Skaergaard intrusion: Difference between revisions
created new section "See also" and added wiki link for "Skaergaardite" |
BrokenSegue (talk | contribs) |
||
| (15 intermediate revisions by 9 users not shown) | |||
| Line 1: | Line 1: | ||
{{coord|68.1683|N|31.7169|W||display=title}} |
{{coord|68.1683|N|31.7169|W||display=title}} |
||
The '''Skaergaard |
The '''Skaergaard intrusion''' is a [[layered intrusion|layered igneous intrusion]] in the [[Kangerlussuaq Fjord, East Greenland|Kangerlussuaq area]] of East [[Greenland]] and is composed of various rocks and minerals including [[gabbro]], [[olivine]], [[apatite]], and [[basalt]].<ref name=":0" /> |
||
== History and background == |
|||
Discovered by [[Lawrence Wager]]<ref>Brooks, CK (2005) ''The Skaergaard intrusion: from icon to precious metal deposit''. Geology Today, v. 21, p. 218-221.</ref> |
|||
[[File:Nielsen 2016 fig 1.png|thumb|Map and section through the Skaergaard intrusion.]][[File:Magma chamber.png|thumb|304x304px|Model of the crystallization of a subsurface magma chamber.]]The Skaergaard intrusion was formed 56 million years ago during the opening of the [[North Atlantic Ocean]].<ref name=":0">{{Cite journal |last=Holness |first=Marian B. |last2=Nielsen |first2=Troels F.D. |last3=Tegner |first3=Christian |date=2017-12-01 |title=The Skaergaard Intrusion of East Greenland: Paradigms, Problems and New Perspectives |url=https://pubs.geoscienceworld.org/elements/article-lookup?doi=10.2138/gselements.13.6.391 |journal=Elements |language=en |volume=13 |issue=6 |pages=391–396 |doi=10.2138/gselements.13.6.391 |issn=1811-5217}}</ref> The intrusion was [[Pluton emplacement|emplaced]] beneath the preexisting rock in the region, including [[Flood basalt|plateau basalt]] and [[gneiss]].<ref name=":0" /><ref name=":1">{{Cite journal |last=Stewart |first=Brian W. |last2=DePaolo |first2=Donald J. |date=1990 |title=Isotopic studies of processes in mafic magma chambers: II. The Skaergaard Intrusion, East Greenland |url=http://dx.doi.org/10.1007/bf00306438 |journal=Contributions to Mineralogy and Petrology |volume=104 |issue=2 |pages=125–141 |doi=10.1007/bf00306438 |issn=0010-7999}}</ref> The intrusion has a general oval shape, which is atypical in igneous emplacement.<ref name=":0" /> Due to the [[Tectonics|tectonic]] activity in East Greenland, the intrusion is now slightly tilted towards the sea.<ref name=":0" /> Specifically, the lower parts of the intrusion are exposed to the north while sections of the roof are conserved to the south.<ref name=":0" /> |
|||
in 1931 during the British [[Arctic]] Air Route Expedition led by [[Gino Watkins]], the intrusion has been important to the development of key concepts in [[igneous rock|igneous]] [[petrology]], including [[magma]] differentiation and [[Fractional crystallization (geology)|fractional crystallisation]]<ref>Wager, LR, Deer, WA (1939) ''Geological investigations in East Greenland Part III. The [[petrology]] of the Skaergaard Intrusion, Kangerdlugssuaq''. Meddelselser om Grønland, v. 105, 346 pp.</ref><ref>McBirney, AR (1975) ''Differentiation of the Skaergaard intrusion''. Nature, v. 253, p. 691-694.</ref> |
|||
and the development of layering.<ref>Wager, LR, [[George Malcolm Brown|Brown, GM]] (1967) Layered Igneous Rocks. WH Freeman, San Francisco, 588 pp.</ref><ref>McBirney, AR, Noyes, RM (1975) ''Crystallization and Layering of the Skaergaard Intrusion''. Journal of Petrology, v. 20, p. 487-554.</ref> |
|||
The Skaergaard intrusion formed when [[Tholeiitic basalt|tholeiitic]] magma was emplaced about 55 million years ago,<ref>Brooks, CK, Gleadow, AJW (1977) ''A fission-track age for the Skaergaard intrusion and the age of the East Greenland basalts''. Geology, v. 5, p. 539-540.</ref> |
|||
during the initial opening of the [[North Atlantic Ocean]]. The body represents essentially a single pulse of magma, which crystallized from the bottom upward and the top downward. The intrusion is characterized by exceptionally well-developed [[cumulate rock|cumulate]] layering defined by variations in the abundance of crystallizing [[olivine]], [[pyroxene]], [[plagioclase]] and [[magnetite]]. |
|||
== Discovery and early studies == |
|||
The Skaergaard is perhaps the simplest and smallest of a group of gabbroic complexes of similar age that occur along the central coast of East Greenland, which together with coeval [[flood basalt]]s are part of the North Atlantic [[large igneous province]]. |
|||
The Skaergaard intrusion was first discovered by [[Lawrence Wager]] on his [[British Arctic Air Route Expedition|Arctic Air-Route Expedition]] in 1930.<ref name=":0" /> In 1933, the first [[aerial photography]] of the region was taken in order to create a [[topographic map]] of the area.<ref name=":0" /> The first scientific expedition to the intrusion took place in 1935 and 1936 and lasted over 13 months.<ref name=":0" /> This expedition was led by Wager accompanied by a small team, including geologist [[William Alexander Deer]].<ref name=":0" /> Through this mission, the team studied the intrusion through [[Reconnaissance|reconnaissance mapping]].<ref name=":0" /> |
|||
== Geologic characteristics == |
|||
The intrusion is made up of three separate [[Sequence (geology)|geologic sequences]] which formed at the floor, roof, and walls, with the formation at the floor being much thicker than that of the other two sequences.<ref name=":0" /> The rocks of these sequences are further divided into three categories: the lower zone, middle zone, and upper zone.<ref name=":0" /> The zone categorization is based on the occurrence of specific minerals such as [[augite]], [[Iron oxide|Fe-Ti oxides]], rounded grains of olivine, apatite, and ferrobustamite.<ref name=":0" /> |
|||
The intrusion formed from the [[crystallization]] of a [[Convection|convecting]] body of magma which resulted in the [[Lineation (geology)|lineation]], [[Stratum|layering]], [[Cross-bedding|cross bedding]], and channel structures within the rocks.<ref name=":0" /> These features result from [[Sedimentary rock|sedimentary]] formations created by grain re-arrangement via magmatic [[Current (fluid)|currents]].<ref name=":0" /> |
|||
Within the solid rocks of the formation, the [[Crystal|crystals]] are classified into two categories: primary precipitate crystals and interprecipitate crystals.<ref name=":0" /> Primary precipitate crystals form in conditions of high presence of liquids while interprecipitate crystals form from interprecipitate liquid, liquid in the spaces between grains which solidify them together.<ref name=":0" /> |
|||
This data was developed from the 1939 memoir written by Lawrence Wager and William Alexander Deer from their 1935 expedition.<ref name=":0" /> |
|||
== Scientific significance == |
|||
Data acquired from researching the Skaergaard intrusion can be used to model how the intrusion was originally formed and how [[magma]] [[Fractional crystallization (geology)|fractional crystallization]] takes place.<ref name=":1" /> Multiple models of magmatic [[Igneous differentiation|assimilation and recharge]] have been developed from the Skaergaard intrusion including the continuous replenishment model, intermittent recharge model, end-member replenishment model, and pulse recharge model.<ref name=":1" /> |
|||
The Skaergaard intrusion also exhibits the formation of one of the largest [[Basalt|basaltic]] magmatic regions in the world.<ref name=":1" /> |
|||
==See also== |
==See also== |
||
| Line 22: | Line 34: | ||
[[Category:Arctic research]] |
[[Category:Arctic research]] |
||
[[Category:Layered intrusions]] |
[[Category:Layered intrusions]] |
||
[[Category:Paleogene magmatism]] |
|||
{{regional-geology-stub}} |
|||
Latest revision as of 02:50, 18 March 2024
68°10′06″N 31°43′01″W / 68.1683°N 31.7169°W The Skaergaard intrusion is a layered igneous intrusion in the Kangerlussuaq area of East Greenland and is composed of various rocks and minerals including gabbro, olivine, apatite, and basalt.[1]
History and background
[edit]
The Skaergaard intrusion was formed 56 million years ago during the opening of the North Atlantic Ocean.[1] The intrusion was emplaced beneath the preexisting rock in the region, including plateau basalt and gneiss.[1][2] The intrusion has a general oval shape, which is atypical in igneous emplacement.[1] Due to the tectonic activity in East Greenland, the intrusion is now slightly tilted towards the sea.[1] Specifically, the lower parts of the intrusion are exposed to the north while sections of the roof are conserved to the south.[1]
Discovery and early studies
[edit]The Skaergaard intrusion was first discovered by Lawrence Wager on his Arctic Air-Route Expedition in 1930.[1] In 1933, the first aerial photography of the region was taken in order to create a topographic map of the area.[1] The first scientific expedition to the intrusion took place in 1935 and 1936 and lasted over 13 months.[1] This expedition was led by Wager accompanied by a small team, including geologist William Alexander Deer.[1] Through this mission, the team studied the intrusion through reconnaissance mapping.[1]
Geologic characteristics
[edit]The intrusion is made up of three separate geologic sequences which formed at the floor, roof, and walls, with the formation at the floor being much thicker than that of the other two sequences.[1] The rocks of these sequences are further divided into three categories: the lower zone, middle zone, and upper zone.[1] The zone categorization is based on the occurrence of specific minerals such as augite, Fe-Ti oxides, rounded grains of olivine, apatite, and ferrobustamite.[1]
The intrusion formed from the crystallization of a convecting body of magma which resulted in the lineation, layering, cross bedding, and channel structures within the rocks.[1] These features result from sedimentary formations created by grain re-arrangement via magmatic currents.[1]
Within the solid rocks of the formation, the crystals are classified into two categories: primary precipitate crystals and interprecipitate crystals.[1] Primary precipitate crystals form in conditions of high presence of liquids while interprecipitate crystals form from interprecipitate liquid, liquid in the spaces between grains which solidify them together.[1]
This data was developed from the 1939 memoir written by Lawrence Wager and William Alexander Deer from their 1935 expedition.[1]
Scientific significance
[edit]Data acquired from researching the Skaergaard intrusion can be used to model how the intrusion was originally formed and how magma fractional crystallization takes place.[2] Multiple models of magmatic assimilation and recharge have been developed from the Skaergaard intrusion including the continuous replenishment model, intermittent recharge model, end-member replenishment model, and pulse recharge model.[2]
The Skaergaard intrusion also exhibits the formation of one of the largest basaltic magmatic regions in the world.[2]
See also
[edit]References
[edit]- ^ a b c d e f g h i j k l m n o p q r s Holness, Marian B.; Nielsen, Troels F.D.; Tegner, Christian (2017-12-01). "The Skaergaard Intrusion of East Greenland: Paradigms, Problems and New Perspectives". Elements. 13 (6): 391–396. doi:10.2138/gselements.13.6.391. ISSN 1811-5217.
- ^ a b c d Stewart, Brian W.; DePaolo, Donald J. (1990). "Isotopic studies of processes in mafic magma chambers: II. The Skaergaard Intrusion, East Greenland". Contributions to Mineralogy and Petrology. 104 (2): 125–141. doi:10.1007/bf00306438. ISSN 0010-7999.