Abstract

This report gives an account of geological investigations and 1:25000 scale mapping of Precambrian rocks of Smithson Bjerge, at the head of Inglefield Bredning, about 150 km north-east of Thule Air Base. Previous work on this area was restricted to a few days of reconnaissance work in 1971 and several helicopter landings in 1975 (Dawes, 1972, and personal communication, 1978). Table 1 gives the principle geological eveJ;lts of the area and results of the mapping are given in outline in fig. 8.

Highlights

  • Geological Divisions Qaqujårssuaq anorthositeHornblende,Iocally with cores of pyroxene, is the dominant ferromagnesian mineral, garnet occurs locally

  • This report gives an account of geological investigations and 1:25000 scale mapping of Precambrian rocks of Smithson Bjerge, at the head of Inglefield Bredning, about 150 km north-east of Thule Air Base

  • Previous work on this area was restricted to a few days of reconnaissance work in 1971 and several helicopter landings in 1975 (Dawes, 1972, and personal communication, 1978)

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Summary

Geological Divisions Qaqujårssuaq anorthosite

Hornblende,Iocally with cores of pyroxene, is the dominant ferromagnesian mineral, garnet occurs locally. The ferromagnesian minerals often occur with fine-grained plagioc1ase as groundmass to recrystallised plagioc1ases 5 to 50 mm in diameter, a relation interpreted as a relict igneous texture. More than 90 per cent of the anorthosite complex is true anorthosite, the remainder being leucogabbro and subordinate gabbro. Deformation Dl to produce recumbent structures (8) Intrusion of amphibo1ite dykes (9) Intrusion of the Qaqujarssuaq anorthosite and perhaps contemparaneously of the Heilprin Gletscher Camplex (10) Formation of early comp1ex consisting af supracrustal sequence and multiphase orthogneisses the southern boundary of the complex where it forms discontinuous horizons up to 100 m thick.

Amphibolite dykes
Supracrustal rocks
Heilprin Gletscher Complex
Relationship between the anorthosite and its envelope
Late minor intrusions
Quaternary deposits
Findings
Structural and metamorphic history
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