文献类型：期刊文献

英文题名：Mechanism and kinetics of a mineral transformation under hydrothermal conditions: Calaverite to metallic gold

作者：Zhao, Jing[1,2];Brugger, Joel[2,3];Grundler, Pascal V.[2,3];Xia, Fang[2,3];Chen, Guorong[1];Pring, Allan[2,3]

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

年份：2009

卷号：94

期号：11-12

起止页码：1541

外文期刊名：AMERICAN MINERALOGIST

收录：;EI(收录号：20211910334065);WOS:【SCI-EXPANDED(收录号:WOS:000272275200004)】；

基金：This project has greatly benefited front the collaboration between South Australian Museum and East China University of Science and Technology. We thank Peter Self, Len Green, and Angus Netting front Adelaide Microscopy Center for their assistance in using the FESEM, EBSD, and electron microprobe. This work has been made possible by the financial support of the Australian Research Council (grant DP0880884). The authors are grateful to Associate Editor Ed Grew and referees Rob Hough and Kilian Pollock for their useful comments on the original manuscript.

语种：英文

外文关键词：Calaverite; gold; dissolution-reprecipitation; pseudomorphism; replacement

摘要：The transformation of calaverite to gold tinder hydrothermal conditions was studied experimentally by probing the effects of temperature (140 to 220 degrees C), pH (2-12), oxidant concentration, geometric specific surface area, and solid-weight to fluid-volume ratio on the sample textures and the reaction kinetics. Under all of the experimental conditions explored, calaverite transformed to various extents to metallic gold. The replacement is pseudomorphic, as gold preserves the external dimensions of calaverite. The resulting elemental gold is porous; consisting of filament-shaped aggregates with diameters ranging from 200 to 500 nm and lengths up to 25 mu m. Gold crystals appear to be randomly oriented with respect to the twinned calaverite grains. The transformation proceeds via a coupled calaverite dissolution-gold precipitation mechanism, with calaverite dissolution being rate-limiting relative to gold precipitation. Tellurium is lost to the bulk solution as Te(IV) complexes, and may further precipitate away from the dissolution site (e.g., autoclave walls) as TeO2(s). In contrast, gold precipitates locally near the calaverite dissolution site. Such local gold precipitation is facilitated by fast heterogeneous nucleation onto the calaverite surface. The dissolution of calaverite and the overall reaction are oxidation reactions, and oxygen diffusion through the porous metallic gold layer probably plays an important role in sustaining the reaction. A similar dissolution-reprecipitation process may be responsible for the formation of mustard gold during the weathering of gold-telluride ores. At 220 degrees C, solid-state replacement of calaverite by gold is slow (months), but calaverite grains similar to 100 mu m in size are fully replaced in <24 h under hydrothermal conditions, providing a possible alternative to roasting as a pre-treatment of telluride-rich gold ores.