期刊
GEOCHIMICA ET COSMOCHIMICA ACTA
卷 267, 期 -, 页码 164-178出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.gca.2019.09.029
关键词
Copper; Sulfur; XAFS; Spectroscopy; Synchrotron; Melt Inclusions; Hawaii
资金
- National Science Foundation Earth Sciences collaborative research grant [EAR-1834930, 1834941, 1834959, 1834939]
- National Science Foundation [1309047]
- National Science Foundation, Earth Sciences [EAR-1128799]
- Department of Energy, Geosciences [DE-FG0294ER14466]
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-06CH11357]
- Smithsonian Institute National Museum of Natural History Department of Mineral Sciences [NMNH 117393, NMNH 11124052, NMNH 113498-1]
- Directorate For Geosciences
- Division Of Earth Sciences [1834939, 1834930] Funding Source: National Science Foundation
- Directorate For Geosciences
- Division Of Earth Sciences [1834941, 1834959] Funding Source: National Science Foundation
Micro-analytical determination of copper (Cu) speciation in natural magmatic glasses, equilibrated below the nickel - nickel oxide (NNO) buffer, reveals that two copper species are commonly stabilized in such basaltic melts. X-ray absorption fine structure (XAFS) spectroscopic analysis of basaltic matrix glasses and melt inclusions (MI) from samples of mid-ocean ridge basalt (MORB), and from Nyamuragira, Etna and Kilauea volcanoes shows that Cu complexes as both Cu(I)-sulfide and Cu (I)-oxide species in silicate melts. The proportion of each species correlates with the measured sulfur (S) abundance of the glass. In glasses with S abundances greater than similar to 1000 ppm, Cu(I)-sulfide species are dominant, whereas in glasses with S abundances between 500 and 1000 ppm, both species are found to coexist. The Cu(I)-oxide species dominate at S concentrations below 500 ppm. In 1 atm S-free experimental glasses of basaltic composition that we analyzed, only Cu(I)-oxide species are detectable, regardless of the oxygen fugacity (fO(2)), even at relatively high fO(2) values well above the NNO buffer. Our results demonstrate that XAFS techniques are highly sensitive in measuring Cu speciation in reduced (below NNO) basaltic glasses and that both oxide and sulfide complexes can be stabilized. The relative proportion of these two species is highly dependent on the concentration of S in the melt, and thus the Cu speciation in natural melts changes as S is lost from the melt by low pressure degassing. (C) 2019 Elsevier Ltd. All rights reserved.
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