Karsten Secher
Geological Survey of Denmark and Greenland
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Featured researches published by Karsten Secher.
Lithos | 1980
Karsten Secher; Lotte Melchior Larsen
Abstract The Sarfartoq carbonatite complex was emplaced in lower Palaeozoic time in a weakness zone within the Precambrian shield. Dolomitic magma intruded in two major stages of activity. In the first stage a steeply dipping conical body of concentric sheets of rauhaugite was formed, while in the second stage several batches of magma were emplaced into the surrounding marginal shock-zone as concentric and radial beforsite dykes and agglomerates. Hydrothermal activity gave rise to several phases of mineralisation in veins and shear zones. The accompanying fenitisation was of the Na-type. The whole complex covers about 90 km 2 . The main rock-forming minerals are dolomite-ankerite, apatite, orange reversely pleochroic phlogopite, richterite-arfvedsonite and magnetite. Important accessories are pyrochlore, zircon and niobian rutile. A complete mineral list is given, together with microprobe data on mineral chemistry. The dolomitic magmas were poor in SiO 2 , Al 2 O 3 and K 2 O in relation to other carbonatites. Nb, U and LREEs are strongly enriched in pyrochloremineralised zones where the Nb content may be up to 40%. Some shear zones are strongly enriched in Th and HREEs (specifically Eu) and lesser Pb and Zn. Niobium, uranium, rare earth elements and phosphorus occur in economically interesting concentrations.
Lithos | 1983
Lotte Melchior Larsen; David C. Rex; Karsten Secher
Abstract Alkaline rocks were intruded into the Precambrian basement in southern West Greenland during at least five separate episodes. The Tupertalik carbonatite intrusion was emplaced around or before 2650 m.y.; it is now metamorphosed in granulite facies but is recognisable by its trace element content. Lamprophyre dykes were intruded at ca. 1800 m.y. and again at ca. 1200 m.y. At ca. 600 m.y. the Sarfartoq carbonatite intrusion and extensive kimberlite dykes were emplaced in the Holsteiborg-Stromfjord region. At 225-115 m.y. the Qaqarssuk carbonatite complex was emplaced in the Sukkertoppen region, and numerous lamprophyre and kimberlite dykes were emplaced between Fishenasset and Ivigtut. All these episodes are correlatable with contemporaneous alkaline activity in Canada and Scandinavia and substantiate the periodicity of carbonatite emplacement. The Mesozoic suite of intrusions is related to rifting prior to continental break-up and the formation of the North Atlantic Ocean. The Eocambrian suite of 600 m.y. is thought to have formed under similar conditions during continental break-up and the formation of the Iapetus ocean.
Lithos | 2009
Karsten Secher; Larry M. Heaman; Troels F. D. Nielsen; Sven Monrad Jensen; F. Schjøth; Robert A. Creaser
Lithos | 2009
Troels F. D. Nielsen; Svend M. Jensen; Karsten Secher; Karina K. Sand
Archive | 2002
Sven Monrad Jensen; Henriette Hansen; Karsten Secher; Agnete Steenfelt; Frands Schjøth; Thorkild M. Rasmussen
Archive | 2006
Agnete Steenfelt; Julie A. Hollis; Karsten Secher
Ore Geology Reviews | 2016
Jochen Kolb; Jakob K. Keiding; Agnete Steenfelt; Karsten Secher; Nynke Keulen; Diogo R. N. Rosa; Bo Møller Stensgaard
Geological Survey of Denmark and Greenland Bulletin | 2006
Sven Monrad Jensen; Martin Jebens; Troels F. D. Nielsen; Karsten Secher
Archive | 2004
Sven Monrad Jensen; Karsten Secher
Archive | 2014
Anna Katerinopoulou; Toni Balic-Zunic; Alfons Berger; Jochen Kolb; Karsten Secher