Gardiner intrusion, an ultramafic complex at Kangerdlugssuaq, East Greenland

W Frisch,H Keusen

doi:10.34194/bullggu.v122.6664

Abstract

The Gardiner intrusion is an ultramafic complex in the inner region of Kangerdlugssuaq fjord, forming part of the East Greenland Tertiary Igneous Province. The rocks of the intrusion can be placed into three categories. (1) An older sequence is composed of dunites, pyroxenites, and a narrow marginal zone of alkali rich rocks. The rocks of the marginal zone consist of melteigite where the bordering country rock is plateau basalt, and of contaminated rocks where the country rock is the basement gneisses. The bordering gneisses have a narrow fenitized zone. (2) A strongly alkaline and undersaturated dyke sequence comprises amphibole pyroxenites, tawites, urtites, and sodalite, nepheline and alkali-feldspar syenites. (3) A younger sequence consists of uncompahgrites (intrusive melilite rich rocks) and calcite carbonatite dykes. Parts of the uncompahgrite show layered accumulations of magnetite, perovskite and apatite on the one hand, and melilite on the other. Massive aggregate concentrations of perovskite and magnetite are also recorded. The intrusion of uncompahgrite and carbonatite has resulted in intense alkali metasomatism of the rocks of the older and the dyke sequences.

Highlights

A previously unknown intrusion was discovered in 1971 by K
(3) Ayounger sequence consists of uncompahgrites and calcite carbonatite dykes
The Gardiner intrusion belongs to the East Greenland Tertiary Igneous Province

Summary

INTRODUCTION

A previously unknown intrusion was discovered in 1971 by K. Vohryzka while engaged in prospecting work for Nordisk Mineselskab It was identified during a reconnaissance flight into the innermost parts of Kangerdlugssuaq, a large fjord on the east Greenland coast at latitude 68° N. The intrusion is circular in shape and has a diameter of about 6 km It is situated between Gardiner Sø and Gardiner Plateau, a glacier plateau, at the south-western edge of Kangerdlugssuaq Gletscher. The Gardiner intrusion belongs to the East Greenland Tertiary Igneous Province. It is unique in the area, being composed predominantly of ultramafic rocks with later intrusions of uncompahgrite and carbonatite. The Gardiner intrusion is one of several plutonic complexes occurring between latitude 66° and 73° N, and forming part of the East Green1and Tertiary Igneous Province. Plateau basalts of Lower Tertiary age cover much of the area between latitude 68° and 71° N, and the Gardiner intrusion occurs near their southern termination (fig. 2)

D Precambnan bosement

CONCLUSIONS

Findings

SUMMARY