Greenland geological environments and mineral resources
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Danmarks og Grønlands Geologiske Undersøgelse Rapport 2005/8 |
Stendal, H., Secher, K., Nielsen, B.M., Schønwandt, H.K. & Thorning, L. 2005:
Greenland geological environments and mineral resources.
Danmarks og Grønlands Geologiske Undersøgelse Rapport 2005/8, 211 pp.
The report gives an overview of the main geological environments in Greenland and elucidate the mineral resource possibilities within such environments.
The report is available from GEUS ( geus@geus.dk ) at a price of DKK 500 (c. USD 90) exclusive VAT and postage.
Contact:
Senior Researcher Henrik Stendal, GEUS
Phone direct: +45 38 14 22 15
E-mail: hst@geus.dk
ABSTRACT
The main geological environments in Greenland and their mineral resource have been described and divided into four main geological environments such as infracrustal regions, supracrustal regions, magmatic regions, and sedimentary basin regions. Within the various geological environment characteristic mineral deposits are outlined.
Within the infracrustal environment, not many mineral occurrences are recorded in Greenland from Table 1 three types are recorded: Gold in gneiss, nickel and copper in mafic intrusions, and olivine in ultramafic rocks.
The supracrustal rocks include metasedimentary rocks, metavolcanics and banded magnetite-quartzite formation. Special attention is given to the mafic metavolcanics because of their high rate of mineral potential, not least with gold and base metal deposits. These deposits are often related to greenstone belts with mafic volcanics or mixed mafic volcanic and sedimentary rocks. Other mineral occurrences than gold are iron, copper, chromium, tungsten, as well as industrial minerals.
The mineral occurrences in the magmatic environment are the porphyry system related to Palaeogene alkalic intrusion in East Greenland and associated vein systems with gold and silver. Veins related to the Caledonian granite and the Julianehåb batholith, which carries tungsten, arsenic, antimony, and gold. The alkaline intrusions in the Gardar province have niobium, tantalum, zirconium, rare earth elements, and cryolite. Carbonatite with niobium, tantalum, apatite and kimberlite-lamproite with diamonds are located within the Kangerlussuaq region of West Greenland.
Many of the global known mineral occurrences in the sedimentary environment also occur in Greenland. Examples are copper in sandstones in Neoproterozoic and Triassic clastic sediments. Lead and zinc in shale/carbonate sequences are widespread in the sedimentary basins. A fossil placer represents a placer deposit and celestite an evaporite deposit. Lead-zinc veins in sediments occur in the Mesters Vig area including the closed Blyklippen Pb-Zn mine, East Greenland.
The aeromagnetic data responses of different geological environments yield valuable information on both the primary geological settings and subsequent geological events. The data can be used on a regional scale, but can also be used on smaller scales when descriptions and interpretations of processes related to specific environments or mineral occurrences/mineralizing events are wanted.
On a regional scale, aeromagnetic data from infracrustal environments will often reflect the deformation and metamorphic history. In general, prograde granulite facies conditions result in heterogeneous higher magnetic anomaly levels than regions at lower metamorphic grade. Large-scale structures and tectonics crosscutting or separating infracrustal environments will in many cases be represented as abrupt changes and/or lineaments in anomaly patterns.
Supracrustal lithologies are in most cases characterized by low magnetic anomaly levels. Strong magnetic rocks, especially ultrabasic/ultramafic lithologies, result in high magnetic level local short-wavelength anomalies.
The aeromagnetic responses of magmatic environments depend mainly on the composition of the magmatic rock. The shape and outline of an intrusion is in most cases derivable from the aeromagnetic responses. The magnetic anomaly levels of extruded basalts are in many cases determined by the polarity of the Earth's field at the extrusion time.
Rocks from non-metamorphosed sediment depositional environments contain in most cases only a small amount of magnetite. Consequently, such environments are characterized by relatively low and smooth level of magnetic anomaly responses.
REPORT CONTENTS
Abstract
Introduction
Geological environments
Infracrustals
Archaean
Palaeoproterozoic mobile belt (reworked Archaean)
Palaeoproterozoic mobile belt (juvenile)
Supracrustals
Nuuk area
Disko Bugt area
Sermiligaarsuk area
Aasiaat, Nassuttooq and Nordre Isortoq areas
Uummannaq area
South Greenland
Magmatic environment
Julianehåb batholith (Ketilidian)
The Gardar Province
Carbonatite and kimberlite suite
Caledonian granite
Palaeogene magma provinces
Sedimentary depositional environment
Mesoproterozoic basins
Neoproterozoic basins
Phanerozoic basins
Mineral resources within the geological environments
Infracrustals
Supracrustal rocks (greenstones)
Magmatic provinces
Sedimentary basins
Geophysical signature
Infracrustal environments
Supracrustal environments
Sediment depositional environments
Summary
References
Appendix - Mineral occurrences
