Schmidt, Burkhard C.

[["dc.bibliographiccitation.firstpage","123"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","European Journal of Mineralogy"],["dc.bibliographiccitation.lastpage","136"],["dc.bibliographiccitation.volume","25"],["dc.contributor.author","Perdikouri, Christina"],["dc.contributor.author","Piazolo, Sandra"],["dc.contributor.author","Kasioptas, Argyrios"],["dc.contributor.author","Schmidt, Burkhard C."],["dc.contributor.author","Putnis, Andrew"],["dc.date.accessioned","2018-11-07T09:27:11Z"],["dc.date.available","2018-11-07T09:27:11Z"],["dc.date.issued","2013"],["dc.description.abstract","The hydrothermal transformation of single aragonite crystals into polycrystalline calcite has been studied under hydrothermal conditions. The transformation involves a fluid-mediated replacement reaction, associated with fracturing of the initial aragonite crystal and growth of calcite throughout various parts of the reacted aragonite. The observed overall preservation of the crystal morphology is typical of an interface-coupled dissolution-reprecipitation mechanism Analysis of the crystallographic orientation of the product calcite using electron backscatter diffraction (EBSD) showed little to no link between the two phases under the studied conditions, with calcite crystallites exhibiting dominantly different crystallographic orientations compared to those of the aragonite and of neighbouring calcite domains. The complexity of the observed textures is mainly a result of the combination of fracturing of the crystal and initiation of nucleation and growth at different points of the exposed aragonite surface. Experiments performed with solutions enriched in O-18 as a tracer for oxygen exchange and monitored by Raman spectroscopy, showed that carbonate ions in the starting solution are mixed with carbonate from the dissolving aragonite, resulting in an O-18 concentration in the product calcite which depended on the local fluid transport through the fractures. As replacement processes among the CaCO3 phases are relevant to a wide range of applications, understanding the mechanisms is essential for the interpretation of observations of natural and/or experimental samples. This study describes the interplay between the replacement process, the fracturing of the crystal and growth of the new phase, calcite, and provides new insights into the mechanism of the aragonite to calcite transition. The combination of the two methods, EBSD and Raman spectroscopy, demonstrates the importance of local fluid composition and transport pathways in determining the isotope and element exchange in mineral replacement reactions."],["dc.identifier.doi","10.1127/0935-1221/2013/0025-2261"],["dc.identifier.isi","000320568600001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/30474"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","E Schweizerbartsche Verlagsbuchhandlung"],["dc.relation.issn","0935-1221"],["dc.title","Hydrothermal replacement of Aragonite by Calcite: interplay between replacement, fracturing and growth"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","19"],["dc.bibliographiccitation.journal","Geochimica et Cosmochimica Acta"],["dc.bibliographiccitation.lastpage","38"],["dc.bibliographiccitation.volume","253"],["dc.contributor.author","Löffler, N."],["dc.contributor.author","Fiebig, J."],["dc.contributor.author","Mulch, A."],["dc.contributor.author","Tütken, T."],["dc.contributor.author","Schmidt, B. C."],["dc.contributor.author","Bajnai, D."],["dc.contributor.author","Conrad, A.C."],["dc.contributor.author","Wacker, U."],["dc.contributor.author","Böttcher, M.E."],["dc.date.accessioned","2020-12-10T14:24:13Z"],["dc.date.available","2020-12-10T14:24:13Z"],["dc.date.issued","2019"],["dc.identifier.doi","10.1016/j.gca.2019.03.002"],["dc.identifier.issn","0016-7037"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/72189"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Refining the temperature dependence of the oxygen and clumped isotopic compositions of structurally bound carbonate in apatite"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","900"],["dc.bibliographiccitation.issue","8"],["dc.bibliographiccitation.journal","Leukemia Research"],["dc.bibliographiccitation.lastpage","906"],["dc.bibliographiccitation.volume","37"],["dc.contributor.author","Braulke, Friederike"],["dc.contributor.author","Jung, Klaus"],["dc.contributor.author","Schanz, Julie"],["dc.contributor.author","Götze, Katharina S."],["dc.contributor.author","Müller-Thomas, Catharina"],["dc.contributor.author","Platzbecker, Uwe"],["dc.contributor.author","Germing, Ulrich"],["dc.contributor.author","Brümmendorf, Tim H."],["dc.contributor.author","Bug, Gesine"],["dc.contributor.author","Ottmann, Oliver G."],["dc.contributor.author","Giagounidis, Aristoteles A. N."],["dc.contributor.author","Stadler, Michael"],["dc.contributor.author","Hofmann, Wolf-Karsten"],["dc.contributor.author","Schafhausen, Philippe"],["dc.contributor.author","Lübbert, Michael"],["dc.contributor.author","Schlenk, Richard F."],["dc.contributor.author","Blau, Igor W."],["dc.contributor.author","Ganster, Christina"],["dc.contributor.author","Pfeiffer, Sebastian"],["dc.contributor.author","Shirneshan, Katayoon"],["dc.contributor.author","Metz, Michael"],["dc.contributor.author","Detken, Sven"],["dc.contributor.author","Seraphin, Jörg"],["dc.contributor.author","Jentsch-Ullrich, Kathleen"],["dc.contributor.author","Böhme, Angelika"],["dc.contributor.author","Schmidt, Burkhard C."],["dc.contributor.author","Trümper, Lorenz"],["dc.contributor.author","Haase, Detlef"],["dc.date.accessioned","2018-11-07T09:22:10Z"],["dc.date.available","2018-11-07T09:22:10Z"],["dc.date.issued","2013"],["dc.description.abstract","The gold standard of cytogenetic analysis in myelodysplastic syndromes (MDS) is conventional chromosome banding (CCB) analysis of bone marrow (BM) metaphases. Most aberrations can also be detected by fluorescence-in situ-hybridization (FISH). For this prospective multicenter German diagnostic study (www.clinicaltrials.gov: #NCT01355913) 360 patients, as yet, were followed up to 3 years by sequential FISH analyses of immunomagnetically enriched CD34+ peripheral blood (PB) cells using comprehensive FISH probe panels, resulting in a total number of 19,516 FISH analyses. We demonstrate that CD34+ PB FISH correlates significantly with CCB analysis and represents a feasible method for a reliable non-invasive cytogenetic monitoring from PB. (C) 2013 Elsevier Ltd. All rights reserved."],["dc.description.sponsorship","Celgene(R) Germany"],["dc.identifier.doi","10.1016/j.leukres.2013.03.019"],["dc.identifier.isi","000321111900012"],["dc.identifier.pmid","23623559"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/29278"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.notes.submitter","Najko"],["dc.relation.issn","0145-2126"],["dc.title","Molecular cytogenetic monitoring from CD34+peripheral blood cells in myelodysplastic syndromes: First results from a prospective multicenter German diagnostic study"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","227"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","American Mineralogist"],["dc.bibliographiccitation.lastpage","238"],["dc.bibliographiccitation.volume","105"],["dc.contributor.author","Rout, Smruti Sourav"],["dc.contributor.author","Schmidt, Burkhard C."],["dc.contributor.author","Wörner, Gerhard"],["dc.date.accessioned","2020-12-10T18:42:56Z"],["dc.date.available","2020-12-10T18:42:56Z"],["dc.date.issued","2020"],["dc.identifier.doi","10.2138/am-2020-7193"],["dc.identifier.eissn","1945-3027"],["dc.identifier.issn","0003-004X"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/78140"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Constraints on non-isothermal diffusion modeling: An experimental analysis and error assessment using halogen diffusion in melts"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","165"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","International Journal of Astrobiology"],["dc.bibliographiccitation.lastpage","175"],["dc.bibliographiccitation.volume","15"],["dc.contributor.author","Schmidt, B. C."],["dc.contributor.author","Mißbach, Helge"],["dc.contributor.author","Duda, Jan-Peter"],["dc.contributor.author","Luensdorf, Nils Keno"],["dc.contributor.author","Thiel, Volker"],["dc.date.accessioned","2020-12-10T15:22:23Z"],["dc.date.available","2020-12-10T15:22:23Z"],["dc.date.issued","2016"],["dc.description.abstract","Lipid biomarkers have been extensively applied for tracing organisms and evolutionary processes through Earth's history. They have become especially important for the reconstruction of early life on Earth and, potentially, for the detection of life in the extraterrestrial realm. However, it is not always clear how exactly biomarkers reflect a paleoecosystem as their preservation may be influenced by increasing temperatures (T) and pressures (P) during burial. While a number of biomarker indices reflecting thermal maturity have been established, it is often less well constrained to which extent biomarker ratios used for paleoreconstruction are compromised by T and P processes. In this study we conducted hydrous pyrolysis of Green River Shale (GRS) kerogen in gold capsules for 2-2400 h at 300 degrees C to assess the maturation behaviour of several compounds used as life tracers and for the reconstruction of paleoenvironments (n-alkanes, pristane, phytane, gammacerane, steranes, hopanes and cheilanthanes). Lignite samples were maturated in parallel with the GRS kerogen to obtain exact vitrinite reflectance data at every sampling point. Our experiment confirms the applicability of biomarker-based indices and ratios as maturity indicators (e.g. total cheilanthanes/hopanes ratio; sterane and hopane isomerization indices). However, several biomarker ratios that are commonly used for paleoreconstructions (e.g. pristane/phytane, pristane/n-C-17, phytane/n-C-18 and total steranes/hopanes) were considerably affected by differences in the thermal degradation behaviour of the respective compounds. Short-term experiments (48 h) performed at 400 degrees C also revealed that biomarkers >C-15 (especially steranes and hopanes) and biological' chain length preferences for n-alkanes are vanished at a vitrinite reflectance between 1.38 and 1.83% R-O. Our data highlight that thermal taphonomy' effects have to be carefully considered in the interpretation of biomarkers in ancient rocks and, potentially, extraterrestrial materials."],["dc.identifier.doi","10.1017/S1473550416000069"],["dc.identifier.eissn","1475-3006"],["dc.identifier.isi","000381033400002"],["dc.identifier.issn","1473-5504"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/73383"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","1475-3006"],["dc.relation.issn","1473-5504"],["dc.title","Testing the preservation of biomarkers during experimental maturation of an immature kerogen"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","Contributions to Mineralogy and Petrology"],["dc.bibliographiccitation.volume","174"],["dc.contributor.author","Schanofski, Maximilian"],["dc.contributor.author","Fanara, Sara"],["dc.contributor.author","Schmidt, Burkhard C."],["dc.date.accessioned","2020-12-10T14:10:32Z"],["dc.date.available","2020-12-10T14:10:32Z"],["dc.date.issued","2019"],["dc.identifier.doi","10.1007/s00410-019-1581-7"],["dc.identifier.eissn","1432-0967"],["dc.identifier.issn","0010-7999"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/70793"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","CO2–H2O solubility in K-rich phonolitic and leucititic melts"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","259"],["dc.bibliographiccitation.issue","3-4"],["dc.bibliographiccitation.journal","Chemical Geology"],["dc.bibliographiccitation.lastpage","268"],["dc.bibliographiccitation.volume","256"],["dc.contributor.author","Schmidt, Burkhard C."],["dc.contributor.author","Behrens, Harald"],["dc.date.accessioned","2018-11-07T11:09:08Z"],["dc.date.available","2018-11-07T11:09:08Z"],["dc.date.issued","2008"],["dc.description.abstract","The water solubility in various phonolite melts was determined experimentally at pressures between 50 and 395 MPa and at temperatures between 850 and 1200 degrees C. The aim of this study was to elucidate to which extent chemical and physical parameters such as relative amounts of alkali and alkaline earth elements or temperature affect the water solubility. For this purpose a total of 10 different phonolite glasses were prepared. For a series of four glasses, the Na/(Na+ K) ratio was varied from 0.2 to 0.8, for another series of four glasses, the (Na+K)/(Ca+Mg) ratio was varied from 2.8 to 10.1, while keeping Na/(Na+K) constant at 0.4. For these two series water solubility experiments were performed at 1200 degrees C and pressures between 50 and 395 MPa in an internally heated pressure vessel. The data show that both chemical variables have rather small effects on the water Solubility. For instance, at 2 kbar and 1200 degrees C an increase in Na/(Na+ K) ratio from 0.2 to 0.8 leads to an increase in water solubility of about 0.4 wt.% (5.58 to 5.94 wt.%), while increasing the (Na+K)/(Ca+Mg) ratio from 2.8 to 10.1 leads to an increase of about 0.2 wt.% water. The effect of temperature was investigated for two phonolite compositions, representative of Montana Blanca, Tenerife, Spain and the Laacher See volcanic complex, East Eifel, Germany at pressures of 50, 100, 150, 200, 250 and 300 MPa, and temperatures between 850 and 1200 degrees C. At these conditions both melts exhibit negative temperature dependence ranging from about -0.1 to -0.24 wt.% water per 100 degrees C. The strongest temperature dependence (most negative values) occurs at 150 to 200 MPa and seems to approach zero slightly above 300 MPa. (c) 2008 Elsevier B.V. All rights reserved."],["dc.description.sponsorship","German Science Foundation (DFG) [SCHM 1622/2]"],["dc.identifier.doi","10.1016/j.chemgeo.2008.06.043"],["dc.identifier.isi","000261563200018"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/52941"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","0009-2541"],["dc.title","Water solubility in phonolite melts: Influence of melt composition and temperature"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","171"],["dc.bibliographiccitation.journal","Chemical Geology"],["dc.bibliographiccitation.lastpage","181"],["dc.bibliographiccitation.volume","461"],["dc.contributor.author","Fanara, Sara"],["dc.contributor.author","Sottili, Gianluca"],["dc.contributor.author","Silleni, Aurora"],["dc.contributor.author","Palladino, Danilo M."],["dc.contributor.author","Schmidt, Burkhard C."],["dc.date.accessioned","2020-12-10T14:23:03Z"],["dc.date.available","2020-12-10T14:23:03Z"],["dc.date.issued","2017"],["dc.identifier.doi","10.1016/j.chemgeo.2016.12.033"],["dc.identifier.issn","0009-2541"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/71819"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","CO2 bubble nucleation upon pressure release in potassium-rich silicate magmas"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","597"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","European Journal of Mineralogy"],["dc.bibliographiccitation.lastpage","614"],["dc.bibliographiccitation.volume","25"],["dc.contributor.author","Angel, Ross J."],["dc.contributor.author","Ross, Nancy L."],["dc.contributor.author","Zhao, Jing"],["dc.contributor.author","Sochalski-Kolbus, Lindsay"],["dc.contributor.author","Krueger, Hannes"],["dc.contributor.author","Schmidt, Burkhard C."],["dc.date.accessioned","2018-11-07T09:21:30Z"],["dc.date.available","2018-11-07T09:21:30Z"],["dc.date.issued","2013"],["dc.description.abstract","The structural variation of monoclinic C2/m alkali feldspars has been analysed, based on 50 previously-determined structures and 10 new structure refinements including three determinations of the structure of an Or90 orthoclase at temperatures of 600 K, 900 K and 1075 K. The influence of temperature, composition and state of Al, Si order on the overall average tetrahedral bond lengths of these structures is statistically insignificant. Analysis of the structures in terms of the tilts of the tetrahedra shows that the tilts evolve uniformly with unit-cell volume irrespective of whether the volume is changed by temperature or exchange of the extra-framework cation. There is a small but systematic decrease in the distortion of the T1 tetrahedron with increasing unit-cell volume. Comparisons of the refined structures with the results of geometric modelling show that volume changes are driven by exchange of the extra-framework cation, or by an increase in its thermal vibrations upon heating. The extreme anisotropy of the changes in the unit-cell parameters of monoclinic feldspars is not due to anisotropic interaction of the extra-framework cation with the anions of the framework, but due to the tilting of the tetrahedra controlled in part by O-O interactions. The anisotropy and tilting is not significantly modified by either Al, Si ordering or the distortions of the tetrahedra provided that the latter remain constant. The monoclinic feldspars show a slightly reduced anisotropy of strains as the unit-cell volume increases as a result of a decrease in the angular distortion of the T1 tetrahedron. The general conclusion is drawn that the pattern of anisotropy of the elastic properties (thermal expansion, compressibility, elastic compliances) and the cell-parameter changes of a tetrahedral framework structure with changing extra-framework species are intrinsic to the topology of the framework. The relative insensitivity of the anisotropy of the strains induced by volume changes to distortions of the tetrahedra also means that framework models which incorporate regular tetrahedra can be safely used to predict anisotropy, provided that the tetrahedral distortions do not change. If, as in the monoclinic feldspars, such a model does not reproduce exactly the observed anisotropy of the real structures, then this immediately indicates that there is a significant change in the distortion of the framework tetrahedra."],["dc.description.sponsorship","National Science Foundation [EAR-1118691]"],["dc.identifier.doi","10.1127/0935-1221/2013/0025-2323"],["dc.identifier.isi","000329296000010"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/29120"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","E Schweizerbartsche Verlagsbuchhandlung"],["dc.relation.issn","1617-4011"],["dc.relation.issn","0935-1221"],["dc.title","Structural controls on the anisotropy of tetrahedral frameworks: the example of monoclinic feldspars"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","6211"],["dc.bibliographiccitation.issue","20"],["dc.bibliographiccitation.journal","Geochimica et Cosmochimica Acta"],["dc.bibliographiccitation.lastpage","6224"],["dc.bibliographiccitation.volume","75"],["dc.contributor.author","Perdikouri, Christina"],["dc.contributor.author","Kasioptas, Argyrios"],["dc.contributor.author","Geisler, Thorsten"],["dc.contributor.author","Schmidt, Burkhard C."],["dc.contributor.author","Putnis, Andrew"],["dc.date.accessioned","2018-11-07T08:50:42Z"],["dc.date.available","2018-11-07T08:50:42Z"],["dc.date.issued","2011"],["dc.description.abstract","The experimental replacement of aragonite by calcite was studied under hydrothermal conditions at temperatures between 160 and 200 degrees C using single inorganic aragonite crystals as a starting material. The initial saturation state and the total [Ca(2+)]:[CO(3)(2-)] ratio of the experimental solutions was found to have a determining effect on the amount and abundance of calcite overgrowths as well as the extent of replacement observed within the crystals. The replacement process was accompanied by progressive formation of cracks and pores within the calcite, which led to extended fracturing of the initial aragonite. The overall shape and morphology of the parent aragonite crystal were preserved. The replaced regions were identified with scanning electron microscopy and Raman spectroscopy. Experiments using carbonate solutions prepared with water enriched in (18)O (97%) were also performed in order to trace the course of this replacement process. The incorporation of the heavier oxygen isotope in the carbonate molecule within the calcite replacements was monitored with Raman spectroscopy. The heterogeneous distribution of (18)O in the reaction products required a separate study of the kinetics of isotopic equilibration within the fluid to obtain a better understanding of the (18)O distribution in the calcite replacement. An activation energy of 109 kJ/mol was calculated for the exchange of oxygen isotopes between [C(16)O(3)(2-)](aq) and [H(2)(18)O] and the time for oxygen isotope exchange in the fluid at 200 degrees C was estimated at similar to 0.9 s. Given the exchange rate, analyses of the run products imply that the oxygen isotope composition in the calcite product is partly inherited from the oxygen isotope composition of the aragonite parent during the replacement process and is dependent on access of the fluid to the reaction interface rather than equilibration time. The aragonite to calcite fluid-mediated transformation is described by a coupled dissolution-reprecipitation mechanism, where aragonite dissolution is coupled to the precipitation of calcite at an inwardly moving reaction interface."],["dc.identifier.doi","10.1016/j.gca.2011.07.045"],["dc.identifier.isi","000295641600024"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/21753"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Pergamon-elsevier Science Ltd"],["dc.relation.issn","0016-7037"],["dc.title","Experimental study of the aragonite to calcite transition in aqueous solution"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]