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U-Pb baddelyit dateringar av basiska gångar längs Romeleåsen i Skåne och deras påverkan av plastisk deformation i Protoginzonen

Cederberg, Julia (2011) In Examensarbeten i geologi vid Lunds universitet
Department of Geology
Abstract
The bedrock in the southwest of Sweden was deformed and metamorphosed during the Sveconorwegian orogeny. The Sveconorwegian Frontal Deformation Zone north of the lake Vättern and the Protogine Zone south of the lake is regarded as the eastmost boundary of Sveconorwegian reworking. South of lake Vättern the Protogine Zone is 20-30 km wide made up of a system of discrete ductile (and locally brittle) shear zones. The spatial continuation of the Protogine Zone southward from northeast Skåne is uncertain and little documented. Three generations of mafic intrusive rocks (dated at ca. 1.56 Ga, 1.2 Ga and 0.95 Ga) indicates that the Protogine Zone was repeatedly reactivated during the Mesoproterozoic (1600-1100 Ma).

The purpose of this study... (More)
The bedrock in the southwest of Sweden was deformed and metamorphosed during the Sveconorwegian orogeny. The Sveconorwegian Frontal Deformation Zone north of the lake Vättern and the Protogine Zone south of the lake is regarded as the eastmost boundary of Sveconorwegian reworking. South of lake Vättern the Protogine Zone is 20-30 km wide made up of a system of discrete ductile (and locally brittle) shear zones. The spatial continuation of the Protogine Zone southward from northeast Skåne is uncertain and little documented. Three generations of mafic intrusive rocks (dated at ca. 1.56 Ga, 1.2 Ga and 0.95 Ga) indicates that the Protogine Zone was repeatedly reactivated during the Mesoproterozoic (1600-1100 Ma).

The purpose of this study was to investigate how far east Sveconorwegian metamorphism can be followed. In order to try to date four dolerites, located on Romeleåsen in central Skåne (Dalby, Veberöd, Stenberget and Beden), the U-Pb method on the mineral baddelyite has been used. They dykes are all affected by deformation and metamorphism (especially along the margins), which means that the crystallization age represents a maximum age of deformation seen in the quarries. With petrographic studies from the four dolerites were investigated if differences in the metamorphic influence between the dolerites in the west and those further east could be seen.

The results of the study show that a Sveconorwegian imprint can be traced through all the quarries. Age data combined with structural observations in the quarries show that the Protogine Zone appears to continue south of the lake Vättern down to the middle of Skåne. No significant lateral movements have occurred along the northern faults associated with the Tornquist zone. Since there is no Sveconorwegian deformation or metamorphism on Bornholm, the eastern boundary of Sveconorwegian reworking seems to be located somewhere between Beden and Bornholm. Petrographic studies of the dated dolerites indicate that grade of metamorphism decreases from west to east.

The age of the dolerites of Dalby and Veberöd suggest they may represent a southern expression of ca. 1.2 Ga Protogine Zone dolerites or dykes of the 1.27-1.25 Ga Central Scandinavian Dolerite Group. The dolerite in Beden must be older than 1.2 Ga and thus cannot represent a reworked dyke of the Protogine Zone dolerites. Alternatively the dolerites have a common generation of older dolerites that can be linked to the Kalseaa dolerite dyke at Bornholm (1326 Ma) and dolerites in Västra Götaland (ca. 1.3Ga). (Less)
Abstract (Swedish)
Berggrunden i sydvästra Sverige består av bergarter som deformerades och metamorfoserades under den Svekonorvegiska kontinent kollisionshändelsen. Den så kallade ”Sveconorwegian Frontal Deformation Zone” norr om Vättern och Protoginzonen söder därom anses utgöra den östligaste gränsen för Svekonorvegisk omarbetning. Söder om Vättern är Protoginzonen en 20-30 km bred N-S deformationszon. Fortsättningen av Protoginzonen söderut från nordöstra Skåne är osäker och ringa dokumenterad. Tre olika generationer av mafiska intrusiva bergarter längs Protoginzonen indikerar att den utgjort någon form av tektonisk svaghetszon under större delen av Mesoproterozoikum.

I studien har fyra diabasgångar i stenbrott belägna på Romeleåsen i mellersta Skåne... (More)
Berggrunden i sydvästra Sverige består av bergarter som deformerades och metamorfoserades under den Svekonorvegiska kontinent kollisionshändelsen. Den så kallade ”Sveconorwegian Frontal Deformation Zone” norr om Vättern och Protoginzonen söder därom anses utgöra den östligaste gränsen för Svekonorvegisk omarbetning. Söder om Vättern är Protoginzonen en 20-30 km bred N-S deformationszon. Fortsättningen av Protoginzonen söderut från nordöstra Skåne är osäker och ringa dokumenterad. Tre olika generationer av mafiska intrusiva bergarter längs Protoginzonen indikerar att den utgjort någon form av tektonisk svaghetszon under större delen av Mesoproterozoikum.

I studien har fyra diabasgångar i stenbrott belägna på Romeleåsen i mellersta Skåne (Dalby, Veberöd, Stenberget och Beden) försökt åldersbestämmas med U-Pb metoden på mineralet baddelyit. Samtliga diabasgångar är påverkade av plastisk deformation vilket gör att kristallisationsåldern utgör en maximum ålder för den deformation och metamorfos man ser i stenbrotten. Med petrografiska studier av tunnslip från de fyra metadiabaserna undersöktes om det finns skillnader i metamorf påverkan mellan de västliga och de östliga metadiabaserna i studien.

Mina resultat bekräftar att den plastiska deformationen i samtliga stenbrott är av Svekonorvegisk ålder. Åldersdatan i kombination med strukturella observationer i stenbrotten visar att Protoginzonen förefaller fortsätta söder om Vättern ner till mellersta Skåne. Inga signifikanta laterala rörelser ha skett längs de norra förkastningarna tillhörande Tornquistzonen. Eftersom det inte förekommer Svekonorvegisk deformation eller metamorfos på Bornholm måste den östra gränsen för Svekonorvegisk deformation vara belägen mellan Beden och Bornholm. Petrografiska studier av de daterade metadiabaserna indikerar att den metamorfa graden avtar från väst mot öst. Metadiabasernas ålder i Dalby och Veberöd kan utgöra sydliga uttryck för ca. 1.2 Ga Protoginzonsdiabas alternativt 1.27-1.1.25 Ga diabas tillhörande Central Scandinavian Dolerite Group. Metadiabasen i Beden måste vara äldre än 1.2 Ga och kan därmed inte vara Protoginzonsdiabas. Alternativt tillhör metadiabaserna en gemensam generation av äldre diabas och kan kopplas till Kalseaa diabasen på Bornholm (1326 Ma) och ett flertal metadiabaser i Västergötaland (ca 1.3 Ga). (Less)
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author
Cederberg, Julia
supervisor
organization
alternative title
U-Pb baddeleyite dating of metadolerite dykes along the Romele-åsen horst in Skåne, and their relations to the Protogine Zone
year
type
M2 - Bachelor Degree
subject
keywords
Romeleåsen, Svekonorvegisk deformation, Protoginezon, U-Pb, baddelyit, Skåne, Baddeleyite, Sweconorwegian deformation zone
publication/series
Examensarbeten i geologi vid Lunds universitet
report number
289
language
Swedish
id
2276841
date added to LUP
2012-01-04 12:06:39
date last changed
2012-01-04 12:18:21
@misc{2276841,
  abstract     = {The bedrock in the southwest of Sweden was deformed and metamorphosed during the Sveconorwegian orogeny. The Sveconorwegian Frontal Deformation Zone north of the lake Vättern and the Protogine Zone south of the lake is regarded as the eastmost boundary of Sveconorwegian reworking. South of lake Vättern the Protogine Zone is 20-30 km wide made up of a system of discrete ductile (and locally brittle) shear zones. The spatial continuation of the Protogine Zone southward from northeast Skåne is uncertain and little documented. Three generations of mafic intrusive rocks (dated at ca. 1.56 Ga, 1.2 Ga and 0.95 Ga) indicates that the Protogine Zone was repeatedly reactivated during the Mesoproterozoic (1600-1100 Ma). 

The purpose of this study was to investigate how far east Sveconorwegian metamorphism can be followed. In order to try to date four dolerites, located on Romeleåsen in central Skåne (Dalby, Veberöd, Stenberget and Beden), the U-Pb method on the mineral baddelyite has been used. They dykes are all affected by deformation and metamorphism (especially along the margins), which means that the crystallization age represents a maximum age of deformation seen in the quarries. With petrographic studies from the four dolerites were investigated if differences in the metamorphic influence between the dolerites in the west and those further east could be seen.

The results of the study show that a Sveconorwegian imprint can be traced through all the quarries. Age data combined with structural observations in the quarries show that the Protogine Zone appears to continue south of the lake Vättern down to the middle of Skåne. No significant lateral movements have occurred along the northern faults associated with the Tornquist zone. Since there is no Sveconorwegian deformation or metamorphism on Bornholm, the eastern boundary of Sveconorwegian reworking seems to be located somewhere between Beden and Bornholm. Petrographic studies of the dated dolerites indicate that grade of metamorphism decreases from west to east.

The age of the dolerites of Dalby and Veberöd suggest they may represent a southern expression of ca. 1.2 Ga Protogine Zone dolerites or dykes of the 1.27-1.25 Ga Central Scandinavian Dolerite Group. The dolerite in Beden must be older than 1.2 Ga and thus cannot represent a reworked dyke of the Protogine Zone dolerites. Alternatively the dolerites have a common generation of older dolerites that can be linked to the Kalseaa dolerite dyke at Bornholm (1326 Ma) and dolerites in Västra Götaland (ca. 1.3Ga).},
  author       = {Cederberg, Julia},
  keyword      = {Romeleåsen,Svekonorvegisk deformation,Protoginezon,U-Pb,baddelyit,Skåne,Baddeleyite,Sweconorwegian deformation zone},
  language     = {swe},
  note         = {Student Paper},
  series       = {Examensarbeten i geologi vid Lunds universitet},
  title        = {U-Pb baddelyit dateringar av basiska gångar längs Romeleåsen i Skåne och deras påverkan av plastisk deformation i Protoginzonen},
  year         = {2011},
}