John Terlet, and Mr. Len Green of Adelaide Microscopy for their technical assistances with FESEM and EBSD, to Mr. Jason Peak of Chemical Engineering Workshop (Adelaide University) for building up and maintaining the hydrothermal flow-through reactor. We are also grateful to Prof. David J. Vaughan, Dr. Thorsten Geisler, and an anonymous reviewer for their valuable comments and suggestions. RX. acknowledges Department of Education, Science and Training, Australian Government, for the EIPRS scholarship, and Australian Institute of Nuclear Science and Engineering, for the AINSE Postgraduate Research Award. This work is financially supported by Australian Research Council (Project ID: DP0772299).

语种：英文

摘要：Although pseudomorphic mineral replacement reactions are common in all geological environments, and have long been considered important to many geological processes such as metamorphism, metasomatism, diagenesis, and chemical weathering, their mechanisms are still not well known. We present a combined textural and kinetic study of the replacement of pentlandite, (Fe,Ni)(9)S-8, by violarite (NiFe)(3)S-4, and describe the mechanisms and kinetic behavior of this reaction by considering the role of the fluid phase, the causes of coupling between pentlandite dissolution and violarite precipitation, the rate-limiting steps controlling the kinetic behavior, and the origin of the length scale of the features preserved during pseudomorphism. The experiments were conducted under mild hydrothermal conditions (80-210 degrees C, vapor saturated pressures). Reaction kinetics shows a complex behavior depending on various physical and chemical parameters including temperature, pH, concentrations of various reaction species, solid-weight-to-fluid-volume-ratio and specific surface area. The rate of replacement (i) increases with temperature from 80 to 125 degrees C, then decreases as temperature further increases to 210 degrees C, (ii) first increases then decreases with decreasing pH from pH 6 to 1, (iii) increases with increasing concentration of oxidants such as O-2(aq), H2O2, and KMnO4, but decreases with increasing concentration of Ni2+ and Fe3+, and with increasing solid-weight-to-fluid-volume ratio, (iv) increases linearly with the specific surface area. This kinetic behavior as well as the resulting textures revealed a coupled dissolution-reprecipitation reaction mechanism. Nanometer-scale pseudomorphic replacement, through which the crystallographic orientation of pentlandite is inherited by violarite, occurs only between 1