Iron oxidation state in garnet from a subduction setting: a micro-XANES and electron microprobe ("flank method") comparative study

被引:24
作者
Borfecchia, Elisa [1 ,2 ,3 ]
Mino, Lorenzo [1 ,2 ,3 ]
Gianolio, Diego [1 ,2 ,3 ]
Groppo, Chiara [4 ]
Malaspina, Nadia [5 ]
Martinez-Criado, Gema [6 ]
Sans, Juan Angel [6 ]
Poli, Stefano [7 ]
Castelli, Daniele [4 ]
Lamberti, Carlo [1 ,2 ,3 ]
机构
[1] Univ Turin, Dept Chem, I-10125 Turin, Italy
[2] NIS Ctr Excellence, I-10135 Turin, Italy
[3] INSTM Ctr Riferimento, I-10135 Turin, Italy
[4] Univ Turin, Dept Earth Sci, I-10125 Turin, Italy
[5] Univ Milano Bicocca, Dept Geol Sci & Geotechnol, I-20126 Milan, Italy
[6] European Synchrotron Radiat Facil, ID22, F-38043 Grenoble, France
[7] Univ Milan, Dept Earth Sci, I-20133 Milan, Italy
关键词
X-RAY-ABSORPTION; NEAR-EDGE STRUCTURE; ELECTROABSORPTION-MODULATED LASERS; FE K-EDGE; FERRIC IRON; IN-SITU; MOSSBAUER MILLIPROBE; OXYGEN FUGACITY; REDOX REACTIONS; MU-XRF;
D O I
10.1039/c2ja30149k
中图分类号
O65 [分析化学];
学科分类号
070302 ; 081704 ;
摘要
The variation of the Fe-redox state across a strongly zoned garnet crystal occurring in a FeTi-oxide metagabbro from a subduction setting has been investigated comparing micro-XANES and electron microprobe ("flank method") results. This sample represents an ideal monitor of the redox processes associated with devolatilization reactions occurring in the subducting slab and likely involved in the oxidation of the mantle wedge, as well as a challenge for the analytical methods. Since in the studied garnet the Fe3+/Sigma Fe variations are small and occur on a micrometric scale, we exploited the X-ray microprobe available at the ESRF ID22 beamline to reach a spot size of 1.7 mu m x 5.3 mu m. Our study represents a first attempt to measure the Fe3+/Sigma Fe variations across a single crystal of garnet, ca. 400 mm in diameter, using the micro-XANES technique. The absolute Fe3+/Sigma Fe values obtained with micro-XANES and "flank method" are perfectly comparable, ranging from a maximum of about 0.1 in the garnet core to a minimum of 0.0 in the garnet rim.
引用
收藏
页码:1725 / 1733
页数:9
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