Kerkhof, Alfons M. van den

[["dc.bibliographiccitation.firstpage","637"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","Contributions to Mineralogy and Petrology"],["dc.bibliographiccitation.lastpage","652"],["dc.bibliographiccitation.volume","146"],["dc.contributor.author","van den Kerkhof, Alfons M."],["dc.contributor.author","Kronz, A."],["dc.contributor.author","Simon, Klaus"],["dc.contributor.author","Scherer, T."],["dc.date.accessioned","2018-11-07T10:52:16Z"],["dc.date.available","2018-11-07T10:52:16Z"],["dc.date.issued","2004"],["dc.description.abstract","Dispersed quartz veinlets in Proterozoic enderbitic charnockite from Tromoy, Bamble sector (southern Norway), with Ti-concentrations of mostly 80-180 ppm, produce bright blue cathodoluminescence (CL), against contrasting micro-textures of secondary pure quartz with low CL intensity. The textures comprise grain boundary alteration, healed micro-fractures, patches of secondary quartz, and euhedral quartz nuclei. The secondary quartz locally makes up 50% of the total quartz. Trace element analysis has been done by electron-probe micro-analysis (EPMA), laser-induced coupled plasma mass spectrometry (LA-ICPMS), and additional electron-paramagnetic resonance (EPR) spectroscopy. These studies testify systematic trace element reduction and extensive quartz recovery during retrograde metamorphism. We assume healing of a part of the aqueous fluid inclusions during a late thermal event, possible correlated with Paleozoic magmatic activity in the Oslo-Rift. During final cooling, aqueous fluids were largely retrapped in patches of secondary quartz associated with healed fractures, whereas carbonic inclusions (without secondary quartz) may have survived retrograde metamorphism. The variable but generally high salinity of fluid inclusions is assumed to be in part the result of quartz recovery by which ion concentrations were increased in the percentage range."],["dc.identifier.doi","10.1007/s00410-003-0523-5"],["dc.identifier.isi","000188246200008"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/49077"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Springer"],["dc.relation.issn","1432-0967"],["dc.relation.issn","0010-7999"],["dc.title","Fluid-controlled quartz recovery in granulite as revealed by cathodoluminescence and trace element analysis (Bamble sector, Norway)"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","559"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","South African Journal of Geology"],["dc.bibliographiccitation.lastpage","576"],["dc.bibliographiccitation.volume","107"],["dc.contributor.author","van den Kerkhof, Alfons M."],["dc.contributor.author","Kronz, A."],["dc.contributor.author","Simon, Klaus"],["dc.contributor.author","Riganti, A."],["dc.contributor.author","Scherer, T."],["dc.date.accessioned","2018-11-07T10:43:39Z"],["dc.date.available","2018-11-07T10:43:39Z"],["dc.date.issued","2004"],["dc.description.abstract","Quartzites from the Patsoana area, part of the Nondweni greenstone belt, South Africa, comprise coarse-grained (1) banded graphite-bearing black and white quartzite, (2) greenish to beige finely-banded quartzite and (3) massive sulphide-bearing quartzite. The quartzites show distinctive Ti and Al-contents (LA-ICPMS analysis) that are highest for the finely-banded quartzite varieties with intense blue cathodoluminescence (CL) and lowest structural water as measured by FT-IR analysis. The quartzites underwent contact metamorphism, but stable oxygen isotope ratios (16.7% to 19.2%.) suggest formation at low temperatures as chert. Complex quartz zoning in CL combined with trace element analysis points at a 2-step evolution after primary formation with (1) prograde recrystallisation of a finer-grained siliceous lithotype accompanied by extensive hydrothermal alteration resulting in high Ti-contents, and (2) retrograde reduction of trace elements by diffusion and by the final formation of pure secondary quartz. Secondary quartz veinlets formed at lower temperatures. The study testifies the local remobilisation of titanium in solution as well as diffusion in quartz at high temperatures. Laser Raman analysis of dispersed graphite shows high crystallinity in most of the quartzites and points at formation temperatures of > 600 degrees C; poorly organised graphite was mainly found in the finely-banded and greenish quartzite and formed during retrogression. Very high concentrations of paramagnetic [TiO4/Li+] and [TiO4/H+] defect centres were found in the finely-banded quartzite, whereas paramagnetic [AlO4] centres are assumed to be largely decayed with time. The perseverance of the Ti-related paramagnetic defects are explained by a long-term position of the Nondweni greenstones in a stable part of the crust."],["dc.identifier.doi","10.2113/107.4.559"],["dc.identifier.isi","000228056600007"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/47107"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Geological Soc South Africa"],["dc.relation.issn","1996-8590"],["dc.relation.issn","1012-0750"],["dc.title","Origin and evolution of Archean quartzites from the Nondweni greenstone belt (South Africa): inferences from a multidisciplinary study"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","683"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","Geoscience Frontiers"],["dc.bibliographiccitation.lastpage","695"],["dc.bibliographiccitation.volume","5"],["dc.contributor.author","van den Kerkhof, Alfons"],["dc.contributor.author","Kronz, Andreas"],["dc.contributor.author","Simon, Klaus"],["dc.date.accessioned","2019-07-09T11:40:48Z"],["dc.date.available","2019-07-09T11:40:48Z"],["dc.date.issued","2014"],["dc.description.abstract","The study of fluid inclusions in high-grade rocks is especially challenging as the host minerals have been normally subjected to deformation, recrystallization and fluid-rock interaction so that primary inclusions, formed at the peak of metamorphism are rare. The larger part of the fluid inclusions found in metamorphic minerals is typically modified during uplift. These late processes may strongly disguise the characteristics of the “original” peak metamorphic fluid. A detailed microstructural analysis of the host minerals, notably quartz, is therefore indispensable for a proper interpretation of fluid inclusions. Cathodoluminescence (CL) techniques combined with trace element analysis of quartz (EPMA, LA-ICPMS) have shown to be very helpful in deciphering the rock-fluid evolution. Whereas high-grade metamorphic quartz may have relatively high contents of trace elements like Ti and Al, low-temperature re-equilibrated quartz typically shows reduced trace element concentrations. The resulting microstructures in CL can be basically distinguished in diffusion patterns (along microfractures and grain boundaries), and secondary quartz formed by dissolution-reprecipitation. Most of these textures are formed during retrograde fluid-controlled processes between ca. 220 and 500 °C, i.e. the range of semi-brittle deformation (greenschist-facies) and can be correlated with the fluid inclusions. In this way modified and re-trapped fluids can be identified, even when there are no optical features observed under the microscope."],["dc.identifier.doi","10.1016/j.gsf.2014.03.005"],["dc.identifier.fs","603668"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/11354"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/58256"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation.orgunit","Fakultät für Geowissenschaften und Geographie"],["dc.rights","CC BY-NC-ND 3.0"],["dc.rights.uri","http://creativecommons.org/licenses/by-nc-nd/3.0/"],["dc.title","Deciphering fluid inclusions in high-grade rocks"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","751"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Mineralogical Magazine"],["dc.bibliographiccitation.lastpage","778"],["dc.bibliographiccitation.volume","82"],["dc.contributor.author","van den Kerkhof, Alfons M."],["dc.contributor.author","Sosa, Graciela M."],["dc.contributor.author","Oberthür, Thomas"],["dc.contributor.author","Melcher, Frank"],["dc.contributor.author","Fusswinkel, Tobias"],["dc.contributor.author","Kronz, Andreas"],["dc.contributor.author","Simon, Klaus"],["dc.contributor.author","Dunkl, István"],["dc.date.accessioned","2019-07-24T08:00:05Z"],["dc.date.available","2019-07-24T08:00:05Z"],["dc.date.issued","2018"],["dc.identifier.doi","10.1180/mgm.2018.80"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/61971"],["dc.language.iso","en"],["dc.relation.issn","0026-461X"],["dc.relation.issn","1471-8022"],["dc.title","The hydrothermal Waterberg platinum deposit, Mookgophong (Naboomspruit), South Africa. Part II: Quartz chemistry, fluid inclusions and geochronology"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]