| 1. |
- Routh, Joyanto, 1968-, et al.
(författare)
-
Sedimentary geochemical record of humanï¿œinduced environmental changes in the Lake Brunnsviken watershed, Sweden
- 2004
-
Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 49:5, s. 1560-1569
-
Tidskriftsartikel (refereegranskat)abstract
- Environmental changes in Lake Brunnsviken, its watershed, and the greater Stockholm region since the middle of the nineteenth century have left interpretable geochemical imprints in the bottom sediments. These human-induced perturbations within the lakeï¿œs watershed included agriculture, urbanization, sewage and industrial disposal, and water column aeration. Smaller d15Ntotal values, high organic carbon mass accumulation rates, low C:N ratios, and larger d13Corg values identify periods of increased nutrient delivery and elevated primary productivity in the lake. C: S ratios that change from high to low trace the transition from an oxic hypolimnion to an anoxic one during the periods of high productivity. Accumulations of redox-sensitive trace elements increase during the anoxic period and are further magnified during a time of industrial waste discharge into the lake. A recent decrease in black carbon concentrations in sediments reflects the conversion from wood and coal to cleaner forms of energy.
|
|
| 2. |
- Baresel, Christian, et al.
(författare)
-
Uncertainty-Accounting Environmental Policy and Management of Water Systems
- 2007
-
Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 41:10, s. 3653–3659-
-
Tidskriftsartikel (refereegranskat)abstract
- Environmental policies for water quality and ecosystemmanagement do not commonly require explicit stochasticaccounts of uncertainty and risk associated with thequantification and prediction of waterborne pollutant loadsand abatement effects. In this study, we formulate andinvestigate a possible environmental policy that does requirean explicit stochastic uncertainty account. We compareboth the environmental and economic resource allocationperformance of such an uncertainty-accounting environmentalpolicy with that of deterministic, risk-prone and riskaverseenvironmental policies under a range of differenthypothetical, yet still possible, scenarios. The comparisonindicates that a stochastic uncertainty-accountingpolicy may perform better than deterministic policies overa range of different scenarios. Even in the absence ofreliable site-specific data, reported literature values appearto be useful for such a stochastic account of uncertainty.
|
|
| 3. |
- Mouyen, Maxime, 1982, et al.
(författare)
-
Expected temporal absolute gravity change across the Taiwanese Orogen, a modeling approach
- 2009
-
Ingår i: Journal of Geodynamics. - : Elsevier BV. - 0264-3707. ; 48:3-5
-
Tidskriftsartikel (refereegranskat)abstract
- The island of Taiwan is located on the convergent boundary between the Philippine Sea plate and the Chinese continental margin. It offers very active mountain building and collapsing processes well illustrated by the rugged topography, rapid uplift and denudation, young tectonic landforms, active faulting and numerous earthquakes. In this paper, using simple models, we have estimated vertical movements and associated absolute gravity variations which can be expected along a profile crossing the southern part of the island and probably suffering the highest rates of rising. The two different tectonic styles proposed for the island, thin-skinned and thick-skinned, were taken into account. Horizontal and vertical movements were modeled by an elastic deformation code. Gravity variations due to these deformations are then modeled at a second step. They are dominated by plate and free-air effects, i.e. elevation of the topography, with several μGal yr-1. By comparison, gravity changes generated by mass transfers are weak: maximum 0.1 μGal yr-1 with the thin-skinned tectonic and 0.3 μGal yr-1 with the thick-skinned tectonic. Though elastic rheology has limitations, this modeling offers interesting results on what gravity signal can be expected from the AGTO project (Absolute Gravity in the Taiwanese Orogen), which proposes to study the dynamic of these mountain ranges using absolute gravimetry (AG) and also including relative gravimetry (RG) and GPS measurements.
|
|
| 4. |
- Klemme, S., et al.
(författare)
-
Synthesis and preliminary characterisation of new silicate, phosphate and titanite reference glasses
- 2008
-
Ingår i: Geostandards and Geoanalytical Research. - 1639-4488. ; 32:1, s. 39-54
-
Tidskriftsartikel (refereegranskat)abstract
- Eleven synthetic silicate and phosphate glasses were prepared to serve as reference materials for in situ microanalysis of clinopyroxenes, apatite and titanite, and other phosphate and titanite phases. Analytical results using different micro-analytical techniques showed that the glass fragments were homogeneous in major and trace elements down to the micrometre scale. Trace element determinations using inductively coupled plasma-mass spectrometry (ICP-MS), multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS), laser-ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) and secondary ionisation mass spectrometry (SIMS) showed good agreement for most elements (Li, Be, B, Cs, Rb, Ba, Sr, Ga, Pb, U, Th, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Er, Tm, Yb, Lu, Zr, Hf, Ta, Nb) studied and provide provisional recommended values.
|
|
| 5. |
- Konrad-Schmolke, Matthias, 1970, et al.
(författare)
-
Combined thermodynamic and rare earth element modelling of garnet growth during subduction: Examples from ultrahigh-pressure eclogite of the Western Gneiss Region, Norway
- 2008
-
Ingår i: Earth and Planetary Science Letters. - 0012-821X. ; 272:1-2, s. 488-498
-
Tidskriftsartikel (refereegranskat)abstract
- Major and trace element zonation patterns were determined in ultrahigh-pressure eclogite garnets from the Western Gneiss Region (Norway). All investigated garnets show Multiple growth zones and preserve complex growth zonation patterns with respect to both major and rare earth elements (REE). Due to chemical differences of the host rocks two types of major element compositional zonation patterns occur: (1) abrupt, step-like compositional changes corresponding with the growth zones and (2) compositionally homogeneous interiors, independent of growth zones, followed by abrupt chemical changes towards the rims. Despite differences in major element zonation, the REE patterns are almost identical in all garnets and can be divided into four distinct zones with characteristic patterns. In order to interpret the major and trace element distribution and zoning patterns in terms of the subduction history of the rocks, we combined thermodynamic forward models for appropriate bulk rock compositions to yield molar proportions and major element compositions of stable phases along the inferred pressure-temperature path with a mass balance distribution of REEs among the calculated stable phases during high pressure metamorphism. Our thermodynamic forward models reproduce the complex major element zonation patterns and growth zones in the natural garnets, with garnet growth predicted during four different reaction stages: (1) chlorite breakdown, (2) epidote breakdown, (3) amphibole breakdown and (4) reduction in molar clinopyroxene at ultrahigh-pressure conditions. Mass-balance of the rare earth element distribution among the modelled stable phases yielded characteristic zonation patterns in garnet that closely resemble those in the natural samples. Garnet growth and trace element incorporation Occurred in near thermodynamic equilibrium with matrix phases during subduction. The rare earth element patterns in garnet exhibit distinct enrichment zones that fingerprint the minerals involved in the garnet-forming reactions as well as local peaks that can be explained by fractionation effects and changes in the mineral assemblage. (C) 2008 Elsevier B.V. All rights reserved.
|
|
| 6. |
- Luvizotto, G. L., et al.
(författare)
-
Nb and Zr behavior in rutile during high-grade metamorphism and retrogression: An example from the Ivrea-Verbano Zone
- 2009
-
Ingår i: Chemical Geology. - 0009-2541. ; 261:3-4, s. 303-317
-
Tidskriftsartikel (refereegranskat)abstract
- Detailed textural observations and in situ analyses (EMP, SIMS and LA-ICP-MS) are used to characterize trace element behavior during prograde and retrograde metamorphic reactions involving rutile. The Ivrea-Verbano Zone is a classic granulite area and rocks from the Strona and d'Ossola valleys are an example of the amphibolite to granulite facies transition. Although different rock types occur in the area, detailed sampling and petrographic work show that rutile only occurs in granulite facies paragneisses. These rocks show a rich inventory of textures that allow not only for the investigation of trace element behavior in response to prograde rutile growth, but also for the effect of post-peak processes on rutile chemistry. Nb concentrations in rutile from lower grade samples show a larger spread (from 500 to 5000 ppm within one sample) when compared to those from higher grades. This pattern can be modeled using prograde rutile growth formed from biotite breakdown. Zr concentrations in rutile are characterized by an anomalously large spread and a bimodal distribution. Maximum Zr concentrations increase according to the general metamorphic gradient known for this area. Temperatures (from Zr-in-rutile thermometry), although feasible, are considerably higher than previous calculations (increasing from ca. 850 to 930 degrees C). A second cluster of Zr concentrations in rutile occurs at rather constant concentrations (ca. 1000 ppm) for all localities and is interpreted to be related to intense fluid influx at high-temperature and/or to post-peak diffusional resetting favored by slow cooling rates. Alteration textures, characterized by a complex network of micro-veins, are evidence for the late fluid influx The fluid strongly affected the rutiles, which is evidenced by corrosion of older rutile grains and formation of rutile veinlets. (C) 2008 Elsevier B.V. All rights reserved.
|
|
| 7. |
- Luvizotto, G. L., et al.
(författare)
-
Rutile crystals as potential trace element and isotope mineral standards for microanalysis
- 2009
-
Ingår i: Chemical Geology. - 0009-2541. ; 261:3-4, s. 346-369
-
Tidskriftsartikel (refereegranskat)abstract
- The present paper reports trace element concentrations of 15 elements (V, Cr, Fe, Zr, Nb, Mo, Sn, Sb, Hf, Ta, W, Lu, Pb, Th and U) as well as Ph and Hf isotope data for four relatively homogeneous and large (centimeter size) rutile grains. Methods employed are SIMS, EMP, LA-ICP-MS, ID-MC-ICP-MS and TIMS. For most elements homogeneity is usually within +/- 10% and occasionally variations are even narrower (+/- 5%), particularly in the core of two of the studied grains. The trace element concentrations of the grains span a broad compositional range (e.g., Zr concentrations are ca. 4, 100, 300 and 800 ppm). Provisional concentration values, calculated based on the homogeneity of the element and agreement between techniques, are presented for Zr, Nb, Sn, Sb, Hf, Ta, W and U. The present work represents a significant step forward in finding a suitable mineral standard for rutile microanalysis and encourages not only further search for mineral standards but also applications of rutile in the field of geochemistry and geochronology. In this sense, the rutiles presented here are useful as mineral standard in general in-situ rutile measurements, particularly for Zr-in-rutile thermometry, quantitative provenance studies (Nb and Cr concentrations as index of source rock type) and U-Pb dating. One of the studied grains has a relatively high U concentration (ca. 30 ppm) and rather constant U-Pb ages (1085.1 to 1096.2 Ma (207)Pb/(235)U ages and 1086.3 to 1096.6 Ma, (206)Pb/(238)U ages), favoring its application as an age standard for U-Pb rutile dating. Since Lu concentrations in rutile are very low and Hf concentrations can be relatively high (tens of ppm), detrital rutiles may be suitable for obtaining initial Hf isotope composition of source rocks, therefore the rutiles presented here can be used as calibration material for in-situ rutile Hf isotope studies. (C) 2008 Elsevier B.V. All rights reserved.
|
|
| 8. |
- Luvizotto, G. L., et al.
(författare)
-
Rutile occurrence and trace element behavior in medium-grade metasedimentary rocks: example from the Erzgebirge, Germany
- 2009
-
Ingår i: Mineralogy and Petrology. - 0930-0708. ; 97:3-4, s. 233-249
-
Tidskriftsartikel (refereegranskat)abstract
- Metamorphic textures in medium-grade (similar to 500-550A degrees C) metasedimentary rocks from the Erzgebirge give evidence of prograde rutile crystallization from ilmenite. Newly-crystallized grains occur as rutile-rich polycrystalline aggregates that pseudomorph the shape of the ilmenites. In-situ trace element data (EMP and SIMS) show that rutiles from the higher-grade samples record large scatter in Nb content and have Nb/Ti ratios higher than coexisting ilmenite. This behavior can be predicted using prograde rutile crystallization from ilmenite and indicates that rutiles are reequilibrating their chemistry with remaining ilmenites. On the contrary, rutiles from the lowest grade samples (similar to 480A degrees C) have Nb/Ti ratios that are similar to the ones in ilmenite. Hence, rutiles from these samples did not equilibrate their chemistry with remaining ilmenites. Our data suggest that temperature may be one of the main factors determining whether or not the elements are able to diffuse between the phases and, therefore, reequilibrate. Newly-crystallized rutiles yield temperatures (from similar to 500 to 630A degrees C, Zr-in-rutile thermometry) that are in agreement with the metamorphic conditions previously determined for the studied rocks. In quartzites from the medium-grade domain (similar to 530A degrees C), inherited detrital rutile grains are detected. They are identified by their distinct chemical composition (high Zr and Nb contents) and textures (single grains surrounded by fine grained ilmenites). Preliminary calculation, based on grain size distribution of rutile in medium-grade metapelites and quartzites that occur in the studied area, show that rutiles derived from quartzites can be anticipated to dominate the detrital rutile population, even if quartzites are a minor component of the exposure.
|
|
| 9. |
- Marks, M. A. W., et al.
(författare)
-
Sodic pyroxene and sodic amphibole as potential reference materials for in situ lithium isotope determinations by SIMS
- 2008
-
Ingår i: Geostandards and Geoanalytical Research. - 1639-4488. ; 32:3, s. 295-310
-
Tidskriftsartikel (refereegranskat)abstract
- Two large pegmatitic crystals of sodic pyroxene (aegirine) and sodic amphibole (arfvedsonite) from the agpaitic igneous Ilimaussaq Complex, south Greenland were found to be suitable as reference materials for in situ Li isotope determinations. Lithium concentrations determined by SIMS and micro-drilled material analysed by MC-ICP-MS generally agreed within analytical uncertainty. The arfvedsonite crystal was homogeneous with [Li] = 639 +/- 51 mu g g(-1) (2s, n = 69, MC-ICP-MS and SIMS results). The aegirine crystal shows strongly developed sector zoning, which is a common feature of aegirines. Using qualitative element mapping techniques (EPMA), the homogeneous core of the crystal was easily distinguished from the outermost sectors of the crystals. The core had a mean [Li] of 47.6 +/- 3.6 mu g g(-1) (2s, n = 33) as determined by SIMS. The seven micro-drilled regions measured by solution MC-ICP-MS returned slightly lower concentrations (41-46 mu g g(-1)), but still overlap with the SIMS data within uncertainty. Based on MC-ICP-MS and SIMS analyses, the variation in delta(7)Li was about 1 parts per thousand in each of the two crystals, which is smaller than that in widely used glass reference materials, making these two samples suitable to serve as reference materials. There was, however, a significant offset between the results of MC-ICP-MS and SIMS. The latter deviated from the MC-ICP-MS results by -6.0 +/- 1.9 parts per thousand (2s) for the amphibole and by -3.9 +/- 1.9 parts per thousand (2s) for the aegirine. This indicates the presence of a significant matrix effect in SIMS determinations of Li isotopes for amphibole and pyroxene relative to the basalt glasses used for calibration. Based on the MC-ICP-MS results, mean delta(7)Li values of +0.7 +/- 1.2 parts per thousand (2s, n = 10) for the arfvedsonite crystal and of -3.7 +/- 1.2 parts per thousand (2s, n = 7) for the core of the aegirine crystal were calculated. Adopting these values, SIMS users can correct for the specific IMF (instrumental mass fractionation) of the ion probe used. We propose that these two crystals serve as reference materials for in situ Li isotope determinations by SIMS and pieces of these two crystals are available from the first author upon request.
|
|
| 10. |
- Triebold, S., et al.
(författare)
-
Deducing source rock lithology from detrital rutile geochemistry: An example from the Erzgebirge, Germany
- 2007
-
Ingår i: Chemical Geology. - 0009-2541. ; 244:3-4, s. 421-436
-
Tidskriftsartikel (refereegranskat)abstract
- This study evaluates the applicability of rutile trace element geochemistry to provenance studies. The study area is the Erzgebirge in eastern Germany, where metamorphic rocks ranging from lower greenschist facies conditions up to granulite facies conditions are exposed. We collected sand and rock samples from small catchment areas for a comparative analysis of rutile geochemistry using wavelength-dispersive electron microprobe. Our results show that rutile geochemistry is a powerful tool in provenance studies, allowing for the identification of source lithologies and an evaluation of the host orogen's metamorphic history. The log (Cr/Nb) ratio has proven to be decisive in discriminating between mafic and metapelitic lithologies. It is also useful for identifying different source rocks when plotted versus a third element or proxy. Furthermore, our results suggest that rutile thermometry can be applied to a much wider range of lithologies than previously assumed. A quantification of temperature populations within single sand samples shows that at high-grade metamorphic conditions, such as those found in the Erzgebirge, more than 65% of rutiles do not re-equilibrate during retrograde metamorphism and thus retain their peak temperature chernistry. Such samples, which have equilibrated at recent metamorphic conditions, can be identified by their 2-sigma standard deviations of less than 120 degrees C. Below 550-600 degrees C, no complete equilibration is reached. Rutiles from greenschist facies and lower metamorphic conditions in the Erzgebirge still inherit relict temperatures from a former metamorphic cycle. They partly record very high temperatures >950 degrees C and supposedly derive from erosion of the west African craton in Ordovician time. (C) 2007 Elsevier B.V. All rights reserved.
|
|
