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Show simple item record Fiebig, Jens de 2001-10-31T15:25:42Z de 2013-01-18T11:25:46Z de 2013-01-30T23:51:05Z de 2001-10-31 de
dc.identifier.uri de
dc.format.mimetype application/pdf de
dc.language.iso eng de
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dc.title Oxygen isotope microanalysis of silicates with application to fluid-rock interfaces de
dc.contributor.referee Hoefs, Jochen Prof. Dr. de 2000-01-27 de
dc.subject.dnb 550 Geowissenschaften de
dc.description.abstracteng In order to investigate crustal fluid-rock interactions an oxygen isotope microprobe was set up. Oygen is extracted from silicates by Ultra-Violet (UV)-laser fluorination and its isotropic 18/16-ration is determined using isotope ration monitoring Gas Chromatography Mass Spectrometry (irm-GC-MS). This technique enables an accurate in situ analysis of all types of silicates, including highly transparent minerals like quartz. To reduce the influence of fluorine derived blanks on isotopic measurements, 3000 nmol oxygen is liberated, while only 30 nmol ist finally used for isotopic analysis. This way, spatial resolution is set to 250 [my]m. Precision is about 0.2o/oo, while a single analysis takes less than 15 minutes. In situ oxygen isotope- and electron microprobe analysis was addressed to a hydrothermally altered granitic pluton from the Schwarzwald, Germany. Both data sets demonstrate that an exchange of oxygen isotopes between granite and fluid occurs preferentially along microcracks. Chemical reaction and dissolution-recrystallisation are the dominant exchange mechanisms. Disequilibirium fractionations between mineral pairs, which have been obtained for the same samples by conventional ''thermal'' fluorintation on a meter-scale, are interpreted to be due to a mixing of two systems exhibiting equilibirium fractionations on a µm-scale. Large parts of the investigated granite have been intensively modified by a Na-rich fluid. On a cm-scale, oxygen isotope exchange between fluid and rock is modelled using a kinetic exchange theory. The number of preexisting microcracks drives kinetic parameters like water-rock ratio and fluid flux and thereby affects the chemical compostition of the fluid and exchange rates. This investigation confirms the hypothesis that a large fossil hydrothermal system of meteoric origin was active in the southern Schwarzwald. Due to an interaction with subsequently intruded granitic plutons the 18O depeleted meteoric fluid became continuously enrichted in 18O. de
dc.contributor.coReferee Wörner, Gerhard Prof. Dr. de
dc.subject.topic Mathematics and Computer Science de
dc.subject.ger Quarz de
dc.subject.ger Flüssigkeitseinschluss de
dc.subject.ger Sauerstoffisotop de
dc.subject.ger Mirkoranalyse de
dc.subject.bk 38.32 de
dc.identifier.urn urn:nbn:de:gbv:7-webdoc-874-9 de
dc.identifier.purl webdoc-874 de Fakultät für Geowissenschaften und Geographie de
dc.subject.gokfull VJC 400: Fluid-Gestein-Wechselwirkungen {Geochemie} de
dc.subject.gokfull VJJ 110: Geochemie der Stabilen Isotopen de
dc.subject.gokfull VJA 240: Spektroskopische Verfahren {Geochemie} de
dc.identifier.ppn 318576244

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