The Tikiusaaq carbonatite: a new Mesozoic intrusive complex in southern West Greenland
Ultrabasic alkaline magmatic rocks are products of melts generated deep within or at the base of the lithospheric mantle. The magmas may reach the surface to form lavas and pyroclastic deposits; alternatively they crystallise at depth to form dykes or central complexes. The rocks are chemically dist...
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ftjgeusbullet:oai:geusjournals.org:article/4905 2023-05-15T16:26:35+02:00 The Tikiusaaq carbonatite: a new Mesozoic intrusive complex in southern West Greenland Steenfelt, Agnete Hollis, Julie A. Secher, Karsten 2006-11-29 application/pdf https://geusbulletin.org/index.php/geusb/article/view/4905 https://doi.org/10.34194/geusb.v10.4905 eng eng Geological Survey of Denmark and Greenland (GEUS) https://geusbulletin.org/index.php/geusb/article/view/4905/10573 https://geusbulletin.org/index.php/geusb/article/view/4905 doi:10.34194/geusb.v10.4905 GEUS Bulletin; Vol. 10 (2006): Review of Survey activities 2005; 41-44 2597-2154 2597-2162 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Rapid Communication. Peer-reviewed Article. 2006 ftjgeusbullet https://doi.org/10.34194/geusb.v10.4905 2022-03-15T17:22:19Z Ultrabasic alkaline magmatic rocks are products of melts generated deep within or at the base of the lithospheric mantle. The magmas may reach the surface to form lavas and pyroclastic deposits; alternatively they crystallise at depth to form dykes or central complexes. The rocks are chemically distinct and may contain high concentrations of economically interesting minerals and chemical elements, such as diamonds, niobium, tantalum, rare earth elements, phosphorus, iron, uranium, thorium, and zirconium. Ultrabasic alkaline rocks are known from several provinces in Greenland, but extrusive facies have only been preserved at a few places; e.g. at Qassiarsuk in South Greenland where pyroclastic rocks occur, and in the Maniitsoq region, where a small volcanic breccia (‘Fossilik’) contains fragments of Palaeozoic limestone. Ultramafic lamprophyre and kimberlite are mainly emplaced as dykes, whereas carbonatite forms large intrusive bodies as well as dykes. The ultrabasic alkaline magmas that have been emplaced at certain times during the geological evolution of Greenland can be related to major episodes of continental break-up (Larsen & Rex 1992). The oldest are Archaean and the youngest dated so far are Palaeogene. Figure 1 shows the distribution of known ultrabasic alkaline rocks in West Greenland. The large and well-exposed bodies of alkaline rocks and carbonatites in the Gardar Province were discovered already in the early 1800s (Ussing 1912), while less conspicuous bodies were discovered much later during geological mapping and mineral exploration. Many alkaline rock bodies, particularly dykes, are difficult to identify in the field because they weather more extensively than the country rock gneisses and form vegetated depressions in the landscape. However, their distinct chemistry and mineralogy render alkaline rocks identifiable in geochemical and geophysical survey data. Thus, the Sarfartôq carbonatite complex was discovered during regional airborne gamma-spectrometric surveying owing to its elevated uranium and thorium contents (Secher 1986). The use of kimberlite indicator minerals has led to the discovery of alkaline rocks such as kimberlites and ultramafic lamprophyres that carry fragments of deep lithospheric mantle. Such rocks may also contain diamonds. Kimberlite indicator minerals are high-pressure varieties of minerals, such as garnet, clinopyroxene, chromite and ilmenite that were formed in the lithospheric mantle. Exploration companies have processed thousands of till samples from southern West Greenland for kimberlite indicator minerals and found many new dykes. Article in Journal/Newspaper Greenland Maniitsoq Qassiarsuk GEUS Bulletin (Geological Survey of Denmark and Greenland) Greenland Maniitsoq ENVELOPE(-55.217,-55.217,72.967,72.967) Geological Survey of Denmark and Greenland (GEUS) Bulletin 10 41 44 |
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GEUS Bulletin (Geological Survey of Denmark and Greenland) |
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English |
description |
Ultrabasic alkaline magmatic rocks are products of melts generated deep within or at the base of the lithospheric mantle. The magmas may reach the surface to form lavas and pyroclastic deposits; alternatively they crystallise at depth to form dykes or central complexes. The rocks are chemically distinct and may contain high concentrations of economically interesting minerals and chemical elements, such as diamonds, niobium, tantalum, rare earth elements, phosphorus, iron, uranium, thorium, and zirconium. Ultrabasic alkaline rocks are known from several provinces in Greenland, but extrusive facies have only been preserved at a few places; e.g. at Qassiarsuk in South Greenland where pyroclastic rocks occur, and in the Maniitsoq region, where a small volcanic breccia (‘Fossilik’) contains fragments of Palaeozoic limestone. Ultramafic lamprophyre and kimberlite are mainly emplaced as dykes, whereas carbonatite forms large intrusive bodies as well as dykes. The ultrabasic alkaline magmas that have been emplaced at certain times during the geological evolution of Greenland can be related to major episodes of continental break-up (Larsen & Rex 1992). The oldest are Archaean and the youngest dated so far are Palaeogene. Figure 1 shows the distribution of known ultrabasic alkaline rocks in West Greenland. The large and well-exposed bodies of alkaline rocks and carbonatites in the Gardar Province were discovered already in the early 1800s (Ussing 1912), while less conspicuous bodies were discovered much later during geological mapping and mineral exploration. Many alkaline rock bodies, particularly dykes, are difficult to identify in the field because they weather more extensively than the country rock gneisses and form vegetated depressions in the landscape. However, their distinct chemistry and mineralogy render alkaline rocks identifiable in geochemical and geophysical survey data. Thus, the Sarfartôq carbonatite complex was discovered during regional airborne gamma-spectrometric surveying owing to its elevated uranium and thorium contents (Secher 1986). The use of kimberlite indicator minerals has led to the discovery of alkaline rocks such as kimberlites and ultramafic lamprophyres that carry fragments of deep lithospheric mantle. Such rocks may also contain diamonds. Kimberlite indicator minerals are high-pressure varieties of minerals, such as garnet, clinopyroxene, chromite and ilmenite that were formed in the lithospheric mantle. Exploration companies have processed thousands of till samples from southern West Greenland for kimberlite indicator minerals and found many new dykes. |
format |
Article in Journal/Newspaper |
author |
Steenfelt, Agnete Hollis, Julie A. Secher, Karsten |
spellingShingle |
Steenfelt, Agnete Hollis, Julie A. Secher, Karsten The Tikiusaaq carbonatite: a new Mesozoic intrusive complex in southern West Greenland |
author_facet |
Steenfelt, Agnete Hollis, Julie A. Secher, Karsten |
author_sort |
Steenfelt, Agnete |
title |
The Tikiusaaq carbonatite: a new Mesozoic intrusive complex in southern West Greenland |
title_short |
The Tikiusaaq carbonatite: a new Mesozoic intrusive complex in southern West Greenland |
title_full |
The Tikiusaaq carbonatite: a new Mesozoic intrusive complex in southern West Greenland |
title_fullStr |
The Tikiusaaq carbonatite: a new Mesozoic intrusive complex in southern West Greenland |
title_full_unstemmed |
The Tikiusaaq carbonatite: a new Mesozoic intrusive complex in southern West Greenland |
title_sort |
tikiusaaq carbonatite: a new mesozoic intrusive complex in southern west greenland |
publisher |
Geological Survey of Denmark and Greenland (GEUS) |
publishDate |
2006 |
url |
https://geusbulletin.org/index.php/geusb/article/view/4905 https://doi.org/10.34194/geusb.v10.4905 |
long_lat |
ENVELOPE(-55.217,-55.217,72.967,72.967) |
geographic |
Greenland Maniitsoq |
geographic_facet |
Greenland Maniitsoq |
genre |
Greenland Maniitsoq Qassiarsuk |
genre_facet |
Greenland Maniitsoq Qassiarsuk |
op_source |
GEUS Bulletin; Vol. 10 (2006): Review of Survey activities 2005; 41-44 2597-2154 2597-2162 |
op_relation |
https://geusbulletin.org/index.php/geusb/article/view/4905/10573 https://geusbulletin.org/index.php/geusb/article/view/4905 doi:10.34194/geusb.v10.4905 |
op_doi |
https://doi.org/10.34194/geusb.v10.4905 |
container_title |
Geological Survey of Denmark and Greenland (GEUS) Bulletin |
container_volume |
10 |
container_start_page |
41 |
op_container_end_page |
44 |
_version_ |
1766015512567873536 |