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  • 1
    Online Resource
    Online Resource
    Integrated German Indian Ocean Study (IGIOS) : from the seafloor to the atmosphere : a possible German contribution to the International Indian Ocean Expedition 2 (IIOE-2) programme : a science prospectus (2016)
    Kiel : GEOMAR, Helmholtz-Zentrum für Ozeanforschung
    Details Availability
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (77 Blatt = 14 MB) , Illustrationen
    Series Statement: GEOMAR Report N.S. 29
    URL: http://oceanrep.geomar.de/33146/
    URL: http://dx.doi.org/10.3289/GEOMAR_REP_NS_29_2016
    DOI: 10.3289/GEOMAR_REP_NS_29_2016
    Language: English
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  • 2
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    Magmatic Evolution and Source Variations at the Nifonea Ridge (New Hebrides Island Arc) (2017)
    Oxford Univ. Press
    In:  Journal of Petrology, 58 (3). pp. 473-494.
    Details
    Publication Date: 2020-02-06
    Description: The Nifonea submarine volcano rises 1000 m above the seafloor of the Vate Trough back-arc basin behind the New Hebrides island arc. This large volcanic edifice has a caldera of ∼8 km diameter and is connected to two ∼20 km long volcanic rift zones in the back-arc basin. We present new chemical and isotope data for volcanic glasses and whole-rocks from both the volcano and its rift zones. Lavas from Nifonea volcano show an evolution towards more incompatible element enrichment, with the most enriched lavas being the youngest eruption products on the caldera floor. These are products of significant fractional crystallization, show minor contamination by hydrothermal fluids (〈0·3%) and reflect mixing of melts derived from depleted upper mantle and melts from an enriched source similar to those occurring in the North Fiji Basin. The enrichment in Nb of these lavas is comparable with that of some lavas from the New Hebrides island arc (e.g. Mota Lava island), where these coexist with typical island arc basalts. The lavas erupted along the rift zones in the Vate Trough back-arc basin are relatively depleted in incompatible elements, indicating melting of depleted upper mantle with a minor addition of a sediment-derived fluid. Our observations suggest that the mantle beneath Vate Trough is heterogeneous on a small scale (〈20 km) and that the occurrence of these enriched and fertile mantle portions has a stronger control on melting processes than the influx from the subducting slab, as all samples were recovered at a similar distance from the trench.
    Type: Article , PeerReviewed
    Format: text
    Format: other
    DOI: 10.1093/petrology/egx023
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Cretaceous seawater and hydrothermal fluid compositions recorded in abiogenic carbonates from the Troodos Ophiolite, Cyprus (2018)
    Elsevier
    In:  Chemical Geology, 494 . pp. 43-55.
    Details
    Publication Date: 2021-02-08
    Description: We evaluate the potential of ophiolites as archives of paleoseawater and hydrothermal fluid compositions by analysing the chemical and isotopic composition of abiogenic carbonates, precipitated from fluids within the oceanic crust of the 91 Ma Troodos Ophiolite, Cyprus. Calculated variations in fluid Mg/Ca, Sr/Ca and Sr-87/ Sr-86 with temperature within the upper sections of the ophiolite are similar to those from drilled oceanic crust, and yield literature values for late Cretaceous seawater Mg/Ca, Sr/Ca and Sr-87/ Sr-86. This indicates that carbonates from ophiolites could be used to estimate the composition of ancient seawater at times before the age of the oldest preserved in-situ oceanic crust. Whereas most carbonates recovered from in-situ oceanic crust were precipitated at temperatures 〈 60 degrees C, abiogenic carbonates from the Troodos Ophiolite formed over a temperature range of 7 degrees C to 218 degrees C. These provide unique insights into the chemical and mineralogical processes that transform seawater into a high temperature hydrothermal fluid within the oceanic crust. We use 'hydrothermal variation diagrams' of Mg/Ca, Sr/Ca, Sr-87/ Sr-86 and delta(44)/Ca-40 versus calculated temperature (delta O-18) to trace this fluid evolution within the Troodos oceanic crust. We find that successive fluid-crust-interaction, the precipitation of Mg- and Ca-bearing minerals and the early formation of anhydrite (〉 44 degrees C) gradually transform Cretaceous seawater into a Troodos hydrothermal fluid. Comparison of the Troodos data with a global dataset of abiogenic carbonates from in-situ oceanic crust shows that the chemical pathways of low-temperature fluid evolution are similar for all Cretaceous sites. These different sites represent varied geotectonic settings (midocean ridge vs. suprasubduction zone), with different basement composition (basalt, basaltic andesite/boninite) and situated in different ocean basins (Atlantic, Pacific, Mediterranean [Tethys]). The similarity in the carbonate record indicates that these differences do not significantly influence seafloor weathering and hydrothermal alteration at low temperatures. However, abiogenic carbonates from younger oceanic crust differ from the Cretaceous trends and follow different fluid evolution pathways. This indicates, that temporal variations in the composition of seawater may control the nature and the extent of seafloor weathering and hydrothermal alteration at low temperatures. A thermodynamic model of fluid-crust interaction, in which modern and Cretaceous seawater are heated to 200 degrees C while an average Troodos basaltic andesite is successively added under otherwise identical conditions predicts that fluid evolution and alteration of the oceanic crust were different in the Cretaceous than they are today, and that initial seawater chemistry affects the nature and the extent of seafloor alteration up to moderate fluid temperatures. For example, twice the amount of carbonate formed during alteration of the oceanic crust in the Cretaceous compared to modern times, indicating that the flux of CO2 from the hydrosphere-atmosphere system into the oceanic crust was greater in the Cretaceous than it is nowadays, and that it probably varied throughout geologic time.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.chemgeo.2018.07.014
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Melts of sediments in the mantle wedge of the Oman ophiolite (2015)
    GSA, Geological Society of America
    In:  Geology, 43 (4). pp. 275-278.
    Details
    Publication Date: 2017-05-17
    Description: The rocks in the crustal section of the Oman ophiolite show an increasing input of a subduction component with time, most likely reflecting the generation of the ophiolite above a subducting slab. Field relations, new geochemical data, and Nd-Hf isotope data for felsic to mafic intrusive rocks in the mantle harzburgite from the Haylayn block in the Oman ophiolite suggest late magmatic events in a mantle wedge shortly before obduction of the ophiolite. Incompatible element contents and low εNd and εHf of the felsic rocks exclude differentiation from mafic magmas, but are consistent with an origin by partial melting of pelagic sediments similar to leucogranites in continental collision zones. These melts apparently mixed with mafic magmas resembling enriched late-stage lavas from the ophiolite. The leucogranitic intrusions into the mantle wedge confirm the transfer of melts of sediments from the subducted plate into the mantle at subduction zones. We suggest that the enrichment of Rb, K, and Pb observed in the Oman boninites is caused by addition of melts of sediments similar to those from the Haylayn block to the boninite source in the mantle wedge.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1130/G36451.1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Compositional variation and 226Ra-230Th model ages of axial lavas from the southern Mid-Atlantic Ridge, 8°48′S (2016)
    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 17 (1). pp. 199-218.
    Details
    Publication Date: 2019-09-23
    Description: We present geological observations and geochemical data for the youngest volcanic features on the slow-spreading Mid-Atlantic Ridge at 8°48'S that shows seismic evidence for a thickened crust and excess magma formation. Young lava flows with high sonar reflectivity cover about 14 km2 in the axial rift and were probably erupted from two axial volcanic ridges each of about 3 km in length. Three different lava units occur along an about 11 km long portion of the ridge, and lavas from the northern axial volcanic ridge differ from those of the southern axial volcanic ridge and surrounding lava flows. Basalts from the axial rift flanks and from a pillow mound within the young flows are more incompatible element depleted than those from the young volcanic field. Lavas from this volcanic area have 226Ra-230Th disequilibria model ages of 1,000 and 4,000 years whereas the older lavas from the rift flank and the pillow mound, but also some of the lava field, are older than 8,000 years. Glasses from the northern and southern ends of the southern lava unit indicate up to 100°C cooler magma temperatures than in the center and increased assimilation of hydrothermally altered material. The compositional heterogeneity on a scale of 3 km suggests small magma batches rising vertically from the mantle to the surface without significant lateral flow and mixing. The observations on the 8°48'S lava field support the model of low frequency eruptions from single ascending magma batches that has been developed for slow-spreading ridges.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2015GC006016
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Geological controls on hydrothermal venting at the Nifonea Volcano, Vate Trough, Vanuatu (2015)
    In:  [Talk] In: 13. SGA Biannual Meeting 2015, 24.-28.08.2015, Nancy, France .
    Details
    Publication Date: 2016-12-02
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Talk
  • 7
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    Melts of sediments in the mantle wedge of the Oman ophiolite (2015)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2015-03-24
    Description: The rocks in the crustal section of the Oman ophiolite show an increasing input of a subduction component with time, most likely reflecting the generation of the ophiolite above a subducting slab. Field relations, new geochemical data, and Nd-Hf isotope data for felsic to mafic intrusive rocks in the mantle harzburgite from the Haylayn block in the Oman ophiolite suggest late magmatic events in a mantle wedge shortly before obduction of the ophiolite. Incompatible element contents and low Nd and Hf of the felsic rocks exclude differentiation from mafic magmas, but are consistent with an origin by partial melting of pelagic sediments similar to leucogranites in continental collision zones. These melts apparently mixed with mafic magmas resembling enriched late-stage lavas from the ophiolite. The leucogranitic intrusions into the mantle wedge confirm the transfer of melts of sediments from the subducted plate into the mantle at subduction zones. We suggest that the enrichment of Rb, K, and Pb observed in the Oman boninites is caused by addition of melts of sediments similar to those from the Haylayn block to the boninite source in the mantle wedge.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 8
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    Magmatic Evidence for Carbonate Metasomatism in the Lithospheric Mantle underneath the Ohre (Eger) Rift (2015)
    Oxford University Press
    Details
    Publication Date: 2015-11-01
    Description: Magmas erupted in intracontinental rifts typically form from melting of variable proportions of asthenospheric or lithospheric mantle sources and ascend through thick continental lithosphere. This ascent of magma is accompanied by differentiation and assimilation processes. Understanding the composition of rift-related intracontinental volcanism is important, particularly in densely populated active rift zones such as the Ohře (Eger) Rift in Central Europe. We have sampled and analysed nephelinites from Železná hůrka (Eisenbühl), the youngest (〈300 ka) Quaternary volcano related to the Ohře Rift where frequent earthquake swarms indicate continuing magmatic activity in the crust. This nephelinite volcano is part of a larger eruptive centre (Mytina Maar) representing a single locality of recurrent volcanism in the Ohře Rift. We present a detailed petrographic, mineralogical and geochemical study (major and trace elements and Sr–Nd–Hf–O isotopes) of Železná hůrka to further resolve the magmatic history and mantle source of the erupted melt. We find evidence for a highly complex evolution of the nephelinitic melts during their ascent to the surface. Most importantly, mixing of melts derived from different sources and of strong chemical contrast controls the composition of the erupted volcanic products. These diverse parental melts originate from a highly metasomatized subcontinental lithospheric mantle (SCLM) source. We use a combined approach based on mineral, glass and whole-rock compositions to show that the mantle underneath the western Ohře Rift is metasomatized dominantly by carbonatitic melts. The nephelinites of Železná hůrka formed by interaction between a carbonatitic melt and residual mantle peridotite, partial crystallization in the lithospheric mantle and minor assimilation of upper continental crust. Thermobarometric estimates indicate that the stagnation levels of the youngest volcanism in this part of the Ohře Rift were deeper than the focal depths of recent earthquake swarms, indicating that those are not directly linked to magma ascent. Furthermore, close mineralogical and geochemical similarities between the Železná hůrka nephelinite and fresh kimberlites may point towards a genetic link between kimberlites, melilitites and nephelinites.
    Print ISSN: 0022-3530
    Electronic ISSN: 1460-2415
    Topics: Geosciences
    Published by Oxford University Press
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  • 9
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    CD25+ FoxP3+ Memory CD4 T Cells Are Frequent Targets of HIV Infection In Vivo [Pathogenesis and Immunity] (2016)
    The American Society for Microbiology (ASM)
    Details
    Publication Date: 2016-10-08
    Description: Interleukin 2 (IL-2) signaling through the IL-2 receptor alpha chain (CD25) facilitates HIV replication in vitro and facilitates homeostatic proliferation of CD25 + FoxP3 + CD4 + T cells. CD25 + FoxP3 + CD4 + T cells may therefore constitute a suitable subset for HIV infection and plasma virion production. CD25 + FoxP3 + CD4 + T cell frequencies, absolute numbers, and the expression of CCR5 and cell cycle marker Ki67 were studied in peripheral blood from HIV + and HIV – study volunteers. Different memory CD4 + T cell subsets were then sorted for quantification of cell-associated HIV DNA and phylogenetic analyses of the highly variable EnvV1V3 region in comparison to plasma-derived virus sequences. In HIV + subjects, 51% (median) of CD25 + FoxP3 + CD4 + T cells expressed the HIV coreceptor CCR5. Very high frequencies of Ki67 + cells were detected in CD25 + FoxP3 + memory CD4 + T cells (median, 27.6%) in comparison to CD25 – FoxP3 – memory CD4 + T cells (median, 4.1%; P 〈 0.0001). HIV DNA content was 15-fold higher in CD25 + FoxP3 + memory CD4 + T cells than in CD25 – FoxP3 – T cells ( P = 0.003). EnvV1V3 sequences derived from CD25 + FoxP3 + memory CD4 + T cells did not preferentially cluster with plasma-derived sequences. Quasi-identical cell-plasma sequence pairs were rare, and their proportion decreased with the estimated HIV infection duration. These data suggest that specific cellular characteristics of CD25 + FoxP3 + memory CD4 + T cells might facilitate efficient HIV infection in vivo and passage of HIV DNA to cell progeny in the absence of active viral replication. The contribution of this cell population to plasma virion production remains unclear. IMPORTANCE Despite recent advances in the understanding of AIDS virus pathogenesis, which cell subsets support HIV infection and replication in vivo is incompletely understood. In vitro , the IL-2 signaling pathway and IL-2-dependent cell cycle induction are essential for HIV infection of stimulated T cells. CD25 + FoxP3 + memory CD4 T cells, often referred to as regulatory CD4 T cells, depend on IL-2 signaling for homeostatic proliferation in vivo . Our results show that CD25 + FoxP3 + memory CD4 + T cells often express the HIV coreceptor CCR5, are significantly more proliferative, and contain more HIV DNA than CD25 – FoxP3 – memory CD4 T cell subsets. The specific cellular characteristics of CD25 + FoxP3 + memory CD4 + T cells probably facilitate efficient HIV infection in vivo and passage of HIV DNA to cell progeny in the absence of active viral replication. However, the contribution of this cell subset to plasma viremia remains unclear.
    Print ISSN: 0022-538X
    Electronic ISSN: 1098-5514
    Topics: Medicine
    Published by The American Society for Microbiology (ASM)
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  • 10
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    Expitope: a web server for epitope expression (2015)
    Oxford University Press
    Details
    Publication Date: 2015-05-27
    Description: Motivation: Adoptive T cell therapies based on introduction of new T cell receptors (TCRs) into patient recipient T cells is a promising new treatment for various kinds of cancers. A major challenge, however, is the choice of target antigens. If an engineered TCR can cross-react with self-antigens in healthy tissue, the side-effects can be devastating. We present the first web server for assessing epitope sharing when designing new potential lead targets. We enable the users to find all known proteins containing their peptide of interest. The web server returns not only exact matches, but also approximate ones, allowing a number of mismatches of the users choice. For the identified candidate proteins the expression values in various healthy tissues, representing all vital human organs, are extracted from RNA Sequencing (RNA-Seq) data as well as from some cancer tissues as control. All results are returned to the user sorted by a score, which is calculated using well-established methods and tools for immunological predictions. It depends on the probability that the epitope is created by proteasomal cleavage and its affinities to the transporter associated with antigen processing and the major histocompatibility complex class I alleles. With this framework, we hope to provide a helpful tool to exclude potential cross-reactivity in the early stage of TCR selection for use in design of adoptive T cell immunotherapy. Availability and implementation: The Expitope web server can be accessed via http://webclu.bio.wzw.tum.de/expitope . Contact: d.frishman@wzw.tum.de
    Print ISSN: 1367-4803
    Electronic ISSN: 1460-2059
    Topics: Biology , Computer Science , Medicine
    Published by Oxford University Press
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