The effect of acid soil leaching on trace element abundance in a medium-sized stream, W. Finland

AbstractThe partitioning of major and trace elements between eclogite and aqueous fluids with variable salinity was studied at 700–800 °C and 4–6 GPa in piston cylinder and multi anvil experiments. Fluid compositions were determined using the diamond trap technique combined with laser ablation ICP-MS measurements in the frozen state. In addition to NaCl, SiO2 is the main solute in the fluids. The fluid/eclogite partition coefficients of the large ion lithophile elements (LILE), such as Rb, Cs, Sr, and Ba as well as those of the light rare earths (LREE), of Pb, and of U increase by up to three orders of magnitude with salinity. These elements will therefore be efficiently transported by saline fluids. On the other hand, typical high field strength elements, such as Ti, Nb, and Ta, are not mobilized even at high salinities. Increasing temperature and pressure gradually increases the partitioning into the fluid. In particular, Th is mobilized by silica-rich fluids at 6 GPa already at low salinities. We show that we can fully reproduce the trace element enrichment pattern of primitive arc basalts by adding a few percent of saline fluid (with 5–10 wt% Cl) released from the basaltic slab to the zone of melting in the mantle wedge. Assuming 2 wt% of rutile in the eclogite equilibrated with the saline fluid produces a negative Nb Ta anomaly that is larger than in most primitive arc basalts. Therefore, we conclude that the rutile fraction in the subducted eclogite below most arcs is likely < 1 wt%. In fact, saline fluids would even produce a noticeable negative Nb Ta anomaly without any rutile in the eclogite residue. Metasomatism by sediment melts alone, on the other hand, is unable to produce the enrichment pattern seen in arc basalts. We, therefore, conclude that at least for primitive arc basalts, the release of hydrous fluids from the basaltic part of the subducted slab is the trigger for melting and the main agent of trace element enrichment. The contribution of sediment melts to the petrogenesis of these magmas is likely negligible. In the supplementary material, we provide a “Subduction Calculator” in Excel format, which allows the calculation of the trace element abundance pattern in primitive arc basalts as function of fluid salinity, the amount of fluid released from the basaltic part of the subducted slab, the fluid fraction added to the source, and the degree of melting.

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Condensation Chemistry of Circumstellar Grains

Symposium - International Astronomical Union ◽

10.1017/s0074180900203185 ◽

1999 ◽

Vol 191 ◽

pp. 279-290 ◽

Cited By ~ 17

Author(s):

Katharina Lodders ◽

Bruce Fegley

Keyword(s):

Trace Element ◽

Total Pressure ◽

Element Abundance ◽

Elemental Abundances ◽

Trace Element Chemistry ◽

Abundance Patterns ◽

Element Chemistry ◽

Circumstellar Shells ◽

Thermochemical Equilibrium ◽

Equilibrium Calculations

Thermochemical equilibrium calculations are successful in predicting the mineralogy as well as the major and trace element chemistry of circumstellar grains found in meteorites. The calculations also explain observations of dust close to AGB stars (within 1–3 stellar radii). The trace element chemistry in circumstellar graphite, SiC, and other refractory carbide grains agrees with equilibrium condensation calculations for circumstellar shells of carbon stars. Observed trace element abundance patterns in N stars are complementary to those found in SiC grains indicating fractional condensation in circumstellar shells. Condensation temperatures depend upon total pressure, C/O ratio, nitrogen abundances, and overall metallicity. Therefore for condensation temperatures to be meaningful, the total pressure and elemental abundances (i.e., C/O ratio, metallicity) must be specified.

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Sulphate soils and the abundance of metals in the surrounding water - a case study from Halland, SW Sweden.

10.5194/egusphere-egu2020-8257 ◽

2020 ◽

Author(s):

Amanda Lindgren ◽

Markus Giese

Keyword(s):

Surface Water ◽

Acid Soil ◽

Water Levels ◽

Estuarine Sediments ◽

Element Abundance ◽

Precipitation Pattern ◽

Groundwater Levels ◽

Acid Sulphate ◽

Acid Sulphate Soils

Acid sulphate soils (AS soils) are in literature described as the &#8220;nastiest soils in the world&#8221; (Dent & Pons, 1995 pg.1) affecting swathes of land around the globe. The changed oxygen conditions in the soil as a result of altered ground water levels, causes a severe decrease in pH, consequently enabling metals to leach out to recipient water streams (e.g. &#197;str&#246;m, 2001). In northern Scandinavia, several fish kills have been reported due to leaching AS soils (e.g. Hudd and Kjellmann, 2002) allowing for these areas to be the focal point of prior investigations (e.g. Nordmyr et al., 2008; Lax, 2005; &#197;str&#246;m, 2001). However, seasonally lowered local groundwater levels caused by altered temperature and precipitation pattern in Scandinavia increases the need for additional research in southern Scandinavia. Therefore, this study investigates the impacts of AS soils on water chemistry in Halland, SW Sweden; an area previously covered by the Littorina sea. In order to estimate potential metal emissions after a period of low groundwater levels, in situ surface water sampling was conducted from smaller ditches draining an active AS soil into a nearby canal. Additional hydro-chemical parameters, such as pH, redox potential and electric conductivity were simultaneously measured in situ and groundwater data from nearby wells were retrieved. The concentrations of several metals, such as Al, Cu, Fe and V were analysed using an inductively coupled plasma mass spectrometry (ICP-MS) instrument and the total organic carbon (TOC) in the samples were determined. The results provided a clear indication of leaching acids to the surface water, through elevated concentrations of numerous metals, along with a pH of 3.82 - 6.64 in the surface water. Several metals such as Al and Mn, were highly elevated, in some cases close to 100 times higher than the background levels. No signal was found in the groundwater data retrieved, presumably due to the great difference in depth between private wells and the AS soil layer.&#160;Sources:Dent, D. L., & Pons, L. J. (1995). A world perspective on acid sulphate soils. Geoderma, 67(3-4), 263-276, DOI: 10.1016/0016-7061(95)00013-E.&#197;str&#246;m, M. (2001). The effect of acid soil leaching on trace element abundance in a medium-sized stream, W. Finland. Applied Geochemistry, 16(3), 387-396, DOI: 10.1016/S0883-2927(00)00034-2.Hudd, R., Kjellman, J., 2002. Bad matching between hatching and acidification: a pitfall for the burbot, Lota lota, off the river Kyr&#246;njoki, Baltic Sea. Fisheries Research 55, 153-160, DOI: 10.1016/S0165-7836(01)00303-4.Lax, K. (2005). Stream plant chemistry as indicator of acid sulphate soils in Sweden. Agricultural and Food Science, 14(1), 83-97, DOI: 10.2137/1459606054224165.Nordmyr, L., &#197;str&#246;m, M., & Peltola, P. (2008). Metal pollution of estuarine sediments caused by leaching of acid sulphate soils. Estuarine, coastal and shelf science, 76(1), 141-152, DOI: 10.1016/j.ecss.2007.07.002.

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