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Eriksson, Per
Alternative names
Publications (4 of 4) Show all publications
Eriksson, P., Riishuus, M. & Elming, S.-å. (2015). Magma flow and palaeo-stress deduced from magnetic fabric analysis of the Álftafjörður dyke swarm: implications for shallow crustal magma transport in Icelandic volcanic systems (ed.). Paper presented at . Geological Society Special Publication, 396, 107-132
Open this publication in new window or tab >>Magma flow and palaeo-stress deduced from magnetic fabric analysis of the Álftafjörður dyke swarm: implications for shallow crustal magma transport in Icelandic volcanic systems
2015 (English)In: Geological Society Special Publication, ISSN 0305-8719, E-ISSN 2041-4927, Vol. 396, p. 107-132Article in journal (Refereed) Published
Abstract [en]

Neogene regional mafic dykes extending north of the Álftafjörður central volcano in east Iceland are studied to test models of dyke swarm emplacement at spreading ridges. This is accomplished by using anisotropy of magnetic susceptibility to define fossilized magma flow regimes. The imbrication of the foliation plane, defined by the minor susceptibility axis, is used as an indicator of the flow direction. Contemporaneous shear resolved on the dyke walls may modify a pure flow-induced fabric and such shear regimes are therefore retracted. The magma flow and palaeo-stress resolved on the dykes are determined in 13 of 24 dykes. The magma flow is interpreted as subhorizontal and northwards directed away from the central volcano for nine dykes, and found to be vertical in three cases. The preferentially subhorizontal magma flow in the Álftafjörður swarm suggests that dyke propagation in this type of Icelandic volcanic system originates in shallow crustal magma chambers. The regional tectonic palaeo-stress field is deduced to cause oblique spreading across the Álftafjörður dyke swarm and govern a subhorizontal dextral shear component on the dyke planes during propagation. This interpretation is not in conflict with the left-stepping en echelon trend distribution of individual dykes relative to the trend of the swarm

National Category
Geophysics
Research subject
Exploration Geophysics
Identifiers
urn:nbn:se:ltu:diva-8014 (URN)10.1144/SP396.6 (DOI)2-s2.0-84924864634 (Scopus ID)6740ef00-b98b-48c7-8124-feb29205b332 (Local ID)6740ef00-b98b-48c7-8124-feb29205b332 (Archive number)6740ef00-b98b-48c7-8124-feb29205b332 (OAI)
Note
Validerad; 2015; Nivå 2; 20140227 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Rüfenacht, R., Murk, A., Kämpfer, N., Eriksson, P. & Buehler, S. A. (2014). Middle-atmospheric zonal and meridional wind profiles from polar, tropical and midlatitudes with the ground-based microwave Doppler wind radiometer WIRA (ed.). Atmospheric Measurement Techniques, 7, 4491-4505
Open this publication in new window or tab >>Middle-atmospheric zonal and meridional wind profiles from polar, tropical and midlatitudes with the ground-based microwave Doppler wind radiometer WIRA
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2014 (English)In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 7, p. 4491-4505Article in journal (Refereed) Published
Abstract [en]

WIRA is a ground-based microwave Doppler spectroradiometer specifically designed for the measurement of profiles of horizontal wind in the upper stratosphere and lower mesosphere region where no other continuously running measurement technique exists. A proof of principle has been delivered in a previous publication. A technical upgrade including a new high-frequency amplifier and sideband filter has improved the signal to noise ratio by a factor of 2.4. Since this upgrade the full horizontal wind field comprising zonal and meridional wind profiles is continuously measured. A completely new retrieval based on optimal estimation has been set up. Its characteristics are detailed in the present paper. Since the start of the routine operation of the first prototype in September 2010, WIRA has been measuring at four different locations at polar, mid- and tropical latitudes (67°22′ N/26°38′ E, 46°57′ N/7°26′ E, 43°56′ N/5°43′ E and 21°04′ S/55°23′ E) for time periods between 5.5 and 11 months. The data presented in this paper are daily average wind profiles with typical uncertainties and resolutions of 10 to 20 m s−1 and 10 to 16 km, respectively. A comparison between the data series from WIRA and European Centre for Medium-Range Weather Forecasts (ECMWF) model data revealed agreement within 10% in the stratospheric zonal wind. The meridional wind profiles agree within their error bars over the entire sensitive altitude range of WIRA. However, significant differences in the mesospheric zonal wind speed of up to 50% have been found.

National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-12449 (URN)10.5194/amt-7-4491-2014 (DOI)000352290900017 ()2-s2.0-84919372449 (Scopus ID)b9a1ec54-7b0a-4f92-ac80-59fc5c805ab2 (Local ID)b9a1ec54-7b0a-4f92-ac80-59fc5c805ab2 (Archive number)b9a1ec54-7b0a-4f92-ac80-59fc5c805ab2 (OAI)
Note

Validerad; 2014; Nivå 2; 20150107 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2019-08-20Bibliographically approved
Eriksson, P., Riishuus, M. S., Sigmundsson, F. & Elming, S.-å. (2011). Magma flow directions inferred from field evidence and magnetic fabric studies of the Streitishvarf composite dike in east Iceland (ed.). Paper presented at . Journal of Volcanology and Geothermal Research, 206(1-2), 30-45
Open this publication in new window or tab >>Magma flow directions inferred from field evidence and magnetic fabric studies of the Streitishvarf composite dike in east Iceland
2011 (English)In: Journal of Volcanology and Geothermal Research, ISSN 0377-0273, E-ISSN 1872-6097, Vol. 206, no 1-2, p. 30-45Article in journal (Refereed) Published
Abstract [en]

Anisotropy of magnetic susceptibility (AMS) and rock magnetic studies have been made on three outcrops separated by 12 km along strike (NNE–SSW) on the Streitishvarf composite dike in east Iceland. Samples for this study have been collected from the inner quartz-porphyry part of the dike, which show clear field evidence of a lateral flow component from north to south at one of the sites. This flow component is consistent with margin AMS results from all three sites. The quartz-porphyry has a substantial bulk magnetic susceptibility (10-2 SI) mainly carried by magnetically soft titanium-poor titanomagnetite (MDF 15 mT). The ferrimagnetic grains yield a characteristic remanent magnetization in all three sites which gives a virtual geomagnetic pole at latitude 52:6°S and longitude 319:6°E. The degree of anisotropy is low (PJ = 1:033) and the magnetic fabrics shifts from oblate to prolate shapes depending on dike margin and outcrop. The magnetic fabric has been interpreted according to the imbrication model, using the minor susceptibility axis as shear plane indicator. The absolute directions given by the minor susceptibility are then quantified using vector algebra. The magma flow is indicated as an upward directed flow, flowing from north to south with an inclination between 30° – 64°, with a 95% confidence ellipse of 3° – 9°. A model for the intrusion of the Streitishvarf dike has been constructed where a magma pocket with felsic magma is punctured by a mafic dike, enabling the felsic magma to rise and extend to the south within the pathway created. The results of this study confirm the applicability of AMS in studies of magma flow directions in igneous dikes of felsic composition.

National Category
Geophysics
Research subject
Applied Geophysics
Identifiers
urn:nbn:se:ltu:diva-4004 (URN)10.1016/j.jvolgeores.2011.05.009 (DOI)000294656300003 ()2-s2.0-79961168277 (Scopus ID)1db2d336-593c-4e20-990a-1c2e94608ea1 (Local ID)1db2d336-593c-4e20-990a-1c2e94608ea1 (Archive number)1db2d336-593c-4e20-990a-1c2e94608ea1 (OAI)
Note
Validerad; 2011; 20110620 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Eriksson, P. (2010). Magnetic properties of Neogene regional dikes from east Iceland with special reference to magma flow (ed.). (Licentiate dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Magnetic properties of Neogene regional dikes from east Iceland with special reference to magma flow
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Alternative title[sv]
Magnetiska egenskaper hos regionala gångar av Neogen ålder från östra Island med speciellt avseende på magmaflöde
Abstract [en]

This thesis deals with rock magnetic measurements on Neogene dikes from the eastern fjords of Iceland. A vast amount of dikes generally striking north-north-east occur as swarms in the glacially eroded lava pile. They are considered as the underlying extensions of fissure swarms in active volcanic systems which like the dike swarms converge at central volcanoes. The dike swarms and associated central volcanoes are uncovered by ca. 1500 m of glacial erosion, leaving the upper parts of these igneous units bare. Two research papers have been prepared based on field studies and measurements of rock magnetism on carefully chosen occurrences of Icelandic dikes in order to test contradicting models of dike origin. The manuscripts are included in the thesis.The first is a detail study of a single composite dike, with a core of fine grained quartz-porphyry surrounded by dolerite margins. The core of the dike was sampled in three locations, separated by ~12 km and measured for magnetic remanence and anisotropy of magnetic susceptibility. Magma flow direction in this dike was interpreted using the mirror imbrication of the minor susceptibility axes from each margin of the quartz-porphyry core of the dike. The flow regime in all three locations showed a marked flow component from north to south, supported by field evidence in the form of parabolically aligned enclaves, and shear folds. Statistical procedures of bootstrapping was utilized to define the flow and handle imbrication in both the vertical and horizontal plane thus defining direction and inclination of flow. The main contribution of this paper was to prove that anisotropy of magnetic susceptibility used to infer flow direction may give consistent and reliable results, and to present new ways (to use old techniques) to define magma flow directions.The same technique used to infer flow in paper one has sub-sequentially been applied to a far larger set of mafic dikes, extending north-east from the exhumed Álftafjörður central volcano. The second paper documents that the flow regimes from the mafic dikes showed a predominantly horizontal flow from the central volcano, supporting tectonic models that suggest shallow magma chambers to be the source of the dikes. The thesis further discusses the results from these studies in comparison to other studies on Icelandic dikes where the magma flow is determined by the direction of the major susceptibility axis.

Abstract [sv]

Denna avhandling behandlar magnetiska egenskaper hos regionala Isländska gångbergarter från de östra fjordarna i landet. Ett stort antal av dessa gångar går att finna i det glacialt eroderade landskapet från den Neogena perioden. Gångarna bildar långträckta stråk vilka i allmänhet stryker mot NNE. Dessa gångar anses vara en underjordisk fortsättning i den övre delen av jordskorpan, av de långsträckta förkastningssprickor vilka likt gångarna sammanstrålar mot centralvulkaner i nu aktiva vulkansystem. Gångarna och centralvulkanerna har bägge blivit avtäcka genom istida nednötning av berggrunden till en utsträckning av 1500 m, vilket lämnat de övre delarna av dessa magmatiska kroppar synliga i landskapet.Två manuskript har skrivits om dessa Isländska gångar. Det första manuskriptet omfattar en detaljerad studie av en kompositgång, bestående av en kärna av finkornig kvartsporfyr omgiven av dolerit. Kärnan i denna gång har blivit provtagen på tre ställen vilka åtskiljs från varandra av 12 km i längd. Provernas magnetiska susceptibilitet och anisotropin av denna har sedan analyserats. Riktning av fossilerat magmaflöde i denna gång har sedan bestämts från tolkningar av minimumaxeln hos den magnetiska susceptsellipsoiden och dess geometriska förhållande till gångens respektive sidor. Flödesriktningen i alla de tre provtagningsställena visade på en horizontell flödeskomponent från norr till syd, vilket stöds av fältrelationer i form av mafiska enklaver vilka lineerats av magmaflöde till formen av en paraboloid. Statistiska metoder användes för att definera flödesriktningen i det geometriska rummet vilket gett oss både riktning och lutning av flödet.Det huvudsakliga vetenskapliga bidraget från det första manuskriptet var att tydliggöra att magnetisk susceptibilitet kan användas för att ta fram flödesriktningar. Ny tillämpning av metodik för att bättre kvantifiera flöde introducerades också. Denna nygamla teknik har sedan använtes för att bestämma magmaflöden i ett betydligt större antal av mafiska gångar, vilka sträcker sig ut mot nordöst från den nu slocknade Álftafjörður-vulkanen. De flödesriktningar vilka definierades i de mafiska gångarna var företrädesvis horizontella, riktade bort från centralvulkanen. Detta stöder tektoniska modeller vilka söker förklara uppkomsten av de mafiska gångarna genom att härleda dem till intrusioner från ytliga magmakammare. Tilläggsvis har resultaten i dessa studier jämnförts med andra internationella studier vilka söker bestämma riktningen på magmaflöde genom användning av maximumaxeln i susceptibilitetsellipsoiden.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2010. p. 195
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Keywords
Natural sciences - Earth sciences, Naturvetenskap - Geovetenskap
National Category
Geophysics
Research subject
Applied Geophysics
Identifiers
urn:nbn:se:ltu:diva-17856 (URN)58a1b530-f2fb-11df-8b36-000ea68e967b (Local ID)978-91-7439-191-6 (ISBN)58a1b530-f2fb-11df-8b36-000ea68e967b (Archive number)58a1b530-f2fb-11df-8b36-000ea68e967b (OAI)
Note
Godkänd; 2010; 20101118 (eriper); LICENTIATSEMINARIUM Ämnesområde: Tillämpad geofysik/Applied Geophysics Examinator: Professor Sten-Åke Elming, Luleå tekniska universitet Diskutant: PhD Håkan Mattsson, Geovista, Luleå Tid: Fredag den 17 december 2010 kl 12.30 Plats: E246, Luleå tekniska universitetAvailable from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
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