Chalcophile behavior of thallium during MORB melting and implications for the sulfur content of the mantle
Nielsen, Sune G.
Lee, Cin-Ty A.
Behn, Mark D.
MetadataShow full item record
We present new laser ablation ICP-MS trace element concentration data for 28 elements in 97 mid-ocean ridge basalt (MORB) glasses that cover all major spreading centers as well as Tl concentration data for all mineral phases in five lherzolites from the Lherz massif, France. The ratio between the elements thallium (Tl) and cerium (Ce) is nearly constant in MORB, providing evidence that the depleted MORB mantle (DMM) has uniform Ce/Tl. Lherzolite mineral data reveal that sulfides are heterogeneous and contain between 23 and 430 ng/g of Tl while all other minerals contain Tl below the analytical detection limit of ∼1 ng/g. We argue that Tl in MORB is controlled by residual sulfide during mantle melting. To investigate the observed relationship between Tl and Ce, we conduct models of fractional mantle melting, which show that the constant Ce/Tl in MORB is only reproduced if the ratio between clinopyroxene and sulfide in the upper mantle varies by less than 10%. In addition, the rate of melting for these two phases must be nearly identical as otherwise melt depletion and refertilization processes would lead to Ce/Tl fractionation. These model results allow us to establish a relationship for the sulfur content of DMM: [S]DMM = SCSS × Mcpx /Rcpx, where SCSS is the sulfur concentration of a silicate melt at sulfide saturation, Rcpx is the melt reaction coefficient, and Mcpx is the modal abundance of clinopyroxene in the DMM. Using this equation, we calculate that the average upper mantle sulfur concentration is 195 ± 45 μg/g.
Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 15 (2014): 4905–4919, doi:10.1002/2014GC005536.
Showing items related by title, author, creator and subject.
Nielsen, Sune G.; Wasylenki, Laura E.; Rehkamper, Mark; Peacock, Caroline L.; Xue, Zichen; Moon, Ellen M. (2013-04-22)We have conducted the first study of Tl isotope fractionation during sorption of aqueous Tl(I) onto the manganese oxide hexagonal birnessite. The experiments had different initial Tl concentrations, amounts of birnessite, ...
Nielsen, Sune G.; Klein, Frieder; Kading, Tristan; Blusztajn, Jerzy S.; Wickham, Katie (2015-09)Fluids driven off the subducting Pacific plate infiltrate the shallow Mariana 26 forearc and lead to extensive serpentinization of mantle peridotite. However, the sources, pathways, and chemical modifications of ascending, ...
Determination of thallium and 17 other trace elements in the USGS glass reference materials BIR-1G, BHVO-2G and BCR-2G and their application to quantitative Tl concentrations by laser ablation ICPMS Nielsen, Sune G.; Lee, Cin-Ty A. (2012-07)Here we present the first determination of thallium (Tl) concentrations in the USGS reference materials BIR-1G, BHVO-2G and BCR-2G measured by solution ICP-MS. The Tl abundances in these three glasses span a range of about ...