ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
  • 2
  • 3
    Publication Date: 2019-06-14
    Description: Causative genetic variants for more than 30 heritable eye disorders in dogs have been reported. For other clinically described eye disorders, the genetic cause is still unclear. We investigated four Golden Retriever litters segregating for highly variable congenital eye malformations. Several affected puppies had unilateral or bilateral retina dysplasia and/or optic nerve hypoplasia. The four litters shared the same father or grandfather suggesting a heritable condition with an autosomal dominant mode of inheritance. The genome of one affected dog was sequenced and compared to 601 control genomes. A heterozygous private nonsense variant, c.487C〉T, was found in the SIX6 gene. This variant is predicted to truncate about a third of the open reading frame, p.(Gln163*). We genotyped all available family members and 464 unrelated Golden Retrievers. All three available cases were heterozygous. Five additional close relatives including the common sire were also heterozygous, but did not show any obvious eye phenotypes. The variant was absent from the 464 unrelated Golden Retrievers and 17 non-affected siblings of the cases. The SIX6 protein is a homeobox transcription factor with a known role in eye development. In humans and other species, SIX6 loss of function variants were reported to cause congenital eye malformations. This strongly suggests that the c.487C〉T variant detected contributed to the observed eye malformations. We hypothesize that the residual amount of functional SIX6 protein likely to be expressed in heterozygous dogs is sufficient to explain the observed incomplete penetrance and the varying severity of the eye defects in the affected dogs.
    Electronic ISSN: 2073-4425
    Topics: Biology
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 2019-04-01
    Description: Voluminous magmatism at active continental margins and collision zones is marked by I-type intrusions. Paleocene-Eocene intrusions, exposed in the Lhasa terrane of the Tibetan Plateau, are part of the Gangdese arc that operated during Neo-Tethyan ocean subduction and subsequent India-Asia collision. Arc-like geochemical trace element signatures and radiogenic isotope systematics are indicative of juvenile I-type magmatism with variable silica contents consequent to igneous differentiation. Here, we present the first Fe isotope data for this fossil arc terrane, which have highly variable δ57Fe values (relative to IRMM-014) of −0.05 to +0.57‰. The data show no obvious correlations with major and trace element systematics, except for highly evolved rocks with 〉70 wt% SiO2. Based on trace element systematics, deuteric fluid exsolution is excluded as a cause for the isotope variations in less evolved rocks. Furthermore, there is no apparent relation between Fe isotope values and the established tectonic evolution from syn- to post-collisional magmatism. Comparison with I-type granites of the Australian Lachlan Fold Belt and Cordilleran Snake River Plain reveals an, on average, lighter δ57Fe in the Gangdese suite in primitive lavas, yet distinctively heavier than intra-oceanic arcs. The heavier δ57Fe values for primitive Lachlan Fold Belt and Snake River Plain rocks are interpreted here as crustal contribution in the form of S-type magmas derived from crustal anatexis, which are absent in the Gangdese arc. Gangdese Belt data yield an average δ57Fe of +0.13 ± 0.02‰ (2σ), which is proposed as the best estimate for juvenile crust at active continental margins.Rhyolite-MELTS modelling suggests that the Gangdese Belt data can be reproduced through fractional crystallization along a liquid line of descent at oxygen fugacity between FMQ = 0 to +2, typical for arc-related melts. Crucially, the majority of data is coherent with partial melts of existing mafic crust as the major contributor to the juvenile component in the intrusions, with minor mantle-derived melts, evidenced through heavier primitive Fe isotopes. This indicates that for the Gangdese Belt samples, the primitive, parental melts are derived from lower crustal successions through predominantly crustal reworking with only subordinate crustal growth. Hence, the Fe isotope data indicates a two-step evolution with melting of underplated mafic material sometime in the geologic past. Although juvenile in nature, these successions are part of the existing crust, supporting scenarios in which crustal reworking in convergent margin intrusions is an important process in evolved magma generation.
    Print ISSN: 0009-2541
    Electronic ISSN: 1872-6836
    Topics: Chemistry and Pharmacology , Geosciences
    Published by Elsevier
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 2021-02-18
    Description: Two-thirds of the Earth is covered by mid-ocean ridge basalts, which form along a network of divergent plate margins. Basalts along these margins display a chemical diversity, which is consequent to a complex interplay of partial mantle melting in the upper mantle and magmatic differentiation processes in lower crustal levels. Igneous differentiation (crystal fractionation, partial melting) and source heterogeneity, in general, are key drivers creating variable chemistry in mid-ocean ridge basalts. This variability is reflected in iron isotope systematics (expressed as δ57Fe), showing a total range of 0.2 ‰ from δ57Fe =  + 0.05 to + 0.25 ‰. Respective contributions of source heterogeneity and magma differentiation leading to this diversity, however, remain elusive. This study investigates the iron isotope systematics in basalts from the ultraslow spreading Gakkel Ridge in the Arctic Ocean and compares them to existing data from the fast spreading East Pacific Rise ridge. Results indicate that Gakkel lavas are driven to heavier iron isotope compositions through partial melting processes, whereas effects of igneous differentiation are minor. This is in stark contrast to fast spreading ridges showing reversed effects of near negligible partial melting effects followed by large isotope fractionation along the liquid line of descent. Gakkel lavas further reveal mantle heterogeneity that is superimposed on the igneous differentiation effects, showing that upper mantle Fe isotope heterogeneity can be transmitted into erupting basalts in the absence of homogenisation processes in sub-oceanic magma chambers.
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
  • 7
    Publication Date: 2021-02-08
    Description: Iron isotopes in ocean floor basalts (OFB) away from convergent margins comprising mid-ocean-ridge and ocean island lavas show significant variation of 〉0.4‰ (expressed in the delta notation δ57Fe relative to IRMM-014), but processes responsible for this variation remain elusive. Bond-valence theory predicts that valence states (Fe3+ vs. Fe2+) control Fe isotopes during partial melting and crystal fractionation along the liquid line of descent and thus contribute substantially to this variation. Memory of past melt extraction or metasomatic re-enrichment in the source of OFB may further add to the observed variability, but systematic investigations to elucidate the respective contributions of these effects have been lacking. Submarine ridges and rifts in the Lau back-arc basin offer a unique opportunity to compare Fe isotopes in OFB from different melting regimes and variably depleted mantle sources. New Fe isotope data is presented for submarine lavas from the Rochambeau Ridges (RR) and the Northwest Lau Spreading Centre (NWLSC), and is compared with published data from the Central Lau Spreading Centre (CLSC). In line with first principle calculations and observations from a range of natural systems, crystal fractionation is identified as the dominant, controlling process for elevating δ57Fe in the lavas with olivine tentatively identified as the key driver. To compensate for the effect of crystal fractionation, olivine is mathematically added towards calculated primitive melt compositions (δ57Feprim). For this, we used a constant Ol-melt isotope fractionation factor based on published equilibrium partition functions adapted to decreasing temperature in a cooling melt. The degree of calculated Fe isotope fractionation through olivine crystal fractionation (monitored as Δ57Fe = δ57Femeasured − δ57Feprim) is positively correlated with increasing S and decreasing Ni content in the cooling lavas, fortifying the validity of the approach. Primitive lavas from individual Lau spreading centres and ridges vary to 0.1‰ in δ57Feprim, similar to primitive open-ocean MORB. However, the entire spread in Fe isotope variability in the primitive melts remains at 0.3‰, which we propose to be the extent of isotope heterogeneity in Earth’s upper mantle, with few extreme exceptions. The largest variability in δ57Feprim is observed for RR intra-plate lavas, which have been associated with the Samoan mantle plume and melting in an edge-driven convection scenario. Low, mid-ocean ridge-like 87Sr/86Sr in RR lavas excludes significant influence of isotopically heavy Samoan EM2-type components. However, co-variations with rare earth element pattern in some RR intra-plate lavas indicate garnet plays a role in elevating δ57Feprim during deeper melting. Excluding these deep-seated melts uncovers systematically decreasing δ57Feprim coupled to the degree of mantle source depletion, as recorded in Lu/Hf and Sm/Nd, in the back-arc basin basalts. This, however, holds only true for a comparison between sources of individual ridges, whereas no co-variation is observed within ridge segment data. This suggests that a process other than source depletion and crystal fractionation further adds to Fe isotope variability in the order of 0.1‰ on scales of individual ridge segments. This either marks the degree of Fe isotope variability below ridge segments, or is caused by secondary processes, such as melt-wallrock interaction or RTX (recharge and crystal fractionation) magma chambers.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Publication Date: 2022-05-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Richter, M., Nebel, O., Schwindinger, M., Nebel-Jacobsen, Y., & Dick, H. J. B. Competing effects of spreading rate, crystal fractionation and source variability on Fe isotope systematics in mid-ocean ridge lavas. Scientific Reports, 11(1), (2021): 4123, https://doi.org/10.1038/s41598-021-83387-7.
    Description: Two-thirds of the Earth is covered by mid-ocean ridge basalts, which form along a network of divergent plate margins. Basalts along these margins display a chemical diversity, which is consequent to a complex interplay of partial mantle melting in the upper mantle and magmatic differentiation processes in lower crustal levels. Igneous differentiation (crystal fractionation, partial melting) and source heterogeneity, in general, are key drivers creating variable chemistry in mid-ocean ridge basalts. This variability is reflected in iron isotope systematics (expressed as δ57Fe), showing a total range of 0.2 ‰ from δ57Fe =  + 0.05 to + 0.25 ‰. Respective contributions of source heterogeneity and magma differentiation leading to this diversity, however, remain elusive. This study investigates the iron isotope systematics in basalts from the ultraslow spreading Gakkel Ridge in the Arctic Ocean and compares them to existing data from the fast spreading East Pacific Rise ridge. Results indicate that Gakkel lavas are driven to heavier iron isotope compositions through partial melting processes, whereas effects of igneous differentiation are minor. This is in stark contrast to fast spreading ridges showing reversed effects of near negligible partial melting effects followed by large isotope fractionation along the liquid line of descent. Gakkel lavas further reveal mantle heterogeneity that is superimposed on the igneous differentiation effects, showing that upper mantle Fe isotope heterogeneity can be transmitted into erupting basalts in the absence of homogenisation processes in sub-oceanic magma chambers.
    Description: This work was supported by an ARC grant FT140101062 to O.N. H.J.B.D was supported by the NSF grants PLR 9912162, PLR 0327591, OCE 0930487 and OCE 1434452.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Richter, M., Nebel, O., Maas, R., Mather, B., Nebel-Jacobsen, Y., Capitanio, F. A., Dick, H. J. B., & Cawood, P. A. An early cretaceous subduction-modified mantle underneath the ultraslow spreading Gakkel Ridge, Arctic Ocean. Science Advances, 6(44), (2020): eabb4340, doi:10.1126/sciadv.abb4340.
    Description: Earth’s upper mantle, as sampled by mid-ocean ridge basalts (MORBs) at oceanic spreading centers, has developed chemical and isotopic heterogeneity over billions of years through focused melt extraction and re-enrichment by recycled crustal components. Chemical and isotopic heterogeneity of MORB is dwarfed by the large compositional spectrum of lavas at convergent margins, identifying subduction zones as the major site for crustal recycling into and modification of the mantle. The fate of subduction-modified mantle and if this heterogeneity transmits into MORB chemistry remains elusive. Here, we investigate the origin of upper mantle chemical heterogeneity underneath the Western Gakkel Ridge region in the Arctic Ocean through MORB geochemistry and tectonic plate reconstruction. We find that seafloor lavas from the Western Gakkel Ridge region mirror geochemical signatures of an Early Cretaceous, paleo-subduction zone, and conclude that the upper mantle can preserve a long-lived, stationary geochemical memory of past geodynamic processes.
    Description: O.N. was supported by the Australian Research Council (grant FT140101062). P.A.C. was supported by the Australian Research Council (grant FL160100168). H.J.B.D. was supported by the NSF (grants PLR 9912162, PLR 0327591, OCE 0930487, and OCE 1434452). M.R. was supported by a graduate scholarship of Monash University and the SEAE.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...