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  • 1
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    Mineral Deposits and Earth Evolution (2005)
    London : The Geological Society
    Details
    Description / Table of Contents: Mineral deposits are not only primary sources of wealth generation, but also act as windows through which to view the evolution and interrelationships of the Earth system. Deposits formed throughout the last 3.8 billion years of the Earth’s history preserve key evidence with which to test fundamental questions about the evolution of the Earth. These include: the nature of early magmatic and tectonic processes, supercontinent reconstructions, the state of the atmosphere and hydrosphere with time, and the emergence and development of life. The interlinking processes that form mineral deposits have always sat at the heart of the Earth system and the potential for using deposits as tools to understand that evolving system over geological time is increasingly recognized. This volume contains research aimed both at understanding the origins of mineral deposits and at using mineral deposits as tools to explore different long-term Earth processes.
    Pages: Online-Ressource (X, 269 Seiten)
    ISBN: 1862391823
    URL: http://sp.lyellcollection.org/content/248/1.toc
    Language: English
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    E-BOOK
  • 2
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    Early oxygenation of the terrestrial environment during the Mesoproterozoic (2010)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2010-11-12
    Description: Geochemical data from ancient sedimentary successions provide evidence for the progressive evolution of Earth's atmosphere and oceans. Key stages in increasing oxygenation are postulated for the Palaeoproterozoic era ( approximately 2.3 billion years ago, Gyr ago) and the late Proterozoic eon (about 0.8 Gyr ago), with the latter implicated in the subsequent metazoan evolutionary expansion. In support of this rise in oxygen concentrations, a large database shows a marked change in the bacterially mediated fractionation of seawater sulphate to sulphide of Delta(34)S 〈 25 per thousand before 1 Gyr to 〉/=50 per thousand after 0.64 Gyr. This change in Delta(34)S has been interpreted to represent the evolution from single-step bacterial sulphate reduction to a combination of bacterial sulphate reduction and sulphide oxidation, largely bacterially mediated. This evolution is seen as marking the rise in atmospheric oxygen concentrations and the evolution of non-photosynthetic sulphide-oxidizing bacteria. Here we report Delta(34)S values exceeding 50 per thousand from a terrestrial Mesoproterozoic (1.18 Gyr old) succession in Scotland, a time period that is at present poorly characterized. This level of fractionation implies disproportionation in the sulphur cycle, probably involving sulphide-oxidizing bacteria, that is not evident from Delta(34)S data in the marine record. Disproportionation in both red beds and lacustrine black shales at our study site suggests that the Mesoproterozoic terrestrial environment was sufficiently oxygenated to support a biota that was adapted to an oxygen-rich atmosphere, but had also penetrated into subsurface sediment.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Parnell, John -- Boyce, Adrian J -- Mark, Darren -- Bowden, Stephen -- Spinks, Sam -- England -- Nature. 2010 Nov 11;468(7321):290-3. doi: 10.1038/nature09538.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉School of Geosciences, University of Aberdeen, Aberdeen AB24 3UE, UK. j.parnell@abdn.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21068840" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/chemistry ; Bacteria/metabolism ; Geologic Sediments/*chemistry/microbiology ; History, Ancient ; Iron/analysis/chemistry ; Oxidation-Reduction ; Oxygen/analysis/*metabolism ; Photosynthesis ; Scotland ; Seawater/chemistry ; Sulfates/metabolism ; Sulfides/analysis/chemistry/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    Microbial sulphate reduction during Neoproterozoic glaciation, Port Askaig Formation, UK (2017)
    Geological Society of London
    Details
    Publication Date: 2017-09-08
    Description: The Neoproterozoic Port Askaig Formation contains widespread pyrite within many diamictite beds, across Scotland and Ireland. The quantity of pyrite is anomalous for coarse-grained rocks, especially in rocks deposited at a time when seawater contained low sulphate levels owing to a continental ice cover, which inhibited weathering. Sulphur isotope compositions evolve from lightest values (down to –3.1) at the base of the formation to highly positive compositions in the overlying Bonahaven Dolomite (mean +44.8). This trend is consistent with progressive utilization of available sulphate by closed-system microbial sulphate reduction. Together with records from other contemporary diamictite successions, there emerges a picture of global microbial activity during Neoproterozoic ‘Snowball Earth’ glaciation. Supplementary material: Details of the sulphur isotopic composition are given at https://doi.org/10.6084/m9.figshare.c.3768959 .
    Print ISSN: 0016-7649
    Topics: Geosciences
    Published by Geological Society of London
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  • 4
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    Helium and oxygen isotope ratios of ODP Sites 193-1188 and 193-1189 (2011)
    PANGAEA
    In:  Supplement to: Webber, A P; Roberts, S; Burgess, R M; Boyce, A J (2011): Fluid mixing and thermal regimes beneath the PACMANUS hydrothermal field, Papua New Guinea: Helium and oxygen isotope data. Earth and Planetary Science Letters, 304(1-2), 93-102, https://doi.org/10.1016/j.epsl.2011.01.020
    Details
    Publication Date: 2024-01-09
    Description: Fluid mixing processes and thermal regimes within the Snowcap and Roman Ruins vent sites of the PACMANUS hydrothermal system, Papua New Guinea, were investigated using 3He/4He ratios from fluid inclusions within pyrite and anhydrite and the d18O signature of anhydrite. Depressed 3He/4He ratios of 0.2-6.91RA appear to be caused by significant atmospheric diffusive exchange, whilst He-Ne diffusive fractionation precludes correction using 20Ne. 40Ar/36Ar ratios of 295-310 are elevated above seawater, indicating the majority of argon is seawater derived but with a magmatic component. d18O anhydrite ratios are 6.5 per mil to 11 per mil for Snowcap and 6.4 per mil to 11.9 per mil for Roman Ruins. Using oxygen isotope fractionation factors for the anhydrite-water system, the temperatures calculated assuming isotopic equilibrium at depth are up to 100 °C cooler than fluid inclusion trapping temperatures. It is likely that anhydrite is precipitated rapidly, preventing d18O equilibration. By comparing new d18O values for anhydrite with corresponding published 87Sr/86Sr ratios, seawater is inferred to penetrate deep into the Snowcap system with little conductive heating. A simple fluid mixing model has been constructed whereby the differing venting styles can be explained by a plumbing system at depth which favors delivery of end-member hydrothermal fluid to the high temperature sites.
    Keywords: Ocean Drilling Program; ODP
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 5
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    (Table 2) Oxygen isotope ratios of anhydrite from subsurface samples of ODP Sites 193-1188 and 193-1189 (2011)
    PANGAEA
    Details
    Publication Date: 2024-01-09
    Keywords: 193-1188A; 193-1188F; 193-1189; Bismarck Sea; COMPCORE; Composite Core; DEPTH, sediment/rock; DRILL; Drilling/drill rig; Event label; Joides Resolution; Leg193; Ocean Drilling Program; ODP; Ratio; Sample code/label; Strontium-87/Strontium-86 ratio; δ18O, anhydrite; δ34S, anhydrite
    Type: Dataset
    Format: text/tab-separated-values, 80 data points
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  • 6
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    (Table 1) Helium and argon within fluid inclusions in precipitates from subsurface samples of ODP Sites 193-1188 and 193-1189 (2011)
    PANGAEA
    Details
    Publication Date: 2024-01-09
    Keywords: 193-1188A; 193-1188F; 193-1189; Argon-40/Argon-36; Argon-40/Argon-36, standard deviation; Bismarck Sea; COMPCORE; Composite Core; DEPTH, sediment/rock; DRILL; Drilling/drill rig; Event label; Helium-4; Joides Resolution; Leg193; Mineral name; Ocean Drilling Program; ODP; Ratio; Sample code/label; Standard deviation
    Type: Dataset
    Format: text/tab-separated-values, 104 data points
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  • 7
    Electronic Resource
    Electronic Resource
    Hydrothermal pyrite chimneys from the Ballynoe baryte deposit, Silvermines, County Tipperary, Ireland (1981)
    Springer
    Mineralium deposita 16 (1981), S. 309-317 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract We report the discovery of pyrite tubes 0.1 to 20mm in diameter in the Ballynoe sedimentary baryte deposit. Well developed tubes comprise concentric layers of pyrite of contrasting crystal sizes 0.05 to 1 mm thick. An outer rim of crystalline baryte ⪕ 10mm thick commonly coats the tubes where these are not touching. The central canals contain myriad pyrite framboids. These tubes have characteristics in common with the chimney spires found on the East Pacific Rise at 21°N from which metal bearing solutions issue at temperatures of up to 380±30°C. Their presence carries the implication that the baryte deposit was not a distal facies of the Silvermines sedimentary pyritic zinc and lead ore, but was produced from local hydrothermal exhalations, though in a shallower part of the basin than the coeval sulphide deposits which had their own feeders. Some epigenetic mineralization may be awaiting discovery beneath the feeder sites at Ballynoe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202742
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  • 8
    Electronic Resource
    Electronic Resource
    A new sulphur isotopic study of some Iberian Pyrite Belt deposits: evidence of a textural control on sulphur isotope composition (1998)
    Springer
    Mineralium deposita 34 (1998), S. 4-18 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The sulphide deposits of the Iberian Pyrite Belt (IPB) represent an ore province of global importance. Our study presents 113 new sulphur isotope analyses from deposits selected to represent the textural spectrum of ores. Measured 34S values range from −26 to +10‰ mostly for massive and stockwork ores, in agreement with data previously published. In situ laser 34S analyses reveals a close correlation of 34S with texture. Primary diagenetic textures are dominated by relatively low 34S (−8‰ to −2‰), whereas stockwork feeder textures are dominated by higher 34S (∼+3‰ to +5‰). Intermediate textures (mainly coarse textures in stratiform zones) have intermediate 34S, although they are mostly dominated by the high 34S component. Rare barite has a homogeneous 34S around +18‰, which is consistent with direct derivation from Lower Carboniferous seawater sulphate. A dual source of sulphide sulphur in the IPB deposits has been considered. A hydrothermal source, derived from reduction of coeval seawater sulphate in the convective systems, is represented by sulphide in the feeder zones. Here variations in 34S are caused by variations in the extent of the sulphate reduction, which governs the SO4:H2S ratio. The second end-member was derived from the bacterial reduction of coeval seawater sulphate at or near the surface, as reflected in the primary textures. A distinct geographical variation in 34S and texture from SW (more bacteriogenic and primary textures) to NE (more hydrothermal textures and 34S) which reflects a variation in the relative input of each source was likely controlled by local geological environments. Given that the sulphur isotope characteristics of the IPB deposits are unlike most VMS and Kuroko deposits, and noting the dominance of a mixed reduced sedimentary and volcanic environment, we suggest that the IPB could represent an ore style which is intermediate between volcanic and sedimentary hosted massive sulphide types.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001260050182
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  • 9
    Electronic Resource
    Electronic Resource
    Why are some genetic diseases common? (1993)
    Springer
    Human genetics 〈Berlin〉 91 (1993), S. 91-117 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Various processes (selection, mutation, migration and genetic dirft) are known to determine the frequency of genetic disease in human populations, but so far it has proved almost impossible to decide to what extent each is responsible for the presence of a particular genetic disease. The techniques of gene and haplotype analysis offer new hope in addressing this issue, and we review relevant studies of three haemoglobinopathies: sickle cell anaemia, and α and β thalassaemia. We show how for each disease it is possible to recognize a pattern of regionally specific mutations, found in association with one or a few haplotypes, that is best explained as the result of selection; other patterns are due to population migration and genetic drift. However, we caution that such conclusions can be drawn in special circumstances only. In the case of the haemoglobinopathies it is possible because a selective agent (malaria) was already suspected, and the investigations could be carried out in relatively genetically homogenous populations whose migratory histories are known. Moreover, some data reviewed here suggest that gene conversion and the haplotype composition of a population may affect the frequency of a mutation, making interpretation of gene frequencies difficult on the basis of standard population genetics theory. Hence attempts to use the same approaches with other genetic diseases are likely to be frustrated by a lack of suitably untrammelled populations and by difficulties accounting for poorly understood genetic processes. We conclude that although this combination of molecular and population genetics is successful when applied to the study of haemoglobinopathies, it may not be so easy to apply it to the study of other genetic diseases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222709
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  • 10
    Electronic Resource
    Electronic Resource
    Demographic reductions and genetic bottlenecks in humans: minisatellite allele distributions in oceania (1993)
    Springer
    Human genetics 〈Berlin〉 91 (1993), S. 445-450 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Polynesians have lower heterozygosities at minisatellite VNTR (Variable Number of Tandem Repeat) loci than have Melanesians; this has been taken as evidence of population-size bottlenecks during the colonisation of Polynesia. We have analysed the allelic distribution of several minisatellite loci in the population of Rapa, a Polynesian island that is known to have undergone a demographic reduction of approximately 95% since first contact with European explorers 200 years ago, leaving a surviving population of 120. We found that the minisatellite diversity of this population does not differ significantly from that of other Polynesian populations, and appears consistent with the neutral expectation of diversity assuming the infinite alleles model. This suggests that the demographic crisis that Rapa underwent did not perturb the allele distribution to the extent that the tests used here could detect. Thus we cannot say that a demographic change of this magnitude constitutes a genetic bottleneck detectable at these loci. The reduced diversity seen in Polynesia must therefore be explained either by more severe bottlenecks as might be expected during colonisation, or else by other causes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217769
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