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https://hdl.handle.net/2440/74140
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Type: | Journal article |
Title: | An XAS study of molybdenum speciation in hydrothermal chloride solutions from 25-385ºC and 600 bar |
Other Titles: | An XAS study of molybdenum speciation in hydrothermal chloride solutions from 25-385 degree(s) C and 600 bar |
Author: | Borg, S. Liu, W. Etschmann, B. Tian, Y. Brugger, J. |
Citation: | Geochimica et Cosmochimica Acta, 2012; 92:292-307 |
Publisher: | Pergamon-Elsevier Science Ltd |
Issue Date: | 2012 |
ISSN: | 0016-7037 1872-9533 |
Statement of Responsibility: | Stacey Borg, Weihua Liu, Barbara Etschmann, Yuan Tian and Joël Brugger |
Abstract: | Molybdenum(VI) is expected to be the main form of Mo in hydrothermal fluids up to magmatic hydrothermal conditions. We conducted an in situ X-ray absorption spectroscopic study of Mo(VI) speciation in H2O-HCl-NaCl brines up to 385°C at a pressure of 600bar. The EXAFS (Extended X-ray Absorption Fine Structure) and XANES (X-ray Absorption Near-Edge Structure) data supported by ab-initio XANES calculations confirm that tetrahedral complexes containing the molybdate anion (MoO42-) predominate in basic to near neutral solutions with chloride concentration up to 5.5m. The geometry of this species changes little over the investigated P-T range, and there is no complexation between MoO42- and chloride. In highly acidic solutions, Mo(VI) speciation is dominated by distorted octahedral oxo-chloro complexes MoOmCln6-2m-n; the number of chloride ligands increases with increasing temperature, to a maximum of ∼5 (e.g., MoOCl5-) at 340°C in 6.21m HCl. These data suggest that Mo speciation is dominated by tetrahedral molybdate species (e.g., HMoO4- or MoO42-) in the basic to near neutral solution phase of natural hydrothermal fluid, and chloride complexes will only play a significant role in highly acidic fluid under our experimental P-T conditions. © 2012 Elsevier Ltd. |
Rights: | Copyright © 2012 Elsevier B.V. |
DOI: | 10.1016/j.gca.2012.06.001 |
Grant ID: | http://purl.org/au-research/grants/arc/DP0878903 |
Published version: | http://dx.doi.org/10.1016/j.gca.2012.06.001 |
Appears in Collections: | Aurora harvest 4 Earth and Environmental Sciences publications |
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