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  • 1
    Publication Date: 2015-09-11
    Description: A glacial dispersal study was conducted around a subcropping Pb–Zn deposit (O28) in the Pine Point Mississippi Valley-type (MVT) district, Northwest Territories, Canada, with the intent of characterizing and documenting the indicator minerals and their dispersal from a known orebody. Mapping of striations adjacent to deposit O28, and throughout the Pine Point district, along with observed glacial stratigraphy, indicate that there are three phases of ice flow that have affected the Pine Point district. Sphalerite, galena, and pyrite were identified in mineralized bedrock samples at deposit O28, and sphalerite and galena were recovered from the sand fraction of till samples up to 500 m from the mineralized subcrop. The majority of sphalerite and galena grains recovered from till samples down-ice of deposit O28 were 0.25–0.5 mm in size. Size and morphology of sphalerite grains in till demonstrate relative proximity to their bedrock source, with the largest and more angular grains being closer to the ore zone (〈50 m) whereas smaller and more rounded grains occur further down-ice (~250 m). The paragenesis, textures, major-element concentrations, and S and Pb isotopic compositions of bedrock samples from deposit O28 and from newly drilled core from four other deposits were characterized. Concentrations of Zn in bedrock sphalerite grains range from 43.95 to 67.48 wt.%, concentrations of S range from 32.03 to 34.01 wt.%, and concentrations of Fe range from 0.02 to 16.94 wt.%. The Fe concentration in bedrock sphalerite decreases from east to west across the district. Concentrations of S in galena grains in bedrock range from 12.50 to 14.00 wt.% and have a bimodal distribution. Generally, the geochemistry of sphalerite grains recovered from till were statistically similar to bedrock grains recovered from deposits O28 and L65. Major-element concentrations were statistically the same between the sphalerite grains recovered from till and the honey-brown and cleiophane varieties in the bedrock samples. Galena grains recovered from till samples were similar to the cubic and fracture-fill varieties of grains recovered from bedrock in the R190 and M67 deposits. Sulphur isotopic values for sphalerite grains from bedrock range from 20.6 to 24.2, while those from till samples range from –5.3 to 24.4. Lead isotopic ratios for galena grains from bedrock and till samples had very little variation, which is a characteristic of the Pine Point district. The S and Pb isotopic studies as well as major-element geochemistry suggest that indicator minerals derived from Pine Point-type mineralization can be distinguished from those sourced from other types of carbonate-hosted mineralized systems (e.g., Cordilleran zinc–lead deposits) and that the methods here can be used as exploration tools for identifying MVT deposit provenance or potential. The results of this study present criteria and highlights additional methods for exploration of MVT deposits in glaciated terrain.
    Print ISSN: 0008-4077
    Electronic ISSN: 1480-3313
    Topics: Geosciences
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  • 2
    Publication Date: 2015-01-30
    Description: Ice flow of the last glaciation in the Buffalo Head Hills kimberlite field of northern Alberta is reconstructed from landform interpretations and clast orientations for the purpose of aiding kimberlite exploration in the region. The paucity of bedrock outcrop and the absence of preserved striae and other erosional ice-flow indicators on the soft Cretaceous marine sediments inhibit detailed interpretations on glacial flow chronology. Poorly developed bedrock drumlins on the Buffalo Head Hills and erosional ice-flow indicators preserved on the kimberlite outcrops indicate southwestward ice flow during the maximum extent of ice during the last glaciation. During the deglaciation of northern Alberta, later phases of ice flow were controlled by lobes of surging ice, which surged into proglacial lakes. West of the Buffalo Head Hills, the maximum phase of southwest flow was followed by southeastward ice movement of the Peace River ice lobe. Similarly, east of the Buffalo Head Hills, the maximum phase of ice flow was superceded by a south-southwest ice advance of the Wasbasca ice lobe.
    Print ISSN: 0008-4077
    Electronic ISSN: 1480-3313
    Topics: Geosciences
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  • 3
    Publication Date: 2015-03-15
    Description: TREK-2 (KCNK10/K2P10), a two-pore domain potassium (K2P) channel, is gated by multiple stimuli such as stretch, fatty acids, and pH and by several drugs. However, the mechanisms that control channel gating are unclear. Here we present crystal structures of the human TREK-2 channel (up to 3.4 angstrom resolution) in two conformations and in complex with norfluoxetine, the active metabolite of fluoxetine (Prozac) and a state-dependent blocker of TREK channels. Norfluoxetine binds within intramembrane fenestrations found in only one of these two conformations. Channel activation by arachidonic acid and mechanical stretch involves conversion between these states through movement of the pore-lining helices. These results provide an explanation for TREK channel mechanosensitivity, regulation by diverse stimuli, and possible off-target effects of the serotonin reuptake inhibitor Prozac.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dong, Yin Yao -- Pike, Ashley C W -- Mackenzie, Alexandra -- McClenaghan, Conor -- Aryal, Prafulla -- Dong, Liang -- Quigley, Andrew -- Grieben, Mariana -- Goubin, Solenne -- Mukhopadhyay, Shubhashish -- Ruda, Gian Filippo -- Clausen, Michael V -- Cao, Lishuang -- Brennan, Paul E -- Burgess-Brown, Nicola A -- Sansom, Mark S P -- Tucker, Stephen J -- Carpenter, Elisabeth P -- 084655/Wellcome Trust/United Kingdom -- 092809/Z/10/Z/Wellcome Trust/United Kingdom -- Biotechnology and Biological Sciences Research Council/United Kingdom -- New York, N.Y. -- Science. 2015 Mar 13;347(6227):1256-9. doi: 10.1126/science.1261512.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK. ; Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK. Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK. ; Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK. OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK. ; Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK. OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK. Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK. ; Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK. Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7FZ, UK. ; Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK. ; Pfizer Neusentis, Granta Park, Cambridge CB21 6GS, UK. ; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK. Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK. ; Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK. OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK. liz.carpenter@sgc.ox.ac.uk stephen.tucker@physics.ox.ac.uk. ; Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK. OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK. liz.carpenter@sgc.ox.ac.uk stephen.tucker@physics.ox.ac.uk.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25766236" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Arachidonic Acid/pharmacology ; Binding Sites ; Crystallography, X-Ray ; Fluoxetine/analogs & derivatives/chemistry/metabolism/pharmacology ; Humans ; *Ion Channel Gating ; Models, Molecular ; Molecular Dynamics Simulation ; Molecular Sequence Data ; Potassium/metabolism ; Potassium Channels, Tandem Pore Domain/antagonists & ; inhibitors/*chemistry/metabolism ; Protein Conformation ; Protein Folding ; Protein Structure, Secondary ; Protein Structure, Tertiary
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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