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The igneous complex of Ekmanfjorden, Svalbard: an integrated field, petrological and geochemical study

Sartell, Anna LU (2021) In Dissertations in Geology at Lund University GEOR02 20211
Department of Geology
Abstract (Swedish)
Stora magmatiska provinser återfinns långt tillbaka i jordens geologiska historia, från Arkeikum till Kenozoikum, och kan ha en stor påverkan på det globala klimatet. Den hög-arktiska stora magmatiska provinsen (HALIP) bildades under tidig Krita och rester av denna storskaliga magmatism kan observeras i hela Arktis. Relativt få U-Pb åldrar har än så länge blivit analyserade och mer geokronologisk data, såväl som detaljerade petrologiska och geokemiska studier behövs för att få en bättre förståelse för utvecklingen av denna stora magmatiska provins. HALIP har studerats i detalj på Kanadas arktiska öar, till skillnad från de relativt outforskade intrusionerna i Svalbard, som kollektivt kallas för ”Diabasodden Suite”. För att minska... (More)
Stora magmatiska provinser återfinns långt tillbaka i jordens geologiska historia, från Arkeikum till Kenozoikum, och kan ha en stor påverkan på det globala klimatet. Den hög-arktiska stora magmatiska provinsen (HALIP) bildades under tidig Krita och rester av denna storskaliga magmatism kan observeras i hela Arktis. Relativt få U-Pb åldrar har än så länge blivit analyserade och mer geokronologisk data, såväl som detaljerade petrologiska och geokemiska studier behövs för att få en bättre förståelse för utvecklingen av denna stora magmatiska provins. HALIP har studerats i detalj på Kanadas arktiska öar, till skillnad från de relativt outforskade intrusionerna i Svalbard, som kollektivt kallas för ”Diabasodden Suite”. För att minska kunskapsluckorna gällande HALIPs bildande i Svalbard, så gjordes en fältundersökning i Ekmanfjorden under hösten 2020 för att samla in bergartsprover och drönarbilder. Ekmanfjorden ligger i norra Isfjorden, i Spetsbergen, och är till största del outforskad när det gäller HALIP. Tidigare fältundersökningar i Isfjorden har på avstånd sett att det finns flera okarterade intrusioner i Ekmanfjorden som behövs undersökas. Bergartsproverna som samlades in under 2020 har använts till geokemiska analyser, både på hela prover och enskilda mineral, och tunnslip har gjorts för petrologiska studier. Drönarbilderna har använts till att göra virtuella modeller över intrusionerna, för att beräkna volymen av de magmatiska bergarterna samt för att uppdatera den geologiska kartan över området. Geometrin av bergarterna har också undersökts med hjälp av dessa bilder, och den tillgängliga geokronologiska datan har granskats för att kunna jämföra den nya datan med HALIP i stort. Resultaten visar att volymen av de intrusiva resterna som kan observeras i Ekmanfjorden är mellan 0.25 och 0.52 km3 och geometrin indikerar att de magmatiska bergarterna som återfinns på den huvudsakliga halvön kan ha intruderats som en stor sammanhängande intrusion, med en volym på åtminstone 3.6 km3. Den geokemiska signaturen från Ekmanfjordens magmatiska bergarter korrelerar väl med andra HALIP intrusioner med ungefär samma ålder runt on i Arktis. Intrusionerna in Ekmanfjorden består av basaltiska toleiiter som visar omfattande kontamination från jordskorpan och en ursprunglig magma lik berikade basalter från mittoceaniska ryggar. Geokemiska analyser på bergartsproverna indikerar att intrusionerna i Ekmanfjorden har en komplex historia, med två separata magmapulser. En av pulserna tyder på tidig smältning av låg grad i granatstabilitetsfältet kombinerad med senare grundare smältning i spinellstabilitetsfältet, medan den andra vanligare pulsen indikerar endast smältning djupare i manteln, i närvaro av granat. För att förstå vilken av dessa två pulser kom först så behövs U-Pb geokronologi med hög precision. Det finns även ett stort behov av mer U-Pb geokronologi av HALIP i hela Svalbard och Arktis, då det idag endast finns 4 U-Pb åldrar tillgängliga från Svalbard och totalt endast 23 U-Pb åldrar av HALIP i hela Arktis. (Less)
Abstract
Large Igneous Provinces are widespread in the geological record, from the Archean to the Cenozoic, and can have a significant impact on the global climate. The High Arctic Large Igneous Province (HALIP) was emplaced during the Early Cretaceous, and remnants of this large-scale magmatism can be found all over the circum-Arctic. Relatively few high-precision U-Pb ages have been analyzed to date, and more geochronological data, as well as thorough petrological and geochemical studies, are needed to understand the evolution of this large igneous province. The HALIP has been studied extensively in the Canadian Arctic, unlike the intrusions emplaced as the Diabasodden Suite on Svalbard, which are still relatively unexplored. In order to bridge... (More)
Large Igneous Provinces are widespread in the geological record, from the Archean to the Cenozoic, and can have a significant impact on the global climate. The High Arctic Large Igneous Province (HALIP) was emplaced during the Early Cretaceous, and remnants of this large-scale magmatism can be found all over the circum-Arctic. Relatively few high-precision U-Pb ages have been analyzed to date, and more geochronological data, as well as thorough petrological and geochemical studies, are needed to understand the evolution of this large igneous province. The HALIP has been studied extensively in the Canadian Arctic, unlike the intrusions emplaced as the Diabasodden Suite on Svalbard, which are still relatively unexplored. In order to bridge some of the knowledge gaps present in the understanding of the emplacement of the HALIP on Svalbard, a field campaign in Ekmanfjorden was made in 2020 to collect samples and drone imagery. Ekmanfjorden is located in northern Isfjorden, Spitsbergen, and is largely undiscovered with regard to the HALIP, as previous fieldwork has showed a multitude of unmapped igneous intrusions present in the area. The samples collected in 2020 were used for analyzing whole-rock geochemistry and mineral chemistry, and thin sections were made for petrological studies. Virtual outcrop models were made using drone images acquired during the field campaign, and volume estimates as well as an updated geological map could be made based on this data. The geometry of the intrusions was also studied using the images captured, and an updated review of the geochronology of the HALIP was made to link the new data to the HALIP in the circum-Arctic. The results show that volume of the intrusions present within Ekmanfjorden today is between 0.25 and 0.52 km3, and the geometry of the intrusions found on the main peninsula indicate that the whole area might have been covered by one large intrusive sill, with a volume of at least 3.6 km3. Furthermore, the geochemical signature of the intrusions in Ekmanfjorden correlate well with other circum-Arctic HALIP intrusions believed to be of the sample age. The Diabasodden Suite in Ekmanfjorden is represented by basaltic tholeiites, which record extensive crustal contamination during the ascent from its source, and a parental magma similar to enriched mid-ocean ridge basalts. The whole-rock geochemistry indicates a complex emplacement history in Ekmanfjorden, with two separate pulses of magma. One pulse records early, low degree melting in the garnet stability field, combined with later, shallower melting in the spinel lherzolite field, while the other dominant pulse records only deeper melting from a garnet-bearing source. In order to determine which pulse came first, high-precision U-Pb geochronology is needed, and this is also needed to understand the complexities of the HALIP on Svalbard and the circum-Arctic as a whole, as only 4 U-Pb ages have been analyzed from Svalbard to date, and 23 U-Pb ages of the HALIP in total. (Less)
Please use this url to cite or link to this publication:
author
Sartell, Anna LU
supervisor
organization
alternative title
Ekmanfjordens magmatiska komplex, Svalbard: en integrerad studie omfattande fältarbete, petrologi och geokemi
course
GEOR02 20211
year
type
H2 - Master's Degree (Two Years)
subject
keywords
High Arctic Large Igneous Province, Svalbard, Ekmanfjorden, geochemistry, petrology, sill, magma, geochronology review
publication/series
Dissertations in Geology at Lund University
report number
625
language
English
additional info
External supervisors: Kim Senger, University Centre in Svalbard. Olivier Galland, University of Oslo
id
9069595
date added to LUP
2022-01-03 19:34:16
date last changed
2022-01-04 11:36:09
@misc{9069595,
  abstract     = {{Large Igneous Provinces are widespread in the geological record, from the Archean to the Cenozoic, and can have a significant impact on the global climate. The High Arctic Large Igneous Province (HALIP) was emplaced during the Early Cretaceous, and remnants of this large-scale magmatism can be found all over the circum-Arctic. Relatively few high-precision U-Pb ages have been analyzed to date, and more geochronological data, as well as thorough petrological and geochemical studies, are needed to understand the evolution of this large igneous province. The HALIP has been studied extensively in the Canadian Arctic, unlike the intrusions emplaced as the Diabasodden Suite on Svalbard, which are still relatively unexplored. In order to bridge some of the knowledge gaps present in the understanding of the emplacement of the HALIP on Svalbard, a field campaign in Ekmanfjorden was made in 2020 to collect samples and drone imagery. Ekmanfjorden is located in northern Isfjorden, Spitsbergen, and is largely undiscovered with regard to the HALIP, as previous fieldwork has showed a multitude of unmapped igneous intrusions present in the area. The samples collected in 2020 were used for analyzing whole-rock geochemistry and mineral chemistry, and thin sections were made for petrological studies. Virtual outcrop models were made using drone images acquired during the field campaign, and volume estimates as well as an updated geological map could be made based on this data. The geometry of the intrusions was also studied using the images captured, and an updated review of the geochronology of the HALIP was made to link the new data to the HALIP in the circum-Arctic. The results show that volume of the intrusions present within Ekmanfjorden today is between 0.25 and 0.52 km3, and the geometry of the intrusions found on the main peninsula indicate that the whole area might have been covered by one large intrusive sill, with a volume of at least 3.6 km3. Furthermore, the geochemical signature of the intrusions in Ekmanfjorden correlate well with other circum-Arctic HALIP intrusions believed to be of the sample age. The Diabasodden Suite in Ekmanfjorden is represented by basaltic tholeiites, which record extensive crustal contamination during the ascent from its source, and a parental magma similar to enriched mid-ocean ridge basalts. The whole-rock geochemistry indicates a complex emplacement history in Ekmanfjorden, with two separate pulses of magma. One pulse records early, low degree melting in the garnet stability field, combined with later, shallower melting in the spinel lherzolite field, while the other dominant pulse records only deeper melting from a garnet-bearing source. In order to determine which pulse came first, high-precision U-Pb geochronology is needed, and this is also needed to understand the complexities of the HALIP on Svalbard and the circum-Arctic as a whole, as only 4 U-Pb ages have been analyzed from Svalbard to date, and 23 U-Pb ages of the HALIP in total.}},
  author       = {{Sartell, Anna}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{Dissertations in Geology at Lund University}},
  title        = {{The igneous complex of Ekmanfjorden, Svalbard: an integrated field, petrological and geochemical study}},
  year         = {{2021}},
}