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Resterden, überwiegend Anhangserden aber auch Verarbeitungsrückstände der Kartoffelpflanze, stellen einen der wichtigsten Verbreitungswege für Quarantäneschadorganismen im Kartoffelanbau dar. Unter dem Aspekt der Pflanzenquarantäne zur Tilgung bzw. Verhinderung einer weiteren Ausbreitung von noch nicht weit verbreiteten Organismen mit hohem Schadpotential müssen Reststoffe frei von Quarantäneschadorganismen sein, wenn sie auf landwirtschaftlich genutzte Habitate zurückgeführt werden sollen. Vor allem Organismen mit langen Ruheperioden und hoher Widerstandsfähigkeit gegen Umwelteinflüsse wie Kartoffelzystennematoden aus der Gattung Globodera stellen dabei eine besondere Bedrohung dar. Im Projekt GlobRISK erfolgte die Erprobung, Optimierung und wissenschaftliche Bewertung der phytosanitären Verfahren Inundation, thermische Behandlung, ionisierende Strahlung, Ozonierung, Kompostierung und anaerobe Bodenbehandlung hinsichtlich ihrer Wirksamkeit gegen Zystennematoden in Resterden. Es wurde eine definierte Anzahl von Referenzzysten behandelt, um anschließend die Schlupffähigkeit juveniler Nematoden und die Fähigkeit zur Reproduktion an anfälligen Kartoffelpflanzen im Vergleich zu unbehandelten Kontrollen zu untersuchen. Genutzt wurden internationale Standardmethoden (Schlupftest, Biotest) zur Ermittlung der Lebens- und Entwicklungsfähigkeit der Nematoden. Weitere im Projekt untersuchte Verfahren zur Vitalitätskontrolle, wie Lebendfärbung, Trehalosegehalts bestimmung sowie molekularbiologische Assays ausgehend von RNA oder DNA erwiesen sich für die Quantifizierung lebender Nematoden als ungeeignet. Es zeigte sich, dass die Behandlungsverfahren, mit Ausnahme des Einsatzes reaktiver Detergenzien in der Ozonierung, unter verschieden hohem technischem Aufwand und Ressourcenverbrauch das Potential zur sicheren Abtötung von Kartoffelzystennematoden in Resterden besitzen. Die vielfältigen Untersuchungen sowohl im Labor- als auch im Praxismaßstab sind im Bericht dargestellt.

Zinc isotopes in primitive magmatic rocks have been used recently to interrogate the origins of mantle heterogeneity. Of special interest are the high d66Zn values obtained for HIMU-type OIBs, and this signature hints possibly at recycled carbon-bearing oceanic crust in their mantle sources. In contrast, other studies argue that large zinc isotope fractionation results from the peridotite melting process, based on correlations between the degree of partial melting and d66Zn of basaltic to komatiitic lavas. To further explore the utility of zinc isotopes in mantle geochemistry and the study of deep volatile cycles, we investigate the d66Zn of kimberlites and lamproites (formerly Group-2 kimberlites) from the Kalahari craton in southern Africa. These rocks formed by H2O-CO2 fluxed partial melting of metasomatized peridotite at >180 km depths, and their contrasting Sr-Nd-Hf isotopic compositions indicate distinct sources near the lithosphere-asthenosphere boundary. Both rock types contain notable amounts of magmatic carbonates with mantle-like d13C values. In keeping with the discrete Sr-Nd-Hf isotope groupings, the kimberlites and lamproites have different d66Zn compositions, with median values of 0.33 ±0.07¿ (n=22) and 0.25 ±0.06¿ (n=18), respectively. They have low zinc concentrations (64 ±35 and 51 ±29 ppm), similar to MORBs (64 ±25 ppm) but different from OIBs (120 ±40 ppm). Given that the degree of partial melting is equally low for kimberlites and lamproites (<1%), our study provides evidence for significant zinc isotope heterogeneity in the deep upper mantle. Modeling shows that the kimberlite and lamproite zinc systematics fit with near-solidus melting of asthenospheric and refractory cratonic peridotites, respectively. The minor alkali-metasomatic components required to explain the petrology of lamproites do not influence the zinc systematics of carbonated mantle melts, probably owed to the compatible nature of zinc in mineralogically exotic metasomes. Althou

Subduction zones are characterized by the highest mass fluxes between crust and mantle and have a direct influence on Earth¿s mantle heterogeneity. Barium isotopes (¿138/134Ba) have emerged as a novel tracer to investigate the subduction recycling of crustal material into the mantle wedge as well as the deep mantle. Ba plays a key role in tracing subduction recycling as generally more than 90% of the Ba in arc lavas is derived from the subducted slab. Significant stable Ba isotope fractionation occurs during Earth¿s surface processes leading to distinct Ba concentrations and Ba isotopic ratios in different marine lithologies that eventually subduct. Characterizing the Ba-isotope composition of subducted marine sediments, altered oceanic crust (AOC), and their complementary subduction output (i.e. arc lavas) is therefore a necessary step towards applying this novel isotope system for the investigation of crust-mantle evolution. Here we report Ba isotope data from input to output at the Tongan subduction zone: pelagic sediment and AOC samples from the DSDP site 595/596 on the subducting SW-Pacific plate, complemented by Tongan arc lavas. Our data show variable and higher 138/134Ba of subducting deep-sea pelagic sediments than previously assumed [1]. Downhole trends in the sedimentary pile likely reflect a mixture of an isotopically heavy authigenic vs. an isotopically light lithogenic component. This authigenic Ba endmember, which is potentially mobilized in aqueous fluids during the early stages of subduction in the forearc, can account for isotopically heavy Ba reported for Tongan arc lavas. However, Tongan arc samples that are thought to be influenced by hydrous melts show lighter isotope signatures close to that of the lithogenic Ba endmember. This implies that the nature of host minerals and their stabilities during prograde subduction metamorphism has an effect on the recycled Ba signature of the subducted slab material that eventually enters the deep mantle.

Zinc isotopes in primitive magmatic rocks have been used recently to interrogate the origins of mantle heterogeneity. Of special interest are the high ¿66Zn values obtained for OIBs and continental alkali basalts, and this signature hints at recycled carbon-bearing oceanic crust (including carbonate sediments) in their mantle sources. Other studies argue however that large ¿66Zn fractionation results from the melting process, based on correlations between the degree of partial melting and ¿66Zn of basaltic to komatiitic lavas. To further explore the utility of zinc in the study of deep volatile cycles, we investigate the ¿66Zn of kimberlites and lamproites from southern Africa. These rocks formed by H2O-CO2 fluxed partial melting of metasomatized peridotite at >180 km depths, and their contrasting Sr-Nd-Hf isotopic compositions indicate distinct sources near the lithosphere-asthenosphere boundary. Both magma types contain notable amounts of carbonates with mantle-like ¿13C values. In keeping with the discrete Sr-Nd-Hf isotope groupings, kimberlites and lamproites have different ¿66Zn compositions, with mean values of 0.33±0.07¿ (n=22) and 0.25±0.06¿ (n=18), respectively. They have low zinc concentrations (64±35 and 51±29 ppm), more similar to MORBs (64±25 ppm) than to OIBs (120±40 ppm). Given that the degree of partial melting is equally low for kimberlites and lamproites (<1%), our study provides evidence for significant zinc isotope heterogeneity in the deep upper mantle. Modelling shows that the kimberlite and lamproite zinc systematics fit with near-solidus melting of asthenospheric and refractory cratonic peridotites, respectively. The alkali-metasomatic components required to explain the petrology of lamproites do not influence the zinc systematics of carbonated mantle melts, probably owed to the compatible nature of zinc in mineralogically exotic metasomes. Although the origins of kimberlites and OIBs are frequently compared because of their apparent link to

Black smoker chimneys are products of submarine hydrothermal venting and have a complex internal zoning that is the result of mineral precipitation and maturation at evolving fluid conditions. The composition of the hydrothermal sulfides is thereby controlled by the fluid composition (e.g., temperature, pH, salinity), processes like fluid boiling, and potential input from magmatic fluids. Advances in analytical techniques allow quantitative analysis of stable isotope ratios of heavy elements, such as Se, which can provide new insights into the cycling of chalcophile elements in magmatic-hydrothermal systems [1, 2]. We sampled different zones of black smoker chimneys from the Nifonea vent field from the inner chalcopyrite lining towards the outer rim. Homogeneous sulfide powders were analyzed for high-precision Se isotopes using a double spike and hydride generation sample introduction system with a ThermoFisher Scientific® NeptuneXT¿ MC-ICP-MS at the IACT, Granada. The same powders were analyzed for S isotopes and the isotope data was combined with in-situ trace element analysis of genetically related sulfides. The 82/76Se values (relative to NIST-3149) of chimney sulfides range from ¿3.7¿ to 0.6¿ ±0.2¿ (2SD), in accordance with previous analysis of seafloor hydrothermal sulfides [3]. The highest ¿82/76Se values occur in chalcopyrite that precipitated from high temperature fluids (370°C) and overlap with ¿82/76Se values of fresh basaltic glass from the surrounding Nifonea caldera. This suggests that metals were leached from the host rocks and that no significant isotope fractionation occurred during high temperature precipitation of chalcopyrite. Decreasing ¿82/76Se values towards the outer and low temperature zones of the black smoker chimney can be related to redox changes during mixing of the hydrothermal fluid with seawater, in accordance with trace element variations in pyrite. Understanding Se isotope fractionation during hydrothermal sulfide precipitation is

Rodingites are formed through hydrothermal alteration of mafic and felsic lithologies induced by reactive fluids from serpentinization of enclosing peridotites in slow MOR, continental passive margins, or subduction zones. During rodingitization, highly reducing fluids promote metasomatic reactions that replace primary assemblage of oceanic crustal rocks with Ca-Al silicates, Ca-Mg silicates, and chlorite. Similar metasomatic reactions between metamafic layers and enclosing ultramafic rocks also contribute to the lithological and compositional heterogeneity of subduction mélanges, which can influence the composition of slab fluids and favor the deep transport of volatiles in subduction zones. Despite their possible contribution to mass exchanges in subduction zones and to the geochemical signature of arc magmas, metamafic rocks formed by Ca-Mg metasomatism are often disregarded in global geochemical balances. We report a detailed sulfur and selenium systematic in petrologically and geochemically well-characterized rodingites and reaction rims [1] in the Almirez massif (S Spain). The study aims to constrain the redox potential of meta-(ultra) mafic lithologies produced by Ca-Mg metasomatic processes compared to that of altered oceanic crust (AOC) and MORB-derived eclogites. Selenium is a redox-sensitive element that mobilizes when oxidative slab fluids dissolve sulfides. Subsequently, recrystallizing sulfides within the metamorphic assemblage scavenge reduced, isotopically lighter Se. As such, redistributed Se with a large isotopic range traces repeated cycles of sulfide reworking within the subducted crust by episodic, highly oxidized fluid pulses from underlying slab serpentinite [2]. Our preliminary results in Almirez show that metarodingites and associated metamorphic rocks are strongly depleted in Se-S relative to eclogites and MORBs, while reaction rims are commonly enriched in these elements. The Se-S systematic is in contrast to much higher Se-S contents prev

Many terrestrial silicate reservoirs display a characteristic depletion in Nb, which has been explained in some studies by the presence of reservoirs on Earth with superchondritic Nb/Ta. As one classical example, K-rich lavas from the Sunda rear-arc, Indonesia, have been invoked to tap such a high-Nb/Ta reservoir. To elucidate the petrogenetic processes active beneath the Java rear-arc and the causes for the superchondritic Nb/Ta in some of these lavas, we studied samples from the somewhat enigmatic Javanese rear-arc volcano Muria, which allow conclusions regarding the across-arc variations in volcanic output, source mineralogy and subduction components. We additionally report some data for an along-arc sequence of lavas from the Indonesian part of the Sunda arc, extending from Krakatoa in the west to the islands of Bali and Lombok in the east. We present major and trace element concentrations, Sr–Nd–Hf–Pb isotope compositions, and high-field-strength element (HFSE: Nb, Ta, Zr, Hf, W) concentrations obtained via isotope dilution and MC-ICP-MS analyses. The geochemical data are complemented by melting models covering different source compositions with slab melts formed at variable P–T conditions. The radiogenic isotope compositions of the frontal arc lavas in combination with their trace element systematics confirm previously established regional variations of subduction components along the arc. Melting models show a clear contribution of a sediment-derived component to the HFSE budget of the frontal arc lavas, particularly affecting Zr–Hf and W. In contrast, the K-rich rear-arc lavas tap more hybrid and enriched mantle sources. The HFSE budget of the rear-arc lavas is in particular characterized by superchondritic Nb/Ta (up to 25) that are attributed to deep melting involving overprint by slab melts formed from an enriched garnet–rutile-bearing eclogitic residue. Sub-arc slab melting was potentially triggered along a slab tear beneath the Sunda arc, which is the re

The later stages of Earth's transition to a permanently oxygenated atmosphere during the Great Oxidation Event (GOE; ∼2.43–2.06 Ga) is commonly linked with the suggestion of an “oxygen overshoot” during the ∼2.22–2.06 Ga Lomagundi Event (LE), which represents Earth's most pronounced and longest-lived positive carbon isotope excursion. However, the magnitude and extent of atmosphere-ocean oxygenation and implications for the biosphere during this critical period in Earth's history remain poorly constrained. Here, we present nitrogen (N), selenium (Se), and carbon (C) isotope data, as well as bio-essential element concentrations, for Paleoproterozoic marine shales deposited during the LE. The data provide evidence for a highly productive and well-oxygenated photic zone, with both inner and outer-shelf marine environments characterized by nitrate- and Se oxyanion-replete conditions. However, the redoxcline subsequently encroached back onto the inner shelf during global-scale deoxygenation of the atmosphere-ocean system at the end of the LE, leading to locally enhanced water column denitrification and quantitative reduction of selenium oxyanions. We propose that nitrate-replete conditions associated with fully oxygenated continental shelf settings were a common feature during the LE, but nitrification was not sufficiently widespread for the aerobic nitrogen cycle to impact the isotopic composition of the global ocean N inventory. Placed in the context of Earth's broader oxygenation history, our findings indicate that O levels in the atmosphere-ocean system were likely much lower than modern concentrations. Early Paleoproterozoic biogeochemical cycles were thus far less advanced than after Neoproterozoic oxygenation.