Abstract
Klokken is a small (3 x 2 km), Gardar igneous complex at 60°56'N, 45°05'W.The intrusion is oval in form and the rock types are arranged in almost perfectly concentric fashion, an outer ring of gabbro giving way inwards via syenogabbros and basic syenites to a strikingly layered body of syenite. Quartz occurs in droses and in aplites and pegmatites, so that although the complex lies only 1 km south of the Igaliko nepheline syenites (Emeleus & Harry, 1970), it is oversaturated and should not be regarded as a satellite of Igaliko. Klokken was visited in 1959 and 1960 by K. Ellitsgaard-Rasmussen in whose field notes many of the observations presented here may be found. The object of the 1971 field work was to obtain comprehensive specimen coverage, to look closely at the remarkable field relations and to extend the detail of the mapping. The complex has sharp contacts with the surrounding Julianehåb granite and the existence of substantial protrusions, roof pendants and rotated xenoliths of country rock can be demonstrated. Hornfelsing and local mobilisation of the country rock has occurred.
Highlights
The intrusion is oval in form and the rock types are arranged in almost perfectly concentric fashion, an oitter ring of gabbro giving way inwards via syenogabbros and basic syenites to a strikingly layered body of syenite
The layers occur as an alternation of material of coarse and fine type, and seem to have arisen by outward deposition of materiaion curved surfaces, after the manner of many zoned pegmatites
The most topographically pionounced bands are of brown-weathering, sugary-textured granular syenite, usually sparsely porphyritic, the alkali feldspar phenocrysts being randomly arranged. These layers, which make up about 15 % of the succession, are separated by thicker units of coarser, often strongly laminated syenite, which is itself subject to repeated banding produced by variation in the proportion of feldspar to mafic constituents
Summary
The intrusion is oval in form and the rock types are arranged in almost perfectly concentric fashion, an oitter ring of gabbro giving way inwards via syenogabbros and basic syenites to a strikingly layered body of syenite. Contacts and most structures within the gabbros, including xenoliths, are vertical or have steep outward dips. As the amount of alkali feldspar increases the tabular habit disappears and the rock gives way to coarse unlaminated syenogabbros and basic syenites, fonning a strip up to 750 m wide adjacent to the ioner layered syenite.
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