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  • 1
    Electronic Resource
    Electronic Resource
    U/Pb, Sm/Nd and Rb/Sr geochronological and isotopic study of northern Sierra Nevada ophiolitic assemblages, California (1989)
    Springer
    Contributions to mineralogy and petrology 102 (1989), S. 205-220 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Distinct ophiolitic assemblages occur as oceanic basement within three of the four regional tectonic belts of the northern Sierra Nevada. New U/Pb zircon, Sm/Nd and Rb/Sr data are presented for each assemblage, providing critical geochronological and isotopic constraints on the petrogenesis and tectonic evolution of the ophiolitic and associated ensimatic assemblages. Ophiolitic assemblages include from west to east the Smartville complex, Central belt and Feather River belt. The Smartville complex represents an island arc volcanic-plutonic sequence with a major late-stage sheeted dike swarm. The Sm/Nd systems from a wide compositional spectrum of rocks record a 178±21 Ma petrogenetic age and an ɛ Nd(T)=+9.2±0.6. Zircon U/Pb systems on an uppermost dacite yield a 164±2 Ma age, and on a number of plagiogranite screens and dikes from the sheeted complex 162±1 Ma ages. The Central and Feather River belts are structurally complex polygenetic assemblages. The U/Pb zircon and Sm/Nd systems record major ∼205 Ma and ∼315 Ma petrogenetic events respectively both involving depleted mantle derived magmas. Such magmatism probably occurred in marginal basin/transform systems developed within an older oceanic depleted mantle basement regime. Both Sm/Nd and U/Pb zircon systems show local components of Proterozoic sialic material. The sialic contaminants were probably introduced into the system as craton derived detritus. It is doubtful that any of the ophiolitic assemblages studied represent genetically related crust-upper mantle sequences generated during the development of new oceanic lithosphere. Integration of the geochronological data with geological relations reveals a pattern of petrogenesis and tectonics whereby progressively younger ensimatic terranes were added to the continental margin through time by plate convergence, and were ultimately welded into North American sial by a crosscutting batholithic belt. This accretionary pattern is reflected in both the protolith ages and deformation-metamorphic ages of each of the regional belts which progressively young westward. Crustal components of the accreted ensimatic terranes grew by mainly basaltic igneous activity within island arc, marginal basin and leaky transform systems adjacent to the continent edge prior to final tectonic accretion. Such complexities are suggested to be typical of Cordilleran-type ophiolites and representative of the circum-Pacific erogenic style.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375341
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Ophiolites and oceanic crust (1974)
    [s.l.] : Nature Publishing Group
    Nature 250 (1974), S. 136-139 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We here attempt to resolve some of these difficulties by comparing data on oceanic crustal structure, with data on selected, relatively complete, ophiolite complexes. We also discuss possible relationships between age, spreading rate, and crustal structure, and suggest a more precise correlation ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/250136a0
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Plate-tectonic Regulation of Faunal Diversity and Sea Level: a Model (1970)
    [s.l.] : Nature Publishing Group
    Nature 228 (1970), S. 657-659 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Among the factors that regulate species diversity are environmental stability2'3, food supply2'4'5 and provinciality6'7. Consider a large land mass composed of an assembly of all the presently dispersed continents. Such a continental state favours great seasonality of marine climate, partly as a ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/228657a0
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    Paper (German National Licenses)
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